近50 a来祁连山及河西走廊极端气候的时空变化研究

 在全球变暖背景下，极端气候发生的频率增大，气象灾害造成的损失也随之增加。利用20个气象站1960-2009年的日平均气温和日降水量资料，运用线性趋势法、Spline空间插值法、Morlet小波分析法，对祁连山及河西走廊极端气候的时空变化特征进行了研究。结果表明：极端高温天数呈显著增加趋势，年际变化率为0.79d/a，20世纪90年代中后期之后极端高温天气发生的频率较高；极端低温天数呈显著减少趋势，年际变化率为-0.54d/a， 80年代中后期以来极端低温天气发生的频率较低；极端降水天数也呈显著增加趋势，年际变化率为0.02d/a，70年代中后期之后极端降水天气发生的频率较高。极端气温和降水的年际变化幅度存在区域差异，南部山区比走廊平原对全球气候变暖的响应敏感。极端高温天数和极端低温天数在8a、22a左右周期变化明显，其中22a是第一主周期；极端降水天数在6a、10a、22a左右周期变化明显，其中22a是第一主周期；从22a的周期变化推测，2010年以后11a左右极端高温天数偏少，极端低温天数偏多，极端降水天数偏少。

Temporal and spatial change of climate extremes in Qilian Mountains and Hexi Corridor during last fifty years

Under the condition of global warming, the frequency of extreme climate and damage of meteorological disasters are increasing. Based on daily temperature and precipitation data of 20 weather stations in the Qilian Mountains and Hexi Corridor from 1960 to 2009, the inter annual change trends of climate extremes were studied by methods of regression analysis and five years moving average, and the spatial distribution characteristics of inter annual change trends and its significance of climate extremes were analyzed by method of Spline interpolation under ArcGIS environment, and the cycles of climate extremes were discussed by method of Morlet wavelet analysis under Matlab environment, so as to bring scientific accordance for local governments to deal with climate change and disaster prevention and alleviation. The results indicate the annual number of extreme high temperature days (EHTD) is on the significant rise by the rate of 0.79 d/a, and the trend of inter annual change of EHTD is accelerative by larger waving scale after the middle late of 1980s, especially the rate of EHTD getting higher after the middle late of 1990s. This is contrary to the extreme low temperature days (ELTD), the annual number of ELTD is decreasing significantly by the rate of -0.54 d/a and the trend of inter annual change of ELTD is reducing by larger waving scale after the middle latte of 1980s, and the rate of ELTD is lower after the middle late of 1980s. The annual number of extreme precipitation days (EPD) is increasing significantly by the rate of 0.02 d/a, and the trend of inter annual change of EPD is rising by larger and smaller waving scale before and after the middle of 1980s respectively, but the trend became contrary after the middle late of 1990s, and the rate of EPD is higher after the middle of 1970s. The spatial distribution characteristics of inter annual change trends and its significance of climate extremes have some differences, but the response to the global climate change is consistent. The changing scale of annual number of extreme temperature and precipitation days in the Qilian Mountains is larger than that in Hexi Corridor, which indicates that the response to global climate warming in high altitude areas is more sensitive than that in low altitude areas. The changes of EHTD and ELTD are with obvious cycle by the time scale of 8 a and 22 a, and the cycle change of 22 a is the first main cycle. The changes of EPD are with obvious cycle by the time scale of 8 a, 10 a and 22 a, and the cycle change of 22 a is the first main cycle. Under the cycle change of 22 a, it is speculated that the annual number of EHTD and EPD will increase in the future of about 11 a after 2010, but ELTD will get into an opposite situation, which suggests that the rate of high temperature and heavy rain disasters will rise. From the cycle change step of 22 a, the variation trend in EHTD and EPD is consistent, but the variation trend in EHTD and ELTD is contrary.