Effects Of Climate Change On Drought And Flooding Disasters In China

In recent decades, the global climate change characterized by the climate warming has become one of the grave threats confronted by the humanity and received great attention and attached great importance worldwide. Light, temperature and water are the most important natural resources for agricultural production. Agriculture meteorological disaster is the most serious abiological agricultural disaster, especially for the flood and drought, as they generally induce heavy social damages and great economic losses due to the long duration and large suffered area. Therefore, the agriculture is one of the most vulnerable industries influenced by the climate change. China has a vast territory and embodies heterogeneous complex of diverse landscapes, cultures, and socioeconomic conditions, resulting in the different climate change characteristics and different impacts on the agricultural production over regions. Based on the meteorological data and disasters data over50years for each province of China, the changing characteristics of temperature, precipitation and sunshine were investigated in this study using the statistical methods. The effects of climate change on the drought and flood disasters were fully addressed for different provinces of China. These results are required for determining suitable options to mitigate negative effect of climate change on the agricultural production.The main research results and conclusions of the dissertation are included:(1) Using the empirical orthogonal function (EOF) method, the weather dataset (e.g., average temperature, temperature anomaly, precipitation, precipitation anomaly, percentage of precipitation anomaly, number of precipitation day, number of precipitation anomaly days, percentage of sunshine and percentage of sunshine anomaly) from630weather stations of China in1960-2008was collected and analysed. Results indicated that the period for1980s is a turning point for temperature increasing with no apparent trend before1988and significant warming trend after1998. This warming tread is greater in the northern China than that in the southern China, especially in the northeast, northwest and Inner Mongolia region. There had no significant inter-annual variability of precipitation but present the decrease in the number of precipitation days. The Jiangxi and Hunan provinces were the flood disaster-prone areas in response to precipitation change in recent years. Precipitation and the number of precipitation days in the northwest area and the Qinghai-Tibet Plateau both presented increasing trends since1990’s. Percentage of sunshine was decreased significantly, especially since the late1980s. The southeast coastal is the prominent area for the percentage of sunshine decreasing.(2) EOF analysis further indicated that the flood and drought disasters have become more and more serious in China. Inner Mongolia, northwest and northeast regions are the most areas suffered by the agricultural drought disaster. Annual flood disaster is fluctuating obviously. The regions located in the middle and lower reaches of the Changjiang River, the Pearl River basin and northeast are the most areas suffered by the flood disaster and flood disaster anomaly.(3) The grey correlation analyses indicated that the flood and drought disasters were both strongly related to the temperature anomaly but were not related to precipitation anomaly at a national level. As the entire country, the flood and drought disasters are not mainly caused by the change of precipitation but may be mainly caused by the change of number of precipitation days that reflects the temporal distributions of precipitation.(4) The dominating factors caused droughts disaster differs over regions. Precipitation declining is the dominative factor in the Bohai region. For example, the changes of above-mentioned four meteorological variables explained59.15%of variability of the drought disaster area percentage with the Direct Path Coefficient (DPC) of precipitation-0.8142in the Hebei province. Climate change contributed66.86%variability of the drought disaster area percentage with the DPC of precipitation and number of precipitation day-0.4987and-0.3269, respectively. The number of precipitation day has more significant effect on droughts disaster than the precipitation in northwest regions. For example, climate change contributes56.55%variability of droughts disaster area percentage with the DPC of precipitation and number of precipitation day-0.9589and-0.0541in Ningxia Autonomy Region, respectively. In general, the area suffered by heavy droughts disaster, such as north region and northeast region, is not in charged of change of yearly precipitation but in charged of number of precipitation day. The regions having less precipitation show this law more obviously.(5) Agricultural flood disaster mainly occurred in the northern region of China, which is closely related to precipitation and number of precipitation day. The increases in precipitation and number of precipitation day are the reasons for explaining the variability of flood disaster area percentage in south region. In Fujian province, for example, climate change contributes53.47%variability of droughts disaster area percentage with the DPC of precipitation and number of precipitation day0.3532and0.6674, respectively. The decrease in number of precipitation day is the domination factor for the variations of flood disaster area percentage in central China and Sichuan province. In Hubei province, for example, climate change contributes62.85%variability of flood disaster area percentage with the DPC of precipitation and number of precipitation day0.8239and-0.3855, respectively. In Sichuan province, climate change contributes54.30%variability of droughts disaster area percentage with the DPC of precipitation and number of precipitation day0.4768and-0.4327, respectively. In Guizhou province, climate change contributes48.57%variability of droughts disaster area percentage with the DPC of precipitation and number of precipitation day0.4843and0.6214, respectively.Considering the vast territory and heterogeneous complex of diverse landscapes, cultures, and socioeconomic conditions for China, it is essential to distinguish the dominant factor causing agricultural flood and drought disasters for different regions. Although it has been well known that excessive precipitation and deficient precipitation is the basic cause for agricultural flood and drought disaster, respectively, on the background of global warming, temporally uneven distribution of precipitation is the main cause for the flood and drought disaster. Accordingly, regional differences in the responses of the flood and drought disasters to climate change are required to be considered in determining and adapting suitable practices to mitigate negative effect of climate change on the agricultural production in China.