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Zhong L.,Chinese Academy of Meteorological Sciences | Mu R.,Chongqing Meteorological Bureau | Zhang D.,University of Maryland University College | Zhao P.,Chinese Academy of Meteorological Sciences | And 2 more authors.
Journal of Geophysical Research D: Atmospheres | Year: 2015

An observational analysis of the multiscale processes leading to the extreme rainfall event in Beijing on 21 July 2012 is performed using rain gauge records, Doppler radar, and satellite products, radiosondes, and atmospheric analysis. This rainstorm process included two heavy rainfall stages in the early afternoon [1300-1400 Beijing Standard time (BST) (0500-0600 UTC)] and the evening (1600-1900 BST), respectively. The first stage exhibited warm-sector rainfall characteristics as it occurred under low-level warm and moist southeasterly flows ahead of a synoptic-scale vortex and a cold front. When the southeasterly flows turned northeastward along a southwest-northeast oriented mountain range in western Beijing, mesoscale convergence centers formed on the windward side of the mountain range in the early afternoon, initiating moist convection. Radar echo showed a northeastward propagation as these flows extended northward. Despite the shallowness of moist convection in the warm sector, atmospheric liquid water content showed the rapid accumulation, and a large amount of supercooled water and/or ice particles was possibly accumulated above the melting level. These appeared to contribute to the occurrence of the largest rainfall rate. During the second stage, as the synoptic-scale vortex moved across Beijing, with southeastward intrusion of its northwesterly flows, the vortex-associated lifting caused the generation of strong updrafts aloft and formed deep convection. This facilitated the further accumulation of supercooled water and/or ice particles above the melting level. Radar echo propagated southeastward. Liquid water showed a decrease in the lower troposphere, and there were strong downdrafts due to evaporation of liquid water particles, which resulted in the relatively weak hourly rainfall rates. Key Points We compare differences between warm-sector and vortex rainstorms in north China High-resolution rain gauge and Doppler radar data are used in mesoscale analysis Shallow convection produces heavy rainfall in warm sector with much liquid water © 2015. The Authors. Source


Wang Y.,Chinese Academy of Meteorological Sciences | Xu X.,Chinese Academy of Meteorological Sciences | Lupo A.R.,University of Missouri | Li P.,Shanxi Meteorological Observatory | Yin Z.,Beijing Meteorological Bureau
Journal of Geophysical Research: Atmospheres | Year: 2011

By using numerical experiments and observational data, this study examined the uplifting and thermal effects of the Tibetan Plateau (TP) on downstream airflow in early summer. Our principal finding is that the uplifting effect of the TP in an Atmospheric General Climate Model (AGCM), including air made warmer than its surroundings climatologically by the huge topography, results mainly in a local response in the atmosphere, i.e., a large ridge north of the TP in the troposphere in June. There was no Rossby wave response to the uplifting effect. However, simulations and statistical analyses strongly suggested that the anomalous TP atmospheric heating associated with global climate warming tends to excite a Rossby wave originating from the TP via Lake Baikal and continuing to move through the Okhotsk Sea to downstream areas. The appearance of the Rossby wave coincides with the positive phase of the eastern part of a normal stationary wave originating in the Caspian Sea traveling via the Okhotsk Sea to the sea area east of Japan that often occurs in June. Thus the TP atmospheric heating acts as an additional wave source in relaying and enhancing the eastern part of the normal wave propagation. Its path usually lies beyond 40°N latitude, which is where the westerly jet stream takes over the role of waveguide. Copyright © 2011 by the American Geophysical Union. Source


Hu L.,National Satellite Meteorological Center | Zhao H.,Shanxi Meteorological Observatory | Ma Y.,Shanxi Meteorological Observatory
Zhongguo Jiguang/Chinese Journal of Lasers | Year: 2014

For the next generation of Chinese geostationary meteorological satellites (FY-4) an optical lightning mapping sensor is planned to observe lightning on a real-time, continual basis. The measurement will detect the radiance discharged by lightning and transferred up to the cloud top at a near-infrared band. One important and urgent attention of the pre-study is how the instrument observation geometry quantitatively impact the received signals. A Monte Carlo approach is applied for simulating the transfer of lightning and the lightning radiation signatures which will be obtained by FY-4 lightning mapping sensor. The study focuses on the quantitative relationships between the observed lightning radiance and several key observation geometry parameters, such as satellite observation angle, pixel size and the horizontal location of lightning in the pixel. This will provide extremely valuable informations for the future application of lightning data observed by FY-4 satellite. Source

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