云贵高原近45年来日照及能见度变化及其成因初步分析

Change Trends and Causes in Sunshine Duration and Visibility over Yunnan-Guizhou Plateau in Recent 45 Years

利用云贵高原1961—2005年184个气象站的日照时数、总云量和能见度的观测资料,分析了高原的日照、云量、中低空水汽和能见度变化趋势。结果表明,云贵高原的总云量、中低层大气水汽含量都没有发生明显变化的条件下,有85%的台站出现日照时数减少,减少量在12.2h.(10a)-1到173.7h.(10a)-1之间。Mann-Kendall检验的结果表明:日照时数减少的台站中有63.7%的站出现突变现象,突变发生的年代从20世纪70年代开始,主要发生在80～90年代,21世纪以来这种减少现象不明显。同时年平均能见度从60年代的34km下降到目前的27km。云量、高空水汽和能见度条件分析表明,高原对流层气溶胶和污染物浓度的增加是导致日照减少的主要原因。

Using the observed data of sunshine duration,total cloud cover and visibility at 184 stations over the Yunnan-Guizhou Plateau （YGP） from 1961／_2005,the long-term trends of sunshine duration,lower-level water vapour in cloud cover,dry visibility （DV） and dry extinction coefficient over the YGP are analyzed.The result shows that when the cloud cover and water vapour content in midand lower-levels over the YGP have no obvious changes,the 85% stations appear the annual sunshine duration decreasing,and their reduced amount is between 12.2 and 173.7 h·（10a）-1.The result of Mann-Kendall test shows that there are 63.7% stations to appear abrupt change in the stations of sunshine duration decreasing.The abrupt changes start from 1970s,and main in 1980s／_1990s.The decreasing trend has been no obvious since the 21 st century.The annual average of DV decreases from 34 km in 1960s to 27 km at present.The analyses of cloud cover,upper-level water vapour and visibility show the increasement of troposphere aerosol and polluter concentration over the YGP is the main reason that lead to sunshine duration reduction.