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

Subseasonal Variations of Wintertime North Pacific Evaporation, Cold Air Surges and Water Vapor... AbstractThis study addresses subseasonal variations of oceanic evaporation ( E ) over the North Pacific during winter, and the connection with the cold air surges (CAS) and atmospheric water vapor transport using the OAFlux and ERA-Interim daily data. By performing an empirical orthogonal function (EOF) analysis, two dominant modes of subseasonal evaporation anomaly ( E′ ) are identified: a zonally wave-train like pattern (EOF1), and an east positive–west negative dipolar pattern (EOF2) in the midlatitude basin. Further analyses yield the following conclusions. (1) The Siberian high (SH)-related CAS has a crucial role in generation of the EOF1 mode of E′. When the dry and cold airmass passes the warm Kuroshio current and its extension (KOE) region, the increased air–sea temperature and moisture differences and intensified wind speed lead to the above-normal oceanic E , and vice versa. (2) The Aleutian low (AL)-related CAS contributes to the EOF2 mode of E′. The intensified AL transports dramatically colder and drier airmass toward the KOE region, and slightly warmer and wetter one toward the west coast of North America, leading to the east positive–west negative structure of E′ in the midlatitude basin. (3) A quasi-linear relationship exists between E′ and divergent water vapor transport anomalies over the KOE region. Positive (negative) E′ is generally accompanied by anomalous vapor source (sink). (4) The divergent water vapor transport anomalies associated with the two EOFs are preliminarily decided by their individual lower-level wind fields anomalies, and secondly by the meridional inhomogeneity of subseasonal specific humidity anomalies. Hydroclimate effects on precipitation over the pan-North Pacific region are also discussed. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Climate American Meteorological Society

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

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Publisher
American Meteorological Society
Copyright
Copyright © American Meteorological Society
ISSN
1520-0442
D.O.I.
10.1175/JCLI-D-17-0140.1
Publisher site
See Article on Publisher Site

Abstract

AbstractThis study addresses subseasonal variations of oceanic evaporation ( E ) over the North Pacific during winter, and the connection with the cold air surges (CAS) and atmospheric water vapor transport using the OAFlux and ERA-Interim daily data. By performing an empirical orthogonal function (EOF) analysis, two dominant modes of subseasonal evaporation anomaly ( E′ ) are identified: a zonally wave-train like pattern (EOF1), and an east positive–west negative dipolar pattern (EOF2) in the midlatitude basin. Further analyses yield the following conclusions. (1) The Siberian high (SH)-related CAS has a crucial role in generation of the EOF1 mode of E′. When the dry and cold airmass passes the warm Kuroshio current and its extension (KOE) region, the increased air–sea temperature and moisture differences and intensified wind speed lead to the above-normal oceanic E , and vice versa. (2) The Aleutian low (AL)-related CAS contributes to the EOF2 mode of E′. The intensified AL transports dramatically colder and drier airmass toward the KOE region, and slightly warmer and wetter one toward the west coast of North America, leading to the east positive–west negative structure of E′ in the midlatitude basin. (3) A quasi-linear relationship exists between E′ and divergent water vapor transport anomalies over the KOE region. Positive (negative) E′ is generally accompanied by anomalous vapor source (sink). (4) The divergent water vapor transport anomalies associated with the two EOFs are preliminarily decided by their individual lower-level wind fields anomalies, and secondly by the meridional inhomogeneity of subseasonal specific humidity anomalies. Hydroclimate effects on precipitation over the pan-North Pacific region are also discussed.

Journal

Journal of ClimateAmerican Meteorological Society

Published: Aug 30, 2017

References

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