19th Conf. on weather Analysis and Forecasting/15th Conf. on Numerical Weather Prediction
21st Conf. on Severe Local Storms


Recent Advances in Diabatic Initialization of a Non-hydrostatic Numerical Model

Keith A. Brewster, CAPS/Univ. of Oklahoma, Norman, OK

Successful initialization of nonhydrostatic storm-scale models with ongoing convection requires a complete specification of the hydrometeor fields and the temperature perturbations resulting from condensation within the cloud updrafts. Improvements to previously described methods for deriving these fields from radar and other data in the ARPS Data Assimilation System (ADAS) are described and tested in a severe storm case. It is found that the initialization of temperature perturbations is more accurately done using parcel trajectories than with latent heat derived from the hydrometeor increments. The temperature perturbation initialization is also aided by the use of an estimate of updraft location derived from Doppler wind data. Further improvements were obtained with updated equations relating the measured radar reflectivity and the cloud hydrometeors. This method, which does not require more than one volume scan from each radar, can be an effective means to initialize a non-hydrostatic model or can be utilized as a pre-processor for time-dependent data assimilation techniques.

extended abstract  Extended Abstract (592K)

Joint Session 6, The Use of Mesoscale Models in Severe Local Storms Forecasting (Joint with 21SLS and 19WAF/15NWP)
Tuesday, 13 August 2002, 11:15 AM-12:00 PM

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