Simulation of ice cover thickness in Inner Mongolia section of Yellow River
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Abstract:
Ice thickness cover is an important index to judge and predict the disaster of ice in the Yellow River.The ice thickening and deglaciation process of the Yellow River during the freeze period is unique.The degreeday model suitable for the Inner Mongolia section of the Yellow River and the typical value of the empirical coefficient depends on the calibration of the field measured data.The heat that affects the thickness of ice cover mainly comes from the heat conduction between ice and atmosphere and the heat transfer between ice and water.The measured data show that the ice thickness varies greatly at different stations,which is not only due to the temperature change but also due to the discharge,velocity,and roughness.Based on the prototype observation data,the ice cover thickness in the Inner Mongolia section of the Yellow River was simulated. Colburn analogy method is used to calculate the heat flux under the ice cover,the factors such as river flow rate,water flow rate,river level slope and ice cover roughness are taken into account,and a model for calculating ice thickness is employed for degreeday method based on Stefan formula.Relevant parameters of the ice thickness calculation model are calibrated by the prototype observation data of four stations in the Bayangaolei to Toutaoguai reach.The calibrated model could calculate the ice thickness through the air temperature and water temperature data.Taking the ice thickness change near Toudaoguai observation station from 2015 to 2016 as an example,the ice thickness calculation formula introduced by Colburn analogy method is compared with the ice thickness calculation results of other formulas.The temperature data of Toudaoguai Station in the Inner Mongolia section of the Yellow River from 2006 to 2017 is analyzed.The ice thickness model is used to calculate the ice thickness during the freezing period from 2009 to 2010,when the cold degree was the coldest and the accumulated temperature value in winter was the largest.The results of different ice thickness calculation models under extreme weather conditions are compared. The results show that the ice thickness calculated by the ice thickness model is close to the measured ice thickness value.The accuracy of the improved ice thickness calculation model reaches 1.97%,which is improved compared with 14.99% of Stefan model,4.77% of the unified degree of the maturity model and 14.98% of dynamic water ice thickness radiation degree of the maturity model.The trend of ice thickness variation is consistent with the measured ice thickness variation trend.According to the accumulated temperature values and the characteristics of the temperature series,the temperature data of Toudaoguai station from 2006 to 2017 is analyzed.After analyzing the temperature data,it is found that the temperature changes in the short period of years under extreme weather conditions are more intense,and the average temperature in winter is also lower.For 2009–2010,when the cold degree was the coldest and the accumulated temperature value in winter was the largest,the accuracy of the model is 7.34%.In extreme weather,the accuracy of the model is higher,and the changing trend of ice thickness in the freeze period is similar to that in normal temperature. In most degree-day models,the convective heat transfer coefficient between ice cover and water body is calculated as a constant.The ice thickness calculation formula with the introduction of the Colburn analogy is improved in the accuracy of the ice thickness calculation results because the convective heat transfer coefficient between water and ice cover is not constant when considering the influence of under ice heat flux on the ice thickness.The calculated results of the model are in good agreement with the measured ice thickness data,which indicates that the model is suitable for the simulation of ice thickness in the Inner Mongolia section of the Yellow River,and can be used for the simulation of ice thickness variation at different points in the reach.The ice thickness calculation results of the improved model under both normal and extreme weather conditions maintain high accuracy,and the research results can provide a theoretical basis for the ice thickness calculation in the study area under extreme weather conditions.
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