1975--2004年中国湿润指数时空变化特征

Spatio-temporal changes of wetness index in China from 1975 to 2004

研究湿润指数的长期变化有助于了解在全球变暖背景下气候干湿状况的演变特征及正确评价农业气候资源并合理有效进行农业气候区划。依据中国616个地面气象台站1975年至2004年的日气象资料,利用联合国粮农组织推荐的参考蒸散计算方法,计算参考作物蒸散(ET0)和湿润指数(W),按照中国气候区划中的干湿指标把中国分为极干旱、干旱、半干旱、半湿润和湿润气候区,并与传统的降水量干湿指标进行对比,揭示在全球气候变化下两种干湿指标的异同,最后对中国近30a干湿状况进行时空分析。结果表明,中国参考作物蒸散总量变化在800～1600mm之间,西北最大,东北最小;与传统的等降水量线对比,Penman-Monteith湿润指数能够更好地表征中国的干湿状况,尤其在过湿、过干地区和东北地区。不同地区湿润指数等值线波动情况不同,中国的西南地区干湿分布状况比较稳定,西北极干旱区的干湿分布稳定性最差;中国湿润化地区增多,但是干旱化程度和进程却大于湿润化地区,中西部干旱化严重。

Through research on variation of wetness index over a long term, it can be under stood how the dry-humid condition has changed under global warming, to make a better assessment on agroclimatic resources and rational agroclimatic zoning. Reference crop evapotranspiration （ET0） and new wetness index （w） were both calculated and analyzed according to Penman-Monteith scheme recommended by FAO with routine meteorological data from 616 weather stations in China from 1975 to 2004. In terms of grades of wetness index from Chinese Climate Classification Criterion, China is classified into severe arid, arid, semi-arid, semi-humid and humid zones, respectively, which are compared with the demarcations from rainfall-based indices in order to reveal the similarity and difference in association with the two schemes under current global climate warming. Besides, the spatio-temporal analysis of climate wetness over the country in the past thirty years was performed. The results show that the total ETo in China ranges from 800 mm to 1600 mm on an annual basis from region to region, with the maximum （minimum） in Northwest（Northeast）; P-M wetness index better expresses dry and humid conditions in China, in over-humid, over-dry and in Northeast region as well, in comparison with traditional climatic boundaries classified by isopluvials. The fluctuation in isopleth of wetness index changes among regions, more stable in the southwest, and the most unstable in the northwestern severe dry region; in the past thirty years, regions getting wet increased in number, but the degree and speed in getting arid were greater than those in getting wet, especially in the middle west part of China.