These images show Evaporative Stress Index (ESI), a measure that can be used to estimate current drought conditions. Colors on the maps show anomalies in the ratio of actual to potential evapotranspiration: drier than normal areas show decreased evapotranspiration and wetter than normal areas show increased evapotranspiration.
Where do these data come from?
Instruments on satellites measure reflectance from Earth's surface at various wavelengths. The Atmosphere-Land Exchange Inversion model (ALEXI) uses the measurements to compute principle surface energy fluxes, including Evapotranspiration (ET). ALEXI ET estimates have been rigorously evaluated over a range of climatic and vegetation conditions, and the results compare well with ground-based data. As the satellite measurements can only be made where skies are clear (no clouds), single daily "snapshots" from the model are averaged together (composited) to provide images with full coverage.
What can I do with these data?
- Identify areas where drought may be developing or present.
- Compare GET-D maps with U.S. Drought Monitor maps to see how well satellite data characterize conditions related to drought as judged by ground-based measurements and observations.