Modeling studies of landfalling atmospheric rivers and orographic precipitation over northern California

摘要: This study investigated a slow-moving long-wave trough that brought four Atmospheric Rivers (AR) “episodes” within week to the U.S. West Coast from 28 November 3 December 2012, bringing over 500 mm some coastal locations. The highest 6- and 12-hourly rainfall rates (131 195 mm, respectively) northern California occurred during Episode 2 along windward slopes of Santa Lucia Mountains. Surface observations NOAA’s Hydrometeorological Testbed sites in California, available GPS Radio Occultation (RO) vertical profiles Constellation Observing System for Meteorology Ionosphere Climate (COSMIC) satellite mission were both assimilated into WRF-ARW via eight combinations observation nudging, grid 3DVAR improve upstream moisture characteristics quantitative precipitation forecast (QPF) this event. Results 6-hourly maximum period revealed models underestimated observed rate on mountain range. grid-nudging experiments smoothed out finer mesoscale details inner domain may affect final QPFs. Overall, did not use nudging more accurate terms less mean absolute error. In time evolution accumulated forecast, experiment included RAOB COSMIC RO data demonstrated results with least error north central Coastal Range cold-start Sierra Nevada. combined cold start, showed most forecasts. further suggest including surface at frequencies than h having cycling intervals would be beneficial short-to-medium range QPFs high-impact AR events California.