Studies Of Desertification Monitoring Methods Based On Remote Sensing Techniques

China is one of the countries suffering the most serious desertification. Based on the results from the fourth national desertification and sandification monitoring, the desertification land area in China is 2,633,700 km2 to the end of 2009, which accounts for 27.36% of the total land area. Accuracy and in time monitoring for desertification plays very important role in desertification combating. Since 1994, for every 5 years, national desertification monitoring has been implemented once and it has been im-plemented 4 times to 2009. It has played very important role for mastering national desertification dy-namics, policy making for combating desertification as well as combating desertification.Based on the UNCCD, the desertification climatic regionalization and the potential extent of deserti-fication in China were detennined using the Thornthwaite method for calculation of potential evapo-transpiration. However, some shortages of the desertification climatic regionalization should be consi-dered for the shortage of Thornthwaite method in China and the shortage climate data (shortage of me-teorological station and also the short period observation time), the desertification climatic regionaliza-tion extend should be adjusted. At the same time, too much monitoring indicators were used and some were duplicated or hard to get. Also every 5 years national desertification monitoring cost a lot in man power, materials and fiscal as well as too longer time monitoring period. It also can't get accuracy of real climate characteristics of annual desertification pattern dynamics and get off the impact of climate fluctuation in the monitoring year to desertification.For solving such questions, in this paper, desertification climatic regionalization is revised by combi-nations of modern remote sensing with ground survey. At the same time, one speediness, economic me-thod, which is suitable for annual desertification monitoring in large scale is proposed. The detailed study methods are as following:1) by using of time series partial correlation analysis method of climate data with NOAA/AVHRR NDVI information to determine the feasibility of inversing moisture index with NDVI, desertification climate zones are divided and the potential extent of desertification is deter-mined based on moisture index.2) Using the methods of regression analysis and sub-pixel decomposi-tion model, national vegetation coverage in recent 11 years are inversed according to multi-scale remote sensing data and the real vegetation coverage got from a large number of ground plots. Then, the deser-tification degrees are divided based on vegetation coverage and the dynamics of national desertification in latest 11 years are analyzed. Through the preliminary research and analysis, the conclusions are as following:(1) As inversed by NDVI and geographic information, moisture index is used to well revise some major deficiencies on climate regionalization. Boundaries of each climate zone moves to the southeast in the Tibetan Plateau. Some areas such as the Hengduan Mountains and the North China Plain are ex- cluded from the potential extent of desertification and some oases in extremely arid region of original climate regionalization were included within this extent. According to the desertification climatic re-gionalization based on NDVI and geographic information, potential extent of desertification reached 3,630,543.7 km2, and 313,511.5 km2 more than the area of the original extent. The boundary of poten-tial extent of desertification mainly changes in the Tibetan Plateau and consistent with the original ex-tent in other regions.(2) Using methods of regression analysis and sub-pixel decomposition model, annual national vegeta-tion coverage in 2000-2010 are inversed according to field surveys, TM and MODIS vegetation indices. The inversed results are objective response to the vegetation coverage change on desertification regions in recent years.(3) Annual desertification degrees and interannual dynamics in China in the latest 11 years are moni-tored based on the inversed vegetation coverage and revised potential extent of desertification. The re-sults show that desertification degrees significantly reduced during 2000-2002, and keep steady in 2002-2010 with fluctuation in local areas. Eastern Inner Mongolia and the Loess Plateau makes major contribution to area change of the national desertification and precipitation is the main driving force of the area fluctuation and degree changes of desertification. These results are basically in accordance with previous national desertification monitoring results.