A 10-yr Climatology of Tibetan Plateau Vortices with NCEP Climate Forecast System Reanalysis
Tóm tắt
A plateau vortex refers to a shallow meso-α-scale cyclonic vortex that is usually confined to near-surface levels (500 hPa) over the Tibetan Plateau during warm seasons. It is the major precipitation-producing weather system over the plateau, but the knowledge of its climatology and understanding of generation mechanisms are limited because of the lack of adequate observations in this harsh mountainous region. In this study, the high-resolution NCEP Climate Forecast System Reanalysis data have been used to perform a statistical survey of these vortices over 10 warm seasons (April–October of 2000–09). The purpose is to document their climatological features, including genesis, size, life cycle, propagation, and diurnal variation.Results show that ~103 plateau vortices occur on average every year. Most are detected from May through August, with the maximum monthly count in July. The primary area of origin exhibits a west–east orientation in correspondence with a large-scale confluence zone, and the most concentrated source lies in the area of 33°–36°N, 84°–90°E in the high elevated central and western plateau. Significant diurnal variations are observed, characteristic of a preferential genesis during late afternoon to evening hours and a late night dissipation peak. The vortex events have an average life span of ~15 h and an average horizontal dimension (effective diameter) of ~280 km. In accordance with the steering environmental flow, an overwhelming majority travel eastward with a mean translation speed of ~10 m s−1. A small fraction of systems (approximately nine cases annually) move off the plateau, predominantly from the eastern edge.
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Tài liệu tham khảo
Carbone, 2002, Inferences of predictability associated with warm season precipitation episodes, J. Atmos. Sci., 59, 2033, 10.1175/1520-0469(2002)059<2033:IOPAWW>2.0.CO;2
Chen, 1996, Numerical simulation of the formation and development of vortices over the Qinghai-Xizang Plateau in summer, Sci. Atmos. Sin., 20, 491
Chen, 2007
Chen, 2004, A case study on coupling interaction between plateau and southwest vortexes, Plateau Meteor., 23, 75
Fritsch, 1994, Warm core vortex amplification over land, J. Atmos. Sci., 51, 1780, 10.1175/1520-0469(1994)051<1780:WCVAOL>2.0.CO;2
He, 2009, The dynamic diagnosis on easterward moving characteristics and developing mechanism of two Tibetan Plateau vortex processes, Acta Meteor. Sin., 67, 599
Huang, 2007, Synoptic and dynamic diagnostic analysis for an eastward-moving plateau vortex, Sci. Meteor. Sin., S1, 36
Laing, 2008, The propagation and diurnal cycles of deep convection in northern tropical Africa, Quart. J. Roy. Meteor. Soc., 134, 93, 10.1002/qj.194
Lhasa Research Group on Qinghai-Xizang Plateau Meteorology, 1981
Liu, 2009, Diurnal variations of summertime precipitation over the Tibetan Plateau in relation to orographically-induced regional circulations, Environ. Res. Lett., 4, 045203, 10.1088/1748-9326/4/4/045203
Luo, 1992
National Climate Center of CMA, 1998
National Meteorological Center and National Satellite Meteorological Center of CMA, 1998
Qian, 1984
Saha, 2010, The NCEP Climate Forecast System Reanalysis, Bull. Amer. Meteor. Soc., 91, 1015, 10.1175/2010BAMS3001.1
Tao, 1981, Observational evidence of the influence of the Qinghai-Xizang (Tibet) Plateau on the occurrence of heavy rain and severe convective storms in China, Bull. Amer. Meteor. Soc., 62, 23, 10.1175/1520-0477(1981)062<0023:OEOTIO>2.0.CO;2
Wang, 1987, The development mechanism for Tibetan Plateau warm vortices, J. Atmos. Sci., 44, 2978, 10.1175/1520-0469(1987)044<2978:TDMFTP>2.0.CO;2
Wang, 2009, Statistical study of the plateau low vortex activities, Plateau Meteor., 28, 64
Yang, 2001, On flood-causing torrential rainfall in the upstream district of Changjiang River in 1998, Meteor. Mon., 27, 9
Ye, 1979
Yu, 2006, Observational analysis on the movement of vortices before/after moving out of the Tibetan Plateau, Plateau Meteor., 64, 392
Yu, 2007, The middle-to-upper-level circulation analyses of the plateau vortex moving out of plateau and influencing flood in east China in recent years, Plateau Meteor., 26, 466
Zhao, 2010, The dynamic diagnosis of eastward moving characteristics and developing mechanism of two Tibetan Plateau vortex processes, Plateau Meteor., 29, 819
Zhou, 2009, Diagnostic analysis of vorticity in a heavy rain event under interaction of plateau vortex and southwest vortex, Meteor. Sci. Technol., 37, 538