lmd_EMC32006.bib
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@article{2006ClDy...27..787H,
author = {{Hourdin}, F. and {Musat}, I. and {Bony}, S. and {Braconnot}, P. and
{Codron}, F. and {Dufresne}, J.-L. and {Fairhead}, L. and {Filiberti}, M.-A. and
{Friedlingstein}, P. and {Grandpeix}, J.-Y. and {Krinner}, G. and
{Levan}, P. and {Li}, Z.-X. and {Lott}, F.},
title = {{The LMDZ4 general circulation model: climate performance and sensitivity to parametrized physics with emphasis on tropical convection}},
journal = {Climate Dynamics},
year = 2006,
month = dec,
volume = 27,
pages = {787-813},
abstract = {{The LMDZ4 general circulation model is the atmospheric component of the
IPSL CM4 coupled model which has been used to perform climate change
simulations for the 4th IPCC assessment report. The main aspects of the
model climatology (forced by observed sea surface temperature) are
documented here, as well as the major improvements with respect to the
previous versions, which mainly come form the parametrization of
tropical convection. A methodology is proposed to help analyse the
sensitivity of the tropical Hadley Walker circulation to the
parametrization of cumulus convection and clouds. The tropical
circulation is characterized using scalar potentials associated with the
horizontal wind and horizontal transport of geopotential (the Laplacian
of which is proportional to the total vertical momentum in the
atmospheric column). The effect of parametrized physics is analysed in a
regime sorted framework using the vertical velocity at 500 hPa as a
proxy for large scale vertical motion. Compared to Tiedtke{\rsquo}s
convection scheme, used in previous versions, the Emanuel{\rsquo}s scheme
improves the representation of the Hadley Walker circulation, with a
relatively stronger and deeper large scale vertical ascent over tropical
continents, and suppresses the marked patterns of concentrated rainfall
over oceans. Thanks to the regime sorted analyses, these differences are
attributed to intrinsic differences in the vertical distribution of
convective heating, and to the lack of self-inhibition by precipitating
downdraughts in Tiedtke{\rsquo}s parametrization. Both the convection and
cloud schemes are shown to control the relative importance of large
scale convection over land and ocean, an important point for the
behaviour of the coupled model.
}},
doi = {10.1007/s00382-006-0158-0},
adsurl = {http://adsabs.harvard.edu/abs/2006ClDy...27..787H},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006ClDy...26..145W,
author = {{Williams}, K.~D. and {Ringer}, M.~A. and {Senior}, C.~A. and
{Webb}, M.~J. and {McAvaney}, B.~J. and {Andronova}, N. and
{Bony}, S. and {Dufresne}, J.-L. and {Emori}, S. and {Gudgel}, R. and
{Knutson}, T. and {Li}, B. and {Lo}, K. and {Musat}, I. and
{Wegner}, J. and {Slingo}, A. and {Mitchell}, J.~F.~B.},
title = {{Evaluation of a component of the cloud response to climate change in an intercomparison of climate models}},
journal = {Climate Dynamics},
year = 2006,
month = feb,
volume = 26,
pages = {145-165},
abstract = {{Most of the uncertainty in the climate sensitivity of contemporary
general circulation models (GCMs) is believed to be connected with
differences in the simulated radiative feedback from clouds. Traditional
methods of evaluating clouds in GCMs compare time-mean geographical
cloud fields or aspects of present-day cloud variability, with
observational data. In both cases a hypothetical assumption is made that
the quantity evaluated is relevant for the mean climate change response.
Nine GCMs (atmosphere models coupled to mixed-layer ocean models) from
the CFMIP and CMIP model comparison projects are used in this study to
demonstrate a common relationship between the mean cloud response to
climate change and present-day variability. Although
atmosphere-mixed-layer ocean models are used here, the results are found
to be equally applicable to transient coupled model simulations. When
changes in cloud radiative forcing (CRF) are composited by changes in
vertical velocity and saturated lower tropospheric stability, a
component of the local mean climate change response can be related to
present-day variability in all of the GCMs. This suggests that the
relationship is not model specific and might be relevant in the real
world. In this case, evaluation within the proposed compositing
framework is a direct evaluation of a component of the cloud response to
climate change. None of the models studied are found to be clearly
superior or deficient when evaluated, but a couple appear to perform
well on several relevant metrics. Whilst some broad similarities can be
identified between the 60{\deg}N-60{\deg}S mean change in CRF to increased
CO$_{2}$ and that predicted from present-day variability, the two
cannot be quantitatively constrained based on changes in vertical
velocity and stability alone. Hence other processes also contribute to
the global mean cloud response to climate change.
}},
doi = {10.1007/s00382-005-0067-7},
adsurl = {http://adsabs.harvard.edu/abs/2006ClDy...26..145W},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006JCli...19.3445B,
author = {{Bony}, S. and {Colman}, R. and {Kattsov}, V.~M. and {Allan}, R.~P. and
{Bretherton}, C.~S. and {Dufresne}, J.-L. and {Hall}, A. and
{Hallegatte}, S. and {Holland}, M.~M. and {Ingram}, W. and {Randall}, D.~A. and
{Soden}, B.~J. and {Tselioudis}, G. and {Webb}, M.~J.},
title = {{How Well Do We Understand and Evaluate Climate Change Feedback Processes?}},
journal = {Journal of Climate},
year = 2006,
volume = 19,
pages = {3445},
doi = {10.1175/JCLI3819.1},
adsurl = {http://adsabs.harvard.edu/abs/2006JCli...19.3445B},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006MAP....94..145D,
author = {{Deb}, S.~K. and {Upadhyaya}, H.~C. and {Grandpeix}, J.~Y. and
{Sharma}, O.~P.},
title = {{On convective entrainment in a mass flux cumulus parameterization}},
journal = {Meteorology and Atmospheric Physics},
year = 2006,
month = nov,
volume = 94,
pages = {145-152},
abstract = {{A new entrainment/detrainment formulation in the Tiedtke{\rsquo}s mass
flux cumulus parameterization is discussed here. Apart from validating
it with observations both in one and three dimensional cases, it is also
evaluated in the light of the results from the original Tiedtke scheme
and another mass flux scheme due to Emanuel. The proposed analytical
profiles of entrainment and detrainment, easier to implement in any mass
flux scheme, give reasonable results in GCM experiments.
}},
doi = {10.1007/s00703-005-0175-2},
adsurl = {http://adsabs.harvard.edu/abs/2006MAP....94..145D},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006JGRD..11121109B,
author = {{Brogniez}, H. and {Roca}, R. and {Picon}, L.},
title = {{A clear-sky radiance archive from Meteosat ``water vapor'' observations}},
journal = {Journal of Geophysical Research (Atmospheres)},
keywords = {Atmospheric Processes: Remote sensing, Atmospheric Processes: Climatology (1616, 1620, 3305, 4215, 8408), Atmospheric Processes: Tropical meteorology, Atmospheric Processes: Instruments and techniques, cloud clearing, water vapor, satellite climatology},
year = 2006,
month = nov,
volume = 111,
number = d10,
eid = {D21109},
pages = {21109},
abstract = {{A long-term archive of clear-sky Meteosat ''water vapor'' observations,
covering the July 1983 to February 1997 period with a 3 hourly time step
and a spatial resolution of 0.625{\deg}, is presented. Cloud clearing is
performed using a scene selection procedure based on the International
Satellite Cloud Climatology Project DX product. In this procedure low
cloud scenes are kept because of the negligible contribution of the low
atmospheric layer in this spectral band. Cloud contamination is shown to
have little influence on the clear-sky radiance (CSR) field and is
mainly confined to the continental Intertropical Convergence Zone with
values less than 0.5 K. This scene selection yields to a significantly
enhanced sampling with respect to pure clear-sky in the subtropical high
regions. Homogenization of the 14 year database is performed in
accordance with existing technique. A comparison to the operational
radiosondes archive indicates a small bias of 0.3 K that is stable
throughout the period. A first analysis of the CSR variability reveals
that the intraseasonal variance over the subtropical dry regions has a
strong seasonal cycle in the Northern Hemisphere that is not observed in
the Southern Hemisphere. Such a data set completes the ones currently
available to document the water vapor variability of the troposphere
from climatic down to regional and daily scales.
