Characteristics Of Extreme Climate Events In Huaihe River Basin In Recent 60 Years

In the context of global climate change,extreme climate events occur frequently.Huaihe River Basin is located in the North-South climate transition zone of China.It is an important geographical and ecological boundary and vulnerable area of ecological environment.It is very sensitive to global climate change.In order to understand the trend and spatial-temporal pattern of extreme climate events in the Huaihe River Basin,based on the daily maximum temperature,minimum temperature and precipitation data of 63 meteorological stations in the Huaihe River Basin from 1960 to 2017,linear trend analysis,m-k mutation test,sliding rank sum test and ordered clustering method were used to analyze the spatial-temporal changes of extreme climate threshold and climate events in the Huaihe River Basin,and to explore the mechanism Objective to study the influencing factors of extreme climate events in Huaihe River Basin.The results show that:(1)The absolute value of extreme low temperature threshold is decreasing from southeast to northwest,and the extreme high temperature threshold is lower in the east coast than in the inland.The extreme precipitation threshold is lower in the East and West,and higher in the north and south.(2)In terms of time variation trend,the extreme cold event index in Huaihe River Basin showed a significant downward trend,while the extreme warm event index showed a significant increasing trend,and the four extreme indexes showed an upward trend.In addition,cold day index and cold night index showed a downward trend,while warm day index and warm night index showed an upward trend.In addition to the significant decrease of SDII,other extreme precipitation indexes have no significant changes.(3)In terms of spatial distribution,the indices of extreme warm events at most stations in the Huaihe River Basin showed a significant increasing trend,especially in the eastern part of the Huaihe River Basin,while the indices of extreme cold events showed a significant decreasing trend.The change trend of extreme precipitation index in Huaihe River Basin is basically the same.Most extreme precipitation indexes in the south,Southeast and central regions show an upward trend,while most extreme precipitation indexes in the northeast region show a downward trend,and the number of stations showing an upward trend is significantly more than the number of stations showing a downward trend.(4)The extreme temperature index showed a significant mutation in 1960-2017,and the cold extreme index showed a significant downward trend after the mutation year,while the warm extreme temperature index showed a significant upward trend.The extreme precipitation index did not appear significant mutation point.(5)There is a significant positive correlation between warm temperature index and annual average temperature,and a significant negative correlation between annual average temperature and cold index.There is a positive correlation between the warm index and the cold index,and a negative correlation between the cold index and the warm index.Each extreme precipitation index has a high correlation with the annual average precipitation,and the extreme precipitation index has a high significant positive correlation.(6)The warm extreme index and extreme index of Huaihe River Basin are generally positively correlated with longitude,and negatively correlated with latitude and altitude;the cold extreme index is generally negatively correlated with longitude,and positively correlated with latitude and altitude,while the extreme precipitation index is mostly positively correlated with longitude and altitude and negatively correlated with latitude.There is a significant negative correlation between AO and the cold extreme temperature index in Huaihe River Basin.EASM has a negative correlation with most extreme precipitation indexes,and the correlation coefficient is generally large.