scholarly journals Aerosol indirect effects in POLDER satellite data and the Laboratoire de Météorologie Dynamique–Zoom (LMDZ) general circulation model

2004 ◽  
Vol 109 (D8) ◽  
Author(s):  
J. Quaas
Keyword(s):  
General Circulation Model ◽  
Satellite Data ◽  
Indirect Effects ◽  
General Circulation ◽  
Circulation Model ◽  
Aerosol Indirect Effects

scholarly journals Evaluation of boundary layer cloud parameterizations in the ECHAM5 general circulation model using CALIPSO and CloudSat satellite data

2014 ◽  
Vol 6 (2) ◽  
pp. 300-314 ◽  
Author(s):  
Christine C. W. Nam ◽  
Johannes Quaas ◽  
Roel Neggers ◽  
Colombe Siegenthaler-Le Drian ◽  
Francesco Isotta
Keyword(s):  
Boundary Layer ◽  
General Circulation Model ◽  
Satellite Data ◽  
General Circulation ◽  
Circulation Model ◽  
Boundary Layer Cloud ◽  
Layer Cloud

scholarly journals Examination of aerosol distributions and radiative effects over the Bay of Bengal and the Arabian Sea region during ICARB using satellite data and a general circulation model

2012 ◽  
Vol 12 (3) ◽  
pp. 1287-1305 ◽  
Author(s):  
R. Cherian ◽  
C. Venkataraman ◽  
S. Ramachandran ◽  
J. Quaas ◽  
S. Kedia
Keyword(s):  
General Circulation Model ◽  
Temporal Resolution ◽  
Satellite Data ◽  
Bay Of Bengal ◽  
Temporal Variability ◽  
General Circulation ◽  
Arabian Sea ◽  
Large Scale ◽  
Circulation Model ◽  
Aerosol Index

Abstract. In this paper we analyse aerosol loading and its direct radiative effects over the Bay of Bengal (BoB) and Arabian Sea (AS) regions for the Integrated Campaign on Aerosols, gases and Radiation Budget (ICARB) undertaken during 2006, using satellite data from the MODerate Resolution Imaging Spectroradiometer (MODIS) on board the Terra and Aqua satellites, the Aerosol Index from the Ozone Monitoring Instrument (OMI) on board the Aura satellite, and the European-Community Hamburg (ECHAM5.5) general circulation model extended by Hamburg Aerosol Module (HAM). By statistically comparing with large-scale satellite data sets, we firstly show that the aerosol properties measured during the ship-based ICARB campaign and simulated by the model are representative for the BoB and AS regions and the pre-monsoon season. In a second step, the modelled aerosol distributions were evaluated by a comparison with the measurements from the ship-based sunphotometer, and the satellite retrievals during ICARB. It is found that the model broadly reproduces the observed spatial and temporal variability in aerosol optical depth (AOD) over BoB and AS regions. However, AOD was systematically underestimated during high-pollution episodes, especially in the BoB leg. We show that this underprediction of AOD is mostly because of the deficiencies in the coarse mode, where the model shows that dust is the dominant component. The analysis of dust AOD along with the OMI Aerosol Index indicate that missing dust transport that results from too low dust emission fluxes over the Thar Desert region in the model caused this deficiency. Thirdly, we analysed the spatio-temporal variability of AOD comparing the ship-based observations to the large-scale satellite observations and simulations. It was found that most of the variability along the track was from geographical patterns, with a minor influence by single events. Aerosol fields were homogeneous enough to yield a good statistical agreement between satellite data at a 1° spatial, but only twice-daily temporal resolution, and the ship-based sunphotometer data at a much finer spatial, but daily-average temporal resolution. Examination of the satellite data further showed that the year 2006 is representative for the five-year period for which satellite data were available. Finally, we estimated the clear-sky solar direct aerosol radiative forcing (DARF). We found that the cruise represents well the regional-seasonal mean forcings. Constraining simulated forcings using the observed AOD distributions yields a robust estimate of regional-seasonal mean DARF of −8.6, −21.4 and +12.9 W m−2 at the top of the atmosphere (TOA), at the surface (SUR) and in the atmosphere (ATM), respectively, for the BoB region, and over the AS, of, −6.8, −12.8, and +6 W m−2 at TOA, SUR, and ATM, respectively.

scholarly journals Aerosol indirect effects – general circulation model intercomparison and evaluation with satellite data

