Paul L. Smith and Donna V. Kliche

ABSTRACT

Several algorithms have been developed for polarimetric radars to infer the characteristics of hydrometeors in the radar contributing region. Efforts are under way to evaluate those algorithms through comparisons with in situ data from the same region. Unless the aircraft flight plan and radar scan strategy can be closely linked in real time, coordinated pairs of observations must be selected from the aircraft cloud penetrations and the radar scans. An algorithm developed by S. Goeke performs this function.

Using her algorithm to select the "matching" data sets, S-Pol radar particle classifications from the 29 June 2000 STEPS storm are compared with particle images from the T-28 storm penetrating aircraft to help evaluate the radar algorithm. Consideration of the aircraft temperature, updraft and LWC data aids in interpreting the particle images and establishing plausibility of the inferred particle types.

Early findings include:

· The algorithm appears to be effective in identifying the presence of hail.

· Raindrop images are not consistently found in regions where the algorithm indicates the presence of rain mixed with graupel or hail.

· In regions with graupel, aggregates, or similar particles the algorithm classification appears to be quite sensitive to the presence or absence of a usable cross-polarized component of the echo (giving valid LDR data).