TROPICAL RAIN CLASSIFICATION AND ESTIMATION OF RAIN FROM Z-R (REFLECTIVITY-RAIN RATE) RELATIONSHIPS

Abstract

A Z-R relation is derived using a data set which consists of nine rain events selected from Singapore's drop size distribution. Rain events are separated into convective and stratiform types of rain using two methods: the Gamache-Houze method, a simple threshold technique, and the Atlas-Ulbrich method. In the Atlas-Ulbrich method, the variability of the rain integral parameters R; Z, Nw, D0 and gamma model parameter are used for the classiflcation of rain into convective, stratiform and transition. Z-R relations are derived for each type of rain after classiflcation. The changes in the coe-cients of the Z-R relations for difierent rain events are plotted and analyzed. The Z-R relations of the difierent methods using the Singapore data are compared and analyzed. It is concluded that the coe-cient A of the Z-R relation is higher for the convective stage followed by the stratiform and transition stages. The coe-cient b values are higher for the transition stage followed by the stratiform and convective stages. Re∞ectivities are extracted from RADAR data above NTU site for rain events and compared with the re∞ectivities derived from the distrometer data. Rain rates retrieved from RADAR data using the proposed relations from Singapore's data set are compared with the distrometer rain rates. The RADAR extracted rain rates are found to be constantly lower than the distrometer derived rain rates but matches well.