| In China, drought has caused the most severe loss in all of the meteorological disasters. In recent years, the effect of drought area is gradually increasing. The remote sensing monitoring has been considered by numerous scientists as one of the important means for drought monitoring. Due to the unique karst features, regional and periodic droughts often occur in the Karst landform area, so it restricts the development of the local residents’ production and life. Based on this, it is necessary to carry out remote sensing drought monitoring in the karst landform areas. The study focused on regional drought monitoring models which combined with the information of vegetation index and surface temperature, such as vegetation supply water index (VSWI) and temperature vegetation dryness index (TVDI), from Satellite for environment disaster reduction (HJ) remote data in Karst landform areas. Then the standard of drought grade is defined according to the feature of geology and landform, the drought situation of calendar year and the meteorological live data. At last, using the Regional Drought Monitoring Model, the spatio-temporal pattern of regional drought was studied from September to November in2009～2011.The main contents and conclusions were as follows:(1) Making use of the percentage of precipitation anomalies, the occurrence frequency and the coverage percentage of drought with the meteorological site data of40years, the spatial and temporal distribution of drought was analyzed in this area. The results showed that, drought in the study area has occurred throughout the year, and the widest coverage appears in the autumn.(2) According to the spectral characteristics of HJ-IRS, land surface temperature (LST) was retrieved with generalized single-channel algorithm, mono-window algorithm and image-based Artis inversion algorithm, then revised the empirical relationship that was used. Finally, the accuracy is compared by the three methods. Results show that the generalized single-channel algorithm which was revised is more suitable to retrieve LST in karst landform area.(3) Using vegetation supply water index (VSWI) model and temperature vegetation dryness index (TVDI) model to monitor drought in the study area based on HJ satellite remote data from September to December in2010. Then the monitoring efficacy of these two models was analyzed. Studies have shown that, the vegetation supply water index(VSWI) model had better drought monitoring efficacy in the Karst landform area that under the influence of unique karst landscape feature.(4) The standard of drought grade is defined according to the feature of geology and landform, the drought situation of calendar year and the meteorological live data. Then using the VSWI model, the spatio-temporal pattern of regional drought from September to November was studied in2009～2011. Besides, VSWI’s spatio-temporal pattern was compared with the real drought condition. Results show that the autumn drought monitoring information which acquired by using VSWI model in the Guangxi karst arid agricultural region can accurately reflect the overall trend of the spatio-temporal distribution of the real drought.(5) The variation of drought between different drought tracts were analyzed, the results showed that the drought in the peak forest plain area is more serious than that in the peak-cluster depression (valley) area. With the land-use data, the variations of drought between different land types were analyzed. The results showed that the proportion of farmland hit by droughts which in the areas of severe and medium drought was the highest, while the forest hit by droughts which in the light drought area had the highest proportion, what more, the proportion of grassland was between the two. So it is proved that there was certain correlation between soil moisture and land use. With the DEM data which divided by degree of altitude, the variations of drought in different elevation were analyzed. The results showed that with increasing degree of elevation, the trend of drought conditions was decreased. |
PDF Full Text Request