scholarly journals Constraining the influence of natural variability to improve estimates of global aerosol indirect effects in a nudged version of the Community Atmosphere Model 5

2012 ◽  
Vol 117 (D23) ◽  
pp. n/a-n/a ◽  
Author(s):  
Gabriel J. Kooperman ◽  
Michael S. Pritchard ◽  
Steven J. Ghan ◽  
Minghuai Wang ◽  
Richard C. J. Somerville ◽  
...  
Keyword(s):  
Indirect Effects ◽  
Natural Variability ◽  
Aerosol Indirect Effects ◽  
Community Atmosphere Model ◽  
Atmosphere Model

scholarly journals Integrating Cloud Processes in the Community Atmosphere Model, Version 5

2014 ◽  
Vol 27 (18) ◽  
pp. 6821-6856 ◽  
Author(s):  
Sungsu Park ◽  
Christopher S. Bretherton ◽  
Philip J. Rasch
Keyword(s):  
Hydrological Cycle ◽  
Cloud Droplet ◽  
Ice Crystals ◽  
Radiation Budget ◽  
Liquid Droplets ◽  
Marine Stratocumulus ◽  
Aerosol Indirect Effects ◽  
Model Version ◽  
Community Atmosphere Model ◽  
Atmosphere Model

Abstract This paper provides a description of the integrated representation for the cloud processes in the Community Atmosphere Model, version 5 (CAM5). CAM5 cloud parameterizations add the following unique characteristics to previous versions: 1) a cloud macrophysical structure with horizontally nonoverlapped deep cumulus, shallow cumulus, and stratus in each grid layer, where each of which has its own cloud fraction, and mass and number concentrations for cloud liquid droplets and ice crystals; 2) stratus–radiation–turbulence interactions that allow CAM5 to simulate marine stratocumulus solely from grid-mean relative humidity without relying on a stability-based empirical formula; 3) prognostic treatment of the number concentrations of stratus liquid droplets and ice crystals, with activated aerosols and detrained in-cumulus condensates as the main sources and with evaporation, sedimentation, and precipitation of stratus condensate as the main sinks; and 4) radiatively active cumulus and snow. By imposing consistency between diagnosed stratus fraction and prognosed stratus condensate, unrealistically empty or highly dense stratus is avoided in CAM5. Because of the activation of the prognostic aerosols and the parameterizations of the radiation and stratiform precipitation production as a function of the cloud droplet size, CAM5 simulates various aerosol indirect effects as well as the direct effects: that is, aerosols affect both the radiation budget and the hydrological cycle. Detailed analysis of various simulations indicates that CAM5 improves upon CAM3/CAM4 in global performance as well as in physical formulation. However, several problems are also identified in CAM5, which can be attributed to deficient regional tuning, inconsistency between various physics parameterizations, and incomplete treatment of physics. Efforts are continuing to further improve CAM5.

Common summertime total cloud cover and aerosol optical depth weekly variabilities over Europe: Sign of the aerosol indirect effects?

2015 ◽  
Vol 153 ◽  
pp. 59-73 ◽  
Author(s):  
A.K. Georgoulias ◽  
K.A. Kourtidis ◽  
G. Alexandri ◽  
S. Rapsomanikis ◽  
A. Sanchez-Lorenzo
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Indirect Effects ◽  
Cloud Cover ◽  
Total Cloud Cover ◽  
Aerosol Indirect Effects

scholarly journals Exploiting the weekly cycle as observed over Europe to analyse aerosol indirect effects in two climate models

2009 ◽  
Vol 9 (21) ◽  
pp. 8493-8501 ◽  
Author(s):  
J. Quaas ◽  
O. Boucher ◽  
A. Jones ◽  
G. P. Weedon ◽  
J. Kieser ◽  
...  
Keyword(s):  
Indirect Effects ◽  
General Circulation ◽  
Climate Models ◽  
General Circulation Models ◽  
Cloud Microphysics ◽  
Liquid Water Path ◽  
Large Variability ◽  
Aerosol Indirect Effects ◽  
Weekly Cycle ◽  
Model Control

Abstract. A weekly cycle in aerosol pollution and some meteorological quantities is observed over Europe. In the present study we exploit this effect to analyse aerosol-cloud-radiation interactions. A weekly cycle is imposed on anthropogenic emissions in two general circulation models that include parameterizations of aerosol processes and cloud microphysics. It is found that the simulated weekly cycles in sulfur dioxide, sulfate, and aerosol optical depth in both models agree reasonably well with those observed indicating model skill in simulating the aerosol cycle. A distinct weekly cycle in cloud droplet number concentration is demonstrated in both observations and models. For other variables, such as cloud liquid water path, cloud cover, top-of-the-atmosphere radiation fluxes, precipitation, and surface temperature, large variability and contradictory results between observations, model simulations, and model control simulations without a weekly cycle in emissions prevent us from reaching any firm conclusions about the potential aerosol impact on meteorology or the realism of the modelled second aerosol indirect effects.

scholarly journals A Diagnostic PDF Cloud Scheme to Improve Subtropical Low Clouds in NCAR Community Atmosphere Model ( CAM 5)

2018 ◽  
Vol 10 (2) ◽  
pp. 320-341 ◽  
Author(s):  
Yi Qin ◽  
Yanluan Lin ◽  
Shiming Xu ◽  
Hsi‐Yen Ma ◽  
Shaocheng Xie
Keyword(s):  
Low Clouds ◽  
Community Atmosphere Model ◽  
Atmosphere Model
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