从地-气温差的长期变化检测中国北部土壤荒漠化

The Desertification over North China through Comparing the Long-time Variation of Air Temperature and 0 cm Soil Temperature

通过研究对比中国北方地区(35oN以北,100oE以东) 1956~2000年间496个台站的观测气温(Ta) 和0 cm地温(Ts) 的变化特征,使用Ta-Ts的距平值建立了一个土壤荒漠化指标。研究表明:1956~2000年的45年间,土壤荒漠化最为严重的是我国西北东部(35o^45oN,100o^110oE),这一地区的土壤荒漠化从20世纪70年代开始逐步加剧,进入80年代以后呈现显著的恶化趋势;东北地区(45o^52oN,120o^135oE) 春季从20世纪90年代以后也出现了微弱的荒漠化倾向;尽管华北地区(35o^45oN,110o^120oE) 的夏季降水明显减少,但是并没有发现这一地区土壤植被的恶化趋势。在年际变动尺度上,土壤荒漠化指数与降水变化有着良好的对应关系,说明降水仍是影响我国北方土壤状况的主要因素。在西北东部的夏季和华北地区的春夏两季,土壤荒漠化指数与归一化土壤植被指数(NDVI) 的良好关系进一步表明使用Ta-Ts作为土壤荒漠化指数的可行性。

In this research, a new type of desertification index is built by using the anomalies of differences between the air temperature (Ta) and the 0cm soil temperature (Ts) over northern part (35 o N north, 100 o E east) of China. Depending on the data from 1956 to 2000, the most serious desertification happens over the eastern part of Northwest China (35 o ~45 o N, 100 o ~110 o E) in both spring and summer, which began from the 1970s, and became much remarkable from the 1980s. A tendency of desertification is also found over Northeast China (45 o ~52 o N, 120 o ~135 o E) from the 1990s. Although the precipitation over central North China (35 o ~45 o N, 110 o ~120 o E) decreased notably from 1956 to 2000, we have not found the tendency of desertification over this area. The desertification indices (Ta-Ts) over the above three areas are correlated to the precipitation very well, which indicates the key roles of precipitation to the desertification index. The high correlations between Ta-Ts and NDVI in summer of eastern part of Northwest China and both spring and summer of central North China show the feasibility of the desertification index used in this research.