多尺度气象干旱与土壤相对湿度的关系研究

通过分析我国东北、华北、西北地区东部、西南以及黄淮、江淮和江汉5个区域不同时间尺度气象干旱指数与20 cm土壤相对湿度的相关关系, 探讨了前期气象干旱对后期土壤湿度的影响, 并利用多元线性回归方法分区域、分季节建立了土壤湿度预测模型.结果表明: 春季, 东北地区土壤湿度主要受前5~6个月, 尤其是上年秋末冬初的降水的影响, 而其他4个区域土壤湿度主要受前1~2个月大气水分的影响;各区域夏季土壤湿度与前1~2个月时间尺度上的大气水分相关最密切;秋季, 东北地区20 cm土壤湿度主要受前2~4个月的气象干旱的影响, 其余区域土壤湿度仍与前1~2个月尺度的大气水分相关最密切.基于前期气象干旱指数建立的各区域、各季节的土壤湿度回归模型对当地土壤湿度具有一定的拟合能力, 平均估计偏差在10.1%~13.9%之间, 其中, 西北地区东部和华北地区春、夏季偏差较大, 2008-2011年间干旱等级拟合准确率在65%~74.9%之间;东北、西南、黄淮、江淮和江汉区域拟合较好, 拟合准确率在88%以上.

Relationship Between Soil Relative Humidity and the Multiscale Meteorological Drought Indexes

Based on the correlation analysis between soil relative humidity and meteorological drought indexes in 5 areas of China, the impact of meteorological drought on the soil moisture is discussed. The results show that due to the differences in water and thermal conditions, the time scale of meteorological drought which causes soil drought is different in different seasons and different areas. In spring, the amount of precipitation since last year, especially in late autumn and early winter, has obviously impact on the soil relative humidity in Northeast China, while in the eastern part of Northwest China, North China, Southwest China, Huanghuai, Jianghuai and Jianghan areas, the soil relative humidity is closely depended on the atmospheric moisture in recent two months. In summer, soil relative humidity in the five areas is closely related to precipitation and temperature in recent two months. In autumn, the meteorological drought in recent two to four months will control the soil drought in the northern part of China and in other four areas;the soil relative humidity is strongly correlated with atmospheric moisture in recent two months. In addition, a soil relative humidity prediction model through multiple linear regressions based on the main indexes is developed with the data from 1992 to 2007 in each area in spring, summer and autumn. The efficiency of each model is also verified with data from 2008 to 2011. The results show that these models have certain ability to fit the soil relative humidity with the mean absolution deviation within 10.1% to 13.9%, (11.7% in average). Among them, the deviation in the east of Northwest China and North China is larger in spring and summer, with the fitting accuracy of drought classes between 65% and 74.9%. In Northeast China, Southwest China, Huanghuai, Jianghuai and Jianghan areas, the model is more effective, with a fitting accuracy above 88%. The fitting curves of soil relative humidity on May 28^th, Aug. 28^th, Sept. 28^th, 2011 also verify the feasibility of these models.