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

Abstract

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 R si and outgoing R so solar or shortwave radiation, using two Kipp and Zonen pyranometers (one inverted), the incoming R li (or atmospheric) and outgoing R lo (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 R n . 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 ( and 12 789.7 MJ m −2 year −1 respectively. This yields about 1634.3 MJ m −2 year −1 as R n , which is about 24% of the annual R si . 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).

Summertime soil hydrological cycle and surface energy balance on the Mongolian steppe

“…On average over the period JJA at the four sites, G, H, and lE shared 6%, 73%, and 21% of R n , respectively. These percentages are similar to those recorded at desert playas by Malek et al (1990) and Malek (2003), while lE from relatively moist grassland is generally the major component, being approximately three-times greater than H (Betts et al, 1996).…”

Evaporation and land surface energy budget at the Salar de Atacama, Northern Chile

“…Allison and Barnes, 1985;Ullman, 1985;Jacobson and Jankowski, 1989;Malek et al, 1990;Tyler et al, 1997;Menking et al, 2000;Malek, 2003) have found that evaporation rates are quite low, due to the high salinity of groundwater and soil moisture and to the formation of salt crusts that either limit capillary rise or form impermeable barriers to liquid water. Although only a few studies have been conducted on the energy budget characteristics of playas (Malek et al, 1990;Tyler et al, 1997;Menking et al, 2000;Malek, 2003), those measurements that exist show that playa salt crusts are particularly suited to inhibiting evaporation, for they reflect the incoming solar radiation that provides the energy source for evaporation and often represent a cap that can be highly resistant to water vapor transport (Malek et al, 1990).…”

Linking surface and subsurface properties of biocrusted and non-biocrusted habitats of fine-grained fluvial sediments (playas) from the Negev Desert

“…Being remnants of previous close-basin lakes during previous wet palaeoclimate (Bowler et al, 1986;Magee et al, 1995) or ephemeral water bodies following occasional inundations (Handford, 1982;Magee et al, 1995), the playas are characterized by low organic matter (Bowler et al, 1986) and low-porosity fine-grained sediments, mainly consisting of silt and clay (Bowler et al, 1986). These flat fine-grained sediments characterized many of the arid and semi-arid regions of the world, reported, among other places, from the arid regions of the southwestern USA (Handford, 1982;Malek, 2003;Wondzell et al, 1990), the Sahara (Hamdi-Aissa et al, 2004;Schild and Wendorf, 2001), Namibia (Ward, 1988), China (Pachur and Wünnemann, 1995;Vengosh et al, 1995) and Australia (Bowler et al, 1986;Magee et al, 1995). In contrast to playa lakes which are wet >75% of the year, playas are defined as sediments which are dry >75% of the year (Briere, 2000).…”