安徽省伏旱特征及预报研究

利用安徽省35个代表站1961—2003年6~8月逐日降水量资料及1961—2002年逐月北半球100 hPa和500 hPa高度场、地面气压场及热带太平洋海温场资料,采用EOF和最大熵谱,分析了安徽省伏旱的时空分布特征。结果表明,安徽伏旱有全省型、北部型、南部型及中部型等几种主要空间类型,全省型伏旱发生的主周期为6~8年,次周期为2~3年。将EOF的前三个时间系数作为预报对象,利用相关普查筛选出通过显著性水平检验的前期环流、海温等物理因子,建立预报方程,然后将预报出的时间系数再恢复成降水场,由此建立一套适用于区域干旱的场预报模型。对2001—2003年的预报结果表明,该模型对安徽大部分地区的旱涝趋势有较好的预报能力,但在强度方面还有一定差距。

Studies on Characteristic and Prediction of Dog-Days Drought in Anhui Province

Using the daily precipitation data of 35 stations in Anhui Province during JJA from 1961 to 2003,100 hPa and 500 hPa geopotential height fields over the Northern Hemisphere,sea level pressure over Northern Hemisphere,sea surface temperature over tropical Pacific Ocean from previous September to next May during 1961-2002,the characteristics of dog-days drought are analyzed.The results of Empirical Orthogonal Function(EOF) show that there are three main rain patterns during dog-days drought period in Anhui province: The whole provincial,the southern or northern,and the middle patterns.The correlation between the three time coefficients and the previousfactors(H100,H500,SLP,SST) are studied, respectively.Then three prediction models for the three time coefficients can be constructed in terms of a stepwise regression with the aid of the previoussignificant correlation factors whose value are area average of the key regions in the correlation fields.After the three time coefficients are predicted by the models,the total of the three time coefficients multiplied by their eigenvectors is the predictive rainfall field.It is concluded that the models are superiorin fitting,and experimental forecasting of 2001,2002 and 2003 indicate that the models have an ability to predict the dog-days drought in Anhui Province.