Microclimate of a desert playa: evaluation of annual radiation, energy, and water budgets components


  • Esmaiel Malek

    Corresponding author
    1. Department of Plants, Soils and Biometeorology, Utah State University, Logan, UT 84322-4820, USA
    • Department of Plants, Soils and Biometeorology, Utah State University, Logan, UT 84322-4820, USA
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We set up two automatic weather stations over a playa (the flat floor of an undrained desert basin that, at times, becomes a shallow lake), approximately 65 km east–west by 130 km north–south, located in Dugway (40° 08′N, 113° 27′W, 1124 m above mean sea level) in northwestern Utah, USA, in 1999. These stations measured the radiation budget components, namely: incoming Rsi and outgoing Rso solar or shortwave radiation, using two Kipp and Zonen pyranometers (one inverted), the incoming Rli (or atmospheric) and outgoing Rlo (or terrestrial) longwave radiation, using two Kipp and Zonen pyrgeometers (one inverted) during the year 2000. These sensors were ventilated throughout the year to prevent dew and frost formation. Summation of these components yields the net radiation Rn. We also measured the air temperatures and humidity at 1 and 2 m and the soil moisture and temperature (Campbell Sci., Inc., CSI) to evaluate the energy budget components (latent (LE), sensible (H), and the soil (Gsur) heat fluxes). The 10 m wind speed U10 and direction (R.M. Young wind monitor), precipitation (CSI), and the surface temperature (Radiation and Energy Balance Systems, REBS) were also measured during 2000. The measurements were taken every 2 s, averaged into 20 min, continuously, throughout the year 2000. The annual comparison of radiation budget components indicates that about 34% of the annual Rsi (6937.7 MJ m−2 year−1) was reflected back to the sky as Rso, with Rli and Rlo amounting to 9943.4 MJ m−2 year−1 and 12 789.7 MJ m−2 year−1 respectively. This yields about 1634.3 MJ m−2 year−1 as Rn, which is about 24% of the annual Rsi. Of the total 1634.3 MJ m−2 year−1 available energy, about 25% was used for the process of evaporation (LE) and 77% for heating the air (H). The annual heat contribution from the soil to the energy budget amounted to 2% during the experimental period. Our studies showed that the total annual measured precipitation amounted to 108.0 mm year−1 during the year 2000, but the total evaporation was 167.6 mm year−1, which means some water was extracted from the shallow water table (about 60 cm on the average depth during the year 2000). Copyright © 2003 Royal Meteorological Society.