基于TVDI的羌塘高原夏季土壤湿度变化分析

Analysis of soil moisture variation in summer of Qiangtang Plateau based on TVDI

土壤湿度是生态系统的关键参数,实时、有效地监测土壤湿度有助于增强对区域气候与环境变化的理解。利用温度植被干旱指数法(TVDI)反演羌塘高原2000-2014年夏季土壤湿度,以2014年为例分析该年夏季土壤湿度空间分布并探讨2000-2014年土壤湿度的动态特征。结果表明:(1)2014年羌塘高原夏季土壤湿度空间分布表现为东南部偏湿润、西北部偏干旱。从东到西土壤湿度逐渐降低,南北干湿状况交替分布。土壤湿度干旱、偏干、正常、偏湿、湿润面积比分别为3.84%、27.17%、37.64%、29.63%、1.72%。(2)2000-2014年羌塘高原北部和中部地区夏季土壤湿度呈现显著变干的趋势,而南部大部分地区土壤湿度变化趋势不显著。15年间土壤干旱和湿润面积比例最小且波动小,偏干、正常、偏湿土壤面积均出现不同程度的波动。(3)降水量是影响TVDI的重要因子且具有一定的滞后性,而气温影响相对较小。

Soil moisture is a key parameter of the ecosystem. Real-time and effective monitoring of soil moisture helps to enhance our understanding of regional climate and environmental change. MOD11 A2 and MOD13 A2 of MODIS synthetic products in DOY（Day of Year） 177-225 between 2000 and 2014 was used to obtain the Land Surface Temperature and Normalized Difference Vegetation Index, and the status of soil moisture on the Qiangtang Plateau covering the summer from 2000 to 2014 was evaluated based on the method of Temperature Vegetation Dryness Index（TVDI）. The spatial distribution of soil moisture in the summer of 2014 was analyzed as an example, and the dynamic changes of soil moisture during2000-2014 were further discussed. The results show that：（1） The soil moisture of the Qiangtang Plateau in 2014 was generally humid in the southeastern part, while it was arid in the northwestern part. Soil moisture gradually reduced from east to west, dry and wet conditions were found alternately between south and north. The percentages of areas of dry soil, partially dry soil, normal humidity soil, partially wet soil, and wet soil were 3.84%,27.17%, 37.64%, 29.63%, and 1.72%, respectively in 2014.（2） In July and August from 2000 to 2014, soil moisture in the northern and central parts of the plateau showed a significant trend of getting dry, while that in the southern part showed a trend of getting wet with little significance. The proportion of area of dry soil and wet soil in the study area was the smallest and had little fluctuation from 2000 to 2014, while that of partially dry soil, normal humidity soil, partially wet soil had different fluctuations.（3） Precipitation was an important factor affecting TVDI, and had the certain hysteresis, while the impact of temperature was relatively small.