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利用NCEP/NCAR再分析资料计算得到江淮流域1961–2011年前冬持续时间, 分析其时空变化特征, 并进一步探究它与后期江淮流域夏季降水的关系. 结果表明, 江淮流域前冬持续时间存在着明显的年际和年代际变化, 前冬持续时间显著偏长年份比偏短年份的前冬温度低、气压高、北风强, 表明温度、气压、经向风可能是反映江淮流域前冬持续时间的关键因子, 且不同区域各气象要素对季节长度的影响存在一定差异; 1961–2011年江淮流域前冬持续时间与该区域夏季降水呈显著正相关关系; 统计分析亦发现, 前冬持续时间显著偏长(偏短)的代表年份中, 夏季降水以偏多(偏少)为主; 对典型代表年份环流场进行合成分析发现, 前冬持续时间显著偏长时, 乌拉尔山与鄂霍次克海地区夏季易形成阻塞形势, 进而会对江淮流域夏季降水产生影响; 最后利用奇异值分解从空间场相关的角度探讨了两者的联系, 发现江淮流域夏季降水与前冬持续时间存在非常显著的关系.By using NCEP/NCAR reanalysis datasets, the length of preceding winter (LPW) in the Yangtze-Huaihe River valley (YHRV) from 1961 to 2011 is derived. We investigate the variation of LPW and the relationship between LPW and following summer precipitation, and the results indicate that LPW clearly displays interannual and decadal changes in the period of 1961-2011. The variation of LPW is closely related to temperature, pressure and meridional wind speed, statistical analysis indicates that a longer LPW corresponds to a lower temperature, a higher pressure and a stronger meridional wind, which shows that temperature, pressure, meridional wind are probably the key factors of adjusting the LPW. These characteristics also vary from region to region. There is significantly positive correlation between the summer precipitation and LPW. The statistical analysis also indicates that the longer (shorter) the LPW, the more (less) the summer precipitation in YHRV is. The comprehensive analysis of the circulation field indicates that when LPW is significantly longer than climatic status, a blocking situation is formed easily in the region of Ural Mountains and the Sea of Okhotsk in the summer, which will affect the summer rainfall in YHRV. By using singular value decomposition method, it is found that the relationship between summer precipitation and LPW is also very significant.
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Keywords:
- Yangtze-Huaihe river valley/
- season division/
- lengths of the preceding winter/
- summer flood season precipitation
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