RAINFALL PARAMETERS DERIVED FROM DUAL POLARIZATION RADAR MEASUREMENTS COMPARED WITH A GROUND-BASED DISDROMETER IN CENTRAL ILLINOIS.

Using radars for accurate measurements of rainfall parameters (rainfall rate, water content, etc. ) is discussed. The conventional procedure for estimating rainfall rate (R) from radar reflectivity factor (Z) measurements is to use a Z-R relationship. A technique which utilizes dual linear polarization measurements to improve the accuracy of radar estimates of rainfall rate over the Z-R method has been promising. A case study is reported that compares rainfall rates estimated from dual linear polarization radar measurements and ground-based disdrometer measurements of raindrop size distributions in central Illinois. The disdrometer in this experiment was located 47. 1 km from the radar. In order to deal with the problems resulting from this large separation, a method that may be used in such comparative studies was also developed.