The Radiation Balance of Typical Terrain Units in the Low Arctic

This study was designed to achieve an understanding of the behavior of the summer radiation balance for a diversity of terrain types characteristic of the low Arctic near treeline in order to promote more accurate modeling of net radiation from measured or calculated solar radiation or all-wave radiation. Components of the radiation balance, including net radiation, incoming and reflected solar radiation, incoming and outgoing longwave radiation, and radiative surface temperatures, were measured or derived for four distinct terrain types near Churchill, Manitoba, from May through August, 1982. The terrain types were upland tundra, upland open spruce forest, lowland peat with moss vegetation, and lowland swamp covered with sedge grass. These represent an assemblage typical of the low Arctic in North America. Snowmelt from the tundra surfaces occurred at the end of April, a month earlier than normal. Snow in the forest persisted until mid-June, which is normal. On average for the summer, incoming solar radiation comprised 41 percent of the total incoming flux, the remainder consisting of longwave sky radiation. Surface albedos in the non-snow period were generally small, being largest and the same for the upland tundra and lowland peat at 0.15, less for the forest at 0.12, and least for the swamp, which ranged between 0.08 and 0.12. Albedos generally increased as the summer progressed. With snow in the forest, albedos above the forest canopy did not exceed 0.42. In common with observations in middle latitudes, the results indicate that under clear skies there was a strongly developed diurnal pattern of large albedos in morning and evening and smaller values at midday. This was not evident for cloudy days. The radiative surface temperatures at nonforested sites were always warmer than the overlying air on a daily basis, which was true also for the forest after final snowmelt. With snow, however, the forest floor was colder and the canopy warmer than the surrounding air. Differences in net radiation between surfaces were small for the full measurement period, and net radiation comprised between 59 to 65 percent of incoming solar radiation and 24 to 27 percent of incoming all-wave radiation. Key Words: radiation balanceterrain typeslow arctic

Albedo (alchemy) · Arctic · Atmospheric sciences · Climatology · Earth's energy budget · Geography · Meteorology · Peat · Permafrost · Physical geography · Snow · Snowmelt · Swamp · Tundra · Climate change and permafrost · Cryospheric studies and observations · Ecology · Environmental Science · Geology · Geology and Paleoclimatology Research · Oceanography · Radiation

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