The Applied Study On Agricultural Drought Monitoring

Drought is the water shortage which is caused by a regional imbalance in water supply and demand. Agricultural drought is the result of inadequate soil water supply led to normal growth and fertility of vegetation ,which has been held all over the world, one of the major natural disasters. Agriculture is the primary industry of our country; agriculture drought will have a huge impact on national product. So it is more significative to explore some feasible methods to monitor drought. It is very important to Industrial production and agricultural production and people's lives. The traditional monitor drought method of using Meteorological data is not timely and accurate. Remote sensing with macro, integrated, dynamic and rapid, can timely, accurately and comprehensively acquire the drought information. it has important practical significance to the promotion of agricultural production, food security and sustainable development in the region .Vegetation Index (NDVI) and land surface temperature (LST) Can reveal soil moisture information and reflect the state of vegetation affected by the drought through response ,which vegetation is stressed by the drought .when they are used alone ,there are both limited. TVDI index composed of two-dimensional feature space Based on vegetation index and land surface temperature is unique combination of two parameters of the physiological and ecological significance. It is not only indicative of environment when vegetation is stressed by water and heat, but also reveals the symptoms in which vegetation is coercive environment. TVDI index can effectively improve the accuracy of drought monitoring and efficiency. Xinjiang is located in arid, semi-arid climate zones, it is climate exacerbated salinization of development and hampered the development of agriculture. Therefore, agricultural drought monitoring has become one of the important topics, which need to be solved.In the first, This article based in thermal infrared remote sensing theory use ETM images combined with meteorological data to obtain the key parameters: brightness temperature, surface emissivity, atmospheric transmission rate, the average atmospheric temperature, and used the mono--window algorithm of Qin zhi hao to retrieve land surface temperature in YU TIAN .Secondly, the author uses the vegetation index - land surface temperature feature space principle as a guide to establish LST-NDVI feature space of the study area, fit the wet edge and dry edge of feature space to build TVDI index, obtain drought distribution picture of the study area and grade to reveal drought distribution information. Then, ETM+ images are selected to retrieve land use / land cover types by maximum likelihood method. finally, we analysis the relationships during TVDI index, vegetation index and land surface temperature and Discuss the relevance between TVDI index and land use / land cover types on the basis of the land use / land cover database and drought monitoring.The conclusions are as follows: the low-value of the land surface temperature in yu tian mainly concentrated in the water, the high-value concentrated in the Gobi and desert. .Land Surface temperature with the oasis for central from the inside to the outside gradually increased. The drought is also progressive severe from the central of the oasis to outlying oasis. The place near the water and with good vegetation is fewer droughts; drought and severe drought are located in the Gobi and desert; the drought in October 3, 2002 is more serious than September 13, 1999. We found that the correlation coefficient between TVDI index and land surface temperature is as high as 0.957, but the correlation coefficient between TVDI index and vegetation index is not high, when Analysising the relationship during TVDI index, land surface temperature, vegetation index. That the vegetation index reflects capacity of the drought is very limited. So it is feasible that land surface temperature predict drought. By analyzing the drought distribution of the different land-use types, we found arable land, woodland is distributed in the lower TVDI value region and need high surface moisture; the TVDI value distribution of high grass is much wider; the distribution of grass and low grass is in drought and severe drought region and do not ask for much of the water. Through the distribution analysis of TVDI of different times, ravages of a drought of all land-use types became severer in October, 2002. Conclusions can be drawn from the impact of land-use types on TVDI that: moisture loss of arable land and woodland is serious in the humid and serious arid regions, whereas it's contrary in arid regions; water-holding capacity of High-density grassland is very strong in arid and serious drought areas; Middle-density and Low-density grassland have a strong capacity to maintain water in serious drought area, and the capacity of Low-density grassland is better.