Disaggregating convective and stratiform precipitation from station weather data

Abstract

We propose an alternative algorithm for disaggregating precipitation amounts into predominantly convective and stratiform based on station weather data. The algorithm is tested at 11 stations in the Czech Republic over 1982–2010, and climatological characteristics and trends of convective and stratiform precipitation are analysed. The results show that, while convective precipitation has a sharp annual cycle, stratiform precipitation is relatively constant throughout the year and does not contribute to the annual cycle of total precipitation. Dependence of precipitation amounts on altitude is stronger for stratiform than convective precipitation consistently across all seasons. The proportion of convective precipitation sharply increases with rising daily temperature in summer, but an analogous relationship is much weaker at the seasonal time scale. Trends in convective precipitation were rising over 1982–2010 in all three seasons in which convective precipitation is important (spring, summer and autumn) and they are stronger than are trends in stratiform precipitation in each season. This shows that the observed increases in total precipitation are mainly due to increases in convective precipitation, and this effect may also be related to an observed warming of surface air temperatures that may enhance instability and support conditions for stronger convection. The resulting time series of convective and stratiform precipitation may have several further applications, including for analysing probability distributions of extremes and evaluating climate models that simulate convective and stratiform precipitation through different parameterizations.