}},
doi = {10.1029/2006JD007238},
adsurl = {http://adsabs.harvard.edu/abs/2006JGRD..11121109B},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006ClDy...27..613K,
author = {{Krinner}, G. and {Boucher}, O. and {Balkanski}, Y.},
title = {{Ice-free glacial northern Asia due to dust deposition on snow}},
journal = {Climate Dynamics},
year = 2006,
month = nov,
volume = 27,
pages = {613-625},
abstract = {{During the Last Glacial Maximum (LGM, 21 kyr BP), no large ice sheets
were present in northern Asia, while northern Europe and North America
(except Alaska) were heavily glaciated. We use a general circulation
model with high regional resolution and a new parameterization of snow
albedo to show that the ice-free conditions in northern Asia during the
LGM are favoured by strong glacial dust deposition on the seasonal snow
cover. Our climate model simulations indicate that mineral dust
deposition on the snow surface leads to low snow albedo during the melt
season. This, in turn, caused enhanced snow melt and therefore favoured
snow-free peak summer conditions over almost the entire Asian continent
during the LGM, whereas perennial snow cover is simulated over a large
part of eastern Siberia when glacial dust deposition is not taken into
account.
}},
doi = {10.1007/s00382-006-0159-z},
adsurl = {http://adsabs.harvard.edu/abs/2006ClDy...27..613K},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006AtmRe..82..276L,
author = {{Liberti}, G.~L. and {Chéruy}, F.},
title = {{Tropospheric dryness and clouds over tropical Indian Ocean}},
journal = {Atmospheric Research},
year = 2006,
month = nov,
volume = 82,
pages = {276-293},
abstract = {{Dry layers in the free troposphere over Tropical Oceans have been
studied for their role in convective activity and for their effects in
the radiation budget. Previous studies concentrated, mostly, on the
Western Pacific region because of the abundance of observations during
the TOGA-COARE. This study aims to document the occurrence of dry layers
over the Indian Ocean and to investigate the cloudiness observed, but
poorly documented, during such events. One month (March 1999, during
INDOEX) of combined Visible/Infrared and Microwave data from the TRMM
radiometers had been processed to classify observations in terms of
total precipitable water vapour (TPWV), cloud occurrence and type.
Soundings (1978-2004) from the Seychelles station have been analysed to
validate the capability, through the analysis of TPWV, to detect dry
layers. The study area (40{\deg}E-80{\deg}E, 30{\deg}S-30{\deg}N) had been
portioned into 2.5{\deg} {\times} 2.5{\deg} boxes to investigate the
spatial distribution of occurrence of dry events with associated
cloudiness. South of the ITCZ cloudiness associated with low TPWV is due
to low-level clouds: probably generated by shallow convection trapped by
the trade inversion. North of the ITCZ cirrus are mostly observed during
relatively dry events. Further analyses, concentrating on possible links
between occurrence of cirrus and TPWV, suggest, in addition to the
obvious mechanism (i.e. the higher the moisture, the higher the
convective activity and as a consequence the higher the occurrence of
cirrus), a second one that would be responsible of relatively high
occurrence of cirrus for low TPWV. A case (14th-15th March 1999) is
studied in detail with TRMM observations, sounding data and METEOSAT
imagery. The observed cirrus, generated by convection, migrate over
relatively dry air of extra-tropical origin. Cirrus extend as filaments
for more than 1000 km in length and about 50 to 100 km in width, and
they last for 2-3 days. A retrieval method is designed and applied to
the data giving as cirrus top pressure approximately 250 hPa while the
retrieved effective radius value is consistent with what expected, from
literature, for dissipating cirrus at that pressure. The vertical
structure of the atmosphere, observed during such event suggests the
hypothesis that a combination of presented radiative and dynamical
mechanisms could be responsible, through the supply of moisture from
lower levels, of increasing the cirrus lifetime and, as a consequence,
increasing the occurrence of cirrus over relatively dry air columns. A
larger data set is investigated to confirm the results based on the
March 1999 data set analysis. The average vertical structure of the
atmosphere, during such events, as obtained from the Seychelles sounding
data set ({\gt} 7000 soundings) analysis confirms the occurrence of the
features observed in the study case. Similarly, the analysis of 105 days
of TRMM orbits over the box containing the Seychelles station, confirms
the statistical features that indicate a possible relationship between
the occurrence of dry air and associated cirrus. However, possible
interaction between dry layer and cirrus occurrence should be
investigated in a detailed modelling framework (beyond the scope of this
study) such as the one offered by the cloud resolving models.
}},
doi = {10.1016/j.atmosres.2005.10.013},
adsurl = {http://adsabs.harvard.edu/abs/2006AtmRe..82..276L},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006ACP.....6.5225S,
author = {{Schulz}, M. and {Textor}, C. and {Kinne}, S. and {Balkanski}, Y. and
{Bauer}, S. and {Berntsen}, T. and {Berglen}, T. and {Boucher}, O. and
{Dentener}, F. and {Guibert}, S. and {Isaksen}, I.~S.~A. and
{Iversen}, T. and {Koch}, D. and {Kirkev{\aa}g}, A. and {Liu}, X. and
{Montanaro}, V. and {Myhre}, G. and {Penner}, J.~E. and {Pitari}, G. and
{Reddy}, S. and {Seland}, {\O}. and {Stier}, P. and {Takemura}, T.
},
title = {{Radiative forcing by aerosols as derived from the AeroCom present-day and pre-industrial simulations}},
journal = {Atmospheric Chemistry \& Physics},
year = 2006,
month = nov,
volume = 6,
pages = {5225-5246},
abstract = {{Nine different global models with detailed aerosol modules have
independently produced instantaneous direct radiative forcing due to
anthropogenic aerosols. The anthropogenic impact is derived from the
difference of two model simulations with prescribed aerosol emissions,
one for present-day and one for pre-industrial conditions. The
difference in the solar energy budget at the top of the atmosphere (ToA)
yields a new harmonized estimate for the aerosol direct radiative
forcing (RF) under all-sky conditions. On a global annual basis RF is
-0.22 Wm$^{-2}$, ranging from +0.04 to -0.41
Wm$^{-2}$, with a standard deviation of {\plusmn}0.16
Wm$^{-2}$. Anthropogenic nitrate and dust are not included
in this estimate. No model shows a significant positive all-sky RF. The
corresponding clear-sky RF is -0.68 Wm$^{-2}$. The
cloud-sky RF was derived based on all-sky and clear-sky RF and modelled
cloud cover. It was significantly different from zero and ranged between
-0.16 and +0.34 Wm$^{-2}$. A sensitivity analysis
shows that the total aerosol RF is influenced by considerable diversity
in simulated residence times, mass extinction coefficients and most
importantly forcing efficiencies (forcing per unit optical depth). The
clear-sky forcing efficiency (forcing per unit optical depth) has
diversity comparable to that for the all-sky/ clear-sky forcing ratio.
While the diversity in clear-sky forcing efficiency is impacted by
factors such as aerosol absorption, size, and surface albedo, we can
show that the all-sky/clear-sky forcing ratio is important because
all-sky forcing estimates require proper representation of cloud fields
and the correct relative altitude placement between absorbing aerosol
and clouds. The analysis of the sulphate RF shows that long sulphate
residence times are compensated by low mass extinction coefficients and
vice versa. This is explained by more sulphate particle humidity growth
and thus higher extinction in those models where short-lived sulphate is
present at lower altitude and vice versa. Solar atmospheric forcing
within the atmospheric column is estimated at +0.82{\plusmn}0.17
Wm$^{-2}$. The local annual average maxima of atmospheric
forcing exceed +5 Wm$^{-2}$ confirming the regional
character of aerosol impacts on climate. The annual average surface
forcing is -1.02{\plusmn}0.23 Wm$^{-2}$. With the
current uncertainties in the modelling of the radiative forcing due to
the direct aerosol effect we show here that an estimate from one model
is not sufficient but a combination of several model estimates is
necessary to provide a mean and to explore the uncertainty.
}},
adsurl = {http://adsabs.harvard.edu/abs/2006ACP.....6.5225S},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006WRR....4210403R,
author = {{Ramillien}, G. and {Frappart}, F. and {G{\"u}ntner}, A. and
{Ngo-Duc}, T. and {Cazenave}, A. and {Laval}, K.},
title = {{Time variations of the regional evapotranspiration rate from Gravity Recovery and Climate Experiment (GRACE) satellite gravimetry}},
journal = {Water Resources Research},
keywords = {Geodesy and Gravity: Time variable gravity (7223, 7230), Hydrology: Evapotranspiration, Geodesy and Gravity: Mass balance (0762, 1223, 1631, 1836, 1843, 3010, 3322, 4532), evapotranspiration, global hydrology, GRACE satellite mission, water mass balance},
year = 2006,
month = oct,
volume = 42,
eid = {W10403},
pages = {10403},
abstract = {{Since its launch in March 2002, the Gravity Recovery and Climate
Experiment (GRACE) mission has been measuring the global time variations
of the Earth's gravity field with a current resolution of {\tilde}500 km.