2009 ◽  
Vol 9 (22) ◽  
pp. 8697-8717 ◽  
Author(s):  
J. Quaas ◽  
Y. Ming ◽  
S. Menon ◽  
T. Takemura ◽  
M. Wang ◽  
...  
Keyword(s):  
Satellite Data ◽  
Indirect Effect ◽  
Indirect Effects ◽  
General Circulation ◽  
Short Wave ◽  
Effect Estimate ◽  
Aerosol Indirect Effects ◽  
Aerosol Indirect Effect ◽  
Aerosol Direct Effect ◽  
Statistical Relationships

Abstract. Aerosol indirect effects continue to constitute one of the most important uncertainties for anthropogenic climate perturbations. Within the international AEROCOM initiative, the representation of aerosol-cloud-radiation interactions in ten different general circulation models (GCMs) is evaluated using three satellite datasets. The focus is on stratiform liquid water clouds since most GCMs do not include ice nucleation effects, and none of the model explicitly parameterises aerosol effects on convective clouds. We compute statistical relationships between aerosol optical depth (τa) and various cloud and radiation quantities in a manner that is consistent between the models and the satellite data. It is found that the model-simulated influence of aerosols on cloud droplet number concentration (Nd) compares relatively well to the satellite data at least over the ocean. The relationship between τa and liquid water path is simulated much too strongly by the models. This suggests that the implementation of the second aerosol indirect effect mainly in terms of an autoconversion parameterisation has to be revisited in the GCMs. A positive relationship between total cloud fraction (fcld) and τa as found in the satellite data is simulated by the majority of the models, albeit less strongly than that in the satellite data in most of them. In a discussion of the hypotheses proposed in the literature to explain the satellite-derived strong fcld–τa relationship, our results indicate that none can be identified as a unique explanation. Relationships similar to the ones found in satellite data between τa and cloud top temperature or outgoing long-wave radiation (OLR) are simulated by only a few GCMs. The GCMs that simulate a negative OLR–τa relationship show a strong positive correlation between τa and fcld. The short-wave total aerosol radiative forcing as simulated by the GCMs is strongly influenced by the simulated anthropogenic fraction of τa, and parameterisation assumptions such as a lower bound on Nd. Nevertheless, the strengths of the statistical relationships are good predictors for the aerosol forcings in the models. An estimate of the total short-wave aerosol forcing inferred from the combination of these predictors for the modelled forcings with the satellite-derived statistical relationships yields a global annual mean value of −1.5±0.5 Wm−2. In an alternative approach, the radiative flux perturbation due to anthropogenic aerosols can be broken down into a component over the cloud-free portion of the globe (approximately the aerosol direct effect) and a component over the cloudy portion of the globe (approximately the aerosol indirect effect). An estimate obtained by scaling these simulated clear- and cloudy-sky forcings with estimates of anthropogenic τa and satellite-retrieved Nd–τa regression slopes, respectively, yields a global, annual-mean aerosol direct effect estimate of −0.4±0.2 Wm−2 and a cloudy-sky (aerosol indirect effect) estimate of −0.7±0.5 Wm−2, with a total estimate of −1.2±0.4 Wm−2.

scholarly journals Examination of aerosol distributions and radiative effects over the Bay of Bengal and the Arabian Sea region during ICARB using satellite data and a general circulation model

2011 ◽  
Vol 11 (5) ◽  
pp. 13911-13946 ◽  
Author(s):  
R. Cherian ◽  
C. Venkataraman ◽  
S. Ramachandran ◽  
J. Quaas ◽  
S. Kedia
Keyword(s):  
General Circulation Model ◽  
Temporal Resolution ◽  
Satellite Data ◽  
Bay Of Bengal ◽  
Temporal Variability ◽  
General Circulation ◽  
Arabian Sea ◽  
Large Scale ◽  
Circulation Model ◽  
Aerosol Index

