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@comment{{This file has been generated by bib2bib 1.95}}
@comment{{Command line: /usr/bin/bib2bib --quiet -c 'not journal:"Discussions"' -c 'not journal:"Polymer Science"' -c '  author:"Boucher"  ' -c year=2006 -c $type="ARTICLE" -oc lmd_Boucher2006.txt -ob lmd_Boucher2006.bib /home/WWW/LMD/public/}}
  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
  doi = {10.1007/s00382-006-0159-z},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  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 = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  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 = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  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 = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  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 = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  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 = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  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 = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  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.
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  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  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 = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  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.
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  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},
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  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 = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  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 = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  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
  doi = {10.1016/j.atmosenv.2005.07.077},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
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