Presentation PDF (1.6 MB)
Over the course of the NASA TRMM Ground Validation Campaigns, The NOAA Aeronomy Laboratory collected several large data sets of profiler-disdrometer reflectivity comparisons, utilizing a Joss-Waldvogel disdrometer (JWD) paired with a 915 and/or 2835 MHz precipitation profiler radar. Examples of successful calibrations and reflectivity comparisons have been presented elsewhere. Here we examine subtle features of these observations made visible by reflectivity binning and time averaging. This procedure allowed us to objectively characterize the degree of contamination by clear air echo at low reflectivities and the saturation thresholds for our higher-powered wind profiling radars, as well as verify the lack of saturation of our lower powered precipitation profilers. In addition, we were able to characterize a reflectivity dependent bias in the particular Joss-Waldvogel disdrometer (JWD) we used. With respect to this last observation, an autopsy of the JWD after the TRMM KWAJEX campaign revealed that its moving parts were highly weathered. A recent profiler/JWD comparison at the NASA Wallops Island disdrometer test bed with a newly reconditioned JWD showed no such reflectivity dependent bias. Without cross-comparison, biases such as those found above can be difficult to detect, let alone characterize. Consequently, these studies reinforce the precept that continual instrument cross-validation should be a key process in the formation of climatological databases.
Supplementary URL: http://ams.confex.com/ams/15AppClimate/presentationreview.cgi?username=93839&password=755678