ESRL/PSD Seminar Series

Abstract

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The origin of air mass and moisture associated with Atmospheric Rivers (ARs) along the west coast of the United States are investigated using a simple Lagrangian quasi-isentropic trajectory model. The Atmospheric Rivers (ARs) - filamentary incursions of extratropical cyclones into low latitudes - are well known features which transport water vapor from moist low-latitudes regions toward the extratropical storm tracks along the paths away from the equator. They often occur in conjunction with moisture plumes emanating from the tropics, resulting in extreme precipitation events. Back-trajectories are computed using the NCEP/NCAR, GMAO MERRA, and ECMWF ERA-Interim reanalysis datasets. Reconstructed water vapor mixing ratios are compared to those among reanalysis datasets. Possible mechanisms that link to extreme rainfall events are discussed using clustering and PDF analysis. Storm tracks and the cold season precipitation characteristics in California are also investigated for the storm events during the December 2004-February 2005 period using trajectory model calculations based on GMAO MERRA reanalysis data and observed hydrologic data.

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