Scale effect and scale correction of land-surface albedo in rugged terrain

Abstract

Influence of topography must be corrected when fine-scale remote sensing data are used to estimate surface albedo in rugged terrain. In the case of coarse-scale satellite remote sensing data, the topographic effect on albedo estimation is generally ignored because the influence to albedo estimation of overall slope in coarse-scale pixels is usually considered negligible; however, because of the scale effect in albedo, neglecting within-pixel topology may cause errors in albedo estimation from coarse-scale data. This paper investigates the scale effect on land-surface albedo estimations, particularly in the case of converting fine-scale albedo to coarse-scale albedo in rugged terrain. Starting from the definition of difference-scale albedo in rugged terrain, a method is presented to convert fine-scale surface albedo to coarse-scale albedo, then deriving a factor to correct coarse-scale land-surface albedo. The performance and accuracy analysis of the method are investigated by using a simulated digital elevation model (DEM) with different mean slopes, as well as real DEM and Thematic Mapper images. Results show that the method is effective for scale-effect correction of land-surface albedo in rugged terrain.

Assessment of long-term WRF–CMAQ simulations for understanding direct aerosol effects on radiation "brightening" in the United States

“…Radiation trends in the western US could be influenced by local terrain (Oliphant et al, 2003;Wen et al, 2009) influences as well as episodic long-range pollution transport, which may contribute to the lack of a clear relationship be-tween trends in aerosol burden and surface radiation at these locations. As stated by Gan et al (2014a), the long-range transport of aerosol/dust plumes can cause enhancements in both surface aerosol concentrations and AOD (Gan et al, 2008;Mathur, 2008;Miller et al, 2011;Uno et al, 2011) and possibly contribute to the noted trends of tropospheric aerosol burden both at the surface and aloft.…”

Simulation and Analysis of the Topographic Effects on Snow-Free Albedo over Rugged Terrain

“…However, with the upscaling approach, many parameters are required, including reflectance characteristics, vegetation structural parameters, illumination conditions, and the radiation of each subpixel slope, which results in more uncertainties and computational complexities. The parameterized idea adopted by Wen [19] is an alternative method to estimate BSA due to its simplicity and efficiency. According to the definition of albedo [1], the BSA ρ BSA_low (θ s , φ s ) over a rugged terrain under a clear sky is calculated by:…”

“…2018, 10, x FOR PEER REVIEW 3 of 19 instead of WSA in this paper. This paper was organized as follows.…”

“…To simulate and evaluate the BSA over a rugged terrain, nine simulated DEMs with 30 m spatial resolution were generated to provide various magnitudes of roughness [19]. The statistical mean values of the elevation, slope and sky view factor are listed in Table 1.…”

Improved Atmospheric Modelling of the Oasis-Desert System in Central Asia Using WRF with Actual Satellite Products

“…This indirectly confirms our speculation that oasis salinization and larger areas with plastic mulching could increase the actual albedo levels. The possible reason for slight differences at the mountaintops between the actual and default albedo is that the surface reflectance estimation from different satellite images has large uncertainties over rugged terrain [42,[76][77][78][79][80]. The spatial distributions of the actual versus default LAI and VF data, as well as the differences between them, are shown in Figure 2c,d,g,h,k,l, respectively.…”