lmd_Bony1997.bib
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@article{1997JCli...10.2055B,
author = {{Bony}, S. and {Lau}, K.-M. and {Sud}, Y.~C.},
title = {{Sea Surface Temperature and Large-Scale Circulation Influences on Tropical Greenhouse Effect and Cloud Radiative Forcing.}},
journal = {Journal of Climate},
year = 1997,
month = aug,
volume = 10,
pages = {2055-2077},
abstract = {{Two independent sets of meteorological reanalyses are used to
investigate relationships between the tropical sea surface temperature
(SST) and the large-scale vertical motion of the atmosphere for spatial
and seasonal variations, as well as for El Ni{\~n}o/La Ni{\~n}a
episodes of 1987-88. Supergreenhouse effect (SGE) situations are found
to be linked to the occurrence of enhanced large-scale rising motion
associated with increasing SST. In regions where the large-scale
atmospheric motion is largely decoupled from the local SST due to
internal or remote forcings, the SGE occurrence is weak. On seasonal and
interannual timescales, such regions are found mainly over equatorial
regions of the Indian Ocean and western Pacific, especially for SSTs
exceeding 29.5{\deg}C. In these regions, the activation of feedback
processes that regulate the ocean temperature is thus likely to be more
related to the large-scale remote processes, such as those that govern
the monsoon circulations and the low-frequency variability of the
atmosphere, than to the local SST change.The relationships among SST,
clouds, and cloud radiative forcing inferred from satellite observations
are also investigated. In large-scale subsidence regimes, regardless of
the SST range, the cloudiness, the cloud optical thickness, and the
shortwave cloud forcing decrease with increasing SST. In convective
regions maintained by the large-scale circulation, the strong dependence
of both the longwave (LW) and shortwave (SW) cloud forcing on SST mainly
results from changes in the large-scale vertical motion accompanying the
SST changes. Indeed, for a given large-scale rising motion, the cloud
optical thickness decreases with SST, and the SW cloud forcing remains
essentially unaffected by SST changes. However, the LW cloud forcing
still increases with SST because the detrainment height of deep
convection, and thus the cloud-top altitude, tend to increase with SST.
The dependence of the net cloud radiative forcing on SST may thus
provide a larger positive climate feedback when the ocean warming is
associated with weak large-scale circulation changes than during
seasonal or El Ni{\~n}o variations.
}},
doi = {10.1175/1520-0442(1997)010<2055:SSTALS>2.0.CO;2},
adsurl = {http://adsabs.harvard.edu/abs/1997JCli...10.2055B},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{1997JGR...10216593C,
author = {{Cess}, R.~D. and {Zhang}, M.~H. and {Potter}, G.~L. and {Alekseev}, V. and
{Barker}, H.~W. and {Bony}, S. and {Colman}, R.~A. and {Dazlich}, D.~A. and
{Del Genio}, A.~D. and {DéQué}, M. and {Dix}, M.~R. and
{Dymnikov}, V. and {Esch}, M. and {Fowler}, L.~D. and {Fraser}, J.~R. and
{Galin}, V. and {Gates}, W.~L. and {Hack}, J.~J. and {Ingram}, W.~J. and
{Kiehl}, J.~T. and {Kim}, Y. and {Le Treut}, H. and {Liang}, X.-Z. and
{McAvaney}, B.~J. and {Meleshko}, V.~P. and {Morcrette}, J.~J. and
{Randall}, D.~A. and {Roeckner}, E. and {Schlesinger}, M.~E. and
{Sporyshev}, P.~V. and {Taylor}, K.~E. and {Timbal}, B. and
{Volodin}, E.~M. and {Wang}, W. and {Wang}, W.~C. and {Wetherald}, R.~T.
},
title = {{Comparison of the seasonal change in cloud-radiative forcing from atmospheric general circulation models and satellite observations}},
journal = {\jgr},
keywords = {Meteorology and Atmospheric Dynamics: Climatology, Meteorology and Atmospheric Dynamics: Numerical modeling and data assimilation, Meteorology and Atmospheric Dynamics: Radiative processes},
year = 1997,
month = jul,
volume = 102,
pages = {16593},
abstract = {{We compare seasonal changes in cloud-radiative forcing (CRF) at the top
of the atmosphere from 18 atmospheric general circulation models, and
observations from the Earth Radiation Budget Experiment (ERBE). To
enhance the CRF signal and suppress interannual variability, we consider
only zonal mean quantities for which the extreme months (January and
July), as well as the northern and southern hemispheres, have been
differenced. Since seasonal variations of the shortwave component of CRF
are caused by seasonal changes in both cloudiness and solar irradiance,
the latter was removed. In the ERBE data, seasonal changes in CRF are
driven primarily by changes in cloud amount. The same conclusion applies
to the models. The shortwave component of seasonal CRF is a measure of
changes in cloud amount at all altitudes, while the longwave component
is more a measure of upper level clouds. Thus important insights into
seasonal cloud amount variations of the models have been obtained by
comparing both components, as generated by the models, with the
satellite data. For example, in 10 of the 18 models the seasonal
oscillations of zonal cloud patterns extend too far poleward by one
latitudinal grid.
