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

In order to study the variation characteristics and the causes of pan evaporation of the BeijingTianjinHebei region, the 87 weather stations with more complete and longer time data sequence and over 70 score of station observation environment are selected from more than 200 stations in the BeijingTianjinHebei region (according to the standard score of the China Meteorological Administration). The evaporation pan evaporation data and other meteorological observation data in the 87 weather stations are used to analyze the evaporation variation characteristics and impact factors in the BeijingTianjinHebei region from 1970 to 2013 with the linear trend estimation method and complete correlation coefficient method. The results indicate that, the annual and seasonal evaporation showed an obvious decreasing trend in recent 44 years in the BeijingTianjinHebei region. The sequence of vaporization rates from big to small is: Piedmont plain > Taihang mountain > Hebei east plain > Yanshan hills > Hebei north plateau. The evaporation rate was gradually increasing from north to south. The drop rate of pan evaporation was: spring > autumn > winter > summer. Evaporation capacity and influence factors are analyzed. The results show that temperature daily range, sunshine duration and average wind speed are the major causes of the evaporation reduction in the BeijingTianjinHebei region. In the plain area, average wind speed is the dominant factor. In the mountainous and plateau areas, sunshine duration is the dominant factor.