Evaluation of TSEB turbulent fluxes using different methods for the retrieval of soil and canopy component temperatures from UAV thermal and multispectral imagery

Abstract

The thermal-based Two Source Energy Balance (TSEB) model partitions the evapotranspiration (ET) and energy fluxes from vegetation and soil components providing the capability for estimating soil evaporation (E) and canopy transpiration (T). However, it is crucial for ET partitioning to retrieve reliable estimates of canopy and soil temperatures and net radiation, as the latter determines the available energy for water and heat exchange from soil and canopy sources. These two factors become especially relevant in row crops with wide spacing and strongly clumped vegetation such as vineyards and orchards. To better understand part of this research was conducted thanks to the MC-COFUND Talentia Program

Incorporation of Unmanned Aerial Vehicle (UAV) Point Cloud Products into Remote Sensing Evapotranspiration Models

“…This feature of VSSIXA can be useful for partitioning total flux into vine and interrow flux. Second, although vegetation indices (such as NDVI) are popular and well-known inputs for modeling LAI, these indices by themselves cannot fully describe the variability in LAI when the amount of active cover crop in the inter row is significant [67]. Therefore, 3D structural metrics can be used as other sources of information to derive spatial maps of LAI.…”

“…According to White et al [14], it was assumed that the LICOR-2200C was measuring LAI in a rectangle 1 m wide and 3 m long. However, the smallest valid resolution in applying the TSEB model for the study area was determined to be 3.6-m grid [67], which means that all required inputs for the TSEB model must be set to 3.6-m grids. Due to inconsistency between the LICOR-2200C footprint and the TSEB model resolution and its unknown impact on the LAI map, vine spectral-structural information is extracted for both rectangular and square buffers around LAI measurements ( Figure 6).…”

“…TSEB-2T is a version of the TSEB model that was developed for when both Ts and Tc can be derived from nadir and off nadir Tr viewing angles [85] or by deriving pure vegetation and soil/cover crop pixels in a contextual spatial domain, namely VI-Tr space [67]. The contextual domain is a 3.6 x 3.6 m grid mapping NDVIs versus Tr (Figure 11).…”

“…In TSEB with Tc and Ts estimates ( Figure 12) using the TSEB-2T version [67,85], net shortwave (Sn) and longwave radiation (Ln) are generally calculated at the first steps. Next, net longwave radiation is separated into canopy and soil net longwave radiation (Ln s and Ln c ) using a formulation developed by Kustas and Norman [86] (Equations (3) and (4)):…”

“…In scenario 2 (the structural-based scenario, S2), GP Model 2 is used to create the LAI map. h vc , f c (vine projected surface area/the grid area), and w c maps (3.35 f c [67]) are estimated by VSSIXA outputs instead of the fixed values used in S1. In Scenario 3 (the spectral-structural-based scenario, S3), the LAI map is created using GP Model 3 and other TSEB inputs the same as S2 (Table 5).…”