| Lakes are an important part of terrestrial water cycle system and cryosphere.Global warming and its interaction with lake environment have attracted wide attention.As important parameters of lake physical and chemical properties,lake surface temperature and lake ice phenology can sensitively indicate the changes of climate and lake environment.As one of the most sensitive areas of climate change in China,a large number of lakes are densely distributed in Northeast China.Therefore,monitoring and studying lake surface temperature and lake ice phenology in Northeast China is helpful to understand the response relationship between lake change and climate change.In this paper,31 typical lakes and reservoirs in Northeast China were selected as the study area,and daily MOD11A1 and MYD11A1 time series for the period HY2001-HY2020 were obtained based on the GEE(Google Earth Engine)platform,and nonlinear curve fitting was used to fill in the missing data of the time series.The lake surface temperature retrieved by MODIS was highly correlated with the air temperature(R~2=0.958,P<0.05)and surface temperature(R~2=0.977,P<0.05).The results showed that the average daytime temperature,nighttime temperature and daily average temperature of 31 lakes in Northeast China decreased by 0.025℃,increased by 0.059℃and increased by 0.017℃respectively every year.The change rate of daily average lake surface temperature in freshwater lakes was higher than that in saltwater lakes during the whole year and ice period.The surface temperature of lakes in Northeast China is mainly controlled by latitude,lake altitude,air temperature and net solar radiation.Based on the lake surface temperature time series data,the freeze-up date(FUD),break-up date(BUD)and ice cover duration(ICD)of the lake during HY2001-HY2020 were obtained.The extracted ice phenology was well correlated with the ice records of hydrological stations and the published ice phenology datasets,which proved that the extraction method of lake ice phenology information was feasible.The results show that the lake ice phenology of the lake group in Songnen Plain of Northeast China presents regional consistency:the FUD of lakes is advanced,the BUD is delayed,and the ICD is prolonged.On average,lakes begin to freeze on November5th and melt on April 8th every year,and the ICD for 155 days.The FUD of lakes in Northeast China are delayed at a rate of 0.234 days/year,the BUD are advanced at a rate of 0.145 days/year,and the ICD is shortened at a rate of 0.313 days/year.The phenology of lake ice in Northeast China is mainly affected by latitude,net solar radiation and air temperature.In this paper,FLake model(Freshwater Lake Model)is used to simulate the surface temperature and ice phenology of Hulun Lake,Chagan Lake and Great Xingkai Lake from HY1980 to HY2020.Comparing MODIS remote sensing inversion results with FLake model simulation results,it is found that there is a high correlation between them,and the simulation results in Hulun Lake and Great Xingkai Lake are the best.During 1980-2020,the DOY corresponding to the simulated maximum lake surface temperature of Hulun Lake,Chagan Lake and Great Xingkai Lake showed a downward trend,and its change rates were 0.248 days/year,0.104 days/year and 0.300days/year,respectively.During HY1981-HY2020,the change trend of ice phenology in Hulun Lake,Chagan Lake and Great Xingkai Lake was analyzed.It was found that the FUD of Hulun Lake and Great Xingkai Lake was delayed(0.062 days/year,0.050days/year),the BUD was advanced(0.111 days/year,0.060 days/year),and the ICD was shortened(0.177 days/year,0.112 days/year),while the FUD of Chagan Lake was delayed(0.146 days/year),the BUD was delayed(0.122 days/year)and the ICD was shortened(0.027 days/year).Temperature was the main factor affecting the change of ice phenology in Hulun Lake,Chagan Lake and Great Xingkai Lake. |
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