Abstract. In this paper we analyse aerosol loading and its direct radiative effects over the Bay of Bengal (BoB) and Arabian Sea (AS) regions for the Integrated Campaign on Aerosols, gases and Radiation Budget (ICARB) undertaken during 2006, using satellite data from the MODerate Resolution Imaging Spectroradiometer (MODIS) on board the Terra and Aqua satellites, the Aerosol Index from the Ozone Monitoring Instrument (OMI) on board the Aura satellite, and the European-Community Hamburg (ECHAM5.5) general circulation model extended by Hamburg Aerosol Module (HAM). By statistical comparison with large-scale satellite data sets, we firstly show that the ship-based ICARB observations are representative for the entire northern Indian Ocean during the pre-monsoon season. In a second step, the modelled aerosol distributions were evaluated by a comparison with the measurements from the ship-based sunphotometer, and the satellites. It was found that the model reproduces the observed spatial and temporal variability in aerosol optical depth (AOD) and simulated AODs to a large extent. However, AOD was systematically underestimated during high-pollution episodes, especially in the BoB leg. We show that this underprediction of AOD is mostly due to deficiencies in the coarse mode, where the model showed that dust was the dominant component. The analysis of simulated dust AOD along with the OMI Aerosol Index showed that the too low dust emissions from the Thar Desert in the model are the main cause for this deficiency. Thirdly, we analysed the spatio-temporal variability of AOD comparing the ship-based observations to the large-scale satellite observations and simulations. It was found that most of the variability along the track was due to geographical patterns, with minor influence by single events. Aerosol fields were homogeneous enough to yield a good statistical agreement between satellite data at a 1° spatial, but only twice-daily temporal resolution, and the ship-based sunphotometer data at a much finer spatial, but daily-average temporal resolution. Finally, we estimated the shortwave aerosol radiative forcing. We found that the cruise represents well the regional-seasonal mean forcings. Constraining simulated forcings using the observed AOD distributions yields a regional-seasonal mean aerosol forcing of −8.6, −21.4 and +12.9 W m−2 at the top of the atmosphere (TOA), at the surface (SUR) and in the atmosphere (ATM), respectively, for the BoB region, and over the AS, of, −6.8, −12.8, and +6 W m−2 at TOA, SUR, and ATM, respectively.

scholarly journals Aerosol indirect effects – general circulation model intercomparison and evaluation with satellite data

2009 ◽  
Vol 9 (3) ◽  
pp. 12731-12779 ◽  
Author(s):  
J. Quaas ◽  
Y. Ming ◽  
S. Menon ◽  
T. Takemura ◽  
M. Wang ◽  
...  
Keyword(s):  
Satellite Data ◽  
Liquid Water ◽  
Indirect Effect ◽  
Indirect Effects ◽  
General Circulation ◽  
Short Wave ◽  
Effect Estimate ◽  
Aerosol Indirect Effects ◽  
Aerosol Indirect Effect ◽  
Statistical Relationships

Abstract. Aerosol indirect effects continue to constitute one of the most important uncertainties for anthropogenic climate perturbations. Within the international AEROCOM initiative, the representation of aerosol-cloud-radiation interactions in ten different general circulation models (GCMs) is evaluated using three satellite datasets. The focus is on stratiform liquid water clouds since most GCMs do not include ice nucleation effects, and none of the models explicitly parameterizes aerosol effects on convective clouds. We compute statistical relationships between aerosol optical depth (τa) and various cloud and radiation quantities in a manner that is consistent between the models and the satellite data. It is found that the model-simulated influence of aerosols on cloud droplet number concentration (Nd) compares relatively well to the satellite data at least over the ocean. The relationship between τa and liquid water path is simulated much too strongly by the models. It is shown that this is partly related to the representation of the second aerosol indirect effect in terms of autoconversion. A positive relationship between total cloud fraction (fcld) and τa as found in the satellite data is simulated by the majority of the models, albeit less strongly than that in the satellite data in most of them. In a discussion of the hypotheses proposed in the literature to explain the satellite-derived strong fcld – τa relationship, our results indicate that none can be identified as unique explanation. Relationships similar to the ones found in satellite data between τa and cloud top temperature or outgoing long-wave radiation (OLR) are simulated by only a few GCMs. The GCMs that simulate a negative OLR – τa relationship show a strong positive correlation between τa and fcld. The short-wave total aerosol radiative forcing as simulated by the GCMs is strongly influenced by the simulated anthropogenic fraction of τa, and parameterisation assumptions such as a lower bound on Nd. Nevertheless, the strengths of the statistical relationships are good predictors for the aerosol forcings in the models. An estimate of the total short-wave aerosol forcing inferred from the combination of these predictors for the modelled forcings with the satellite-derived statistical relationships yields a global annual mean value of −1.5±0.5 Wm−2. An alternative estimate obtained by scaling the simulated clear- and cloudy-sky forcings with estimates of anthropogenic τa and satellite-retrieved Nd – τa regression slopes, respectively, yields a global annual mean clear-sky (aerosol direct effect) estimate of −0.4±0.2 Wm−2 and a cloudy-sky (aerosol indirect effect) estimate of −0.7±0.5 Wm−2, with a total estimate of −1.2±0.4 Wm−2.

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