Especially over the continents, these measurements represent the
integrated land water mass, including surface waters (lakes, wetlands
and rivers), soil moisture, groundwater, and snow cover. In this study,
we use the GRACE land water solutions computed by Ramillien et al.
(2005a) through an iterative inversion of monthly geoids from April 2002
to May 2004 to estimate time series of basin-scale regional
evapotranspiration rate and associated uncertainties. Evapotranspiration
is determined by integrating and solving the water mass balance
equation, which relates land water storage (from GRACE), precipitation
data (from the Global Precipitation Climatology Centre), runoff (from a
global land surface model), and evapotranspiration (the unknown). We
further examine the sensibility of the computation when using different
model runoff. Evapotranspiration results are compared to outputs of four
different global land surface models. The overall satisfactory agreement
between GRACE-derived and model-based evapotranspiration prove the
ability of GRACE to provide realistic estimates of this parameter.
}},
doi = {10.1029/2005WR004331},
adsurl = {http://adsabs.harvard.edu/abs/2006WRR....4210403R},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006JGRD..11118201S,
author = {{Stier}, P. and {Seinfeld}, J.~H. and {Kinne}, S. and {Feichter}, J. and
{Boucher}, O.},
title = {{Impact of nonabsorbing anthropogenic aerosols on clear-sky atmospheric absorption}},
journal = {Journal of Geophysical Research (Atmospheres)},
keywords = {Atmospheric Composition and Structure: Aerosols and particles (0345, 4801, 4906), Atmospheric Composition and Structure: Radiation: transmission and scattering, Global Change: Atmosphere (0315, 0325), aerosol absorption, radiative forcing, aerosol aging},
year = 2006,
month = sep,
volume = 111,
number = d10,
eid = {D18201},
pages = {18201},
abstract = {{Absorption of solar radiation by atmospheric aerosol has become
recognized as important in regional and global climate. Nonabsorbing,
hydrophilic aerosols, such as sulfate, potentially affect atmospheric
absorption in opposing ways: first, decreasing absorption through aging
initially hydrophobic black carbon (BC) to a hydrophilic state,
enhancing its removal by wet scavenging, and consequently decreasing BC
lifetime and abundance, and second, increasing absorption through
enhancement of the BC absorption efficiency by internal mixing as well
as through increasing the amount of diffuse solar radiation in the
atmosphere. On the basis of General Circulation Model studies with an
embedded microphysical aerosol module we systematically demonstrate the
significance of these mechanisms both on the global and regional scales.
In remote transport regions, the first mechanism prevails, reducing
atmospheric absorption, whereas in the vicinity of source regions,
despite enhanced wet scavenging, absorption is enhanced owing to the
prevalence of the second mechanisms. Our findings imply that the sulfur
to BC emission ratio plays a key role in aerosol absorption.
}},
doi = {10.1029/2006JD007147},
adsurl = {http://adsabs.harvard.edu/abs/2006JGRD..11118201S},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006ACP.....6.4321D,
author = {{Dentener}, F. and {Kinne}, S. and {Bond}, T. and {Boucher}, O. and
{Cofala}, J. and {Generoso}, S. and {Ginoux}, P. and {Gong}, S. and
{Hoelzemann}, J.~J. and {Ito}, A. and {Marelli}, L. and {Penner}, J.~E. and
{Putaud}, J.-P. and {Textor}, C. and {Schulz}, M. and {van der Werf}, G.~R. and
{Wilson}, J.},
title = {{Emissions of primary aerosol and precursor gases in the years 2000 and 1750 prescribed data-sets for AeroCom}},
journal = {Atmospheric Chemistry \& Physics},
year = 2006,
month = sep,
volume = 6,
pages = {4321-4344},
abstract = {{Inventories for global aerosol and aerosol precursor emissions have been
collected (based on published inventories and published simulations),
assessed and prepared for the year 2000 (present-day conditions) and for
the year 1750 (pre-industrial conditions). These global datasets
establish a comprehensive source for emission input to global modeling,
when simulating the aerosol impact on climate with state-of-the-art
aerosol component modules. As these modules stratify aerosol into dust,
sea-salt, sulfate, organic matter and soot, for all these aerosol types
global fields on emission strength and recommendations for injection
altitude and particulate size are provided. Temporal resolution varies
between daily (dust and sea-salt), monthly (wild-land fires) and annual
(all other emissions). These datasets benchmark aerosol emissions
according to the knowledge in the year 2004. They are intended to serve
as systematic constraints in sensitivity studies of the AeroCom
initiative, which seeks to quantify (actual) uncertainties in aerosol
global modeling.
}},
adsurl = {http://adsabs.harvard.edu/abs/2006ACP.....6.4321D},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006JAtS...63.2140Z,
author = {{Zurovac-Jevti}, D. and {Bony}, S. and {Emanuel}, K.},
title = {{On the Role of Clouds and Moisture in Tropical Waves: A Two-Dimensional Model Study.}},
journal = {Journal of Atmospheric Sciences},
year = 2006,
month = aug,
volume = 63,
pages = {2140-2155},
abstract = {{Observations show that convective perturbations of the tropical
atmosphere are associated with substantial variations of clouds and
water vapor. Recent studies suggest that these variations may play an
active role in the large-scale organization of the tropical atmosphere.
The present study investigates that possibility by using a
two-dimensional, nonrotating model that includes a set of physical
parameterizations carefully evaluated against tropical data. In the
absence of cloud radiation interactions, the model spontaneously
generates fast upwind (eastward) moving planetary-scale oscillations
through the wind-induced surface heat exchange mechanism. In the
presence of cloud radiative effects, the model generates slower upwind
(eastward) propagating modes in addition to small-scale disturbances
advected downwind (westward) by the mean flow. Enhanced cloud radiative
effects further slow down upwind propagating waves and make them more
prominent in the spectrum. On the other hand, the model suggests that
interactions between moisture and convection favor the prominence of
moist Kelvin-like waves in tropical variability at the expense of
small-scale advective disturbances. These numerical results, consistent
with theoretical predictions, suggest that the interaction of water
vapor and cloud variations with convection and radiation plays an active
role in the large-scale organization of the tropical atmosphere.
{\lt}HR ALIGN=''center'' WIDTH=''30\%''{\gt}
}},
doi = {10.1175/JAS3738.1},
adsurl = {http://adsabs.harvard.edu/abs/2006JAtS...63.2140Z},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006ACP.....6.3391P,
author = {{Penner}, J.~E. and {Quaas}, J. and {Storelvmo}, T. and {Takemura}, T. and
{Boucher}, O. and {Guo}, H. and {Kirkev{\aa}g}, A. and {Kristj{\'a}nsson}, J.~E. and
{Seland}, {\O}.},
title = {{Model intercomparison of indirect aerosol effects}},
journal = {Atmospheric Chemistry \& Physics},
year = 2006,
month = aug,
volume = 6,
pages = {3391-3405},
abstract = {{Modeled differences in predicted effects are increasingly used to help
quantify the uncertainty of these effects. Here, we examine modeled
differences in the aerosol indirect effect in a series of experiments
that help to quantify how and why model-predicted aerosol indirect
forcing varies between models. The experiments start with an experiment
in which aerosol concentrations, the parameterization of droplet
concentrations and the autoconversion scheme are all specified and end
with an experiment that examines the predicted aerosol indirect forcing
when only aerosol sources are specified. Although there are large
differences in the predicted liquid water path among the models, the
predicted aerosol first indirect effect for the first experiment is
rather similar, about -0.6 Wm$^{-2}$ to -0.7
Wm$^{-2}$. Changes to the autoconversion scheme can lead to
large changes in the liquid water path of the models and to the response
of the liquid water path to changes in aerosols. Adding an
autoconversion scheme that depends on the droplet concentration caused a
larger (negative) change in net outgoing shortwave radiation compared to
the 1st indirect effect, and the increase varied from only 22\% to more
than a factor of three. The change in net shortwave forcing in the
models due to varying the autoconversion scheme depends on the liquid
water content of the clouds as well as their predicted droplet
concentrations, and both increases and decreases in the net shortwave
forcing can occur when autoconversion schemes are changed. The
parameterization of cloud fraction within models is not sensitive to the
aerosol concentration, and, therefore, the response of the modeled cloud
fraction within the present models appears to be smaller than that which
would be associated with model ''noise''. The prediction of aerosol
concentrations, given a fixed set of sources, leads to some of the
largest differences in the predicted aerosol indirect radiative forcing
among the models, with values of cloud forcing ranging from -0.3
Wm$^{-2}$ to -1.4 Wm$^{-2}$. Thus, this
aspect of modeling requires significant improvement in order to improve
the prediction of aerosol indirect effects.
