Changing Characteristics And Trend Determine Temporal Drought In North China

Drought-flood is one of the most common meteorological disasters which can cause huge economic losses every year, and even pose a serious threat to human survival and development. Based on analysis of mathematical statistics, Mann-Kendall test method, SPI and Z-index, the context analyzed the spatial-temporal characteristics of climate change and drought-flood in the North China with the data of daily average temperature, monthly average temperature, daily precipitation, monthly precipitation and annual precipitation during1961-2010.Then the context determined all grades drought-flood years and judged the trend based on the mechanism of symmetry and the method of commensurability and butterfly structure diagram. At last, the context put forward some adaptive measures in order to provide a reference for the related department and theoretical guidance meaning for disaster prevention and mitigation work.The main research conclusion of this context is as follows:(1) The rising trend of temperature was obvious in the North China. The annual average temperature roughly presented latitudinal distribution characteristics that decreases from the south to the north, and the inclination rate increased from south to north. Thus the temperature gap would be more and more smaller between the south and the north during the50years.(2) The seasonal distribution of precipitation was uneven and the precipitation in spring and winter showed an increasing trend; and the average annual precipitation presented a fluctuant decreasing trend on the whole, while the change is not obvious. The precipitation rendered a decreasing trend from southeast to northwest; in the meantime, the inclination rate overall presented a decreasing trend from the south to the north, which would cause the gap between the south and north bigger and bigger.(3) The drought year mainly occurred in1965,1968,1972,1981,1986,1992,1997,1999,2001,2002and2006during recent50years; the flood year mainly occurred in1962,1964,1969,1973,1984,1990,1996,1998and2003. Through analyzing station level of drought-flood, the drought would result in a wide range of impact, while the flood was often territorial.The frequency of drought presented an increasing tendency from the south to the north. The region where frequently occurred drought mainly because the rate of light drought was high; in general case, the drought was often severe once it occurred in the place where the frequency of drought was low. The inclination rate of drought-flood showed a decreasing trend from southwest to northeast during1961-2010. The variability rate of drought-flood was rather high in the North China and all reached20%, which showed that the climate was unstable in the North China, and the frequency of drought-flood was rather high.(4)The drought-flood years showed better structural features of commensurability and had obvious time symmetry. Synthesizing3judgment methods of time symmetry: formula of commensurability, diagram of commensurability system and butterfly structure diagram, the context made a conclusion that a wide range of drought may occur in2015with the probability of91.6%; the flood may occur in2013with the probability of58.3%. The situation that drought and flood may rapidly transform is likely to happen in2013.The drought-flood years in Beijing and Shijiazhuang similarly showed better structural features of commensurability and had obvious time symmetry. Synthesizing3judgment methods, the drought may occur in2013with a random probability of61.5%and the flood in2015with the probability of58.3%in Beijing; The drought may occur in2014with a random probability of66.7%; and the flood in2016with the probability of63.6%in Shijiazhuang. The conclusions are just one exploratory study.(5)The drought-flood years and the El Nino years showed a better correlation while the flood years and the La Nina years presented better correlation. The relations between drought-flood and occurring years of ENSO event was not obvious, while a significant correlation with years around the ENSO events.During1961-2010,4drought years appeared in the sunspot valley years, the rest of drought years occurred in the falling stage of sunspot;4flood years appeared in the sunspot peak years and the rest also occurred in the falling stage even the valley. Flood years have a significant correlation with sunspot in all seasons, and it always appeared in the falling stage of the sunspot. The drought years have a poor correlation with sunspot.