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Evapotranspiration
Evapotranspiration
Evapotranspiration
Evapotranspiration
Microclimatevv0
Responsible:Niccolò Calandri
Layer Evapotranspiration on real sites
Real Estate UK
Catania
Mina el Cerrejon
Evapotranspiration
Overview
Evapotranspiration (ET) represents the total amount of water transferred from the land surface to the atmosphere, combining evaporation from the soil (conversion of liquid water to vapour) and transpiration by plants (release of water vapour through leaf stomata). It is one of the fundamental processes of the hydrological cycle and one of the most sensitive indicators of terrestrial ecosystem health.
Under conditions of water or heat stress, ET can increase significantly, signalling high evaporative demand that can lead to soil desiccation, reduced water availability for vegetation, and biodiversity loss. For this reason the KPI is inverted: high ET values indicate worse stress conditions for the ecosystem.
Calculation Methodology
Data come from the MODIS Evapotranspiration product, available in two complementary satellite versions:
| Code | Satellite | Product | Resolution | Coverage |
|---|---|---|---|---|
WRD_MAQET_99 | Aqua (MYD16A2) | 8-day Evapotranspiration | 1000 m | 2021–present |
WRD_MTRET_99 | Terra (MOD16A2) | 8-day Evapotranspiration | 1000 m | 2021–present |
The final value for each 8-day composite is calculated as the mean of Aqua and Terra values, combining the two satellite overpasses to reduce sensitivity to cloud cover and single-acquisition anomalies.
Unit: millimetres per period (mm/period)
Data Sources
| Code | Name | Provider | Resolution | Availability |
|---|---|---|---|---|
WRD_MAQET_99 | NASA MODIS Aqua MYD16A2 | NASA LP DAAC | 1000 m | 2021 — present |
WRD_MTRET_99 | NASA MODIS Terra MOD16A2 | NASA LP DAAC | 1000 m | 2021 — present |
Quality Range and Levels
| Indicator | Unit | Range | Inverted |
|---|---|---|---|
et | mm/day | [0, 1, 2.5, 5, 8, 10] | Yes |
Inverted = Yes: high ET indicates intense evaporative demand, potentially associated with water stress and deteriorating conditions for biodiversity.
| Level | ET (mm/day) | Interpretation |
|---|---|---|
| A (Excellent) | 0 – 1 | Minimal evaporative demand; high water availability |
| B (Good) | 1 – 2.5 | Low evaporative demand; balanced hydrological cycle |
| C (Moderate) | 2.5 – 5 | Moderate evaporative demand; slight pressure on the water system |
| D (Poor) | 5 – 8 | High evaporative demand; significant water stress |
| E (Critical) | > 8 | Extreme evaporative demand; severe water deficit and ecosystem risk |
References
- Mu, Q., Zhao, M., Running, S.W. (2011). "Improvements to a MODIS global terrestrial evapotranspiration algorithm". Remote Sensing of Environment, 115(8), 1781–1800.
- Running, S., Mu, Q., Zhao, M. (2017). "MOD16A2 MODIS Global Evapotranspiration 8-Day L4 Global 500 m SIN Grid V006". NASA LP DAAC.
Quality Ranges and Levels
et
(mm/day)ACritical
BLow
CModerate
DGood
EExcellent
0 → 0.99
1 → 2.49
2.5 → 4.99
5 → 7.99
8 → 10
A
Critical0 – 0.99B
Low1 – 2.49C
Moderate2.5 – 4.99D
Good5 – 7.99E
Excellent8 – 10Data Sources & References
Sources
WRD_MAQET_99WRD_MTRET_99
Methodology
Source: MODIS Evapotranspiration (NASA LP DAAC). Two products: Aqua MYD16A2 and Terra MOD16A2, both at 1000 m, 8-day composites, available from 2021. The final value for each composite is the mean of Aqua and Terra values. Unit: mm/period. Inverted indicator: high ET = water stress = worse for ecosystems.