午夜欧美大片免费观看,欧美激情综合五月色丁香,亚洲日本在线视频观看,午夜精品福利在线

By means of the data of daily precipitation, temperature, humidity, wind speed, and wind direction from 10 May to 10 June, 1971 to 2005 as well as thousand grain weight data of winter wheat from 1981 to 2005 in Hebei winter wheat production area, with the statistical methods, such as wavelet analysis, regression analysis, etc., the temporalspatial distribution features, the variation periods of dryhot wind and its impacts on thousand grain weight of winter wheat are analyzed. The results indicate that the annual mean number of mild dryhot wind days is consistent with that of severe dryhot wind days; the interdecadal variation of mild and severe dryhot wind has same characteristics; the total number of dryhot wind days has a negative correlation with the thousand grain weight of winter wheat.