青藏高原总云量的气候变化及其稳定性

利用青藏高原80个测站1961-2000年1～12月总云量资料,分析40 a来青藏高原总云量的气候变化规律及其稳定性.结果表明:青藏高原的总云量从东南向西北减少,云量的稳定性夏季高于冬季,东部高于西部.因此,江河上源区域、藏东高原、川西高原、甘南高原和祁连山区是青藏高原总云量多而稳定的地区;青藏高原南部和西部总云量月变化振幅大,夏季云量最多,高原东部祁连山区和中部江河上源区3～9月云量多而起伏变化小,6月出现峰值;总云量具有显著持续性的空间范围较大,但持续时间短,持续时间为7～8月和5～6月;总云量的年际变化总体呈显著下降趋势, 江河上源区和祁连山区的总云量变化缓慢,20世纪90年代云量有上升的趋势.在季节上表现为冬、春、夏西北上升东南下降,秋季西北下降东南上升的变化趋势.

Climatic Change and Stability of Total Cloud Amount over the Qinghai-Tibetan Plateau

The climate change and stability of total cloud amount over the Qinghai-Tibetan Plateau since recent 40 years is analyzed based on the monthly total cloud amount data observed by 80 meteorological stations during the period from January 1961 to December 2000. The result shows that the total cloud amount over the plateau decreases from the southeastern part to the northwestern part of the plateau. The stability of cloud amount in summer is higher than that in winter and higher in the eastern part than that in the western part. Therefore, the total cloud amount is high and stable over the headwaters of the rivers, eastern part of the Qinghai-Tibetan Plateau, western part of the Sichuan Plateau, Gannan Plateau and the Qilian Mountains; the monthly change of total cloud amount is significant over the southern and western parts of the Qinghai-Tibetan Plateau, where the cloud amount is the highest in summer. The cloud amount is high and its fluctuation is small over the eastern part of the Qinghai-Tibetan Plateau, Qilian Mountains and headwaters of the rivers in the central part of the plateau during the period from March to September, and its maximum occurs in June. The spatial extent of significant durative of the total cloud amount is large, but its duration is short and occurs mainly during the periods from July to August and from May to June. In annual variation, the total cloud amount is in a decrease trend. The variation of the total cloud amount is slow and has been in a slight increase trend over the headwaters of the rivers and the Qilian Mountains since the 1990s. Seasonally, the total cloud amount increases over the northwestern part but decreases over the southeastern part of the plateau in winter, spring and summer, it, however, decreases over the northwestern part but increases in the southeastern part in autumn.