内蒙古典型草原作物系数和实际蒸散量的时空分布特征

Spatial and Temporal Distribution of Crop Coefficient and Actual Evapotranspiration in Typical Steppe of Inner Mongolia

利用内蒙古典型草原21个气象站点的气象和牧草观测资料,结合潜在蒸散量和改进的作物系数计算方法,模拟计算了2009年草原植被作物系数和实际蒸散量。在GIS软件的支持下,分析了二者的时空分布特点,并通过反映牧草长势的NDVI变化趋势予以验证。结果表明:5—8月间随着月份的增加作物系数Kcx最大值的变化趋势由0.6→1.2→1.4→1.4,平均值是0.28→0.36→0.40→0.38。4个时期的Kcx值以0.2～0.6之间的区域占主体,为55%以上。实际蒸散量在时间变化和空间分布上与Kcx值基本一致。随着月份的增加实际蒸散量低值级的区域面积逐渐缩小,相对应的高值级的面积逐渐增大,整个生长季以30～90 mm的蒸散量为主。5—8月牧草实际蒸散量和NDVI值的相关系数达到0.446,通过了0.01水平的显著性检验。

Based on meteorological and forage observation data from 21 meteorological stations in typical steppe, Inner Mongolia, together with potential evapotranspiration model and improved crop coefficient, crop coefficient and actual evapotranspiration were studied. This study analyzed spatial and temporal distribution characteristics using GIS, which were tested based on the NDVI variation trend. The result shows the maximum of Kcx rose from 0.6 to 1.4 from May to August, while the mean value was 0. 28, 0. 36, 0. 40 and 0. 38 respectively. The Kcx value region from 0.2 to 0. 6 accounts for more than 55% of the total Kcx value region. The spatial and temporal distribution of actual evapotranspiration was consistent with Kcx value. Low-value region area decreased gradually over the four-month period, while the high-value region area went up. The evapotranspiration value region ranged from 30 to 90 mm, constituting the main part during the entire growing season. The correlation coefficient of forage actual evapotranspiration and NDVI value is 0. 446 （P 〈0. 01 ）. It is practicable to use this research method in analyzing the evapotranspiration in steppe area.