| In the context of the global climate change more and more complex, China was affected frequently by drought in recent decades, which has brought potential hazards to the safety of China’s grain production. Therefore, the research of spatial-temporal evolution characteristics and development trend of drought in region will have important meaning for drought relief of the local government and regional agricultural planning. The thesis analyzes the causing hazard factors and remote sensing monitoring mechanism from the perspective of the circulation of atmospheric water vapor, soil water stress and vegetation response to drought hazards. A large number of drought associated factor data was mined using spatial data fuzzy mining technology of classification and regression tree and a semi-empirical and semi-mechanistic drought monitoring model was built. A synthesized drought index from2000to2010in Shandong province was calculated using this model and the temporal and spatial information of drought been constructed. Based on this, the characteristics of spatiotemporal evolution of drought were studied using five kinds of spatial data timing analysis method in Shandong. This research work realized the precise monitoring and quantitative description of drought process over the past decade in Shandong province. The study obtained the following results and conclusions:(1) From the point of view of drought mechanism and hazard response, the thesis analyzes that the drought process deduced by many causing hazard factors including atmosphere, soil, vegetation and so on. It pointed out that a single meteorological drought, agricultural drought or hydrological drought is difficult to accurately define the natural process of drought. Only the drought monitoring mechanism model which comprehensive considering the atmospheric precipitation, vegetation growth and soil water balance of supply and demand and their internal coupling process can accurately monitor and simulate this natural phenomenon from the point of view land surface water balance system.(2) The thesis constructed TRMM-Z index using3B43monthly precipitation data of Tropical Rainfall Measuring Mission (TRMM) and single station based Z index drought monitoring method and it was validated using standardized precipitation index (SPI). The results showed that TRMM-Z index could well reflect the occurring and developing process of regional drought and the monitoring results were accord well with actual situation. All the correlation coefficients of the average value of TRMM-Z index with the corresponding station based SPI value were more than0.8and passed the significant test (p-value<0.01).(3) Two kinds of data quality control algorithm were developed for MODIS surface temperature products (MOD11A2/MYD11A2) and vegetation index products (MOD13A3) and they can remove the noise of the time series data and improve data quality significantly. Besides, the Savitzky-Golay filter was used in time series vegetation index to smoothing and reducing noise. Based on the mechanism of drought events can affect the growth of vegetation and ground temperature periodically changes rules, the thesis put forward standardized vegetation anomaly index and standardized land surface temperature anomaly index and used them to drought monitoring and follow-up model building.(4) Based on the theory of fuzzy spatial data mining, a classification and regression tree model was built using training variables and it been used to calculate synthesized drought index. Synthesized drought index not only takes into account the meteorological precipitation deficit, soil water stress, vegetation growth status, but also consider the type of land use, the available water capacity of soil and other factors. Therefore, it can used to assess the complex water balance breaking of drought process. As an example, the monthly synthesized drought index of Shandong province was used to analyze the spatiotemporal variation of drought. The results showed that occurring and developing of drought event in2010was monitored and it in accord with actual situation. The time series synthesized drought index from2U0U to2010accurately monitored the event and duration of drought in historical periods which was caused by large climatic events such as El Nino-Southern Oscillation.(5) The validation results show that synthesized drought index and standardized crop yields variable are correlate and most correlation coefficient over0.6and passed significance test (p-value<0.05) in major crop growing season. The correlation coefficient of synthesized drought index and drought affected crop area is between-0.67to-0.85and most them passed significance test (p-value<0.01) which was slightly higher than the correlation coefficient of other existing drought index and drought affected crop area in same period. Moreover, synthesized drought index can indicated the changes of soil moisture and it was significantly correlated with meteorological drought index such as SPEI, SPI.(6) The spatial and temporal changes of four season’s drought in Shandong province from2000to2010were studied using synthesized drought index and different spatiotemporal analysis methods. The coefficient of variation of synthesized drought index from2000to2010was sequenced as spring, summer, autumn and winter. The linear regression and correlation analysis of synthesized drought index and times show that drought is weakened in spring and summer, but intensified in winter. The results of rescaled range analysis show that the synthesized drought index has a long persistent characteristic in spring and summer, but has anti-persistent characteristic in winter. At different level of significance, Sen’s trend analysis has also got the same developing trend of drought. In summary, the drought in Shandong province will have a significant weakening trend in spring and summer, a intensifying trend in winter and still not a clear evolution direction in autumn. |
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