}},
adsurl = {http://adsabs.harvard.edu/abs/2006ACP.....6.3391P},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006JGRD..11114317C,
author = {{Collins}, W.~D. and {Ramaswamy}, V. and {Schwarzkopf}, M.~D. and
{Sun}, Y. and {Portmann}, R.~W. and {Fu}, Q. and {Casanova}, S.~E.~B. and
{Dufresne}, J.-L. and {Fillmore}, D.~W. and {Forster}, P.~M.~D. and
{Galin}, V.~Y. and {Gohar}, L.~K. and {Ingram}, W.~J. and {Kratz}, D.~P. and
{Lefebvre}, M.-P. and {Li}, J. and {Marquet}, P. and {Oinas}, V. and
{Tsushima}, Y. and {Uchiyama}, T. and {Zhong}, W.~Y.},
title = {{Radiative forcing by well-mixed greenhouse gases: Estimates from climate models in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4)}},
journal = {Journal of Geophysical Research (Atmospheres)},
keywords = {Atmospheric Processes: Global climate models (1626, 4928), Atmospheric Processes: Radiative processes, Global Change: Global climate models (3337, Global Change: Impacts of global change (1225), radiation, models, greenhouse gas},
year = 2006,
month = jul,
volume = 111,
number = d10,
eid = {D14317},
pages = {14317},
abstract = {{The radiative effects from increased concentrations of well-mixed
greenhouse gases (WMGHGs) represent the most significant and best
understood anthropogenic forcing of the climate system. The most
comprehensive tools for simulating past and future climates influenced
by WMGHGs are fully coupled atmosphere-ocean general circulation models
(AOGCMs). Because of the importance of WMGHGs as forcing agents it is
essential that AOGCMs compute the radiative forcing by these gases as
accurately as possible. We present the results of a radiative transfer
model intercomparison between the forcings computed by the radiative
parameterizations of AOGCMs and by benchmark line-by-line (LBL) codes.
The comparison is focused on forcing by CO$_{2}$, CH$_{4}$,
N$_{2}$O, CFC-11, CFC-12, and the increased H$_{2}$O
expected in warmer climates. The models included in the intercomparison
include several LBL codes and most of the global models submitted to the
Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment
Report (AR4). In general, the LBL models are in excellent agreement with
each other. However, in many cases, there are substantial discrepancies
among the AOGCMs and between the AOGCMs and LBL codes. In some cases
this is because the AOGCMs neglect particular absorbers, in particular
the near-infrared effects of CH$_{4}$ and N$_{2}$O, while in
others it is due to the methods for modeling the radiative processes.
The biases in the AOGCM forcings are generally largest at the surface
level. We quantify these differences and discuss the implications for
interpreting variations in forcing and response across the multimodel
ensemble of AOGCM simulations assembled for the IPCC AR4.
}},
doi = {10.1029/2005JD006713},
adsurl = {http://adsabs.harvard.edu/abs/2006JGRD..11114317C},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006JAtS...63.1878H,
author = {{Hallegatte}, S. and {Lahellec}, A. and {Grandpeix}, J.-Y.},
title = {{An Elicitation of the Dynamic Nature of Water Vapor Feedback in Climate Change Using a 1D Model.}},
journal = {Journal of Atmospheric Sciences},
year = 2006,
month = jul,
volume = 63,
pages = {1878-1894},
abstract = {{The concept of feedback has been used by several authors in the field of
climate science to describe the behavior of models and to assess the
importance of the different mechanisms at stake. Here, a simple 1D model
of climate has been built to analyze the water vapor feedback. Beyond a
static quantification of the water feedback, a more general formal
definition of feedback gain based on the tangent linear system is
introduced. This definition reintroduces the dynamical aspect of the
system response to perturbation from Bode's original concept.In the
model here, it is found that, even though the water vapor static gain
proves consistent with results from GCMs, it turns out to be negative
for time scales below 4 yr and positive only for longer time scales.
These results suggest two conclusions: (i) that the water vapor feedback
may be fully active only in response to long-lived perturbations; and
(ii) that the water vapor feedback could reduce the natural variability
due to tropospheric temperature perturbations over short time scales,
while enhancing it over longer time scales. This second conclusion would
be consistent with studies investigating the influence of air sea
coupling on variability on different time scales.
{\lt}HR
ALIGN=''center'' WIDTH=''30\%''{\gt}
}},
doi = {10.1175/JAS3725.1},
adsurl = {http://adsabs.harvard.edu/abs/2006JAtS...63.1878H},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006ClDy...27...17W,
author = {{Webb}, M.~J. and {Senior}, C.~A. and {Sexton}, D.~M.~H. and
{Ingram}, W.~J. and {Williams}, K.~D. and {Ringer}, M.~A. and
{McAvaney}, B.~J. and {Colman}, R. and {Soden}, B.~J. and {Gudgel}, R. and
{Knutson}, T. and {Emori}, S. and {Ogura}, T. and {Tsushima}, Y. and
{Andronova}, N. and {Li}, B. and {Musat}, I. and {Bony}, S. and
{Taylor}, K.~E.},
title = {{On the contribution of local feedback mechanisms to the range of climate sensitivity in two GCM ensembles}},
journal = {Climate Dynamics},
year = 2006,
month = jul,
volume = 27,
pages = {17-38},
abstract = {{Global and local feedback analysis techniques have been applied to two
ensembles of mixed layer equilibrium CO$_{2}$ doubling climate
change experiments, from the CFMIP (Cloud Feedback Model Intercomparison
Project) and QUMP (Quantifying Uncertainty in Model Predictions)
projects. Neither of these new ensembles shows evidence of a
statistically significant change in the ensemble mean or variance in
global mean climate sensitivity when compared with the results from the
mixed layer models quoted in the Third Assessment Report of the IPCC.
Global mean feedback analysis of these two ensembles confirms the large
contribution made by inter-model differences in cloud feedbacks to those
in climate sensitivity in earlier studies; net cloud feedbacks are
responsible for 66\% of the inter-model variance in the total feedback in
the CFMIP ensemble and 85\% in the QUMP ensemble. The ensemble mean
global feedback components are all statistically indistinguishable
between the two ensembles, except for the clear-sky shortwave feedback
which is stronger in the CFMIP ensemble. While ensemble variances of the
shortwave cloud feedback and both clear-sky feedback terms are larger in
CFMIP, there is considerable overlap in the cloud feedback ranges; QUMP
spans 80\% or more of the CFMIP ranges in longwave and shortwave cloud
feedback. We introduce a local cloud feedback classification system
which distinguishes different types of cloud feedbacks on the basis of
the relative strengths of their longwave and shortwave components, and
interpret these in terms of responses of different cloud types diagnosed
by the International Satellite Cloud Climatology Project simulator. In
the CFMIP ensemble, areas where low-top cloud changes constitute the
largest cloud response are responsible for 59\% of the contribution from
cloud feedback to the variance in the total feedback. A similar figure
is found for the QUMP ensemble. Areas of positive low cloud feedback
(associated with reductions in low level cloud amount) contribute most
to this figure in the CFMIP ensemble, while areas of negative cloud
feedback (associated with increases in low level cloud amount and
optical thickness) contribute most in QUMP. Classes associated with
high-top cloud feedbacks are responsible for 33 and 20\% of the cloud
feedback contribution in CFMIP and QUMP, respectively, while classes
where no particular cloud type stands out are responsible for 8 and 21\%.
