Study On The Law Of Drought And Flood In Huang - Huai - Hai Basin Based On Modified Palmer Drought Index

Droughts and floods are two major natural disasters in China. With escalation of climatechange in recent years, occurrence of droughts and floods has aggravated. On the one hand,Huang-Huai-Hai river basin locates in East Asian monsoon region and is very sensitive toclimate change response; on the other hand, this river basin is one of the importantagricultural production areas in China, any climate disaster could cause huge loss forindustrial and agricultural production and economic development. Therefore study on theregulation of the droughts and floods in this region has significant scientific and practicalvalue. There are many evaluation methods nowadays, and each has its own limitationsbecause of different factors considered. Among them Palmer index has considered a wideranged factors and has a more reasonable description to droughts and floods characteristics.According to meteorological, hydrological and soil data set, this article set up basic model ofPalmer index and choose typical23meteorological stations in Huang-Huai-Hai region. Basedon that, research is conducted on evolution characteristics of droughts and floods in time andspace, and comparison with other droughts and floods indexes to finally obtain the bestjudgment criteria for studying this region’s droughts and floods features.The main results are as follows:(1) Based on measured meteorological data, runoff data and effective moisture in soilfrom European medium-term forecasts center data, modified from Palmer drought index, adroughts and floods favored this region is established. According to Huang-Huai-Haidroughts and floods record, make comparison in modified Yellow River Palmer droughts andfloods index from time and space. In time dimension, modified Palmer index successfullysimulated the typical droughts. In space dimension has a very good match with historicalrecord.(2) From1961to2010, Huang-Huai-Hai has tendency to have more droughts. Itscoverage has a increasing trend and is dominated by regional droughts. It has tendency tohave less floods and is dominated by regional floods. Four levels of droughts have shown asignificant period of22-27years. Four levels of flooding ranges are20to22for the maincycle. Mutational analysis showed that, in addition to extreme droughts and floods, the rest ofthe grade ranges all present mutation point around1977to1978.(3) In space dimension, high-frequency area of mild drought has a wider range, mainlylocated in Ningxia, Neimenggu, Gansu, Shanxi province. High frequency area of moderateand severe droughts has significant reduction, and high frequency area of extreme drought is very less. Frequency of floods is totally lower than droughts frequency in research area,Through the amendment Palmer Index EOF analysis, the first eigenvector field presentsoverall consistency in positive phase change characteristics, which is affected by large-scaleclimate anomalies. The second eigenvector field showed anti-phase pattern in north and southof latitude37°N regions, showing zonal distribution space, which could most possibly beinfluenced by the role of latitude and monsoon climate. The third eigenvector field is boundedby113.5°E, reflecting anti-phase spatial distribution pattern in east and west, which could beconnected with continent sea distribution.(4) By comparing different drought index period, mutation point and the trend, we canconclude that, under the circumstances of large temperature and evaporation variability,Palmer index has a better performance than the standardized precipitation index andprecipitation mean percentage with illustrating strength, properties and continuity of droughtfloods.