The proposed research will combine NASA satellite data and model output from the chemistry-climate modeling initiative (CCMI) to investigate atmospheric gravity waves and their effects on…

This $269,851.58 NASA grant was awarded to Northwest Research Associates, Inc. (Nwra), a for-profit research organization, to investigate the effects of atmospheric gravity waves on circulation and composition in the Southern Hemisphere. The research will utilize NASA satellite data and climate model output to understand why models typically have biases in temperatures and winds in this region, which impacts the ability to accurately model the ozone hole and climate change. The goal is to identify key sources of missing gravity wave drag in models and recommend improvements to gravity wave parameterizations. This grant is not associated with a larger contract vehicle and does not have a set-aside designation.

The proposed research will combine NASA satellite data and model output from the chemistry-climate modeling initiative (CCMI) to investigate atmospheric gravity waves and their effects on circulation and atmospheric composition in the southern hemisphere. Recent research suggests that large-amplitude gravity waves generated by convection are important drivers of circulation, temperatures, and transport in the lower stratosphere, which influence atmospheric constituents such as ozone and water vapor. However most atmospheric models have biases in temperatures and winds because of deficiencies in the way that gravity waves and their effects on circulation are represented. This problem is especially pronounced in the southern hemisphere stratosphere, where winds are generally too strong and temperatures too cold in most chemistry-climate models. Additionally, the stratospheric final warming in the southern hemisphere is typically one or two weeks late in models compared to observations. This leads to major temperature biases in the lower stratosphere and associated effects on ozone chemistry. The reasons for these biases are not well understood, although IT has been suggested that missing southern hemisphere gravity wave drag in models is a major culprit. Possible sources of the missing gravity wave drag include inadequate continental orographic gravity wave drag, orographic gravity wave drag from small, unresolved islands, lateral propagation of gravity waves generated at other latitudes, and nonorographic gravity waves generated by fronts and convection. Deficiencies in modeled gravity wave effects and the resulting model biases in wind and temperature in the southern hemisphere hinder our ability to accurately model the ozone hole and its recovery, which also has implications for our ability to model surface climate change. This project will identify the important sources of the missing gravity wave drag in the southern hemisphere and improve our understanding of gravity wave sources and gravity wave impacts on circulation, transport, and composition. The methods will focus on data from NASA satellite instruments, including precipitation and latent heating from the global precipitation measurement (GPM) mission, infrared brightness temperatures from the atmospheric infrared sounder (AIRS), and temperatures from the high resolution dynamics limb sounder (HIRDLS). For example, at the extremes of the HIRDLS measurement latitudes (near 63 degrees in the southern hemisphere), the zonal sampling is very dense and provides an abundance of information on waves spanning many spatial scales. This information has not yet been exploited to investigate the missing southern hemisphere drag. The gravity wave information obtained from the satellite instruments will be used to evaluate the sources of missing drag in the CCMI models. This will result in recommendations for improved gravity wave parameterizations, which will ultimately improve our ability to simulate the ozone hole and its recovery in a changing climate.