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@article{han_asymmetry_2024,
	title = {Asymmetry in the {Diurnal} {Variation} of {Land} {Surface} {Albedo} and {Its} {Impacts} on {Daily} {Mean} {Albedo} {Estimation}},
	volume = {129},
	issn = {2169-897X, 2169-8996},
	url = {https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2023JD039728},
	doi = {10.1029/2023JD039728},
	abstract = {Abstract
            Daily mean albedo, a crucial variable of the earth radiation budget, is significantly affected by the diurnal variation of land surface albedo (DVLSA). The DVLSA typically exhibits asymmetry, thereby affecting the estimation of the daily mean albedo. However, the asymmetry in the DVLSA is generally ignored in daily mean albedo estimation. In this study, we investigated the influencing factors of the asymmetry in the DVLSA and evaluated its impacts on estimating the daily mean albedo based on field observations and simulated data. Our findings reveal that the asymmetry in the DVLSA varies among land cover types, with forests exhibiting more pronounced asymmetry compared to croplands, grasslands, and bare soil. The diurnal variation of the atmospheric conditions is the primary factor controlling the asymmetry in the DVLSA, with that of land surface conditions being a secondary factor. Neglecting the asymmetry in the DVLSA leads to estimation error in daily mean albedo, particularly pronounced during winter. The relative error of daily mean albedo can exceed 10\% when the mean asymmetry index of diffuse irradiance fraction reaches 40\%. However, the DVLSA retrieved from the satellite Bidirectional Reflectance Distribution Function product inadequately captures asymmetry, resulting in a relative error of approximately 13.7\% in estimating daily mean albedo.
          , 
            Plain Language Summary
            The amount of sunlight reflected by the ground is different in the morning and afternoon, which is important for climate research. This study looked at factors that cause this difference in reflection and found that it depends on things like land cover types and atmospheric visibility. Ignoring this difference in reflection can make it difficult to accurately estimate how much heat the earth absorbs each day, especially in the winter. Existing methods for estimating this are not perfect and can introduce errors of up to 13.7\%. A better understanding of these variations can improve our ability to study and address climate change.
          , 
            Key Points
            
              
                
                  The asymmetry in the diurnal variation of albedo varies with land cover types
                
                
                  The atmospheric conditions control the asymmetry in the diurnal variation of albedo
                
                
                  The asymmetry in the diurnal variation of albedo impacts the daily mean albedo estimation},
	language = {en},
	number = {14},
	urldate = {2025-02-14},
	journal = {Journal of Geophysical Research: Atmospheres},
	author = {Han, Yuan and Wen, Jianguang and Xiao, Qing and You, Dongqin and Meng, Lei and Wu, Shengbiao and Hao, Dalei and Tang, Yong and Chen, Xi and Liu, Qinhuo and Zhao, Congcong},
	month = jul,
	year = {2024},
	pages = {e2023JD039728},
}