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西藏高原汛期大到暴雨的时空分布和环流特征

Spatio-temporal distribution and general circulation of heavy rainfall
in rainy season over Tibetan Plateau

  • 摘要: 利用1980—2011 年西藏高原汛期5—9 月的逐日降水资料,分析此期间高原大到暴雨天气的时空分布特征,包括大到暴雨次数的空间分布、季节差异和年际变化特征,结果表明:大到暴雨日数最多的地区是雅鲁藏布江中下游地区和怒江流域;大到暴雨日数年变化呈单峰分布,7 月大到暴雨最多;近32 a 来,大到暴雨日数呈不显著的增加趋势,1998 年前以2.6 站次/(10 a)趋势增加,之后以12 站次/(10 a)减少。通过同期NCEP/NCAR 再分析资料用合成分析法分析32 a 来88个高原区域性大到暴雨过程的环流特征,其环流形势主要可分为4 种类型:副热带高压型、印度低压型、南北支槽型和高原低涡/切变型,分别占大到暴雨天气过程的36%、17%、21%和26%,其中副热带高压型又可以根据副热带高压的位置分为西北太平洋副热带高压西伸型、伊朗高压东伸型和两高夹一低型。

     

    Abstract: Using daily rainfall dataset in rainy seasons of May to September during 1980 to 2011, the spatio-temporal distribution of heavy rainfall over Tibetan Plateau is analyzed, including the spatial distribution of the heavy rainfall days, its seasonal differences and interannual variation. The results are as follows. The number of heavy rainfall days has its maximum near the Yarlung Zangbo River and the Nujiang River Basins. Its annual distribution showed a single peak only in July. Heavy rain days showed no significant increasing trend in the recent 32 years; the trend shows a 2.6 point-times per 10 a increase before 1998, followed by a 12 point-times per 10 a decrease. Total 88 typical heavy rainfall weather cases are analyzed with composite method using the NCAR/NCEP daily reanalysis dataset and FY2 series Geostationary Meteorological Satellite data. Of them, 4 general models of atmospheric circulation can be classified, i.e., subtropical high model (SHM), Indian Low model (ILM), south-north sub troughs model (STM) and Tibetan Plateau vortex/shear-line model (VSL). SHM constitutes 36%, ILM 17%, STM 21% and VSL 25% of the total cases, respectively. SHM is further classified into 3 subtypes named West Pacific subtropical high model, Iran subtropical high model and low pressure in between the two highs model.

     

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