A Critical Evaluation on the Role of Aerodynamic and Canopy–Surface Conductance Parameterization in SEB and SVAT Models for Simulating Evapotranspiration: A Case Study in the Upper Biebrza National Park Wetland in Poland

Kaniska Mallick,Malgorzata Kleniewska,Renaud Hostache,Loise Wandera,Jaroslaw Chormanski,Nishan Bhattarai

doi:10.3390/w10121753

Abstract

Evapotranspiration (ET) estimation through the surface energy balance (SEB) and soil-vegetation-atmosphere-transfer (SVAT) models are uncertain due to the empirical parameterizations of the aerodynamic and canopy-substrate conductances (gA and gS) for heat and water vapor transfers. This study critically assessed the impact of conductance parameterizations on ET simulation using three structurally different SEB and SVAT models for an ecologically important North-Eastern European wetland, Upper Biebrza National Park (UBNP) in two consecutive years 2015 and 2016. A pronounced ET underestimation (mean bias −0.48 to −0.68 mm day−1) in SEBS (Surface Energy Balance System) was associated with an overestimation of gA due to uncertain parameterization of momentum roughness length and bare soil’s excess resistance to heat transfer (kB−1) under low vegetation cover. The systematic ET overestimation (0.65–0.80 mm day−1) in SCOPE (Soil Canopy Observation, Photochemistry and Energy fluxes) was attributed to the overestimation of both the conductances. Conductance parameterizations in SEBS and SCOPE appeared to be very sensitive to the general ecohydrological conditions, with a tendency of overestimating gA (gS) under humid (arid) conditions. Low ET bias in the analytical STIC (Surface Temperature Initiated Closure) model as compared to SEBS/SCOPE indicated the critical need for calibration-free conductance parameterizations for improved ET estimation.

Highlights

Evapotranspiration (ET) monitoring in the wetlands are important for evaluating the hydrological budget, estimating groundwater discharge, quantifying seasonal water availability, and tracking as well as anticipating drought conditions [1]
Closure (STIC) [56,57], and the SVAT model is the Soil-Canopy-Observation of Photosynthesis and the Energy balance (SCOPE) [58]
STIC1.2 revealed marginal underestimation of half-hourly and daily λE and ET during both years (2015 and 2016), whereas SCOPE1.7 showed a tendency of overestimation and Surface Energy Balance System (SEBS) showed a tendency of underestimation especially in the beginning of the spring season

Summary

Introduction

Evapotranspiration (ET) (or latent heat flux, λE) monitoring in the wetlands are important for evaluating the hydrological budget, estimating groundwater discharge, quantifying seasonal water availability, and tracking as well as anticipating drought conditions [1]. Water 2018, 10, 1753 variables, ET is the most reliable indicator of hydrological recovery [2,3], and the difference between annual precipitation (P) and ET is a measure of the wetland health [3]. A detailed knowledge of wetland ET is crucial for predicting and monitoring the functioning of these ecosystems or for restoring the transformed wetlands to their original condition [7]. Among the range of techniques used to measure wetland ET (e.g., lysimetric, Bowen-ratio energy balance and the eddy-covariance), eddy covariance (EC) is the most promising for continuous monitoring of ET. It is hindered by a number of technical, economic and environmental factors. The EC sensors can malfunction when their measurement paths are obstructed by water droplets, water films, snow/ice particles, or other solids or liquids that interfere with the transmission or reception of the sensor signals (as described in [9])

Methods

Discussion

Conclusion