近50年来临沂市日照时数的变化特征分析

ANALYSIS ON CHANGE CHARACTERISTICS OF THE NUMBER OF SUNSHINE HOURS DURING THE PAST 50 YEARS IN LINYI

采用临沂市50 a（1961-2010）日照时数以及总云量、低云量、降水量、视程障碍现象日数等资料，采用气候倾向率分析其变化趋势，利用滑动T检验法和累积距平结合的方法进行突变分析，并根据各气象要素的年、季变化趋势及其与日照时数变化趋势的对应关系对日照时数变化原因进行分析．结果表明临沂市年日照时数呈显著减少趋势（P＜0．05）．从年代际变化看，20世纪60-70年代，年均日照时数呈持续减少趋势，70-80年代，年均日照时数呈持续增加趋势，80年代至21世纪初呈现持续减少趋势．四季中夏季日照时数减小趋势极显著（P＜0．01），冬季日照时数减小显著（P＜0．05）．各月日照时数均呈减小趋势，6月日照时数减小趋势极显著，8月呈显著减小趋势．年日照时数在1979年和1996年发生突变，季日照时数发生突变是导致年突变的原因．日照时数减少与云量关系密切，还与年、春、秋季水汽压以及春、夏、秋季降水量密切相关．

Based on data of sunshine hours,cloud cover,low cloud cover,precipitation and impair vision phenomenon days during the past 50 years in Linyi,climate trend rate and sliding T-test method combined with the cumulative anomaly are used to analyze the change trend and mutation respectively.Furthermore,the reason of the change on sunshine hours is discussed according to the correspondence between the annual and seasonal trends of meteorological elements and trend of sunshine hours change.It indicates that the annual sunshine hours in Linyi show a significant decreasing trend （P〈0.05）.Regarding to the decadal changes,average annual sunshine hours showed a decreasing trend during 1 960s and 1 970s,a increasing trend from then to 1 980s,and again a decreasing trend from 1 980s to the earlier 21 st century.Additionally,sunshine hours decrease significantly（P〈0.01 ）in summer and decrease obviously （P 〈0.05 ）in winter.Sunshine hours show decrease trend in every month. especially significantly in June and August.Annual hours mutation happened in 1 979 and 1 996 due to the mutation of quarter sunshine hours.The decrease of sunshine hours is closely related to the cloud cover,annual vapor pressure,vapor pressure in spring and fall,and precipitation in spring,summer,and fall.