Assessing aerosol indirect effect through ice clouds in CAM5

2013 ◽  
Author(s):  
Kai Zhang ◽  
Xiaohong Liu ◽  
Jin-Ho Yoon ◽  
Minghuai Wang ◽  
Jennifer M. Comstock ◽  
...  
Keyword(s):  
Indirect Effect ◽  
Ice Clouds ◽  
Aerosol Indirect Effect

scholarly journals Dust aerosol impact on North Africa climate: a GCM investigation of aerosol-cloud-radiation interactions using A-Train satellite data

2012 ◽  
Vol 12 (4) ◽  
pp. 1667-1679 ◽  
Author(s):  
Y. Gu ◽  
K. N. Liou ◽  
J. H. Jiang ◽  
H. Su ◽  
X. Liu
Keyword(s):  
Solar Radiation ◽  
Direct Effect ◽  
North Africa ◽  
Satellite Data ◽  
Indirect Effect ◽  
Ir Radiation ◽  
Ice Clouds ◽  
Aerosol Indirect Effect ◽  
Cloud Forcing ◽  
Dust Aerosols

Abstract. The climatic effects of dust aerosols in North Africa have been investigated using the atmospheric general circulation model (AGCM) developed at the University of California, Los Angeles (UCLA). The model includes an efficient and physically based radiation parameterization scheme developed specifically for application to clouds and aerosols. Parameterization of the effective ice particle size in association with the aerosol first indirect effect based on ice cloud and aerosol data retrieved from A-Train satellite observations have been employed in climate model simulations. Offline simulations reveal that the direct solar, IR, and net forcings by dust aerosols at the top of the atmosphere (TOA) generally increase with increasing aerosol optical depth. When the dust semi-direct effect is included with the presence of ice clouds, positive IR radiative forcing is enhanced since ice clouds trap substantial IR radiation, while the positive solar forcing with dust aerosols alone has been changed to negative values due to the strong reflection of solar radiation by clouds, indicating that cloud forcing associated with aerosol semi-direct effect could exceed direct aerosol forcing. With the aerosol first indirect effect, the net cloud forcing is generally reduced in the case for an ice water path (IWP) larger than 20 g m−2. The magnitude of the reduction increases with IWP. AGCM simulations show that the reduced ice crystal mean effective size due to the aerosol first indirect effect results in less OLR and net solar flux at TOA over the cloudy area of the North Africa region because ice clouds with smaller size trap more IR radiation and reflect more solar radiation. The precipitation in the same area, however, increases due to the aerosol indirect effect on ice clouds, corresponding to the enhanced convection as indicated by reduced OLR. Adding the aerosol direct effect into the model simulation reduces the precipitation in the normal rainfall band over North Africa, where precipitation is shifted to the south and the northeast produced by the absorption of sunlight and the subsequent heating of the air column by dust particles. As a result, rainfall is drawn further inland to the northeast. This study represents the first attempt to quantify the climate impact of the aerosol indirect effect using a GCM in connection with A-Train satellite data. The parameterization for the aerosol first indirect effect developed in this study can be readily employed for application to other GCMs.

scholarly journals Aerosol indirect effect studies at Southern Great Plains during the May 2003 Intensive Operations Period

2006 ◽  
Vol 111 (D5) ◽  
Author(s):  
Graham Feingold ◽  
Reinhard Furrer ◽  
Peter Pilewskie ◽  
Lorraine A. Remer ◽  
Qilong Min ◽  
...  
Keyword(s):  
Great Plains ◽  
Indirect Effect ◽  
Aerosol Indirect Effect ◽  
Southern Great Plains

Aerosol indirect effect during the aberrant Indian Summer Monsoon breaks of 2009

2012 ◽  
Vol 60 ◽  
pp. 153-163 ◽  
Author(s):  
M.G. Manoj ◽  
P.C.S. Devara ◽  
Susmitha Joseph ◽  
A.K. Sahai
Keyword(s):  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Indirect Effect ◽  
Aerosol Indirect Effect

scholarly journals Dust aerosol impact on North Africa climate: a GCM investigation of aerosol-cloud-radiation interactions using A-Train satellite data

2011 ◽  
Vol 11 (11) ◽  
pp. 31401-31432
Author(s):  
Y. Gu ◽  
K. N. Liou ◽  
J. H. Jiang ◽  
H. Su ◽  
X. Liu
Keyword(s):  
Direct Effect ◽  
North Africa ◽  
Indirect Effect ◽  
Ice Crystal ◽  
Ir Radiation ◽  
Ice Clouds ◽  
Cloud Forcing ◽  
Dust Aerosols ◽  
Ice Water Content ◽  
Ice Water

