Variation characteristics and forecast of freeze-up dates of major rivers in Heilongjiang Province
As an important part of the cryosphere,under the background of global warming,this paper studies the freeze-up dates of major rivers in Heilongjiang Province,so as to provide a scientific basis for disaster pre-vention and mitigation. Based on the observation data of the freeze-up dates of the hydrological observation sta-tions in Heilongjiang Province from 1962 to 2020,this paper used the Mann-Kendall mutation test and linear trend analysis method to explore the characteristics of the river freeze-up dates of Heihe Station of Heilongjiang River,Harbin Station of Songhua River,Jiangqiao Station of Nenjiang River and Raohe Station of Wusuli River with the influence of meteorological factors. The freeze-up date,average temperature,surface temperature,minimum temperature,average wind speed and average sunshine hours were analyzed,and the freeze-up dates of Heihe Station,Harbin Station,Jiangqiao Station and Raohe Station were simulated and predicted by informa-tion diffusion theory and multiple linear regression analysis method. The results showed that:(1) From 1962 to 2020,the average freeze-up date of Harbin Station,Jiangqiao Station,Heihe Station and Raohe Station was be-tween November 12 and November 22. The results of Mann-Kendall mutation test showed that from 1962 to 2020,Harbin Station,Jiangqiao Station,Heihe Station and Raohe Station all had mutation dates,and the muta-tion years were 1970,2005,2000 and 2012,respectively. Over the past 59 years,the freeze-up dates of Jiangqiao Station and Heihe Station have been significantly postponed (P<0.05),with a change rate of 2.46 d·(10a)-1,1.35 d·(10a)-1,which was postponed by 15 d and 8 d,respectively. (2) The results of correlation analysis show that the average temperature,surface air temperature and minimum temperature are the key factors affect-ing the freeze-up date of Heihe Station,Harbin Station,Jiangqiao Station and Raohe Station. Specifically,the freeze-up dates of Jiangqiao Station and Heihe Station in relatively high latitude areas are mainly affected by the average temperature,surface temperature and minimum temperature in early November,while the Harbin Sta-tion and Raohe Station are mainly affected by the average temperature,surface temperature and minimum tem-perature in mid-November. (3) According to the information diffusion theory,when the negative accumulated temperature is-180 ℃,the probability of river freeze-up at Heihe Station,Harbin Station,Jiangqiao Station and Raohe Station reaches 80％～90％,and when the negative accumulated temperature reaches-240 ℃,the rivers of Heihe Station,Harbin Station,Jiangqiao Station and Raohe Station are basically frozen. (4) Based on the key factors such as mean temperature,surface air temperature and minimum temperature,this paper uses multi-ple linear stepwise regression analysis to simulate and predict the freeze-up dates of Harbin Station,Jiangqiao Station,Heihe Station and Raohe Station. The forecast accuracy of the constructed multiple linear regression model for river freeze-up forecast is more than 80％. It has a good effect on predicting the freeze-up date of Har-bin Station,Jiangqiao Station,Heihe Station and Raohe Station,which provides a scientific basis for disaster prevention and mitigation in this area.
freeze-up dateriver iceice forecastingclimatic changeHeilongjiang Province
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