Evaporation Measurement

Abstract

This chapter summarises the practical methods available to estimate evaporation, E . It describes the background of methods based on soil physical, micrometeorological and plant physiological concepts. The most appropriate method will mainly depend on required spatial and temporal scales of E , accuracy needed, and the available resources (financial and manpower). These issues are taken into account during the discussion.

Methods to separate observed global evapotranspiration into the interception, transpiration and soil surface evaporation components

“…There are several evaporation measurement techniques that measure the total evaporation from a surface. For a comprehensive review of these, Verhoef and Campbell (), Shutov et al . (), Burt et al .…”

Changes to the energy budget and evapotranspiration following conversion of tropical savannas to agricultural lands in São Paulo State, Brazil

“…Evapotranspiration can be estimated through a variety of approaches, including soil‐water monitoring, lysimeter measurements, and micrometeorologic methods (using the Bowen ratio or eddy covariance procedure) (Abtew and Melesse , Verhoef and Campbell ). However, these approaches are all based on point‐scale or field‐scale measurements and thus have limited value for assessing ET at large scales.…”

The use of remote sensing for reliable estimation of net radiation and its components: a case study for contrasting land covers in an agricultural hotspot of the Brazilian semiarid region

“…Estimation of R n is very important in the context of turbulent energy flux estimates (latent heat flux (i.e., evapotranspiration), and sensible heat flux), particularly in those studies devoted to the assessment of evapotranspiration based on remote sensing techniques (Bastiaanssen et al, 1998(Bastiaanssen et al, , 2005Allen et al, 2007;Silva et al, 2015;Elnmer et al, 2019) and those employing the Bowen ratio method, where R n (as a key component of the available energy) is crucial for the reliable calculation of latent and sensible heat fluxes (Verhoef and Campbell, 2005). Reliable values of R n are also required to check the closure of the energy balance when turbulent energy fluxes have been directly determined with the eddy covariance technique, because there may be an underestimation due to the existence of storage of heat in canopies or in the layer below the instrumentation, horizontal advection, errors in the frequency response of sensors, and regional scale heterogeneity that can cause large-scale eddies that are not readily sensed by eddy covariance systems.…”