Improving evapotranspiration estimates in Mediterranean drylands: The role of soil evaporation

TY - JOUR

T1 - Improving evapotranspiration estimates in Mediterranean drylands

T2 - The role of soil evaporation

AU - Morillas, Laura

AU - Leuning, Ray

AU - Villagarcia, Luis

AU - Garcia, Monica

AU - Serrano-Ortiz, Penelope

AU - Domingo, Francisco

PY - 2013/10/1

Y1 - 2013/10/1

N2 - An adaptation of a simple model for evapotranspiration (E) estimations in drylands based on remotely sensed leaf area index and the Penman-Monteith equation (PML model) (Leuning et al., 2008) is presented. Three methods for improving the consideration of soil evaporation influence in total evapotranspiration estimates for these ecosystems are proposed. The original PML model considered evaporation as a constant fraction (f) of soil equilibrium evaporation. We propose an adaptation that considers f as a variable primarily related to soil water availability. In order to estimate daily f values, the first proposed method (fSWC) uses rescaled soil water content measurements, the second (fZhang) uses the ratio of 16 days antecedent precipitation and soil equilibrium evaporation, and the third (f drying), includes a soil drying simulation factor for periods after a rainfall event. E estimates were validated using E measurements from eddy covariance systems located in two functionally different sparsely vegetated drylands sites: a littoral Mediterranean semiarid steppe and a dry-subhumid Mediterranean montane site. The method providing the best results in both areas was fdrying (mean absolute error of 0.17 mm day-1) which was capable of reproducing the pulse-behavior characteristic of soil evaporation in drylands strongly linked to water availability. This proposed model adaptation, fdrying, improved the PML model performance in sparsely vegetated drylands where a more accurate consideration of soil evaporation is necessary. Key Points An adaptation of an evapotranspiration model is presented for drylands Three methods for improving the soil contributions are presented The capacity of the adapted model is demonstrated in drylands

AB - An adaptation of a simple model for evapotranspiration (E) estimations in drylands based on remotely sensed leaf area index and the Penman-Monteith equation (PML model) (Leuning et al., 2008) is presented. Three methods for improving the consideration of soil evaporation influence in total evapotranspiration estimates for these ecosystems are proposed. The original PML model considered evaporation as a constant fraction (f) of soil equilibrium evaporation. We propose an adaptation that considers f as a variable primarily related to soil water availability. In order to estimate daily f values, the first proposed method (fSWC) uses rescaled soil water content measurements, the second (fZhang) uses the ratio of 16 days antecedent precipitation and soil equilibrium evaporation, and the third (f drying), includes a soil drying simulation factor for periods after a rainfall event. E estimates were validated using E measurements from eddy covariance systems located in two functionally different sparsely vegetated drylands sites: a littoral Mediterranean semiarid steppe and a dry-subhumid Mediterranean montane site. The method providing the best results in both areas was fdrying (mean absolute error of 0.17 mm day-1) which was capable of reproducing the pulse-behavior characteristic of soil evaporation in drylands strongly linked to water availability. This proposed model adaptation, fdrying, improved the PML model performance in sparsely vegetated drylands where a more accurate consideration of soil evaporation is necessary. Key Points An adaptation of an evapotranspiration model is presented for drylands Three methods for improving the soil contributions are presented The capacity of the adapted model is demonstrated in drylands

KW - soil evaporation

KW - actual evapotranspiration

KW - Penman-Monteith equation

KW - drylands

U2 - 10.1002/wrcr.20468

DO - 10.1002/wrcr.20468

M3 - Journal article

SN - 0043-1397

VL - 49

SP - 6572

EP - 6586

JO - Water Resources Research

JF - Water Resources Research

IS - 10

ER -