In sloping terrain, albedo measured in the horizontal plane is typically not representative for the underlying surface. Accordingly, albedo should be measured either parallel (termed slope-parallel albedo) or corrected from horizontal measurements (termed slope-corrected albedo) to represent the actual sloping surface. This study presents the theory and the effect when applying a simple slope correction with the aim to transform albedo measured in the horizontal plane over a slope (termed horizontally measured albedo) to the sloping surface. Simultaneous measurements of horizontal and slope-parallel albedo for three different classes of atmospheric clearness conditions (clear, partly overcast, cloudy) and for four different terrain aspects (north, east, west, south) were collected during the study period. The results show that applying the slope correction improved the linear correlation coefficient between the slope-parallel and horizontally measured albedo by 0.60, 0.51 and 0.24 for clear, partly overcast, and cloudy conditions, respectively. During clear atmospheric conditions, slope-parallel and slope-corrected albedo deviated by 5% in terms of mean absolute error, while the slope correction reduced the deviation between the horizontally measured and slope-parallel albedo by 70%. Diurnal trends revealed a large discrepancy with smaller/larger horizontally measured albedo than slope-parallel albedo for the western/eastern slope during morning (opposite during afternoon). For the southern/northern slope the horizontal orientation of the radiation sensors overestimated/underestimated the albedo for all atmospheric clearness conditions. The horizontally measured reflected radiation had on average a difference of 3 Wm^-2 from the slope-parallel reflected radiation, corresponding to a deviation of 3%. The findings show that the simple slope correction considerably improve the reliability of the horizontally measured albedo in sloping terrain when slope-parallel measurements are not possible. However, during partly overcast conditions, the simple slope correction suffers under the complex radiation regime and should preferably not be applied.

在倾斜地形中，在水平面上测量的反照率通常不能代表下垫面。因此，应平行测量反照率（称为斜坡平行反照率）或根据水平测量值校正（称为斜率校正反照率）以表示实际倾斜表面。本研究介绍了应用简单坡度校正的理论和效果，目的是将在坡度上的水平面上测量的反照率（称为水平测量的反照率）转换为倾斜表面。在研究期间收集了三种不同级别的大气晴朗条件（晴、部分阴、多云）和四种不同地形方面（北、东、西、南）的水平和斜坡平行反照率的同步测量值。结果表明，在晴朗、部分阴天和多云条件下，应用斜率校正后，平行斜率和水平测量的反照率之间的线性相关系数分别提高了 0.60、0.51 和 0.24。在晴朗的大气条件下，平行斜率和斜率校正反照率的平均绝对误差偏差为 5%，而斜率校正使水平测量反照率与斜坡平行反照率之间的偏差减少了 70%。昼夜趋势显示，早上西坡/东坡的水平测量反照率较小/较大的反照率与斜坡平行反照率存在较大差异（下午相反）。对于南坡/北坡，辐射传感器的水平方向高估/低估了所有大气晴朗条件下的反照率。^-2来自斜坡平行反射辐射，对应于 3% 的偏差。研究结果表明，当无法进行平行坡度测量时，简单的坡度校正可显着提高坡度地形中水平测量反照率的可靠性。然而，在部分阴天条件下，简单的斜率校正在复杂的辐射状态下会受到影响，最好不要应用。