| Lake albedo is an important parameter to describe the energy balance of the water-air interface.It can describe the reflection capacity of the lake surface to the solar short-wave radiation,regulate the distribution process of the radiation energy between the lake and the atmosphere,and has an important impact on the local climate and ecological environment.However,previous studies have mostly focused on surface albedo,rarely involving lake albedo,and inadequate consideration of factors affecting water albedo.Most of the existing remote sensing inversion models of albedo have good applicability to land and will produce large errors when applied to lakes.Therefore,this paper intends to analyze lake albedo,focusing on the effects of astronomical factors(solar elevation angle),meteorological factors(wind speed)and water quality factors(chlorophyll-a concentration,turbid suspended matter)on lake albedo.Moreover,the sentinel-2 MSI sensor remote sensing method for lake albedo estimation was established for the first time by using sentinel-2 images and taking the energy transfer equation as the entry point.The specific work of this paper includes:(1)Detailed analysis of the effects of astronomical,meteorological and water quality factors on lake albedo.The solar elevation angle is the primary controlling factor of the change of lake albedo.The lake albedo decreases with the increase of the sun elevation angle.The parametric models of albedo and solar elevation angle developed in the ocean show different degree of underestimation in the inversion of inland lakes.Due to the strong backscattering of TSM in different solar elevation angle,the lake albedo increases with the increase of TSM,and the relationship is more obvious at high solar elevation angle,with the determination coefficient reaching 0.76.There was no significant correlation between lake albedo and chlorophyll-a concentration at low solar elevation angle,and the determination coefficient was 0.11.At high solar elevation angle,the albedo showed a positive correlation with the increase of chlorophyll-a concentration,with a determination coefficient of 0.47.However,compared with the TSM to the size of lake albedo,the concentration of chlorophyll a was much smaller.Wind waves indirectly affect lake albedo by affecting the TSM in shallow lakes.Therefore,the lake albedo is positively correlated with wind speed in the high solar elevation angle and the low solar elevation angle,with the determination coefficients of 0.62 and 0.50 respectively.CDOM and particle absorption have strong absorption effects at shorter wavelengths,affecting the distribution of incident solar radiation and its spectral distribution.However,there is not enough evidence to show that CDOM and particulate matter absorption will reduce the albedo of lakes.The change of lake albedo in this study area mainly depends on the backscattering characteristics of inorganic particulate matter.Atmospheric transmittance is closely related to water albedo.The water albedo decreases when the atmospheric transmittance increases,and the lake albedo has little relation with the solar altitude Angle when the atmospheric transmittance is low.(2)The lake albedo inversion model based on sentinel-2 MSI sensor was obtained for the first time.From the perspective of energy transmission,this paper selects an inversion method of converting narrowband albedo to broadband albedo,and using Sentinel-2 A spatial resolution image for the study area for 10 m lakes albedo product,Based on the measured albedo data,using the determination coefficient(R2)and root mean square error(RMSE)for validation,the result of the inversion results show that the R2 is 0.62,RMSE is 0.039.The values of lake albedo in the study area ranged from 0 to 0.45,with an average value of 0.14.The high value of lake albedo appears in the south of the Songnen Plain lake area,with a size between 0.28 and 0.45,and the low-value gathering area appears in the Qiqihar Lake Group.The central lake area of Jilin also has a low value,with a size between 0 and 0.10.From the west to the middle of Jilin Province,the albedo value tends to decrease gradually,and some areas have higher values.In a typical lake,the average albedo is arranged as follows:Yangsha lake>Shitoukoumen reservoir>Chagan lake>Moon lake>Erlong lake>Xinlicheng reservoir.(3)The spatial correlation between lake albedo and water quality factors was clarified.Taking chagan lake as an example,the TSM and Chl-a concentration of the same period were inverted,and the correlation was established.It was found that in different water quality factors,the TSM is the dominant factor affecting the spatial distribution of lake Albedo.The correlation between TSM and Albedo reach 0.85,while the correlation between Chl-a concentration and Albedo is 0.47... |
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