Interfacing Major Field Experiments with Physical Parameterizations in Atmospheric General Circulation Models

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An important physical process that must be well represented in climate models is horizontal momentum transport. This is the motivation for this project, the goal of which is to improve and validate momentum transport schemes in global climate models. Toward this end, the PI will develop integrated datasets, from major field campaigns, of large-scale forcing and sub-grid sources and sinks of horizontal momentum. These will be used to force and evaluate Single Column Models (SCM), Cloud System Resolving Models (CSRM), and physical parameterizations to improve General Circulation Models (GCM). The Principal Investigator (PI) will use a new variational approach, based on his group's previous research on advective tendencies of temperature and water using balloon sounding arrays, to analyze atmospheric momentum budgets in which column-integrated conservations of dry air and water vapor mass, enthalpy and momentum will be preserved. Apparent momentum sources and sinks will be derived for four field experiments in the tropics, the Tropical Ocean Global Atmospheres/Coupled Ocean Atmosphere Response Experiment (TOGA-COARE), The Kwajalein Experiment (KWAJEX), The South China Sea Monsoon Experiment (SCSMEX), and the Tropical Warm Pool - International Cloud Experiment (TWP-ICE) and several in the middle latitudes (the Department of Energy (Atmospheric Radiation Program Southern Great Plains (ARM-SGP) sites). Uncertainties of the data products will be quantified through sensitivity studies and Observational Simulation System Experiments (OSSE). The developed integrated data products will be used to answer three main questions: (a) Under what large-scale conditions is subgrid momentum transport upscale and under what conditions is it downscale? (b) How do GCM parameterizations of momentum transport compare with observations? (c) How can we improve the momentum source/sink parameterizations in atmospheric models. Broader impacts of this work are in advancing our understanding of atmospheric momentum sources and sinks from observations and their better parameterizations in climate models, which is necessary for them to predict future climate changes, and of the mechanism of atmospheric variability in the tropics. A postdoc and a graduate student will be mentored and trained in research.