ESTIMATION OF AREA RAIN-RATE FIRST PRODUCT MOMENT AND COVARIANCE BY THE THRESHOLD METHOD

Abstract

Threshold methods for estimating area rain-rate first product moment and covariance are proposed. Empirically, we observed a strong correlation between the first product moment and the probability of exceeding two threshold values for two geographically different locations, land and island, for Tokyo Metropolitan rainfall data. Theoretical optimal thresholds under the bivariate lognormal distibution as a model are chosen by minimizing the asymptotic normalized variance. A good agreement between the emprical and theoretical results is observed and this observation can be reproduced for other locations too.