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Quantification and Prediction of Nighttime Evapotranspiration for Two Distinct Grassland Ecosystems
Author(s) -
Groh J.,
Pütz T.,
Gerke H. H.,
Vanderborght J.,
Vereecken H.
Publication year - 2019
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2018wr024072
Subject(s) - evapotranspiration , environmental science , lysimeter , eddy covariance , daytime , bowen ratio , precipitation , atmospheric sciences , grassland , sunrise , water cycle , sunset , wind speed , vegetation (pathology) , hydrology (agriculture) , diurnal cycle , dew , water balance , ecosystem , soil water , soil science , meteorology , geography , ecology , geology , geotechnical engineering , biology , condensation , medicine , physics , pathology , astronomy
Evapotranspiration ( ET ) is, after precipitation, the second largest flux at the land surface in the water cycle and occurs mainly during daytime. Less attention has been given to water fluxes from the land surface into the atmosphere during nighttime (i.e., between sunset and sunrise). The nighttime ET ( ET N ) may be estimated based on models that use meteorological data; however, due to missing experimental long‐term data, the verification of ET N estimates is limited. In this paper, the amount of ET N for two grassland ecosystems was determined from highly temporally resolved and precise weighing lysimeter data. We found that annual ET N ranged between 3.5% and 9.5% of daytime annual ET ( ET D ) and occurred mainly during wet soil and canopy surface conditions, which suggests that ET N is largely related to evaporation. ET N was positively correlated with wind speed. Dew formation, ranging from 4.8% to 6.4% of annual precipitation, was in absolute terms larger than ET N . The prediction of ET N with the Penman‐Monteith model improved if the aerodynamic and surface resistance parameters were based on vegetation height observations and the nighttime stomatal resistance parameter was assumed to be zero. The occurrence of hot days during the observation period showed to increase average ET N rates. Our results suggest that ET N can be observed with precision weighing lysimeters, was a not negligible component in the water balance of the grassland ecosystems, and thus needs more attention when simulating land surface hydrological processes.