Simultaneous X-band and K-band study of precipitation to derive specific Z– R relationships

Abstract

Using a simple reflectivity X-band scanning radar and a vertically looking K-band Micro Rain Radar, we investigate the high spatial and temporal variability of precipitating systems at scales internal to the system itself. In order to improve rain rate estimates, we propose to classify rain regimes such that specific Z–R relationships can be applied. These selection schemes are based either on the trend of the reflectivity intensity (increasing, decreasing, stagnating) or on its intensity itself (reflectivity classes) while a last method make use of a statistical approach. Our study shows that using the trend of the rain offers good prospect for improved rain rate restitution but still needs some work to refine the selection criteria. Furthermore, intensity scheme better accommodates the micro-physical properties of the corresponding rain regimes, although possible calibration effects on the high reflectivity periods produce some underestimates of rain rates. Finally, the statistical approach proves efficient but can only be applied on sub-sets of the data for which there is good stability of the reflectivity signal which means that it cannot be applied alone to an entire data set.