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Ecological Forecasting

The example below highlights one way in which the mission will contribute to Ecological Forecasting and Water Resources by providing detailed surface temperature maps of the land surface of the Earth. These surface temperatures maps can be used to measure the Evapotranspiration (ET). ET is the key climate variable linking the water, carbon, and energy cycles, controlled both through the atmosphere and the biosphere. Plants regulate water loss (transpiration) by closing the pores on their leaves, but at the expense of shutting off CO2 uptake for photosynthesis and risking carbon starvation. Transpiration also performs the same cooling function as sweat—if plants cannot adequately cool themselves, they risk overheating and mortality due to dehydration.

The Evaporative Stress Index (ESI) describes temporal anomalies in evapotranspiration (ET), highlighting areas with anomalously high or low rates of water use across the land surface. Here, ET is retrieved via energy balance using remotely sensed land-surface temperature (LST) time-change signals. LST is a fast- response variable, providing proxy information regarding rapidly evolving surface soil moisture and crop stress conditions at relatively high spatial resolution. The ESI also demonstrates capability for capturing early signals of “flash drought”, brought on by extended periods of hot, dry and windy conditions leading to rapid soil moisture depletion.

ESI values quantify standardized anomalies (s values) in the ratio of clear-sky actual-to-potential ET (fPET), derived using thermal infrared (TIR) satellite imagery from geostationary platforms. Geostationary satellited provide data with far lower spatial resolution than will be provided by the HyspIRI mission. In the figure below areas of drought are highlighted in red but it is not possible to resolve individual fields. With HyspIRI we will be able to measure the ET from individual fields and provide actionable information to farmers so they can obtain the maximum benefits from often dwindling water supplies.