Dynamical and microphysical retrieval from doppler radar observations using a cloud model and its adjoint. Part II: Retrieval experiments of an observed Florida convective storm

Abstract

The variational Doppler radar analysis system developed in part I of this study is tested on a Florida airmass storm observed during the Convection and Precipitation/Electrification Experiment. The 3D wind, temperature, and microphysical structure of this storm are obtained by minimizing the difference between the radar-observed radial velocities and rainwater mixing ratios (derived from reflectivity) and their model predictions. Retrieval experiments are carried out to assimilate information from one or two radars. The retrieved fields are compared with measurements of two aircraft penetrating the storm at different heights. The retrieved wind, thermodynamical, and microphysical fields indicate that the minimization converges to a solution consistent with the input velocity and rainwater fields. The primary difference between using single-Doppler and dual-Doppler information is the reduction of the peak strength of the storm on the order of 10% when information from only one radar is provided. The comparison with aircraft data shows good agreement for the vertical velocity, buoyancy, and the water vapor mixing ratio in terms of the general structure and strength of the fields, but less agreement for the cloud water and rainwater field. The sensitivities of the retrieval system to the neglect of the time difference at each grid point in a radar volume and to the inclusion of the background information at the initial time of the assimilation period are examined. Both show rather sensitive response. The experiments also show that the microphysical retrieval is quite sensitive to the relation used to derive the rainwater mixing ratio from reflectivity observations.