}},
doi = {10.1007/s00382-006-0111-2},
adsurl = {http://adsabs.harvard.edu/abs/2006ClDy...27...17W},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006ACP.....6.1815K,
author = {{Kinne}, S. and {Schulz}, M. and {Textor}, C. and {Guibert}, S. and
{Balkanski}, Y. and {Bauer}, S.~E. and {Berntsen}, T. and {Berglen}, T.~F. and
{Boucher}, O. and {Chin}, M. and {Collins}, W. and {Dentener}, F. and
{Diehl}, T. and {Easter}, R. and {Feichter}, J. and {Fillmore}, D. and
{Ghan}, S. and {Ginoux}, P. and {Gong}, S. and {Grini}, A. and
{Hendricks}, J. and {Herzog}, M. and {Horowitz}, L. and {Isaksen}, I. and
{Iversen}, T. and {Kirkev{\aa}g}, A. and {Kloster}, S. and {Koch}, D. and
{Kristjansson}, J.~E. and {Krol}, M. and {Lauer}, A. and {Lamarque}, J.~F. and
{Lesins}, G. and {Liu}, X. and {Lohmann}, U. and {Montanaro}, V. and
{Myhre}, G. and {Penner}, J. and {Pitari}, G. and {Reddy}, S. and
{Seland}, O. and {Stier}, P. and {Takemura}, T. and {Tie}, X.
},
title = {{An AeroCom initial assessment - optical properties in aerosol component modules of global models}},
journal = {Atmospheric Chemistry \& Physics},
year = 2006,
month = may,
volume = 6,
pages = {1815-1834},
abstract = {{The AeroCom exercise diagnoses multi-component aerosol modules in global
modeling. In an initial assessment simulated global distributions for
mass and mid-visible aerosol optical thickness (aot) were compared among
20 different modules. Model diversity was also explored in the context
of previous comparisons. For the component combined aot general
agreement has improved for the annual global mean. At 0.11 to 0.14,
simulated aot values are at the lower end of global averages suggested
by remote sensing from ground (AERONET ca. 0.135) and space (satellite
composite ca. 0.15). More detailed comparisons, however, reveal that
larger differences in regional distribution and significant differences
in compositional mixture remain. Of particular concern are large model
diversities for contributions by dust and carbonaceous aerosol, because
they lead to significant uncertainty in aerosol absorption (aab). Since
aot and aab, both, influence the aerosol impact on the radiative
energy-balance, the aerosol (direct) forcing uncertainty in modeling is
larger than differences in aot might suggest. New diagnostic approaches
are proposed to trace model differences in terms of aerosol processing
and transport: These include the prescription of common input (e.g.
amount, size and injection of aerosol component emissions) and the use
of observational capabilities from ground (e.g. measurements networks)
or space (e.g. correlations between aerosol and clouds).
}},
adsurl = {http://adsabs.harvard.edu/abs/2006ACP.....6.1815K},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006ACP.....6.1777T,
author = {{Textor}, C. and {Schulz}, M. and {Guibert}, S. and {Kinne}, S. and
{Balkanski}, Y. and {Bauer}, S. and {Berntsen}, T. and {Berglen}, T. and
{Boucher}, O. and {Chin}, M. and {Dentener}, F. and {Diehl}, T. and
{Easter}, R. and {Feichter}, H. and {Fillmore}, D. and {Ghan}, S. and
{Ginoux}, P. and {Gong}, S. and {Grini}, A. and {Hendricks}, J. and
{Horowitz}, L. and {Huang}, P. and {Isaksen}, I. and {Iversen}, I. and
{Kloster}, S. and {Koch}, D. and {Kirkev{\aa}g}, A. and {Kristjansson}, J.~E. and
{Krol}, M. and {Lauer}, A. and {Lamarque}, J.~F. and {Liu}, X. and
{Montanaro}, V. and {Myhre}, G. and {Penner}, J. and {Pitari}, G. and
{Reddy}, S. and {Seland}, {\O}. and {Stier}, P. and {Takemura}, T. and
{Tie}, X.},
title = {{Analysis and quantification of the diversities of aerosol life cycles within AeroCom}},
journal = {Atmospheric Chemistry \& Physics},
year = 2006,
month = may,
volume = 6,
pages = {1777-1813},
abstract = {{Simulation results of global aerosol models have been assembled in the
framework of the AeroCom intercomparison exercise. In this paper, we
analyze the life cycles of dust, sea salt, sulfate, black carbon and
particulate organic matter as simulated by sixteen global aerosol
models. The differences among the results (model diversities) for
sources and sinks, burdens, particle sizes, water uptakes, and spatial
dispersals have been established. These diversities have large
consequences for the calculated radiative forcing and the aerosol
concentrations at the surface. Processes and parameters are identified
which deserve further research. {\lt}P style=''line-height: 20px;''{\gt} The
AeroCom all-models-average emissions are dominated by the mass of sea
salt (SS), followed by dust (DU), sulfate (SO$_{4}$), particulate
organic matter (POM), and finally black carbon (BC). Interactive
parameterizations of the emissions and contrasting particles sizes of SS
and DU lead generally to higher diversities of these species, and for
total aerosol. The lower diversity of the emissions of the fine
aerosols, BC, POM, and SO$_{4}$, is due to the use of similar
emission inventories, and does therefore not necessarily indicate a
better understanding of their sources. The diversity of
SO$_{4}$-sources is mainly caused by the disagreement on
depositional loss of precursor gases and on chemical production. The
diversities of the emissions are passed on to the burdens, but the
latter are also strongly affected by the model-specific treatments of
transport and aerosol processes. The burdens of dry masses decrease from
largest to smallest: DU, SS, SO$_{4}$, POM, and BC. {\lt}P
style=''line-height: 20px;''{\gt} The all-models-average residence time is
shortest for SS with about half a day, followed by SO$_{4}$ and DU
with four days, and POM and BC with six and seven days, respectively.
The wet deposition rate is controlled by the solubility and increases
from DU, BC, POM to SO$_{4}$ and SS. It is the dominant sink for
SO$_{4}$, BC, and POM, and contributes about one third to the
total removal of SS and DU species. For SS and DU we find high
diversities for the removal rate coefficients and deposition pathways.
Models do neither agree on the split between wet and dry deposition, nor
on that between sedimentation and other dry deposition processes. We
diagnose an extremely high diversity for the uptake of ambient water
vapor that influences the particle size and thus the sink rate
coefficients. Furthermore, we find little agreement among the model
results for the partitioning of wet removal into scavenging by
convective and stratiform rain. {\lt}P style=''line-height: 20px;''{\gt}
Large differences exist for aerosol dispersal both in the vertical and
in the horizontal direction. In some models, a minimum of total aerosol
concentration is simulated at the surface. Aerosol dispersal is most
pronounced for SO$_{4}$ and BC and lowest for SS. Diversities are
higher for meridional than for vertical dispersal, they are similar for
the individual species and highest for SS and DU. For these two
components we do not find a correlation between vertical and meridional
aerosol dispersal. In addition the degree of dispersals of SS and DU is
not related to their residence times. SO$_{4}$, BC, and POM,
however, show increased meridional dispersal in models with larger
vertical dispersal, and dispersal is larger for longer simulated
residence times.
}},
adsurl = {http://adsabs.harvard.edu/abs/2006ACP.....6.1777T},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006ACP.....6.1657B,
author = {{Bates}, T.~S. and {Anderson}, T.~L. and {Baynard}, T. and {Bond}, T. and
{Boucher}, O. and {Carmichael}, G. and {Clarke}, A. and {Erlick}, C. and
{Guo}, H. and {Horowitz}, L. and {Howell}, S. and {Kulkarni}, S. and
{Maring}, H. and {McComiskey}, A. and {Middlebrook}, A. and
{Noone}, K. and {O'Dowd}, C.~D. and {Ogren}, J. and {Penner}, J. and
{Quinn}, P.~K. and {Ravishankara}, A.~R. and {Savoie}, D.~L. and
{Schwartz}, S.~E. and {Shinozuka}, Y. and {Tang}, Y. and {Weber}, R.~J. and
{Wu}, Y.},
title = {{Aerosol direct radiative effects over the northwest Atlantic, northwest Pacific, and North Indian Oceans: estimates based on in-situ chemical and optical measurements and chemical transport modeling}},
journal = {Atmospheric Chemistry \& Physics},
year = 2006,
month = may,
volume = 6,
pages = {1657-1732},
abstract = {{The largest uncertainty in the radiative forcing of climate change over
the industrial era is that due to aerosols, a substantial fraction of
which is the uncertainty associated with scattering and absorption of
shortwave (solar) radiation by anthropogenic aerosols in cloud-free
conditions (IPCC, 2001). Quantifying and reducing the uncertainty in
aerosol influences on climate is critical to understanding climate
change over the industrial period and to improving predictions of future
climate change for assumed emission scenarios. Measurements of aerosol
properties during major field campaigns in several regions of the globe
during the past decade are contributing to an enhanced understanding of
atmospheric aerosols and their effects on light scattering and climate.
