The NCAR CESM system is facilitating the investigation of the interactions among different components of the earth-atmospheric system. One of the available atmospheric models is WACCM, which was specifically developed to simulate interactions between chemistry and climate across all levels of the atmosphere. WACCM simulations are particularly valuable in exploring the impact of middle atmosphere dynamics and chemistry on the climate system.

In collaboration with researchers from the State University of New York’s College of Environmental Science and Forestry in Syracuse, ACD scientists have measured the fractionation of deuterated methoxy radicals, CH₂DO, which are formed in the atmospheric oxidation of methane. Methane, CH₄, is the most-abundant hydrocarbon in the atmosphere, as a result of its large source strength and low rate of reaction with OH radicals. Its oxidation provides a global background sink for OH and a source of CO.

Photochemical smog is a byproduct of the NOx-catalyzed oxidation of volatile organic compounds (VOCs) under solar ultraviolet (UV) radiation.  While the chemical regime can be NOx-limited, VOC-limited, or NOx-inhibited, it is always photon limited and therefore sensitive to changes in the UV radiation field.  In polluted regions, these radiation changes can be caused by the smog itself, especially ozone (O₃), nitrogen dioxide (NO₂), and aerosol particles.

The new Version 5 (“V5”) MOPITT (Measurements of Pollution in the Troposphere) product for carbon monoxide (CO) is the first satellite product to exploit simultaneous near-infrared (NIR) and thermal-infrared (TIR) observations to enhance retrieval sensitivity in the lower troposphere. Since most major sources of tropospheric CO are found at or near the Earth's surface, this feature will improve air quality forecasts and studies of CO sources.

Aura’s High Resolution Dynamics Limb Sounder (HIRDLS) reveals the global pattern of the double tropopause using the HIRDLS high vertical resolution profiles. Composition and structure near the tropopause are important for the Earth radiative balance and quantifying transport of ozone and other stratospheric species into the troposphere.

A new ozonesonde climatology for the period 1995-2009 was compiled for model evaluation and comparison to other observations [Tilmes et al., 2011]. This climatology allows evaluating the performance of ozone especially in the troposphere and lower stratosphere. Various models still show significant shortcomings to reproduce the structure and seasonality of ozone, one of the most important trace gases in the atmosphere.

The Whole Atmosphere Community Climate Model (WACCM) simulates many features of the stratosphere, including the very active dynamics in Northern Hemisphere winter. During midwinter in some years, there are major breakdowns of the polar winter vortex known as sudden stratospheric warmings. The frequency and development of these events simulated in WACCM are similar to observations.