云贵高原1961-2006年大气能见度和消光因素变化趋势及原因

Long-term trends in visibility and atmospheric extinction coefficient over Yunnan-Guizhou Plateau in southwest China for 1961-2006

根据云贵高原203个气象台站1961—2006年大气能见度、降水、相对湿度、风速和天气现象等观测资料,采用倾向率方法对能见度和大气消光系数的变化趋势进行了分析。还应用Mann-Kendall方法对>19km能见度、霾日数和消光系数的多年变化进行了气候突变检验。结果表明,有84.2%台站出现了能见度减少趋势。减少最多为-11km·10a-1,最少为-1km·10a-1。减少的平均气候倾向率在1961—1979年为0.96km·10a-1,1980—2006年为1.6km·10a-1,高原平均能见度从60年代的约34km下降到目前的约27km。另一方面,有15.8%台站能见度有增加趋势,且多集中在人类活动较为稀少的高海拔山区。有71%的台站>19km能见度频率出现减少的趋势,平均倾向率为-2%·10a-1,主要出现在高原东部和中部人口和工业稠密区。该地区同时也出现霾日增加的现象。Mann-Kendall检测结果表明,>19km能见度频率减少和霾日数增加现象出现突变的时间相同。年平均消光系数发生突变的时间稍推后。认为能见度下降、消光因素增加的原因与人为排放污染物浓度增加有密切关系。

In this study on the regional climatic variability of visual range,atmospheric extinction coefficient （AEO） and haze episodes,we applied the data of visibility,precipitation,relative humidity,wind speed and weather phenomenon observed at 203 stations across the Yunnan-Guizhou Plateau （YGP） in Southwest China from 1961 to 2006.Long-term trends of the annual mean visibility and AEO were calculated as a linear tendency by using a linear regression model for each station.An analysis of the annual frequency of visibility 19 km,AEO and the annual days of haze was also performed with the Mann-Kendall test for detecting a significant trend with an abrupt change over the 46 years.It was found that the visibility of 84.2% stations decreased on the YGP with the negative trends from-11 to-1 km per 10 years,while the visibility at 15.8% stations increased mostly on the high level and sparsely-populated areas.An overall decline in the annual mean visibility from 34km in 1960s to about 27 km in the 21st century across the YGP was with the negative trends of-0.96 km/10yrs and-1.6 km/10yrs respectively during 1961—1979 and 1980—2006.The annual frequency of visibility19 km lessened at 71% stations over YGP with an averaged trend of-2% per year.The annual mean haze episodes rose on the east and central region of YGP.Using the Mann-Kendall test,the interannual changes in frequency of visibility19 km,haze episodes and AEO were characterized with the abrupt changes.The abrupt changes occurred during the 1970s and the1990s,respectively.The negative trend in visibility and the positive trend in AEO could result from the enhanced aerosol concentrations and atmospheric pollution over the YGP.