Associations between Western European air-masses and river flow regimes

This paper identifies and models statistical associations between monthly air-mass frequencies and annual flow regime shape (seasonality) and magnitude for Western Europe, using 141 river and 48 climate stations (1974-1990). The month of regime peak, or month before the peak, is associated with increased (decreased) frequencies of moister (drier) air-masses. Low (high) magnitude regimes are associated with increased (decreased) frequencies of drier air-masses and decreased (increased) frequencies of moister air-masses. An a priori, weighted regional model yields the greatest predictive ability for regime shape; either an a priori, weighted global or regional model produces "best" predictions for regime magnitude. Overall model skill is lower for regime magnitude than shape, with model accuracy varying regionally. The development of methods and process knowledge, as herein, is vital to assessing climate-river flow sensitivity and predicting water resource variability in a changing climate.