| Title: | A new temperature-vegetation triangle algorithm with variable edges (TAVE) for satellite-based actual evapotranspiration estimation |
| Authors: | Zhang, H., S.M. Gorelick, N. Avisse, A. Tilmant, D. Rajsekhar and J. Yoon |
| Year: | 2017 |
| Journal: | Remote Sensing |
| Volume (Issue): | 8(9) |
| Pages: | |
| Article ID: | 735 |
| DOI: | 10.3390/rs8090735 |
| URL (non-DOI journals): | |
| Model: | SWAT |
| Broad Application Category: | hydrologic only |
| Primary Application Category: | evapotranspiration assessment |
| Secondary Application Category: | none |
| Watershed Description: | 42,046 km^2 drainage area located in western Jordan. |
| Calibration Summary: | |
| Validation Summary: | |
| General Comments: | |
| Abstract: | The estimation of spatially-variable actual evapotranspiration (AET) is a critical challenge
to regional water resources management. We propose a new remote sensing method, the Triangle
Algorithm with Variable Edges (TAVE), to generate daily AET estimates based on satellite-derived
land surface temperature and the vegetation index NDVI. The TAVE captures heterogeneity in AET
across elevation zones and permits variability in determining local values of wet and dry end-member
classes (known as edges). Compared to traditional triangle methods, TAVE introduces three unique
features: (i) the discretization of the domain as overlapping elevation zones; (ii) a variable wet
edge that is a function of elevation zone; and (iii) variable values of a combined-effect parameter
(that accounts for aerodynamic and surface resistance, vapor pressure gradient, and soil moisture
availability) along both wet and dry edges. With these features, TAVE effectively addresses
the combined influence of terrain and water stress on semi-arid environment AET estimates.
We demonstrate the effectiveness of this method in one of the driest countries in the world—Jordan,
and compare it to a traditional triangle method (TA) and a global AET product (MOD16) over different
land use types. In irrigated agricultural lands, TAVE matched the results of the single crop coefficient
model (-3%), in contrast to substantial overestimation by TA (+234%) and underestimation by
MOD16 (-50%). In forested (non-irrigated, water consuming) regions, TA and MOD16 produced
AET average deviations 15.5 times and -3.5 times of those based on TAVE. As TAVE has a simple
structure and low data requirements, it provides an efficient means to satisfy the increasing need
for evapotranspiration estimation in data-scarce semi-arid regions. This study constitutes a much
needed step towards the satellite-based quantification of agricultural water consumption in Jordan. |
| Language: | English |
| Keywords: | evapotranspiration; remote sensing; triangle method; water stress; water resources |