The present study, which focuses on three regions downwind of major
urban/population centers (North Indian Ocean (NIO) during INDOEX, the
Northwest Pacific Ocean (NWP) during ACE-Asia, and the Northwest
Atlantic Ocean (NWA) during ICARTT), incorporates understanding gained
from field observations of aerosol distributions and properties into
calculations of perturbations in radiative fluxes due to these aerosols.
This study evaluates the current state of observations and of two
chemical transport models (STEM and MOZART). Measurements of burdens,
extinction optical depth (AOD), and direct radiative effect of aerosols
(DRE - change in radiative flux due to total aerosols) are used as
measurement-model check points to assess uncertainties. In-situ measured
and remotely sensed aerosol properties for each region (mixing state,
mass scattering efficiency, single scattering albedo, and angular
scattering properties and their dependences on relative humidity) are
used as input parameters to two radiative transfer models (GFDL and
University of Michigan) to constrain estimates of aerosol radiative
effects, with uncertainties in each step propagated through the
analysis. Constraining the radiative transfer calculations by
observational inputs increases the clear-sky, 24-h averaged AOD
(34{\plusmn}8\%), top of atmosphere (TOA) DRE (32{\plusmn}12\%), and TOA
direct climate forcing of aerosols (DCF - change in radiative flux due
to anthropogenic aerosols) (37{\plusmn}7\%) relative to values obtained
with ''a priori'' parameterizations of aerosol loadings and properties
(GFDL RTM). The resulting constrained clear-sky TOA DCF is
-3.3{\plusmn}0.47, -14{\plusmn}2.6, -6.4{\plusmn}2.1
Wm$^{-2}$ for the NIO, NWP, and NWA, respectively. With the
use of constrained quantities (extensive and intensive parameters) the
calculated uncertainty in DCF was 25\% less than the ''structural
uncertainties'' used in the IPCC-2001 global estimates of direct aerosol
climate forcing. Such comparisons with observations and resultant
reductions in uncertainties are essential for improving and developing
confidence in climate model calculations incorporating aerosol forcing.
}},
adsurl = {http://adsabs.harvard.edu/abs/2006ACP.....6.1657B},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006JGRD..111.7208V,
author = {{Verma}, S. and {Boucher}, O. and {Venkataraman}, C. and {Reddy}, M.~S. and
{M{\"u}ller}, D. and {Chazette}, P. and {Crouzille}, B.},
title = {{Aerosol lofting from sea breeze during the Indian Ocean Experiment}},
journal = {Journal of Geophysical Research (Atmospheres)},
keywords = {Atmospheric Composition and Structure: Aerosols and particles (0345, 4801, 4906), Atmospheric Composition and Structure: Pollution: urban and regional (0305, 0478, 4251), Atmospheric Composition and Structure: Troposphere: constituent transport and chemistry, Atmospheric Processes: Middle atmosphere dynamics (0341, 0342), aerosol lofting, INDOEX, sea breeze, convergence, northeast monsoon, west coast of India},
year = 2006,
month = apr,
volume = 111,
eid = {D07208},
pages = {7208},
abstract = {{This work was carried out to understand the mechanisms leading to
lofting and large-scale advection of aerosols over the Indian Ocean
region due to interaction of the sea breeze with the northeast monsoon
winds along the west coast of India. European Centre for Medium-Range
Weather Forecasts (ECMWF) wind fields for the months of February and
March 1999 were analyzed at various times of day. Intense sea breeze
activity was observed at 1200 UT (1730 local time) along the west coast
of India with average intensity larger in March than in February. The
sea breeze was seen to extend inland deeper in March than in February.
Lofting of air observed as high as 800 hPa (approximately 2 km above sea
level) could lead to entrainment of aerosols into the free troposphere
and long-range transport. Upward motion of air was observed everywhere
along the west coast of India (from 8{\deg} to 20{\deg}N), on average
higher in March than in February, because of convergence between the sea
breeze and the synoptic-scale flow. A region of intense lofting of air
and well-defined convergence was observed along the coast of the
Karnataka region (12{\deg}-16{\deg}N). A simulation with a general
circulation model nudged with ECMWF data indicated that the intrusion of
marine air masses with low concentrations of organic matter is seen as
deep as 64 km inland in the evening (1500 UT). Intrusion of the sea-salt
plume is seen to a maximum distance of around 200 km from 1500 until
2300 UT. A well-developed lofted layer of aerosols as high as 3 km was
also simulated during sea breeze activity along the west coast of India.
The general circulation model simulation shows a clear diurnal evolution
of the vertical profile of the aerosol extinction coefficient at Goa but
fails to reproduce several features of the lidar observations, for
example, the marked diurnal variability of the upper layers between 1
and 3 km. However, the model simulates a diurnal cycle at the surface
(0-0.7 km) that is not apparent in lidar measurements. The model
simulates long-range transport and captures the lofted plume downwind of
the west coast of India. However, there was a 1-2 day delay in the model
transport of lofted aerosols at higher layers to Hulule, 700 km downwind
of India, when compared to lidar observations.
}},
doi = {10.1029/2005JD005953},
adsurl = {http://adsabs.harvard.edu/abs/2006JGRD..111.7208V},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006BAMS...87S...1E,
author = {{Emanuel}, K. and {Ravela}, S. and {Vivant}, E. and {Risi}, C.
},
title = {{Supplement to A Statistical Deterministic Approach to Hurricane Risk Assessment}},
journal = {Bulletin of the American Meteorological Society},
year = 2006,
month = mar,
volume = 87,
pages = {1},
doi = {10.1175/BAMS-87-3-Emanuel},
adsurl = {http://adsabs.harvard.edu/abs/2006BAMS...87S...1E},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006BAMS...87..299E,
author = {{Emanuel}, K. and {Ravela}, S. and {Vivant}, E. and {Risi}, C.
},
title = {{A Statistical Deterministic Approach to Hurricane Risk Assessment.}},
journal = {Bulletin of the American Meteorological Society},
year = 2006,
month = mar,
volume = 87,
pages = {299-314},
abstract = {{Hurricanes are lethal and costly phenomena, and it is therefore of great
importance to assess the long-term risk they pose to society. Among the
greatest threats are those associated with high winds and related
phenomena, such as storm surges. Here we assess the probability that
hurricane winds will affect any given point in space by combining an
estimate of the probability that a hurricane will pass within some given
radius of the point in question with an estimate of the spatial
probability density of storm winds.To assess the probability that storms
will pass close enough to a point of interest to affect it, we apply two
largely independent techniques for generating large numbers of synthetic
hurricane tracks. The first treats each track as a Markov chain, using
statistics derived from observed hurricanetrack data. The second
technique begins by generating a large class of synthetic, time-varying
wind fields at 850 and 250 hPa whose variance, covariance, and monthly
means match NCEP-NCAR reanalysis data and whose kinetic energy follows
an {$\omega$}$^{-3}$ geostrophic turbulence spectral frequency
distribution. Hurricanes are assumed to move with a weighted mean of the
850- and 250-hPa flow plus a {\ldquo}beta drift{\rdquo} correction, after
originating at points determined from historical genesis data. The
statistical characteristics of tracks generated by these two means are
compared.For a given point in space, many (10$^{4}$) synthetic
tracks are generated that pass within a specified distance of a point of
interest, using both track generation methods. For each of these tracks,
a deterministic, coupled, numerical simulation of the storm's intensity
is carried out, using monthly mean upper-ocean and potential intensity
climatologies, together with time-varying vertical wind shear generated
from the synthetic time series of 850- and 250-hPa winds, as described
above. For the case in which the tracks are generated using the
synthetic environmental flow, the tracks and the shear are generated
using the same wind fields and are therefore mutually consistent.The
track and intensity data are finally used together with a vortex
structure model to construct probability distributions of wind speed at
fixed points in space. These are compared to similar estimates based
directly on historical hurricane data for two coastal cities.
