Dynamic monitoring of vegetation water content based on microwave remote sensing in the Qinghai -Tibetan Plateau region from 2002 to 2010

Water is an important parameter governing vegetation physiological status and formation structure.The Qinghai-Tibetan Plateau plays an important role in the regional ecological environment and global climate changes,but there is a lack of research on spatial temporal variation of vegetation water content and the relationship between water content and climatic factors.Using the"Leave One Out Cross Validation"(LOOCV) method,an inversion model of vegetation water content was established in the Qinghai-Tibetan Plateau region based on 236observed data with corresponding AMSR-E daily brightness temperature data.By simulating the distribution of water content in the Qinghai-Tibetan Plateau,the dynamic variations of vegetation water content and the relationship between water content and climatic factor were analyzed from 2001to 2010.The Microwave Polarization Index(MPI)is superior to the microwave vegetation index in this region,and the power model based on 18GHz MPI AWC=128.93×MPI-0.67 has the highest accuracy,and better reflects the condition of the Absolute Vegetation Water Content(AWC).Daily vegetation water content of the Qinghai-Tibetan Plateau in July shows a belt with an increasing trend from northwest to southeast,in which the vegetation water content is mainly below 800kg/ha in the western and central regions.Compared with the northwest,the southeast vegetation water content has an increased trend,mainly between 800and 4 000kg/ha.The intermonthly variability of vegetation water content has obvious spatial differences in recent years which increases from west to east on the Qinghai-Tibetan plateau.Some relationships between temperature,precipitation and the vegetation water content,show a hysteresis response to rainfall.