关键词: 全球变化, 区域干湿, 夏季风

Abstract: Based on the various data analyses, the paper aims to making a discussion of the impacts of the past global warm/cold variations on the humidity changesalong the low-latitudinal summer monsoon ranges in Asia and Africa. The ways the regional climates respond to global changes may be quite different at different time-scales.In fact, it is widely noted that at the time-scale longer than 102yr, the summer monsoons are generally stronger during global warmer periods, thus leading to wetter conditions in the presently semiarid and arid regions in Asia and Africa. Dry conditions prevail the most of the areas concerned during cold periods, accompanied by rapid accumulation of loess in north China, lower lake-levels in Qinhai-Tibetan Plateau. desert development in northwestern India, Arabian Peninsula and Sahara.Because the thermal sensibility is generally larger in continent than in ocean. the globally warmer (colder) condition at long time-scale almost always implies a larger (smaller) thermal contrast between continent and ocean in summer, which is nothing but an essential force of monoson. The hightropospheric Easterly Jet and the relevant atmospheric circulations were also proposed as important factors to explain the in-phase humidity variations along Asian and African monsoon ranges.The mentioned global-regional relationship become weaker with decreasing time-scales. At 101-102-year-scales. which receive serious attention at the present in the field of global change study.temperature fluctuations are relatively small but may be locally considerable. Therefore. the themally driven circulations such as monsoons in different areas may not identically change. In recent history some wet/dry alterations at century-scale along the monsoon zones were found to be accompanied with the mild /cold variations of the Little Ice Age, but few evidences indicated the same at decadescale.During the mordern observation period. it was found that the 1920’s global warming was clearly accompanied with the enhanced monsoon rainfall along the Asian and African semi-arid regions and that the 1960s’ cooling led the event drying tend-ency along the same zones. However. the case of the 1980s’/global warming prevent us from clearly defining the global-regional relationship at the medium-term climate scale. We need to not only carefully analyze the long historical evolutions, but also pay much attention to the large-scale geographical patterns of climate changes and their atmospheric circulation backgrounds. The latter remains nowadays a particularly weak link in studying the regional climate changes and their relationship with global change.

Key words: global change, regional wet/dry alternation, summer monsoon