Subseasonal Variations of Wintertime North Pacific Evaporation, Cold Air Surge and Water Vapor Transport

Strong subseasonal variations of oceanic evaporation are observed in the western North Pacific, especially around the Kuroshio current and its extension (KOE) region during winter. This study addresses this variations, and the connection with the cold air surge (CAS) and related atmospheric water vapor transport on subseasonal time scale by using the OAFlux and ERA-Interim daily data. Two dominant modes of oceanic evaporation anomaly are revealed by performing an EOF analysis on subseasonal evaporation anomaly in the region (120°E-120°W, 0°-55°N) for 30 winters. The qualitative description of the connection is obtained by lead-lag regressing the atmospheric variable and water vapor transport and its divergent fields in winter against the two principal components of the EOFs, respectively. Furthermore, three individual physical processes of atmospheric water vapor transport involving multi-scale interactions of wind field and specific humidity are addressed based on the scale decomposition method. Hydroclimate effects on Atmospheric River (AR), storm track and precipitation over the pan-North Pacific region are also discussed.