Journal cover Journal topic
Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/hess-2017-338
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
27 Jul 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Hydrology and Earth System Sciences (HESS).
Controls on surface soil drying rates observed by SMAP and simulated by the Noah land surface model
Peter J. Shellito and Eric E. Small Geological Sciences, University of Colorado Boulder, Boulder, 80309, USA
Abstract. Drydown periods that follow precipitation events provide an opportunity to assess the mechanisms by which soil moisture dissipates from the land surface. We use SMAP (Soil Moisture Active Passive) observations and Noah simulations from drydown periods to quantify the role of soil moisture, potential evaporation, vegetation cover, and soil texture on soil drying rates. Rates are determined using finite differences over intervals of 1 to 3 days. In the Noah model, the drying rates are a good approximation of direct soil evaporation rates. Data cover the domain of the North American Land Data Assimilation System phase 2 and span the first 1.8 years of SMAP's operation.

Drying of surface soil moisture observed by SMAP is faster than that simulated by Noah. SMAP drying is fastest when surface soil moisture levels are high, potential evaporation is high, and when vegetation cover is low. Soil texture plays a minor role in SMAP drying rates. Noah simulations show similar responses to soil moisture and potential evaporation, but vegetation has a minimal effect and soil texture has a much larger effect compared to SMAP. When drying rates are normalized by potential evaporation, SMAP observations and Noah simulations both show that increases in vegetation cover lead to decreases in evaporative efficiency from the surface soil. However, the magnitude of this effect simulated by Noah is much weaker than that determined from SMAP observations.


Citation: Shellito, P. J. and Small, E. E.: Controls on surface soil drying rates observed by SMAP and simulated by the Noah land surface model, Hydrol. Earth Syst. Sci. Discuss., https://doi.org/10.5194/hess-2017-338, in review, 2017.
Peter J. Shellito and Eric E. Small
Peter J. Shellito and Eric E. Small
Peter J. Shellito and Eric E. Small

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