什邡市近52年日照时数变化特征及原因分析

为充分利用什邡农业气候资源、合理安排农业生产提供科学依据，笔者利用什邡1961—2012年逐月、逐年日照时数及相关要素等资料，采用统计学、Mann-Kendall法等方法，研究分析什邡近52年日照时数变化特征及其原因。结果表明：（1）年日照时数整体呈明显减少趋势，气候倾向率达-47.3 h/10 a；从21世纪初开始有显著减少趋势；夏季减少趋势最显著，气候倾向率达-27.9 h/10 a；月日照时数变化呈单峰特征。（2）年、夏、冬季日照时数检测到突变点，均呈显著减少趋势。（3）年日照时数与晴天日数、降水量呈正相关，与平均气温呈负相关；日出、日落时段日照时数明显减少与日出、日落方向障碍物增多、仰角增大有关。

Variation Characteristics of Sunshine Hours and Cause Analysis in Shifang in Recent 52 Years

To provide scientific basis for the use of agro-climatic resources in Shifang and the reasonable arrangement of agricultural production, based on methods such as Mann-Kendall model and statistics as well as the monthly and yearly data of sunshine duration and the related factors in Shifang from 1961 to 2012, the author studied the variation characteristics of sunshine duration in that period. The result showed that: (1) the annual sunlight ratio demonstrated a significant reduction on the whole (tendency rate: -47.3 h/10 a), which was patently seen from the beginning of the 21st century and was mostly significant in summers with the tendency rate of -27.9 h/10 a; and the variation of monthly sunshine hours was characterized by a single peak; (2) the sunshine duration showed an abrupt change (significant reduction) in summers and winters as well as on a whole-year scale; (3) the annual sunlight ratio was positively correlated with the number of sunny days and the amount of precipitation, and negatively correlated with the average temperature; the significant reduction of sunshine hours at sunrise and sunset was relevant to the increase of obstacles and angle of elevation.