Detection Of Ice Thermodynamic Parameters And Research On Ice Thickness Model Optimization At Mohe Reach Of Heilongjiang River

The ice jam,at the upstream and midstream of Heilongjiang River,poses great threats to the local people's life and property safety,hydraulic structure and ecological environment.Due to the special location and extreme cold climate in winter,it's really difficult to acquire the ice/snow regime and hydrological and meteorological observation data at the upstream and midstream of Heilongjiang River.Current researches about the Heilongjiang River ice jam based on the limited manual observation data are empirical and can't describe the dynamic evolution of the ice/snow regime during winter.Therefore,it remains urgent to conduct automatic and continuous ice/snow regime observation experiment at the typical basin of upstream and midstream of Heilongjiang River to obtain sufficient ice/snow regime and hydrological and meteorological data,especially the thermodynamic parameters of ice cover,to research and analyze the ice evolution systematically and lay the theoretical foundation for the ice jam study at the upstream and midstream of Heilongjiang River.This manuscript utilized the R-T-O ice and snow regime monitoring system developed by the ice detection group of Taiyuan university of Technology,and conducted the ice/snow observation experiment with the Ta Hsing-an Ling Hydrologic Bureau,Heilongjiang Province and China Institute of Water Resources and Hydropower Research at the Mohe reach of Heilongjiang River(122.35°E,53.47°N)from the January to April in 2016.After analyzing and studying the ice thickness,snow depth and temperature profiles data,we calculated the ice cover conductive heat flux and water heat flux at ice bottom and optimized the ice thickness model,the research contents and results as follow:(1)We summarized the current development of ice simulation and detection technology on the basis of reviewing large number of references.We proposed an ice thickness parameter discriminant algorithm based on the temperature differences,this algorithm could determine the ice thickness by determining the positions of air-ice interface and ice-water interface.For the determination of ice-water interface,this algorithm chose the 0? as the threshold value,if Tn<0?,Tn-1<0?,Tn+2<0?,then the position of No.n detection unit was the position of the ice-water interface.For the determination of the air-ice interface,this algorithm utilized the obvious difference of conductivity between ice and air,if?max=|Tm+1-Tm|,then the position of No.m detection unit was the position of the air-ice interface,thus the ice thickness H =a(m-n),a was the distance between adjacent temperature detection units.(2)After analyzing the meteorological data,there were several extreme cold days with the lowest air temperature below-40 ?.The largest ice thickness was 94cm,snow depth was 15cm and the largest ice growth rate was 2cm/d during the observation experiment.The ice temperature profiles in the rapid growth period were approximately linear distribution and the ice temperature profiles in the melting period tended to ?.In special days,the ice temperature profiles were not linear distribution and appeared relatively cold layer,the position of relatively cold layer moved with the change of air temperature.The ratio of ice surface temperature and air temperature at 8:00 was 0.68,there was lag time when radiation,air temperature and ice surface temperature reached the maximum in a day and the lag time was affected by the snow depth.We calculated the conductive heat flux at the ice top with the temperature gradient method and the force-recovery method,the calculated results of the two methods were consistent.Besides,we calculated the conductive heat flux at ice bottom with the temperature gradient method and compared with the conductive heat flux at the ice top.The conductive heat flux at the ice top fluctuated more greatly and frequently.With the increase of ice thickness,the fluctuation frequency and amplification of conductive heat flux at the ice top and bottom all decreased.We established the heat energy balance relation at the ice bottom with the residual method and calculated the water heat flux at ice bottom.The water heat flux at ice bottom was controlled by the conductive heat flux and latent heat flux at ice bottom,the maximum of ice bottom water heat flux was around 25 W/m2,in addition,we analyzed the possible sources of calculation errors.(3)We analyzed the characteristics of the Stefan's Law and the ice thermodynamic model.With consideration of the differences between the air temperature and the ice surface temperature,the snow insulation effect and the influence of water heat flux at ice bottom,we optimized the ice thickness model on the basis of Stefan's Law.We estimated the ice thickness with the optimized model and compared with the estimation results of Stefan's Law and the atmosphere-ice coupling model,the estimation result of optimized model agreed best with the observation ice thickness value and the smallest root mean square error of the optimized model was 1.52cm.