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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 partic ularly 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. [ABSTRACT FROM AUTHOR]

The article presents a study that demonstrates the procedure for tagging ozone produced from nitrogen oxide (NO) sources through an existing chemical mechanism. It highlights the method of the study that uses the Model for Ozone and Related Chemical Tracers (MOZART-4) and compares the ozone contribution to the tagging technique. It also details the result of the study, which shows that the tagged ozone is 2-4 times the contribution that was deduced from perturbing emission.

The article focuses on the Model of Emissions of Gases and Aerosols from Nature version 2.1 (MEGAN2.1) which estimates fluxes of 147 biogenic compounds between terrestrial ecosystems and the atmosphere using mechanistic algorithms. It says that emission estimates from MEGAN2.1 are within the range of estimates reported by other approaches. Moreover, the offline version of MEGAN2.1 driving variables and source code is available from http://acd.ucar.edu/guenther/MEGAN/MEGAN.htm.

Several charts which show the atmospheric chemistry in the Community Atmosphere Model (CAM) version 4 which include the isoprene emissions, ozone sondes, and climatology are presented.

The article explores the evaluation and description of the global Community Atmosphere Model (CAM) version 4 for atmospheric chemistry in Community Earth System Model (CESM). It reports that the atmospheric chemistry is responsible for the distribution of non-carbon dioxide gases and aerosols which influence the climate and air quality. Details on topics including the offline meteorology, chemical mechanisms, and emissions are discussed.

The article discusses a research study which examines the Fire Inventory from National Center for Atmospheric Research (NCAR) version 1.0 (FINNv1). It FINNv1 provides global estimates of trace gas emissions from open biomass burning such as wildfires. Moreover, it offers global estimates for key organic compounds including formaldehyde and methanol.