}},
doi = {10.1175/BAMS-87-3-299},
adsurl = {http://adsabs.harvard.edu/abs/2006BAMS...87..299E},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006ACP.....6..947Q,
author = {{Quaas}, J. and {Boucher}, O. and {Lohmann}, U.},
title = {{Constraining the total aerosol indirect effect in the LMDZ and ECHAM4 GCMs using MODIS satellite data}},
journal = {Atmospheric Chemistry \& Physics},
year = 2006,
month = mar,
volume = 6,
pages = {947-955},
abstract = {{Aerosol indirect effects are considered to be the most uncertain yet
important anthropogenic forcing of climate change. The goal of the
present study is to reduce this uncertainty by constraining two
different general circulation models (LMDZ and ECHAM4) with satellite
data. We build a statistical relationship between cloud droplet number
concentration and the optical depth of the fine aerosol mode as a
measure of the aerosol indirect effect using MODerate Resolution Imaging
Spectroradiometer (MODIS) satellite data, and constrain the model
parameterizations to match this relationship. We include here
''empirical'' formulations for the cloud albedo effect as well as
parameterizations of the cloud lifetime effect. When fitting the model
parameterizations to the satellite data, consistently in both models,
the radiative forcing by the combined aerosol indirect effect is reduced
considerably, down to -0.5 and -0.3 Wm$^{-2}$,
for LMDZ and ECHAM4, respectively.
}},
adsurl = {http://adsabs.harvard.edu/abs/2006ACP.....6..947Q},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006Natur.439..835G,
author = {{Gedney}, N. and {Cox}, P.~M. and {Betts}, R.~A. and {Boucher}, O. and
{Huntingford}, C. and {Stott}, P.~A.},
title = {{Detection of a direct carbon dioxide effect in continental river runoff records}},
journal = {\nat},
year = 2006,
month = feb,
volume = 439,
pages = {835-838},
abstract = {{Continental runoff has increased through the twentieth century despite
more intensive human water consumption. Possible reasons for the
increase include: climate change and variability, deforestation, solar
dimming, and direct atmospheric carbon dioxide (CO$_{2}$) effects
on plant transpiration. All of these mechanisms have the potential to
affect precipitation and/or evaporation and thereby modify runoff. Here
we use a mechanistic land-surface model and optimal fingerprinting
statistical techniques to attribute observational runoff changes into
contributions due to these factors. The model successfully captures the
climate-driven inter-annual runoff variability, but twentieth-century
climate alone is insufficient to explain the runoff trends. Instead we
find that the trends are consistent with a suppression of plant
transpiration due to CO$_{2}$-induced stomatal closure. This
result will affect projections of freshwater availability, and also
represents the detection of a direct CO$_{2}$ effect on the
functioning of the terrestrial biosphere.
}},
doi = {10.1038/nature04504},
adsurl = {http://adsabs.harvard.edu/abs/2006Natur.439..835G},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006ACP.....6..613Y,
author = {{Yu}, H. and {Kaufman}, Y.~J. and {Chin}, M. and {Feingold}, G. and
{Remer}, L.~A. and {Anderson}, T.~L. and {Balkanski}, Y. and
{Bellouin}, N. and {Boucher}, O. and {Christopher}, S. and {Decola}, P. and
{Kahn}, R. and {Koch}, D. and {Loeb}, N. and {Reddy}, M.~S. and
{Schulz}, M. and {Takemura}, T. and {Zhou}, M.},
title = {{A review of measurement-based assessments of the aerosol direct radiative effect and forcing}},
journal = {Atmospheric Chemistry \& Physics},
year = 2006,
month = feb,
volume = 6,
pages = {613-666},
abstract = {{Aerosols affect the Earth's energy budget directly by scattering and
absorbing radiation and indirectly by acting as cloud condensation
nuclei and, thereby, affecting cloud properties. However, large
uncertainties exist in current estimates of aerosol forcing because of
incomplete knowledge concerning the distribution and the physical and
chemical properties of aerosols as well as aerosol-cloud interactions.
In recent years, a great deal of effort has gone into improving
measurements and datasets. It is thus feasible to shift the estimates of
aerosol forcing from largely model-based to increasingly
measurement-based. Our goal is to assess current observational
capabilities and identify uncertainties in the aerosol direct forcing
through comparisons of different methods with independent sources of
uncertainties. Here we assess the aerosol optical depth ({$\tau$}), direct
radiative effect (DRE) by natural and anthropogenic aerosols, and direct
climate forcing (DCF) by anthropogenic aerosols, focusing on satellite
and ground-based measurements supplemented by global chemical transport
model (CTM) simulations. The multi-spectral MODIS measures global
distributions of aerosol optical depth ({$\tau$}) on a daily scale, with a
high accuracy of {\plusmn}0.03{\plusmn}0.05{$\tau$} over ocean. The annual
average {$\tau$} is about 0.14 over global ocean, of which about
21\%{\plusmn}7\% is contributed by human activities, as estimated by MODIS
fine-mode fraction. The multi-angle MISR derives an annual average AOD
of 0.23 over global land with an uncertainty of \~{}20\% or {\plusmn}0.05.
These high-accuracy aerosol products and broadband flux measurements
from CERES make it feasible to obtain observational constraints for the
aerosol direct effect, especially over global the ocean. A number of
measurement-based approaches estimate the clear-sky DRE (on solar
radiation) at the top-of-atmosphere (TOA) to be about -5.5{\plusmn}0.2
Wm$^{-2}$ (median {\plusmn} standard error from various methods)
over the global ocean. Accounting for thin cirrus contamination of the
satellite derived aerosol field will reduce the TOA DRE to -5.0
Wm$^{-2}$. Because of a lack of measurements of aerosol absorption
and difficulty in characterizing land surface reflection, estimates of
DRE over land and at the ocean surface are currently realized through a
combination of satellite retrievals, surface measurements, and model
simulations, and are less constrained. Over the oceans the surface DRE
is estimated to be -8.8{\plusmn}0.7 Wm$^{-2}$. Over land, an
integration of satellite retrievals and model simulations derives a DRE
of -4.9{\plusmn}0.7 Wm$^{-2}$ and -11.8{\plusmn}1.9 Wm$^{-2}$
at the TOA and surface, respectively. CTM simulations derive a wide
range of DRE estimates that on average are smaller than the
measurement-based DRE by about 30-40\%, even after accounting for thin
cirrus and cloud contamination. {\lt}P style=''line-height: 20px;''{\gt} A
number of issues remain. Current estimates of the aerosol direct effect
over land are poorly constrained. Uncertainties of DRE estimates are
also larger on regional scales than on a global scale and large
discrepancies exist between different approaches. The characterization
of aerosol absorption and vertical distribution remains challenging. The
aerosol direct effect in the thermal infrared range and in cloudy
conditions remains relatively unexplored and quite uncertain, because of
a lack of global systematic aerosol vertical profile measurements. A
coordinated research strategy needs to be developed for integration and
assimilation of satellite measurements into models to constrain model
simulations. Enhanced measurement capabilities in the next few years and
high-level scientific cooperation will further advance our knowledge.
}},
adsurl = {http://adsabs.harvard.edu/abs/2006ACP.....6..613Y},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006Sci...311..201R,
author = {{Rannou}, P. and {Montmessin}, F. and {Hourdin}, F. and {Lebonnois}, S.
},
title = {{The Latitudinal Distribution of Clouds on Titan}},
journal = {Science},
year = 2006,
month = jan,
volume = 311,
pages = {201-205},
abstract = {{Clouds have been observed recently on Titan, through the thick haze,
using near-infrared spectroscopy and images near the south pole and in
temperate regions near 40{\deg}S. Recent telescope and Cassini orbiter
observations are now providing an insight into cloud climatology. To
study clouds, we have developed a general circulation model of Titan
that includes cloud microphysics. We identify and explain the formation
of several types of ethane and methane clouds, including south polar
clouds and sporadic clouds in temperate regions and especially at
40{\deg} in the summer hemisphere. The locations, frequencies, and
composition of these cloud types are essentially explained by the
large-scale circulation.