}},
doi = {10.1029/97JD00927},
adsurl = {http://adsabs.harvard.edu/abs/1997JGR...10216593C},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{1997JCli...10.1441B,
author = {{Bony}, S. and {Sud}, Y. and {Lau}, K.~M. and {Susskind}, J. and
{Saha}, S.},
title = {{Comparison and Satellite Assessment of NASA/DAO and NCEP-NCAR Reanalyses over Tropical Ocean: Atmospheric Hydrology and Radiation.}},
journal = {Journal of Climate},
year = 1997,
month = jun,
volume = 10,
pages = {1441-1462},
abstract = {{This study compares the atmospheric reanalyses that have been produced
independently at the Data Assimilation Office (DAO) of Goddard
Laboratory for Atmospheres and at the National Centers for Environmental
Prediction (NCEP). These reanalyses were produced by using a frozen
state-of-the-art version of the global data assimilation system
developed at these two centers. For the period 1987-88 and for the
tropical oceanic regions of 30{\deg}S-30{\deg}N, surface and atmospheric
fields related to atmospheric hydrology and radiation are compared and
assessed, wherever possible, with satellite data. Some common biases as
well as discrepancies between the two independent reassimilation
products are highlighted.Considering both annual averages and
interannual variability (1987-88), discrepancies between DAO and NCEP
reanalysis in water vapor, precipitation, and clear-sky longwave
radiation at the top of the atmosphere are generally smaller than
discrepancies that exist between corresponding satellite estimates.
Among common biases identified in the reanalyses, the authors note an
underestimation of the total precipitable water and an overestimation of
the shortwave cloud radiative forcing in warm convective regions. Both
lead to an underestimation of the surface radiation budget. The authors
also note an overestimaton of the clear-sky outgoing longwave radiation
in most tropical ocean regions, as well as an overestimation of the
longwave radiative cooling at the ocean surface.Surface latent and
sensible heat fluxes differ by about 20 and 3 W m$^{2}$,
respectively, in the two reanalyses. Differences in the surface
radiation budget are larger than the uncertainties of satellite-based
estimates. Biases in the surface radiation fluxes derived from the
reanalyses are primarily due to incorrect shortwave cloud radiative
forcing and, to a lesser degree, due to a deficit in the total
precipitable water and a cold bias at lower-tropospheric
temperatures.This study suggests that individual features and biases of
each set of reanalyses should be carefully studied, especially when
using analyzed surface fluxes to force other physical or geophysical
models such as ocean circulation models. Over large regions of the
tropical oceans, DAO and NCEP reanalyses produce surface net heat fluxes
that can differ by up to 50 W m$^{2}$ in the average and by a
factor of 2 when considering interannual anomalies. This may lead to
vastly different thermal forcings for driving ocean circulations.
}},
doi = {10.1175/1520-0442(1997)010<1441:CASAON>2.0.CO;2},
adsurl = {http://adsabs.harvard.edu/abs/1997JCli...10.1441B},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{1997JCli...10..381L,
author = {{Lau}, K.-M. and {Wu}, H.-T. and {Bony}, S.},
title = {{The Role of Large-Scale Atmospheric Circulation in the Relationship between Tropical Convection and Sea Surface Temperature.}},
journal = {Journal of Climate},
year = 1997,
month = mar,
volume = 10,
pages = {381-392},
abstract = {{In this paper, the authors study the influence of the large-scale
atmospheric circulation on the relationship between sea surface
temperature (SST) and tropical convection inferred from outgoing
longwave radiation (OLR). They find that under subsidence and clear sky
conditions there is an increase in OLR with respect to SST at a rate of
1.8-2.5 Wm$^{2}$ ({\deg}C)$^{1}$. In regions of large-scale
ascending motions, which is correlated to, but not always collocated
with, regions of warm water, there is a large reduction of OLR with
respect to SST associated with increase in deep convection. The rate of
OLR reduction is found to be a strong function of the large-scale motion
field. The authors find an intrinsic OLR sensitivity to SST of
approximately 4 to 5 Wm$^{2}$ ({\deg}C)$^{1}$ in the SST
range of 27{\deg}-28{\deg}C, under conditions of weak large-scale
circulation. Under the influence of strong ascending motion, the rate
can be increased to 15 to 20 Wm$^{2}$ ({\deg}C)$^{1}$ for the
same SST range. The above OLR-SST relationships are strongly dependent
on geographic locations. On the other hand, deep convection and
large-scale circulation exhibit a nearly linear relationship that is
less dependent on SST and geographic locations.The above results are
supported by regression analyses. In addition, they find that on
interannual timescales, the relationship between OLR and SST is
dominated by the large-scale circulation and SST changes associated with
the El Ni{\~n}o-Southern Oscillation. The relationship between
anomalous convection and local SST is generally weak everywhere except
in the equatorial central Pacific, where large-scale circulation and
local SST appear to work together to produce the observed OLR-SST
sensitivity. Over the equatorial central Pacific, approximately 45\%-55\%
of the OLR variance can be explained by the large-scale circulation and
15\%-20\% by the local SST.Their results also show that there is no
fundamental microphysical or thermodynamical significance to the
so-called SST threshold at approximately 27{\deg}C, except that it
represents a transitional SST between clear-sky/subsiding and
convective/ascending atmospheric conditions. Depending on the ambient
large-scale motion associated with basin-scale SST distribution, this
transitional SST can occur in a range from 25.5{\deg} to 28{\deg}C.
Similarly, there is no magic to the 29.5{\deg}C SST, beyond which
convection appears to decrease with SST. The authors find that under the
influence of strong large-scale rising motion, convection does not
decrease but increases monotonically with SST even at SST higher than
29.5{\deg}C. The reduction in convection is likely to be influenced by
large-scale subsidence forced by nearby or remotely generated deep
convection.
}},
doi = {10.1175/1520-0442(1997)010<0381:TROLSA>2.0.CO;2},
adsurl = {http://adsabs.harvard.edu/abs/1997JCli...10..381L},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
