Drought Monitoring And Temporal And Spatial Analysis Of Zhejiang Province Based On Modis Data

Drought is a more harmful natural disaster, and it has a large sphere of influence, and lasted for a long time. With economic development and population growth, the water shortage situation is increasingly serious, which leads to the expansion of drought areas and the increase of the degree of drought. The frequent occurrence of drought has become one of the natural disasters which have severely affected agricultural production in Zhejiang Province. The natural disaster for drought led a great loss to agriculture, and all levels of government attach a great importance to drought. Thus, exploring possible ways to monitor the drought situation and application of GIS technology to analyze the temporal and spatial distribution of drought in Zhejiang Province provide the basis for taking appropriate measures and countermeasures on drought, and are significant to agricultural production and the people living in Zhejiang province.Traditional methods of drought monitoring are using precipitation at ground-based observations, soil moisture and other weather data to estimate indirectly drought, but there are many disadvantage in the data acquisition, data representation, expenses and adaptability of methods: conventional methods can not achieve real-time or near-time observation on the surface observation. It can't cover a wide range in the observation area, and some data can not be easy to obtain(such as temperature on the land surface, soil moisture on the land surface).With the development of satellite remote sensing technology, remote sensing with its objective, dynamic, macroscopic, real-time, rapid, low-cost advantages and application of remote sensing technology are monitored the drought, and they fully utilize the features of the spectra of the surface, time, space and the direction (multi-angle)information. Therefore, remote sensing technology provides a new solution for drought monitoring. At present, our country focuses on in the optical remote sensing in this field, which is the application of visible - near infrared - thermal infrared and microwave optical bands.The occurrence of drought is affected by many factors, thus, the selection of factors is one of the final deciding factors in drought monitoring. A variety of factors have their own advantages and disadvantages, such as optical remote sensing, the thermal inertia method and Crop Water Stress Index can separately be applied to monitor soil moisture of bare land and crop-covered field. Vegetation Condition Index uses the vegetation index factor to implement agricultural drought monitoring. Temperature vegetation index and Vegetation Temperature Condition Index are taking crop vegetation index and surface temperature into account at the same time. Microwave remote sensing is considered as the most effective way to monitor soil moisture. Active microwave remote sensing has a higher spatial resolution, but it is sensitive to soil roughness and vegetation. Though passive microwave remote sensing has a lower spatial resolution, the re-visit cycle is short, thus, it has a greater potential for large-scale agriculture drought monitoring.Because of more of vegetation cover in Zhejiang Province, so drought is studied from the perspective of vegetation in this paper. The status of vegetation growth is related with water(there is a little change in the light and temperature), the level of water supply has become a key factor in vegetation growth. If the water supply is adequate, vegetation grows well, on the contrary, vegetation grows bad. So the state of vegetation growth can reflect changes of drought, and there is a clear relationship between the vegetation moisture content and soil moisture content. If soil moisture content is high, the leaves absorb fully water, on the contrary, the leaves absorb less water, thus, soil moisture content can also be used as an indicator of drought. In this paper, the reflectance characteristics of the 7-bands of the MODIS which are more sensitive to the land are analyzed, thus, vegetation and soil moisture-sensitive bands are selected, and a vegetation index and soil water sensitive index are built to analyze the extent of response to drought, and the distribution of drought can be further inverted.