}},
doi = {10.1126/science.1118424},
adsurl = {http://adsabs.harvard.edu/abs/2006Sci...311..201R},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006QJRMS.132..585H,
author = {{Hourdin}, F. and {Talagrand}, O. and {Idelkadi}, A.},
title = {{Eulerian backtracking of atmospheric tracers. II: Numerical aspects}},
journal = {Quarterly Journal of the Royal Meteorological Society},
keywords = {ADJOINT, ATMOSPHERIC TRANSPORT, BACKTRACKING, INVERSE METHODS},
year = 2006,
month = jan,
volume = 132,
pages = {585-603},
abstract = {{In Part I of this paper, a mathematical equivalence was established
between Eulerian backtracking or retro-transport, on the one hand, and
adjoint transport with respect to an air-mass-weighted scalar product,
on the other. The time symmetry which lies at the basis of this
mathematical equivalence can however be lost through discretization.
That question is studied, and conditions are explicitly identified under
which discretization schemes possess the property of time symmetry.
Particular consideration is given to the case of the LMDZ model. The
linear schemes used for turbulent diffusion and subgrid-scale convection
are symmetric. For the Van Leer advection scheme used in LMDZ, which is
nonlinear, the question of time symmetry does not even make sense. Those
facts are illustrated by numerical simulations performed in the
conditions of the European Transport EXperiment (ETEX). For a model that
is not time-symmetric, the question arises as to whether it is
preferable, in practical applications, to use the exact numerical
adjoint, or the retro-transport model. Numerical results obtained in the
context of one-dimensional advection show that the presence of slope
limiters in the Van Leer advection scheme can produce in some
circumstances unrealistic (in particular, negative) adjoint
sensitivities. The retro-transport equation, on the other hand,
generally produces robust and realistic results, and always preserves
the positivity of sensitivities. Retro-transport may therefore be
preferable in sensitivity computations, even in the context of
variational assimilation.
}},
doi = {10.1256/qj.03.198.B},
adsurl = {http://adsabs.harvard.edu/abs/2006QJRMS.132..585H},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006QJRMS.132..567H,
author = {{Hourdin}, F. and {Talagrand}, O.},
title = {{Eulerian backtracking of atmospheric tracers. I: Adjoint derivation and parametrization of subgrid-scale transport}},
journal = {Quarterly Journal of the Royal Meteorological Society},
keywords = {ADJOINT, ATMOSPHERIC TRANSPORT, BACKTRACKING, INVERSE METHODS},
year = 2006,
month = jan,
volume = 132,
pages = {567-583},
abstract = {{The problem of identification of sources of atmospheric tracers is most
classically addressed through either Lagrangian backtracking or adjoint
integration. On the basis of physical considerations, the
retro-transport equation, which is at the basis of Lagrangian
backtracking, can be derived in a Eulerian framework as well. Because of
a fundamental time symmetry of fluid transport, Lagrangian or Eulerian
backtracking can be used for inverting measurements of the concentration
of an atmospheric tracer. The retro-transport equation turns out to be
the adjoint of the direct transport equation, with respect to the scalar
product defined by integration with respect to air mass. In the present
paper, the exact equivalence between the physically-derived
retro-transport and adjoint equations is proved. The transformation from
the direct to the retro-transport equation requires only simple
transformations. The sign of terms describing explicit advection is
changed. Terms describing linear sources or sinks of tracers are kept
unchanged. Terms representing diffusion by unresolved time-symmetric
motions of the transporting air are also unchanged. This is rigorously
shown for turbulent eddy-diffusion or mixing length theory. The case of
subgrid-scale vertical transport by non-time-symmetric motions of air is
studied using the example of the Tiedtke mass-flux scheme for cumulus
convection. The retro-transport equation is then obtained by simply
inverting the roles of updraughts and downdraughts, as well as of
entrainment and detrainment. Conservation of mass of the transporting
air is critical for all those properties to hold.
}},
doi = {10.1256/qj.03.198.A},
adsurl = {http://adsabs.harvard.edu/abs/2006QJRMS.132..567H},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006JCli...19.2665L,
author = {{Lin}, J.-L. and {Kiladis}, G.~N. and {Mapes}, B.~E. and {Weickmann}, K.~M. and
{Sperber}, K.~R. and {Lin}, W. and {Wheeler}, M.~C. and {Schubert}, S.~D. and
{Del Genio}, A. and {Donner}, L.~J. and {Emori}, S. and {Gueremy}, J.-F. and
{Hourdin}, F. and {Rasch}, P.~J. and {Roeckner}, E. and {Scinocca}, J.~F.
},
title = {{Tropical Intraseasonal Variability in 14 IPCC AR4 Climate Models. Part I: Convective Signals}},
journal = {Journal of Climate},
year = 2006,
volume = 19,
pages = {2665},
doi = {10.1175/JCLI3735.1},
adsurl = {http://adsabs.harvard.edu/abs/2006JCli...19.2665L},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006BAMS...87....1E,
author = {{Emanuel}, K. and {Ravela}, S. and {Vivant}, E. and {Risi}, C.
},
title = {{Supplement to A Statistical Deterministic Approach to Hurricane Risk Assessment}},
journal = {Bulletin of the American Meteorological Society},
year = 2006,
volume = 87,
pages = {1},
doi = {10.1175/BAMS-87-3-Emanuel},
adsurl = {http://adsabs.harvard.edu/abs/2006BAMS...87....1E},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006AtmEn..40.7953V,
author = {{Verma}, S. and {Boucher}, O. and {Upadhyaya}, H.~C. and {Sharma}, O.~P.
},
title = {{Sulfate aerosols forcing: An estimate using a three-dimensional interactive chemistry scheme}},
journal = {Atmospheric Environment},
year = 2006,
volume = 40,
pages = {7953-7962},
abstract = {{The tropospheric sulfate radiative forcing has been calculated using an
interactive chemistry scheme in LMD-GCM. To estimate the radiative
forcing of sulfate aerosol on climate, a consistent interaction between
atmospheric circulation and radiation computation has been allowed in
LMD-GCM. The model results indicate that the change in the sulfate
aerosols number concentration is negatively correlated to the indirect
radiative forcing. The model simulated annual mean direct radiative
forcing ranges from -0.1 to -1.2 W m $^{-2}$, and indirect forcing
ranges from -0.4 to -1.6 W m $^{-2}$. The global annual mean
direct effect estimated by the model is -0.48 W m $^{-2}$, and
that of indirect is -0.68 W m $^{-2}$.
}},
doi = {10.1016/j.atmosenv.2006.07.010},
adsurl = {http://adsabs.harvard.edu/abs/2006AtmEn..40.7953V},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2006AtmEn..40.1909H,
author = {{Habib}, G. and {Venkataraman}, C. and {Chiapello}, I. and {Ramachandran}, S. and
{Boucher}, O. and {Shekar Reddy}, M.},
title = {{Seasonal and interannual variability in absorbing aerosols over India derived from TOMS: Relationship to regional meteorology and emissions}},
journal = {Atmospheric Environment},
year = 2006,
volume = 40,
pages = {1909-1921},
abstract = {{The objective of this study is an analysis of the spatial, seasonal and
interannual variability of regional-scale aerosol load over India,
detected by TOMS during 1981-2000, with an evaluation of potential
contributing factors, including estimated anthropogenic aerosol emission
trends and regional meteorology (rainfall and circulation patterns).
Spatial distributions in TOMS Ai were related to the emission densities
of anthropogenic absorbing aerosols in April-May, but varied seasonally
and were modified significantly by higher atmospheric dispersion in
January-March and rainfall in June-September, both of which lead to low
TOMS Ai, even in regions of high aerosol emissions. Dust emissions
explain the high TOMS Ai over northwest region during April-May and
June-September when rainfall is scanty and significant air-mass decent
occurs in this region. The magnitude of TOMS Ai correlated with the
anthropogenic absorbing aerosol (black carbon and inorganic matter)
emission flux in five selected regions, dominated by biomass/biofuel
burning and fossil fuel combustion, but not in a region with significant
mineral dust emissions. The seasonal cycle in TOMS Ai was related to the
seasonal variability in dust, biomass burning emissions and rainfall.
Interannual variability in TOMS Ai was linked to that in forest burning
emissions in the northeast, as evidenced by a correlation with ATSR
fire-counts, both significantly enhanced in 1999. Trends in
anthropogenic emissions during 1981-2000 potentially contribute to
increases in the aerosol load detected by TOMS. This would need further
investigation using analysis incorporating both trends in anthropogenic
emissions and the interannual variability in natural sources of
aerosols.
}},
doi = {10.1016/j.atmosenv.2005.07.077},
adsurl = {http://adsabs.harvard.edu/abs/2006AtmEn..40.1909H},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
