2—5月我国低温连阴雨和南方冷害时空特征

The Spatial and Temporal Characteristics of China Continuous Cold Rainy Weather and South Cold Damage from February to May

  • 摘要: 利用1951-2007年25月我国546个站逐日平均气温和24h降水量观测资料以及南方早稻区代表站日照时数观测资料,定义了全国统一的低温连阴雨标准和早稻区低温冷害标准,并采用统计分析方法,给出了1951—2007年2—5月我国低温连阴雨和低温冷害的时空变化特征。57年中,2—5月低温连阴雨平均日数以四川盆地、贵州、江南西部和华南最多。2—5月,低温连阴雨日数呈现由长江以南向黄河流域逐渐增加且范围扩大的特征。各月低温连阴雨日数20世纪50年代较少,1997年后呈现显著减少的趋势。1963-1996年,各月低温连阴雨日数的EOF第1特征向量呈现出月际反相变化,并有年代际振荡特征。对于各地区的早稻播种而言,1951年以来,四川盆地和长江中下游地区低温冷害较华南地区偏多、偏重,但2000年以来各早稻区的低温冷害都在减少,早稻区低温冷害存在显著的年际和年代际周期振荡特征。

     

    Abstract: Based on observed daily temperature and precipitation data of China 546 observation stations and daily sunlight hours of some representative stations in spring rice producing regions from 1951 to 2007, a uniform standard for continuous cold rainy weather all over China and cold damage of spring rice producing regions is defined. Temporal and spatial characteristics are also summarized using some statistical methods, for example, Empirical Orthogonal Function Decomposition (EOF) and Morlet wavelet analysis. The results show that usually more continuous cold rainy weather occur in the regions of Sichuan Basin, Guizhou Province, western parts in the south of the Yangtze and South China during the period of February to May. The maximum occurring in Sichuan Basin and Guizhou Province reaches up to 4-6 days per spring month averaged from 1951-2007. The scope of continuous cold rainy weather gradually expands northward and westward from the south of the Yangtze to the Yellow River Basin in spring, in which obviously continuous cold rain weather occurs in the southeastern parts of Northwest China and the southeastern Tibet since March and in Northeast China in May. The decadal changes of the continuous cold rainy days in spring denote that there are less days than climate average during the 1950s and from 1997 to present, and the temporal variations of the first EOF mode of the continuous cold rainy days of China show the characteristics of decade oscillations including inter-month seesaw during the period of 1963-1996.The spatial and temporal characteristics of cold damage for China spring rice producing regions during the period of 1951-2007 show that the frequency of cold damage occurring in Sichuan Basin and mid-lower Reaches of the Yangtze are once in every 1.5 years, more than that of the northern and southern parts of South China with once in every 2.5 years, where severe cold damage occurs frequently in Sichuan Basin and mid-lower Reaches of the Yangtze but the frequencies of moderate and severe cold damages are equivalent in the northern and southern parts of South China. The analyses also show that 3-4 years significant oscillation period of cold damage exists in the aforementioned 4 spring rice producing regions and moreover, a significant decadal oscillation of cold damage exists in Sichuan Basin. In 4 spring rice producing regions, there have been less cold damages since 2000. Moreover, cold damages are excessive and severe during the period of 1990s except for the northern of South China regions.

     

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