Study On The Relationship Between TVDI And Meteorological Drought Index Under Different Land Use Types

China's Shaanxi-Gansu-Ningxia area is in arid and semi-arid region, with dry and unstable climate. Droughts occur frequently which can cause serious influences and huge losses to the social production and life, especially the agricultural production, at the same time, it can cause great threat to the food security and economic stability of the region. The Temperature Vegetation Drought Index (TVDI) is an effective method to monitor drought by monitoring the growth condition of vegetation to get inversion of soil moisture content. Currently, TVDI has been widely used in agricultural drought monitoring. Because the changes of vegetation drought condition and moisture content have the hysteresis qualities, in addition, the suitability and effectiveness caused by land use type differences have some differences, so, This paper takes TVDI and meteorological drought index as the drought index to analysis temporal and spatial evolution characteristics of Shaanxi-Gansu-Ningxia region, and discusses the correlation between different land-use types'TVDI (grassland, cultivated land and forest land) and meteorological drought index to reveal the suitability and timeliness of TVDI between different land-use types, it has a great significance to drought monitoring and drought control measures making.This paper takes the Shaanxi-Gansu-Ningxia region as the study area, We use satellite remote sensing data, for example:MODIS vegetation index data, and the ground surface temperature data as well as use meteorological data, such as: soilhumidity. ground meteorological stations precipitation, temperature and other measuring meteorological data to establish remote sensing drought monitoring index TVDI and meteorological drought index (SPI index, MI index. PA index, CI index and z indices). On the basis of verification to TVDI, it analyzes temporal and spatial evolution characteristics in drought of 2000-2010 from March to October of the Shaanxi-Gansu-Ningxia region, as well as the correlation between different land-use types (meadows, arable land, and forest land) TVDI and meteorological drought index. The main results and conclusions are as follows:(1)Between 2000 and 2010, the TVDI of Shaanxi-Gansu-Ningxia region shows an "down-up-down" trend on the whole, with showing a fluctuating decline trend in 2000-2006, showing an upward trend in 2006-2009 and showing a sharp downward trend in the middle of 2009-2010.(2) The coverage of drought in Shaanxi-Gansu-Ningxia region is up to 61% over this decade. The drought was very serious. Meanwhile, wide range of drought existed for a long time, especially in spring. Among them, middle range light drought and small range heavy drought are main cases.(3) On the whole, the severity of the drought is lower in the south and higher in the north on the spatial patterns and large range drought occurred in Shanxi-Gansu-Ningxia region. Northern Shaanxi "Fugu-Shenmu-JIAXIAN-Yokoyama" Ningxia area and southeastern drought are particularly serious, with long-term occurrence of severe drought, long time light drought or above grade drought occurred in Gansu East area while the southern region is relatively moist.(4) The TVDI in grassland area has the highest correlation with 20cm soil humidity, then, has a higher correlation with 10cm soil humidity, MI and CI. There is no obvious lag effect between TVDI and meteorological drought index.(5) The TVDI in cultivated land area has the highest correlation with CI index, then, it has a higher correlation with PA and MI. TVDI has a lag with 50cm soil humidity about 8-9ten days and there is certain correlation between relative humidity of 20cm soil and TVDI which is late 9 ten days, while there is no obvious lag related to SPI, MI, PA, CI and z-index,.(6) The TVDI in forest area has the highest correlation with CI, TVDI has a lag with 10cm soil humidity about 4 ten days. There is certain correlation between relative humidity of 20cm and 50cm soil and TVDI which is late 4 ten days, there is no obvious lag between soil humidity and SPI?CI.The characteristics of the article lie on deep analysis of temporal and spatial evolution characteristics in drought of Shaanxi-Gansu-Ningxia region from 2000-2010 based on Temperature Vegetation Drought Index on the smaller time scale, it also discuss the correlation between different land-use types (meadows, arable land, and forest land) TVDI and meteorological drought index to reveal the suitability and timeliness of TVDI between different land-use types.it provides scientific theoretical basis for the improvement of drought monitoring and the drought relief measures developing.