Studies On Optical Properties Of Wuliangsuhai Lake Ice Based On Field Observations

The freezing of lakes has a great influence on the energy balance and radiation distribution in the cold region in winter,which is mainly caused by the optical properties of lake ice.When the lake surface freezes,the energy entering the water body will decrease,while the reflected energy will increase,therefore changing the heat and energy exchange efficiency between water and air,as well as the ecological processes in the water body under ice.In order to better explore the optical properties of lake ice,based on the field investigation of winter lake ice in Wuliangsuhai Lake,Inner Mongolia,the optical properties of lake ice are studied in the present paper,which provides theoretical and data support for the study of winter energy transmission and remote sensing observation of lake ice.In the winter of 2018?2019,the apparent optical properties of Wuliangsuhai Lake ice and various typical underlying surfaces near the shore were observed by using Trios hyperspectral sensors.The lake ice at the observation point was sampled and the microstructure was observed.Through the detailed analysis of the collected data,the conclusions on the optical properties of the lake ice were drawn as follows.There are many kinds of near shore areas in winter in Wuliangsuhai Lake and the spectral characteristics of the underlying surface are different,while the spectral albedo of lake ice is different from other underlying surfaces.The diurnal variation curve of lake ice albedo on a clear day has obvious characteristics of two peaks,and the peak time is closely related to the sunrise time of the day.A parameterized scheme of lake ice albedo is proposed,which uses the commonly used probability density distribution function in mathematics to overlay,and describes the characteristics of the two peaks with its function images,four probability density distribution function combination modes are constructed,and realized.In addition,the best combination mode of Laplace is selected from the four combination modes of the parameterization scheme.The parameterization scheme has a good fitting effect on the lake ice albedo in a long time range,simple form and convenient application.It can effectively predict the lake ice albedo in a long time,with relative small error.The analysis shows that the content of bubbles in lake ice is 2.74%.Smaller bubbles have large quantity,and its distribution conforms to the power function.On the basis of bubble observation,the inherent optical properties of lake ice are calculated.The results show that the scattering coefficient of lake ice is 94m-1.