A Comparison of the Radiation and Energy Balance during the Growing Season for an Arctic and Alpine Tundra

Abstract

For arctic tundra at Barrow, Alaska [USA], and alpine tundra on Niwot Ridge in the Front Range of Colorado [USA], the components of the radiation and energy balance for the growing season [of Kobresia] from June-Aug. are examined. Where sufficient data are available, the radiation fluxes are also compared for the other seasons. There is a remarkable similarity in the mean daily totals of net radiation for the growing season. Insolation receipt is greater in the alpine tundra but the net longwave radiative loss is also greater so that the 2 effects nearly compensate each other. The difference in net radiation between the 2 sites is only 3% of the daily total. When hourly data are examined, maximum intensities and diurnal ranges are considerably greater in the Alpine than in the Arctic. Differences in the energy balance regimes are apparent both in the daily totals and hourly fluxes. At Barrow there is generally little or no moisture stress due to a continual standing water supply. Most of the available radiant energy at the surface is used in the latent heat flux rather than the enthalpy flux. The opposite is the case on Niwot Ridge where the major moisture source is from slowly melting snowbanks. A greater moisture stress develops through the growing season which apparently cannot be alleviated by convective precipitation. More of the net radiation is used in the enthalpy flux than the latent heat flux.