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Web End = Boundary-Layer Meteorol (2016) 159:521538 DOI 10.1007/s10546-015-0058-0
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Web End = Playa Soil Moisture and Evaporation Dynamics During the MATERHORN Field Program
Chaoxun Hang1 Daniel F. Nadeau2
Derek D. Jensen1 Sebastian W. Hoch3 Eric R. Pardyjak1
Received: 16 October 2014 / Accepted: 23 June 2015 / Published online: 15 July 2015 Springer Science+Business Media Dordrecht 2015
Abstract We present an analysis of eld data collected over a desert playa in western Utah, USA in May 2013, the most synoptically active month of the year, as part of the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) program. The results show that decreasing surface albedo, decreasing Bowen ratio and increasing net radiation with increasing soil moisture sustained a powerful positive feedback mechanism promoting large evaporation rates immediately following rain events. Additionally, it was found that, while nocturnal evaporation was negligible during dry periods, it was quite signicant (up to 30 % of the daily cumulative ux) during nights following rain events. Our results further show that the highest spatial variability in surface soil moisture is found under dry conditions. Finally, we report strong spatial heterogeneities in evaporation rates following a rain event. The cumulative evaporation for the different sampling sites over a ve-day period varied from
0.1 to 6.6mm. Overall, this study allows us to better understand the mechanisms under
lying soil moisture dynamics of desert playas as well as evaporation following occasional rain events.
Keywords Bare soil evaporation Dry lake Gravimetric method Nocturnal evaporation
Spatial heterogeneity Surface energy balance
1 Introduction
Drylands, dened as regions in which potential evapotranspiration exceeds annual precipitation, cover more than 40 % of the exposed earth surface (DOdorico and Porporato 2006). Particularly in arid areas, where the average annual precipitation is less than 250mm, soil
B Eric R. Pardyjak
[email protected] Department of Mechanical Engineering, University of Utah, Salt Lake City, UT 84112, USA2 Department of Civil and Water Engineering, Universit Laval, Quebec City, Canada3 Department of Atmospheric Sciences, University of Utah, Salt Lake City, UT 84112, USA
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moisture is known to be a...