Identification

Title

Climatology and structures of southwest vortices in the NCEP climate forecast system reanalysis

Abstract

The southwest vortex (SWV) is a meso-a-scale cyclonic low pressure system originating in southwest China. It is a high-impact precipitation-generating weather system in this region and a large downstream area. A climatology of the SWV over 1979-2010 is presented here. Results indicate that the SWV is a common regional weather system with about 73 annual occurrences. Two primary genesis regions are identified, one in the Sichuan basin and another one in the southeast flank of the Tibetan Plateau. SWV genesis displays seasonality with a spring-summer preference and diurnal variations. The average life cycle, horizontal dimension, and translation speed are 15.1 h, 435 km, and 8.6 m s(-1), respectively. SWVs are classified into four types that show regional and seasonal contrasts in structure. In type I, the winter-spring elevated dry vortex in the basin is vertically confined to a shallow layer between 850 and 600 hPa and tilts northeastward. The low-level vortex has a cold center, and the middle to upper levels feature baroclinicity. In type II, the nighttime warm-season precipitating vortex system in the basin has a deep structure with the cyclonic vorticity extending from the surface into the upper troposphere. The nonsevere precipitating vortex (type IIa) is weakly baroclinic and tilts northward with height, whereas the severe precipitating vortex (type IIb) is vertically aligned. For type III, in the southern mountains, the shallow surface-based vortex develops in a well-mixed boundary layer and vertically tilts in the upslope direction and has a warm and lowhumidity core. For type IV, the heavy precipitating vortex in the mountainous region is large, deep, and nearly upright with a fairly barotropic environment.

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document

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http://n2t.net/ark:/85065/d7bg2qpg

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Dataset language

eng

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geoscientificInformation

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title

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reference date

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publication

effective date

2016-01-01T00:00:00Z

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publication

effective date

2016-11-01T00:00:00Z

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Copyright YYYY American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be "fair use" under Section 107 or that satisfies the conditions specified in Section 108 of the U.S. Copyright Law (17 USC, as revised by P.L. 94-553) does not require the Society's permission. Republication, systematic reproduction, posting in electronic form on servers, or other uses of this material, except as exempted by the above statements, requires written permission or license from the AMS. Additional details are provided in the AMS Copyright Policies, available from the AMS at 617-227-2425 or amspubs@ametsoc.org. Permission to place a copy of this work on this server has been provided by the AMS. The AMS does not guarantee that the copy provided here is an accurate copy of the published work.

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None

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OpenSky Support

organisation name

UCAR/NCAR - Library

full postal address

PO Box 3000

Boulder

80307-3000

email address

opensky@ucar.edu

web address

http://opensky.ucar.edu/

name: homepage

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pointOfContact

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