Weather radar anaprop conditions at a Mediterranean coastal site

Many weather radars are affected by some type of anomalous propagation (AP) with a wide variety of frequency and intensity. Some geographical areas have been described to be particularly prone to AP, Even in some sites, AP is not statistically abnormal at all but dominant. Severe AP cases have been reported in coastal areas affected by strong temperature inversions and humidity contrasts such as the Baltic Sea, the Indic Ocean or the Mediterranean. In this paper we present average and extreme propagation conditions in the coastal area of Barcelona (NE Spain) calculated using three years of radiosonde data. Occurrence of different propagation conditions is discussed and related to local prevailing circulations such as the sea breeze with particular interest in the nearby Vallirana weather radar. The effect of some extreme ducting episodes seems to be remarkable in beam blocking correction procedures leading to wrong precipitation estimates when anaprop and rainfall occur at the same time. The use of radiosonde and mesoscale NWP data to derive operationally propagation conditions jointly with other existing techniques based in the analysis of radar data is overviewed. (C) 2000 Elsevier Science Ltd. All rights reserved.