Radar and raingauge observations of orographic rain over south Wales

摘要: Eight detailed case studies are summarized to clarify the structure and mechanism of orographically enhanced frontal rain over hills modest height. observations were obtained as part a field project in south Wales which data from 3-dimensionally scanning radar combined with autographic raingauge data. results show that generation orographic is consistent Bergeron's seeder-feeder mechanism, according raindrops upper-level (seeder) clouds wash out small droplets within low-level (feeder) formed hills. It demonstrated enhancement strongly influenced by wind speed. largest rainfall occurred association strong winds, also high relative humidity, below 2km. showed 80% lowest 1.5 km above periods associated passage pre-existing areas precipitation. precise value upwind rate was rather unimportant influencing increment provided exceeded about 0.5mmh−1, These findings compared theoretical calculations based upon washout model Bader Roach.