Correlation properties of rainfall rates in the United Kingdom

Rainfall-rate data acquired from the UK Meteorological Office are analysed to obtain spatial correlation properties of rainfall rates at 23 locations in the UK. Correlation coefficients of the rainfall rates between two locations are derived, and dependences of separation distance, season, and integration time on the coefficients are clarified. Conditional correlation coefficients, obtained from rainfall-rate data only larger than 1 mm/h at both locations simultaneously, are obtained and related to the nonconditional coefficients. Finally, joint probability distributions of rainfall rates at two locations are approximated by a bivariate log-normal distribution function, in which a modified correlation coefficient is used.