Sahel气候与环境变化研究进展

对 Sahel地区气候及环境变化的研究 ,对理解和加强我国干旱半干旱地区许多相关问题有较好的借鉴意义。Sahel地区的干旱化持续了近 30年 ,虽然 1 999年降水出现了自 1 968年以来的最高值 ,但整个 90年代降水仍然偏低。造成 Sahel降水波动的因素包括大西洋海表温度、陆面反馈、全球变暖等。其中海洋的影响起重要作用 ,在某些年份里土壤水分可能会起到比较大的作用 ,而大气内部的动力作用则可能没有明显影响 ,从大尺度看人类活动对此地区整体环境和气候的变化贡献不大。

PROGRESS IN THE STUDY ON SAHEL CLIMATE AND ENVIRONMENTAL CHANGE

This paper examines the Sahel climate and environmental changes. It is helpful to understand the environmental problems in China's arid and semiarid regions. The severe drought has continued for about 30 years since the late 1960s. There are upward trends in Sahel rainfall since 1980s with the magnitude of +12%/10 a, and the rainfall in July September of 1999 is the highest since 1968. But the decadal mean of 1990s is also very low, there is no signal showing the end of the prolonged desiccation. Many factors show influence in Sahel rainfall, including sea surface temperature (especially over the Atlantic Ocean), land surface processes,global warming and human activities such as overgrazing. In some years, soil moisture interaction may play a key role but sea surface temperatures are the dominant control factor. Internal dynamics are shown to have little effect. Looking at the Sahel as a whole, human activities also show little contribution to the Sahel climate and environmental changes. Some studies found that there are abrupt changes during the middle 1960s for the rainfall in both Sahel and northern China. The rainfall changes in these two regions show strong connection, thus the studies on Sahel drought is helpful for understanding the causes of variations of rainfall over northern China.