The spatial distribution of precipitation frequency for atmospheric river storms in Northern California

A key missing piece on the role of atmospheric rivers (ARs ) in flooding events in California is knowledge of the detailed spatial distribution of precipitation over the slopes of the Coastal Range and Sierra Nevada. Existing rain gauges provide incomplete information on precipitation in this region, particularly over rugged mountainous terrain. We utilize operational radar data from National Weather Service WSR-88D radars at six locations in California and Nevada to determine the spatial distribution of precipitation frequency for selected AR events. Preliminary results suggest that the southerly moisture transport by the Sierra Barrier Jet becomes more southeasterly toward the north end of the Sacramento Valley and enhances precipitation in the lee of the Coastal Range.