Western European water vapor flux-southwest England rainfall associations

The relationship between monthly rainfall anomalies over southwest England and vapor flux anomalies at five western European radiosonde stations (Bres t, La Coruna, Crawley, Keflavik, Valentia) is analyzed over the period from January 1961 to June 1997. Monthly rainfall anomalies are positively assoc iated with zonal, meridional, and vector flux anomalies over the British Is les, France, and Spain but are inversely related to the flux anomalies of t he Icelandic station, Keflavik. An enhanced westerly and/or southerly flux over Iceland is thus more likely to be accompanied by below-average rainfal l over southwest England. A six-variable vapor flux anomaly model can accou nt for 69.0% of the intermonthly variance in a regional rainfall anomaly (R RA) index. Independent validation of this equation over the period from Jul y 1997 to May 2000 confirmed the physical robustness of this equation (vari ance = 61.5%, number of months = 35). Vapor flux rainfall anomaly associati ons vary not only intraregionally and seasonally but also between drought e vents. Study results reveal that RRA is more dependent on zonal flux variat ions during the winter. RRA is also generally more dependent on variations in Brest's 850-hPa zonal flux anomaly during drought events when the contro lling anticyclone is positioned to the north and east of Britain rather tha n to the south and west.