Abstract. The climatic effects of dust aerosols in North Africa have been investigated using the atmospheric general circulation model (AGCM) developed at the University of California, Los Angeles (UCLA). The model includes an efficient and physically based radiation parameterization scheme developed specifically for application to clouds and aerosols. Parameterization of the effective ice particle size in association with the aerosol first indirect effect based on ice cloud and aerosol data retrieved from A-Train satellite observations have been employed in climate model simulations. Offline simulations reveal that the direct solar, IR, and net forcings by dust aerosols at the top of the atmosphere (TOA) generally increase with increasing aerosol optical depth (AOD). When the dust semi-direct effect is included with the presence of ice clouds, positive IR radiative forcing is enhanced since ice clouds trap substantial IR radiation, while the positive solar forcing with dust aerosols alone has been changed to negative values due to the strong reflection of solar radiation by clouds, indicating that cloud forcing associated with aerosol semi-direct effect could exceed direct aerosol forcing. With the aerosol first indirect effect, the net cloud forcing is generally reduced for an ice water path (IWP) larger than 20 g m−2. The magnitude of the reduction increases with IWP. AGCM simulations show that the reduced ice crystal mean effective size due to the aerosol first indirect effect results in less OLR and net solar flux at the top of the atmosphere over the cloudy area of the North Africa region because ice clouds with smaller size trap more IR radiation and reflect more solar radiation. The precipitation in the same area, however, increases due to the aerosol indirect effect on ice clouds, corresponding to the enhanced convection as indicated by reduced OLR. The increased precipitation appears to be associated with enhanced ice water content in this region. The 200 mb radiative heating rate shows more cooling with the aerosol first indirect effect since greater cooling is produced at the cloud top with smaller ice crystal size. The 500 mb omega indicates stronger upward motion, which, together with the increased cooling effect, results in the increased ice water content. Adding the aerosol direct effect into the model simulation reduces the precipitation in the normal rainfall band over North Africa, where precipitation is shifted to the south and the northeast produced by the absorption of sunlight and the subsequent heating of the air column by dust particles. As a result, rainfall is drawn further inland to the northeast. This study represents the first attempt to quantify the climate impact of the aerosol indirect effect using a GCM in connection with A-train satellite data. The parameterization for the aerosol first indirect effect developed in this study can be readily employed for application to other GCMs.

scholarly journals Quantifying the Dependence of Satellite Cloud Retrievals on Instrument Uncertainty

2017 ◽  
Vol 30 (17) ◽  
pp. 6959-6976 ◽  
Author(s):  
Yolanda L. Shea ◽  
Bruce A. Wielicki ◽  
Sunny Sun-Mack ◽  
Patrick Minnis
Keyword(s):  
Climate Change ◽  
Optical Thickness ◽  
Indirect Effect ◽  
Effective Temperature ◽  
Radiative Forcing ◽  
Cloud Fraction ◽  
Effective Radius ◽  
Aerosol Indirect Effect ◽  
Sources Of Uncertainty ◽  
Water Cloud

Cloud response to Earth’s changing climate is one of the largest sources of uncertainty among global climate model (GCM) projections. Two of the largest sources of uncertainty are the spread in equilibrium climate sensitivity (ECS) and uncertainty in radiative forcing due to uncertainty in the aerosol indirect effect. Satellite instruments with sufficient accuracy and on-orbit stability to detect climate change–scale trends in cloud properties will improve confidence in the understanding of the relationship between observed climate change and cloud property trends, thus providing information to better constrain ECS and radiative forcing. This study applies a climate change uncertainty framework to quantify the impact of measurement uncertainty on trend detection times for cloud fraction, effective temperature, optical thickness, and water cloud effective radius. Although GCMs generally agree that the total cloud feedback is positive, disagreement remains on its magnitude. With the climate uncertainty framework, it is demonstrated how stringent measurement uncertainty requirements for reflected solar and infrared satellite measurements enable improved constraint of SW and LW cloud feedbacks and the ECS by significantly reducing trend uncertainties for cloud fraction, optical thickness, and effective temperature. The authors also demonstrate improved constraint on uncertainty in the aerosol indirect effect by reducing water cloud effective radius trend uncertainty.

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