# Review of Land Surface Albedo: Variance Characteristics, Climate Effect and Management Strategy
## 3 Variance Characteristics of Surface Albedo for Essential Land Types and Scales
### Albedo Variances for Typical Land Types
#### 3.1.3 Snow, Ice and Water Albedos  
Studies on snow albedo mainly focus on snow surfaces at a large scale at the north pole [107], the south pole [68] and alpine regions, and both pure [65] and contaminatedsnow [111] have been investigated. Similar to vegetation, a series of snow physical parameters also show a significant influence on surface albedo [78; 112], such as snow type [113], density [114], snow grain properties [18], snow depth, the SZA [112], roughness [115] and impurities [78]. Impurities can generally lead to a reduction in snow albedo [78; 116; 117], including light-absorbing particles of black carbon [18; 118] and soot [64]. In addition, microscopic plants of algae [116] and tundra [107] can also reduce surface albedo in snow-covered areas.  
Similar to those focused on snow, studies on ice albedo also focus on sea ice in the Arctic [119; 120] and Antarctica [121]. In particular, the Kangerlussuaq transect (K-transect, Greenland ice sheet) has attracted much attention in recent years [122; 123; 124; 125; 126]. Moreover, ice albedo changes with a series of physical properties, such as ice type [113; 127], concentration [121], roughness (e.g., weathering crust) [115; 126], melt-pond depth and ice thickness [128]. In addition, impurities are another essential contributing factor. For example, salt precipitation can lead to an increase in ice albedo [129]. However, lower ice albedo is observed when ice is contaminated with many impurities, such as algae [123; 126] and even algal blooms [18], soot [64], ashfall [130], Saharan dust and black carbon [131], and fire-induced aerosols [132].  
In terms of water, many studies have focused on ocean surfaces that represent approximately 70% of the Earth's surface [133; 134]. Ocean breaking waves [135] and ship wakes [136] can increase ocean albedo, and ocean water albedo has been calculated as a function of sun glint, whitecaps, and water-leaving reflectance [133]. Generally, the water surface presents a lower albedo than the surrounding terrestrial landscape [137]. In addition, water albedos at smaller scales are also investigated. For example, saline lake albedo increases with salt concentration [138]. For low-gradient, non-white water (flatwater) streams, the solar elevation angle, suspended sediment concentration, aeration and proportion of diffuse to direct solar radiation can enhance surface albedo from 0.025 to 0.33 [139].  
Snow, ice and water can be interchangeable across seasons, which leads to varying albedos. For example, the albedo of Arctic sea ice varies during melting and refreezing periods [17; 71], and impurity-induced albedo reduction of snow and glacier has enhanced glacier melt in the Tibetan Plateau [117] and the Alps [131]. Similarly, known drivers of algal blooms and cryoconite always lead to albedo reduction on ice sheets, glaciers, and snowfields [26], and microbial dark sediments also reduce the albedo of Greenland ice sheet supraglacial streams and lead to melting [125].