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Amelioration of Convective and Nonconvective Condensation with the Assimilation of Rainfall for Improving initial Conditions

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  • 1 National Meteorological Center, Development Division, Washington, D.C.
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Abstract

Three new schemes to assimilate the rainfall observations for improving the initial conditions are developed and tested. A reverse cumulus parameterization procedure is used in which the model convective precipitation is nudged in scheme 1, and the model total precipitation is nudged in schemes 2 and 3, toward the observations. At the nonconvective grid points, the reverse procedure is not invoked. A method to enhance the rainfall at such points, in case the predicted total rainfall is weaker than the observed, is included in scheme 3. Numerical results are presented to show that the thermodynamic and wind fields and the distribution of condensational heating are improved with the use of any of the above rainfall assimilation schemes. The incorporation of the method to enhance the rainfall at the nonconvective grid points and the use of the total rainfall in place of only the convective rainfall in the reverse procedure ameliorate the initial conditions.

Abstract

Three new schemes to assimilate the rainfall observations for improving the initial conditions are developed and tested. A reverse cumulus parameterization procedure is used in which the model convective precipitation is nudged in scheme 1, and the model total precipitation is nudged in schemes 2 and 3, toward the observations. At the nonconvective grid points, the reverse procedure is not invoked. A method to enhance the rainfall at such points, in case the predicted total rainfall is weaker than the observed, is included in scheme 3. Numerical results are presented to show that the thermodynamic and wind fields and the distribution of condensational heating are improved with the use of any of the above rainfall assimilation schemes. The incorporation of the method to enhance the rainfall at the nonconvective grid points and the use of the total rainfall in place of only the convective rainfall in the reverse procedure ameliorate the initial conditions.

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