Influence of large-scale climatic circulation on precipitation and river discharge for a selection of British catchments

This study investigates the spatial and temporal variation of large-scale climatic control on precipitation and discharge for three near-natural British river basins; the Dun (south Britain), Dyfi (west Britain) and Ewe (northwest Britain). Monthly ranked correlation analysis is undertaken to establish concurrent statistical relationships between large-scale gridded atmospheric data and basin precipitation and discharge. For the Dyfi and Ewe, precipitation and discharge have significant negative correlation with mean sea level pressure, MSLP and significant positive correlation with the zonal wind. The Dun also has significant negative correlation between MSLP and precipitation, but not for discharge, which illustrates the effect of basin properties. Regions of strongest correlation shift from month-to-month, highlighting the different precipitation and discharge generating weather systems throughout the year. Because the North Atlantic Oscillation Index has a fixed geographical definition, it can not detect the seasonal movements, and thus has systemically lower correlation with basin precipitation and discharge when compared with gridded data.