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Qiaoping Li, Song Yang, Tongwen Wu, and Xiangwen Liu

1. Introduction Cold surges are the most conspicuous weather events during winter in East Asia, especially those associated with intensified Siberian high (SH), and exert a major impact on socioeconomical human activities. During the occurrence of a cold surge, cold air breaks out and moves southward along the edge of the expanded SH, leading to severe weather events such as a large temperature drop, strong wind, and heavy freezing rain or snowfall ( Boyle and Chen 1987 ; Ding 1994 ; Chan and

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Joseph M. Sienkiewicz, John D. Locatelli, Peter V. Hobbs, and Bart Geerts

rainbands were observed in association with the frontal system. All of these rainbands developed withinthe region of coverage of the NWS WSR-57 radar at Cape Hatteras, North Carolina. Two were upper-levelfeatures, associated with a prefrontal surge of cold air and the main push of cold dry air aloft. These rainbandswere similar in structure to prefrontal surge and wide cold-frontal rainbands, respectively, observed on thePacific Northwest Coast. The microphysical and small mesoscale structures of the

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C-P. Chang and K. M. W. Lau

-scale disturbances. The main findings suggest a picture of coherent variations of several planetary-scale circulationfeatures which may be described by the following sequence of events: 1) The East Asia local Hadley circulation strengthens as the cooling due to .cold air advection overnorthern China increases prior to a cold surge on the South China coast. This is accompanied by anintensified jet stream maximum centered over Japan, which is apparently a result of the upstreamacceleration by the upper level

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Brian A. Colle and Clifford F. Mass

VOLUME 123 MONTHLY WEATHER REVIEW SEPTEMBER 1995The Structure and Evolution of Cold Surges East of the Rocky Mountains BRIAN A. COLLE AND CLIFFORD F. MASSDepartment of Atmospheric Sciences, University of Washington, Seattle, Washington(Manuscript received 3 May 1994, in final form 10 January 1995) ABSTRACT Northerly surges of cold air often move southward along the

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James S. Boyle

1985) East Asian cold surges during two periods of contrasting surge intensity, December 1974 (strong) and December1978 (weak), are studied. It is shown that the midlatitude mechanisms initiating cold surges during both monthsare quite similar in nature. Synoptic scale short waves passing through the long-wave trough position near theEast Asian coast act to release the cold air southward from the main reservoir over eastern Siberia. Dynamicdescent is initiated by these synoptic scale waves

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merging ofwith a similar situation in which gales were anticipated but the rising currents with strong winds aloft seemed to havedid not occur. In both cases, cold air accumulated over reinforced upslope winds near the surface in the first case,Syria and Northern Iraq. In the first case, deep moist which lifted the warm air in front of the advancing coldconvection over the mountains of Northwestern Iran was air. This explanation is made plausible by a simple energycoupled with a rapid southwest surge

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C-P. Chang, J. E. Erickson, and K. M. Lau

pre-Winter Monsoon Experiment (Winter MONEI() pilot study to examine the possibleinteractions between the northeasterly cold surges off the Asia continent and the convective disturbancesin the near equatorial region. Based on surface and 850 mb wind and temperature analyses, satellitedata, and synoptic weather charts of the Hong Kong Royal Observatory, a sequence of synopticevents associated with two cold air surges and near-equatorial disturbances over the Winter MONEXarea of South China Sea and

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Jennifer Fletcher, Shannon Mason, and Christian Jakob

1. Introduction Marine cold air outbreaks (MCAOs) are high-impact weather events in which air masses of polar or cold continental origin are advected over relatively warm open ocean. The resulting instability can lead to strong boundary layer turbulence and surface heat loss from the ocean ( Brümmer 1996 ), as well as severe weather such as polar lows and boundary layer fronts ( Businger 1985 ; Carleton and Song 1997 ; Rasmussen and Turner 2003 ). During MCAOs the air–sea temperature

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Richard H. Johnson and Jeffery R. Zimmerman

data have been used to document the boundary layerstructure over the South China Sea during the period of a 3-day moderate cold surge that occurred during theDecemlaer 1978 Winter Monsoon Experiment (Winter MONEX). Throughout the cold surge event, equatorward deepening of the cumulus layer is observed over the northernSouth China Sea (to the south of a coastal cloud-free region) as cold air streaming off the coast encounterssubstantial, surface, sensible and latent heat fluxes. Following the

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Carolina S. Vera and Paula K. Vigliarolo

opportune superposition of a short-wave trough, when the long-wave trough in the Atlantic neared peak development, might be an important factor in introducing anomalously cold air into the subtropics. Similar precursors have also been found in cold surges events in the lee of other mountain ranges [ Colle and Mass (1995) and Schultz et al. (1997) on the lee side of the Rockies, Wu and Chan (1997) for cold surges at the east side of the Tibetan Plateau, among others]. Schultz et al. (1998) showed

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