An Investigation of the Short-Term Predictability of Precipitation Using High-Resolution Composite Radar Observations

Abstract

he short-term predictability of precipitation patterns observed by meteorological radar is an important concept as it establishes a means to characterize precipitation and provides an upper limit on the extent of useful nowcasting. Predictability also varies on the basis of spatial and temporal scales of the observed meteorological phenomena. This paper describes an investigation of the short-term predictability of precipitation patterns containing microalpha (0.2?2 km) to mesobeta (20?200 km) scales using high-resolution (0.5 km?1 min?1 dBZ) composite radar reflectivity data, extending the analysis presented in previous work to smaller space and time scales. An experimental approach is used in which continuous and categorical lifetimes of radar reflectivity fields in Eulerian and Lagrangian space are used to quantify short-term predictability. The space?time scale dependency of short-term predictability is analyzed, and a practical upper limit on the extent of Lagrangian persistence-based nowcasting is estimated. Connections to the predictability of larger scales are made within the context of previous work. The results show that short-term predictability estimates in terms of lifetime are approximately 14?15 and 20?21 min in Eulerian and Lagrangian space, respectively, and suggest that a linear relationship exists between predictability and space?time structure from microalpha to macrobeta (2000?10 000 km) scales.