Analysis Of Drought And Flood Events Caused By Climate Change In Haihe River Basin

In the past 100 years,the global climate has been characterized by warming.As a result,temperature rise,water circulation,evaporation have increased,and the stability of the climate system has decreased.The frequency,intensity and extent of impact of extreme weather events have increased.The characteristics of climate change and drought and flood disasters in China,including intensity and coverage,are basically consistent with global changes.The overall trend is increasing.Due to climate change and human activities,China's drought and heavy rain events alternate.And a sharp change has seriously threatened regional water security,ecological security and food security,and has become a new trend in China's flood and drought disasters.Therefore,studying the climate change characteristics of the Haihe River Basin with temperature and precipitation as the main factors and the change of precipitation intensity after drought and whether the drought will lead to more concentrated and more intense precipitation is crucial for understanding the driving mechanism of drought and flood and its evolution trend.At the same time,it can help guide the disaster prevention and mitigation strategy.In this paper,the SOM clustering analysis method is used to divide the Haihe River Basin into five sub-areas.Based on the data of 43 meteorological stations in the Haihe River Basin and surrounding areas(1960-2015),the climate change characteristics of the Haihe River Basin are analyzed.The number of continuous no-day precipitation days is the evaluation standard,and the characteristics of drought caused by climate change are analyzed.According to the 24 h rainfall standard prescribed by the National Meteorological Administration,the water-reducing water is of different grades.The Pearson-III distribution curve is used to compare the statistical Haihe River Basin.The maximum daily rainfall data after five degrees of drought occurred were analyzed,and the frequency of occurrence of each grade of precipitation was calculated,and the relationship between precipitation intensity and drought duration and frequency was analyzed.The conclusions drawn are as follows:(1)Characteristics of climate changeThe Haihe River Basin is constantly developing in the direction of warming and drying.Using the linear trend method,Mann-Kendell non-parametric trend to test the temperature and precipitation of the Haihe River Basin.It is found that the annual average temperature of the basin increases year by year,and since the 1990 s,the temperature fluctuations are more obvious.The temperature change trend of sub-areas is consistent with that of the Haihe River Basin,and both of them are significantly rising.In different seasons,the temperature in I,II and III regions showed a significant upward trend,but the average temperature in the IV and V regions showed a downward trend in summer.The seasons are all rising,and the trend of temperature changes in each sub-area is similar to that of the Haihe River Basin.The annual precipitation in the Haihe River Basin shows a downward trend,and the summer decline trend is particularly significant.The other seasons are not obvious.From the perspective of each sub-area,the annual precipitation in the five sub-areas is decreasing,and the summer reduction is most obvious.In particular,V There is an upward trend in spring precipitation in the district.(2)Characteristics of drought changesDrought is increasing.The drought frequency of the entire Haihe River Basin showed a relatively stable growth trend.The summer drought was more common,the frequency of winter drought was the smallest,the drought change trend of each district was consistent with that of the Haihe River Basin,and the frequency of IV and V drought occurred more frequently.The frequency of drought is the highest,and it is still rising.It occurs mostly in summer.The changes of moderate drought and severe drought are not obvious,and the frequency of extreme drought has a slight decreasing trend,and it is rare in summer.(3)Frequency analysis of alternating precipitation eventsAs the duration of the drought increased,the frequency of light rain increased,while the probability of moderate rain and heavy rain decreased.The frequency of heavy rain and heavy rain is irregular.Extreme storms occur less frequently and only after extreme droughts.Therefore,prolonged droughts do not lead to more concentrated and more severe precipitation;With the increasing frequency of drought,the frequency of light rain and moderate rain did not change significantly.Areas I,II and III have a higher frequency of heavy rain,while areas IV and V have a lower frequency of heavy rain.In all subregions except region IV,the frequency of heavy rain and heavy rain increased.With the increase of the number of droughts,the duration of the drought becomes shorter,and the intensity of rainfall increases the first day after the drought,which is more likely to lead to the occurrence of drought and flood emergency.(4)Causes of droughts and floods and countermeasuresDue to the weakening of the summer monsoon in Southeast Asia,atmospheric anomalies,topography,rapid urbanization and human activities,the occurrence of droughts and floods in the Haihe River Basin has become more frequent in recent years,resulting in greater losses.In this regard,specific countermeasures have been given from the aspects of giving full play to the role of engineering facilities,adjusting the industrial layout,and strengthening the early warning and forecasting system.