A Physically Based Method for the Conversion of Rainfall Statistics From Long to Short Integration Time

A new physically based methodology for the derivation of the complementary cumulative distribution function (CCDF) of point rain rate with 1-minute integration time, P (R )₁ , from a rain rate CCDF with longer integration time T, P (R )T, up to 60 min is presented. The method is based on the simulation of the integration process of a virtual raingauge, over which the population of synthetic exponential cells, provided by the EXCELL model for the representation of the local meteorological environment, translate according to the local mean yearly wind velocity at the 600 hPa isobar level, extracted from the ERA-15 database. The performance of the proposed conversion method is assessed against an extensive database of rainfall statistics measured in various climatic regions and with different integration times. Results, compared with those achieved by the ITU-R conversion method currently in force, highlight the benefits of using a physical approach to the conversion of rainfall statistics.