黄土高原作物生长季近地层干湿状况变化特征

Change of Terrestrial Surface Drought and Wet Conditions in the Growth Period on Loess Plateau

深入分析黄土高原近地层作物生长季干湿变化及其分布特征,为应对气候变化、保护生态与自然环境提供依据。基于黄土高原气候要素资料,应用Penman-Monteith模型计算作物生长季湿润指数,研究近地层干湿特征。研究区域作物生长季湿润指数从东南向西北依次减小。作物生长季近地层干湿状况的异常空间分布可分为以下3个关键区：高原东北部区、高原南部区、高原西部区,除高原东北部区外,近地层年平均湿润指数均呈显著下降趋势,分别在1978年和1979年发生了由湿变干的显著突变。作物生长季近地层干湿状况的3个空间分区中,近地层年湿润指数存在显著的3~4年的周期振荡;高原南部和西部区域还存在显著的5~6年和7~8年的周期振荡。黄土高原干旱化趋势腹地最大,边缘次之。干旱化呈现出明显从腹地向四周扩散状态分布特征。

To provide foundation for tackling climate change and protecting ecology and environment, the humidity change and distribution characteristics of the terrestrial surface during plant growth period on Loess Plateau were deeply analyzed. Based on climatic factors observed on Loess plateau and by using Penman- Monteith Mode, the humidity index of plant growth period was computed and terrestrial surface humidity characteristic was studied. Humidity index decreased successively from southeast to northwest during the of plant growth period in the research region. The abnormal spatial distribution of the terrestrial surface humidity condition during plant growth period was divided into three key regions： northeast part of the plateau, south part of the plateau and west part of the plateau. Apart from northeast part of the plateau, the other two regions have a remarkable descending trend on annual mean terrestrial surface humidity index; each of them had a notable mutation from wet to dry in 1978 and 1979 respectively. In the three spatial distributed regions, the terrestrial surface＇s annual humidity index had a remarkable 3-4 years periodic oscillation; remarkable 5-6 years and 7-8 years periodic oscillations also appeared in south olateau and west regions. The desiccation tendency appeared to decrease from the center to the edge of Loess Plateau. The desiccation obviously showed the distribution characteristics extending from the center of the plateau to all around the region.