| The Huai River basin in Anhui province is located in the middle of the basin. The area of the basin is about 67000 square kilometers and takes about a quarter of the whole basin. It is the most important production base of grain, cotton and fossil oil in China. It is also the traffic fortress of north-south China. So this area is very important to the national economy and agriculture and occupies an important place in the social development. The Huai River is also a natural boundary of north and south of China, which 0℃ isotherm in January and isohyet of 800 millimeters roughly along the Huai River. Huai river basin is located on the transition zone of north and south China climate demarcation and the boundry is Huai River. North of the Huai River belongs to the warm temperate semi-humid area and south of the river belongs to the north subtropical humid area. The special factors of geographical environment, climate conditions and underlying surface condition lead to the meteorological disasters such as flood, drought or alternation in Huai River basin. The present situation of the frequent natural disasters seriously restricted the development of economy and social. In recent years, with the increasing tendency of global warming and demand of water resources, the effects of drought and flood disaster for our country is increasingly serious. Frequency, strength and influence of meteorological disasters have been significant growth. It has been a serious threat to our food production security and ecological security. It has become one of the major natural disasters which restric the development of economic and social sustainable in China. Researches of the cause and tendency of the drought and flood are very important to reduce the losses by the disasters. Researching the relationship between north-south climate demarcation and the pattern evolution of regional drought and flood is from the perspective of internal water circulation and climate geographical origin of flood and drought. It reveals the regularity of regional evolution of the drought and flood disasters. By studying the difference situation of drought and flood under the condition of wet season or drought season, combining with the historical situation, the relationship between the climate demarcation relation and index of drought and flood has been analyzed. The influence from the fluctuations of climate demarcation to the pattern evolution of drought and flood disasters in Huai River has been illustrated. It is helpful to further recognize the formation mechanism and driving mechanism of the risk of flood and drought disasters, to perfect the regional dynamic disaster early warning mechanism, and to improve the level of regional drought and flood disaster risk management and disaster prevention and mitigation capacity, so as to avoid or reduce disaster losses, to ensure the safety of area of food production, to promote the rational allocation and utilization of water resources. Thus, this article is based on the establishing of regional comprehensive index, deducting the drought and flood in area evolution and the north-south climate demarcation, from the more general to specific, made the following main results:(1)Raw data (precipitation and temperature) of this area in the research was selected from 1955 to 2013. SPI, SPEI and SAPI were used as the evaluation indexes. The performance of the three indexes was compared. Result showed that SPEI index was better than the other two. The attributes of precipitation and temperature it contained can better reflect the regional drought and flood situation.(2)Through the historical data, the value of SPEI in each site is calculated. GIS space simulation technology was used to draw the region of drought and flood in different years. The regional distribution of drought and flood and space-time change regularity of nearly 50 years is analyzed. The regional drought and flood model in the Huai river region was built based on the time and space evolution. In general, wet season and dry season showed a similar drought or flood situation. In this basin, drought and flood has a similar tendency. Along Huai River is the main disaster areas and disasters tended to serious and frequently.(3)Combined with historical data, GIS space simulation technology is been used to draw area north-south climate demarcations figure in each interval time. The changing regular of the demarcations of north-south region was analyzed in the research. Both of the isohyets and the accumulated temperature line were between 32° to 34°north latitude. Combined with the charts and data, the influence from the fluctuation of north-south climate demarcation to the evolution of regional drought and flood has been found. The relationship of the climate demarcation and the droughts and floods, and the impact of the change of regional drought and flood have been analyzed. It is clear that area north-south climate demarcation line has a great influence on the regional pattern of drought and flood.800 mm isohyet has especially significant impact on the regional pattern of drought and flood. The higher latitude 800 mm isohyet stays, the more likely to the area in flood.(4)In genetic analysis indicates that the El Nino and the Pacific oscillation phenomenon have some negative correlation on north-south demarcation. East Asian Monsoon has some positive correlation on north-south demarcation. Drought and flood situation of the district also will be affected. Through the research on the study area based on geographical climate factors influence mechanism of drought and flood disasters, further expounds find that the regional climate geographical conditions have some impact on the pattern of drought and flood. And these effects are combined to draw up the evolution trend of regional drought and flood pattern. The research provides a reference for disaster prevention and mitigation work. |
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