A Study on Typhoon-Induced Rainfalls over Beijing: Statistics and Case Analysis |
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Authors: | Deping Ding Ying Li |
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Institution: | Beijing Meteorological Bureau, Beijing 100089;State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081 |
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Abstract: | Based on the Shanghai Typhoon Institute (STI) Typhoon Year Book and typhoon precipitation data, Japan Meteorological Agency
satellite TBB data, and National Centers for Environmental Prediction (NCEP) reanalysis data, the climatic characteristics
of rainfalls in Beijing associated with typhoons were analyzed for the period 1949–2006, and two typhoon cases with remarkable
differences in rainfall intensity over Beijing were compared and diagnosed. The 58-yr statistical results show that rainfall
events associated with typhoons occurred in Beijing about once every three years during June–September. These typhoons were
mainly active in the region 20°–50°N, 109°–128°E and most of them moved northwestward while the others turned to the northeast.
The typhoon rainfall over Beijing in general sustained for 2–5 days. Typhoon centers were usually located in the areas from
Jiangxi to Anhui, the Yellow Sea, or near Beijing, when rainstorms occurred over Beijing. Case study indicates that the 2-day
torrential rainfall event that happened in Beijing in 1984 was due to the interaction between Typhoon Freda (8407) and a westerly
trough, while only a medium-strength rainfall event occurred in Beijing in 2005 in spite of the dominating cyclonic circulation
of Typhoon Matsa (0509) directly over Beijing. It is found that both Freda and Matsa underwent extratropical transition and
possessed an asymmetric structure. The rainfall difference was caused by the fact that Beijing was located in different convective
development areas of the two typhoons. On the other hand, the lifting conditions were different although plentiful atmospheric
moisture and convective unstable energy existed over Beijing during both events. The ascending motion of warm southerly in
Beijing was stronger and deeper and a larger vertical wind shear was associated with Typhoon Freda. However, the lifting of
water vapor was restrained by the descending motion of northerly cold airflow in Beijing under the impact of Typhoon Matsa.
Besides, it is also found that topography played an important role in the typhoon rainfall over Beijing. |
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Keywords: | Beijing rainfall typhoon climatic features interaction |
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