Atmospheric Radar Research Seminar Series presents...
The Impact of Evaporation on Polarimetric Characteristics of Rain
Matthew R. Kumjian
The University of Oklahoma School of Meteorology
Atmospheric Radar Research Center, Norman, OK
26 February 2009, 1:00 PM
National Weather Center, Room 5600
120 David L. Boren Blvd.
University of Oklahoma
Norman, OK
Directions to the NWC (.pdf, 60 kb)
The National Weather Service WSR-88D radar network will be undergoing an upgrade to allow dual-polarization capabilities, which is scheduled to begin this year. Therefore, it is imperative to understand the impact of microphysical processes on the polarimetric variables. Though melting and size sorting of hydrometeors has been investigated, there has been relatively little focus devoted to the impact of evaporation on the polarimetric characteristics of rainfall. In this study, a simple explicit bin microphysics one-dimensional model is constructed to quantify the impact of evaporation in different thermodynamic conditions and with varying rainfall rates and initial drop size distributions aloft.
In addition to exploring and quantifying the effects of evaporation, we offer a simple method of estimating the amount of evaporation that occurs in a given environment based on polarimetric radar measurements of ZH and ZDR aloft. Such a technique may be useful to operational meteorologists and hydrologists in estimating the amount of precipitation reaching the surface, especially in regions of poor low-level radar coverage such as mountainous regions in the western United States or locations at large distances from the radar.