scholarly journals Arctic and Antarctic Sea Ice Mean State in the Community Earth System Model Version 2 and the Influence of Atmospheric Chemistry

2020 ◽  
Vol 125 (8) ◽  
Author(s):  
Alice K. DuVivier ◽  
Marika M. Holland ◽  
Jennifer E. Kay ◽  
Simone Tilmes ◽  
Andrew Gettelman ◽  
...  
Keyword(s):  
Sea Ice ◽  
Atmospheric Chemistry ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Model Version ◽  
Antarctic Sea Ice ◽  
Community Earth System Model ◽  
Mean State

scholarly journals High Climate Sensitivity in the Community Earth System Model Version 2 (CESM2)

2019 ◽  
Vol 46 (14) ◽  
pp. 8329-8337 ◽  
Author(s):  
A. Gettelman ◽  
C. Hannay ◽  
J. T. Bacmeister ◽  
R. B. Neale ◽  
A. G. Pendergrass ◽  
...  
Keyword(s):  
Climate Sensitivity ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Model Version ◽  
Community Earth System Model

scholarly journals CAM-chem: description and evaluation of interactive atmospheric chemistry in the Community Earth System Model

2012 ◽  
Vol 5 (2) ◽  
pp. 369-411 ◽  
Author(s):  
J.-F. Lamarque ◽  
L. K. Emmons ◽  
P. G. Hess ◽  
D. E. Kinnison ◽  
S. Tilmes ◽  
...  
Keyword(s):  
United States ◽  
Atmospheric Chemistry ◽  
Surface Ozone ◽  
The United States ◽  
Earth System Model ◽  
System Model ◽  
Ozone Production ◽  
Positive Bias ◽  
Earth System ◽  
Community Earth System Model

Abstract. We discuss and evaluate the representation of atmospheric chemistry in the global Community Atmosphere Model (CAM) version 4, the atmospheric component of the Community Earth System Model (CESM). We present a variety of configurations for the representation of tropospheric and stratospheric chemistry, wet removal, and online and offline meteorology. Results from simulations illustrating these configurations are compared with surface, aircraft and satellite observations. Major biases include a negative bias in the high-latitude CO distribution, a positive bias in upper-tropospheric/lower-stratospheric ozone, and a positive bias in summertime surface ozone (over the United States and Europe). The tropospheric net chemical ozone production varies significantly between configurations, partly related to variations in stratosphere-troposphere exchange. Aerosol optical depth tends to be underestimated over most regions, while comparison with aerosol surface measurements over the United States indicate reasonable results for sulfate , especially in the online simulation. Other aerosol species exhibit significant biases. Overall, the model-data comparison indicates that the offline simulation driven by GEOS5 meteorological analyses provides the best simulation, possibly due in part to the increased vertical resolution (52 levels instead of 26 for online dynamics). The CAM-chem code as described in this paper, along with all the necessary datasets needed to perform the simulations described here, are available for download at www.cesm.ucar.edu.

scholarly journals Description and evaluation of tropospheric chemistry and aerosols in the Community Earth System Model (CESM1.2)

2014 ◽  
Vol 7 (6) ◽  
pp. 8875-8940 ◽  
Author(s):  
S. Tilmes ◽  
J.-F. Lamarque ◽  
L. K. Emmons ◽  
D. E. Kinnison ◽  
P.-L. Ma ◽  
...  
Keyword(s):  
Surface Area ◽  
Atmospheric Chemistry ◽  
Earth System Model ◽  
Tropospheric Chemistry ◽  
System Model ◽  
Earth System ◽  
Chemical Production ◽  
Area Density ◽  
Community Earth System Model ◽  
The Difference

Abstract. The Community Atmosphere Model (CAM), version 5, is now coupled to extensive tropospheric and stratospheric chemistry, called CAM5-chem, and is available in addition to CAM4-chem in the Community Earth System Model (CESM) version 1.2. Both configurations are well suited as tools for atmospheric-chemistry modeling studies in the troposphere and lower stratosphere, whether with internally derived "free running" (FR) meteorology, or "specified dynamics" (SD). The main focus of this paper is to compare the performance of these configurations against observations from surface, aircraft, and satellite, as well as understand the origin of the identified differences. We particularly focus on comparing present-day methane lifetime estimates within the different model configurations, which range between 7.8 years in the SD configuration of CAM5-chem and 8.8 years in the FR configuration of CAM4-chem. We find that tropospheric surface area density is an important factor in controlling the burden of the hydroxyl radical (OH), which causes differences in tropical methane lifetime of about half a year between CAM4-chem and CAM5-chem. In addition, different distributions of nitrogen oxides (NOx) produced from lightning production explain about half of the difference between SD and FR model versions in both CAM4-chem and CAM5-chem. Remaining differences in the tropical OH burden are due to enhanced tropical ozone burden in SD configurations compared to the FR versions, which are not only caused by differences in chemical production or loss, but also by transport and mixing. For future studies, we recommend the use of CAM5-chem, due to improved aerosol description and inclusion of aerosol-cloud interactions. However, smaller tropospheric surface area density in the current version of CAM5-chem compared to CAM4-chem results in larger oxidizing capacity in the troposphere and therefore a shorter methane lifetime.

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