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An evaluation of modeled evaporation regimes in Europe using observed dry spell land surface temperature

Harris, Phil P.; Folwell, Sonja S.; Gallego-Elvira, Belen; Rodriguez, Jose; Milton, Sean; Taylor, Christopher M.. 2017 An evaluation of modeled evaporation regimes in Europe using observed dry spell land surface temperature. Journal of Hydrometeorology, 18 (5). 10.1175/JHM-D-16-0227.1

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Abstract/Summary

Soil moisture availability exerts control over the land surface energy partition in parts of Europe. However, determining the strength and variability of this control is impeded by the lack of reliable evaporation observations at the continental scale. This makes it difficult to refine the broad range of soil moisture–evaporation behaviours across global climate models (GCMs). Previous studies show that satellite observations of land surface temperature (LST) during rain-free dry spells can be used to diagnose evaporation regimes at the GCM grid box scale. This Relative Warming Rate (RWR) diagnostic quantifies the increase in dry spell LST relative to air temperature, and is used here to evaluate a land surface model (JULES) both offline and coupled to a GCM (HadGEM3-A). It is shown that RWR can be calculated using outputs from an atmospheric GCM provided the satellite clear-sky sampling bias is incorporated. Both offline JULES and HadGEM3-A reproduce the observed seasonal and regional RWR variations, but with weak springtime RWRs in central Europe. This coincides with sustained bare soil evaporation (Ebs) during dry spells, reflecting previous site-level JULES studies in Europe. To assess whether RWR can discriminate between surface descriptions, the bare soil surface conductance and the vegetation root profile are revised to limit Ebs. This increases RWR by increasing the occurrence of soil moisture limited dry spells, yielding more realistic springtime RWRs as a function of antecedent precipitation but poorer relationships in summer. This study demonstrates the potential for using satellite LST to assess evaporation regimes in climate models.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1175/JHM-D-16-0227.1
CEH Sections: Reynard
ISSN: 1525-755X
Additional Keywords: atmosphere-land interaction, soil moisture, surface fluxes, surface temperature, climate models, land surface model
NORA Subject Terms: Earth Sciences
Meteorology and Climatology
Atmospheric Sciences
Date made live: 23 Mar 2017 10:37 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/514374

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