Studies On Variation Characteristics And Future Prediction Of The Ice Regime Driven By Multiple Factors In The Lower Yellow River

Due to its special geographical location and climatic conditions,the ice regime of the lower Yellow River has become the most prominent and main flood season in the local winter and spring.In history,the disasters are named for the frequent breakups,serious disasters and difficulties in rescue and protection.In recent years,with the change of temperature,the process of cold air,water and sediment regulation,water diversion along the Yellow River,reservoir regulation and other factors,the ice situation of the lower Yellow River has been greatly alleviated,and the ice regime situation has changed a lot.Based on the historical measured ice conditions in the lower Yellow River from 1950 to 2017,this paper first analyzes the variation rules of ice regime on multiple time scales in detail and reveals the spatial and temporal distribution characteristics.Secondly,based on the temperature data,the temperature evolution law of transition period was studied from three perspectives,including temperature distribution,extreme low temperature index change and cold air invasion.Finally,the correlation coefficient method was used to extract the main controlling factors affecting it,and the characteristics of the ice condition in the past years were classified according to the three indicators of temperature,water and ice regime,so as to estimate the future ice regime and put forward the countermeasures of ice condition prevention and disaster reduction.The main research results are as follows:(1)The evolution characteristics of the ice condition along the time scale are as follows:the frequency of freeze-up and break-up were unstable in a single ice flood season;the length of freeze-up river sections,the number of days of freeze-up river sections and the maximum ice volume all decreased significantly;the freeze-up flow and break-up flow decreased obviously;the temperature of the freeze-up increased obviously.(2)After the operation of Xiaolangdi reservoir,the ice condition changed and decreased significantly.(3)The number of frost days,ice days,cold day days,cold night days,and cold wave days decreased significantly;the maximum and minimum of monthly minimum temperature increased significantly.The mutation years of the extreme low temperature index were concentrated in the 1980s,and the significant periods were concentrated in 9?14a on the time scale of nearly 67a.(4)December is the period of cold wave and strong cold air;the cooling intensity of cold wave and strong cold air reached the maximum in February and January respectively.The frequency of cold wave invasion is more in 1950s and 1960s than in 1990s.(5)The number of ice days,the number of cold niehts and the minimum temperature of monthly minimum temperature can be used as the sensitive factors of the severity of the transit;when the lower Yellow River encounter extreme low temperature weather in the future,there is still the possibility of severe flooding disaster.The results of this study can provide the conditions for setting the most unfavorable flood control standards for the lower Yellow River in the future,and it is of great significance to the security,mass relocation and economic and social aspects of the lower Yellow River.