Radiation Measurements At Lewis Glacier, Mount Kenya, Kenya

Short- and long-wave radiation on variously oriented vertical surfaces, direct solar radiation, global radiation, and long-wave radiation on a horizontal surface were measured on Lewis Glacier, Mount Kenya, at 4 800 m. For the orientation of vertical surfaces, the following azimuths were selected: 45°, facing the steep slope of the upper glacier; 135°, facing a rock ridge and some glacier surface in the foreground; 225°, facing down-glacier towards the Teleki valley with open sky occupying much of the view; and 315°, directed towards the steep south-east face of the Nelion peak. The horizontal components of diffuse short-wave radiation reach a magnitude comparable to those of direct radiation. As a result of contrastingly different albedos of natural surfaces, the horizontal component of diffuse short-wave radiation is particularly large from the direction of the upper glacier, with values around 330-500 W m-', and smallest from the direction of the rock face of Nelion peak, where values are around 150-330 W m-'. Long-wave radiation seems enhanced from the direction of the Nelion face, and reduced from the azimuth of the upper glacier, thus apparently reflecting differences in emissivity and temperature. (author)