Julio Bacmeister (PI)
University of Maryland Baltimore County
bacmj@janus.gsfc.nasa.gov

Improving Gravity Wave Parameterization for Next Generation Troposphere/Middle Atmospheric General Circulation Models

This proposal unites the efforts of 3 major national modeling groups in an attempt to unify and extend gravity wave parameterizations (GWPs) for forecast and climate models.The project has 3 major goals: 1) Development of “best practices” approach for existing GW parameterizations in 3 modeling systems NASA’s GMAO-GEOS5, NCAR’s WACCM, and NRL’s NOGAPS-ALPHA; 2) Incorporation of GW-induced temperature variability into cloud and chemical codes; and 3) Development of prototype ray-based GW parameterizations.  GWP remains an obstacle to realistic global model simulations at both weather and climate time-scales.  Despite over 20 years of application in global models, many important aspects of current GWPs depend on ad hoc specifications of wave forcing, as well as on empirically-chosen“tuning” parameters.  The first element of this effort will attempt to unify treatments of convective GW forcing, orographic blocking, and orographic source specification in the 3 participating models.  The approach will involve relatively straightforward intercomparisons of model runs, as well as “parameterization swapping” between models.  The second element of the proposed effort seeks to parameterize GW-induced temperature fluctuations and to examine the effects of these fluctuations on cloud formation and chemical processing in the atmosphere.  In this work high-resolution satellite retrieved radiances, and aircraft measurements will be compared with assimilation mode global model simulations employing new GW-induced temperature fluctuation estimates.  Finally, this effort will develop novel ray-based GWPs.  The main aim of this development is to capture horizontal and temporal spread in GW propagation.  Both of these can be expected to become more important as model resolution increases in both space and time.  Validation of possible ray-based GWP will conducted using offline calculations with analyzed atmospheric background fields that will be compared with satellite data and in situ data.  All codes developed within this effort will use the Earth System Modeling Framework (ESMF), which will ease parallelization in the case of ray-based approaches, and will increase portability in all cases.

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