An analysis of the AWSderived surface fluxes

For the year 2000, all components of the surface energy balance are calculated from the AWS data (Fig. 34.1). Daily mean incoming shortwave radiation shows a clear annual cycle. The day to day variation is due to clouds. In winter, reflected shortwave radiation almost equals incoming shortwave radiation owing to the high surface albedo, which drops in May when snow is starting to melt and ice appears at the surface. The mean annual albedo is 0.53. Incoming longwave radiation is generally less than outgoing longwave radiation. On cloudy days, however, it sometimes exceeds longwave radiation emitted by the glacier surface. In summer when the surface is at melting point, fluctuations in outgoing longwave radiation are small.

The sensible and latent turbulent heat fluxes are estimated from measured air temperature, humidity and wind speed using a bulk approach and a constant turbulent exchange coefficient of 0.00153 (Oerlemans & Klok, 2002). The sensible turbulent heat flux is positive throughout the entire year because mean daily air temperature always exceeds the surface temperature at our site. It is largest in summer when the surface temperature is limited to the melting point and the vertical temperature gradients are largest. This also generates a strong katabatic flow, which in turn enhances the turbulent exchange. The latent turbulent heat flux is small and on average positive, indicating that normally condensation or riming takes place. This adds about 2 cm water-equivalent per year to the glacier surface at the AWS site. Between

Figure 34.1 Daily mean values of the surface energy balance derived from an automatic weather station on the tongue of Morteratschgletscher for the year 2000.

Figure 34.1 Daily mean values of the surface energy balance derived from an automatic weather station on the tongue of Morteratschgletscher for the year 2000.

day 127 and 303, when the AWS site was free of snow, 7.3 m ice melted according to the surface energy balance calculations. Altogether, 75% of the energy for this melt was supplied by net solar and longwave radiation and 25% by the turbulent heat fluxes.

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Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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