Assistant Professor University of Idaho, Idaho, United States
Abstract Submission: Climate change is understood to exert influence on both average and extreme measures of environmental conditions, possibly by different magnitudes. Despite robust observations of increased evaporative demand of the atmosphere historically, it has not been evaluated for changes in extremes, especially during prolonged episodes of elevated evaporative demand. When defined using a fully physical, combination-based model (ASCE Penman-Monteith short crop reference evapotranspiration), evaporative demand represents compound conditions of temperature, humidity, wind speed, and solar radiation, and thus, is more encompassing and meaningful for agrohydrological processes and outcomes than heatwaves. In this note, we introduce the concept of thirstwaves, which are prolonged periods of extremely elevated evaporative demand and map its historical characteristics (intensity, duration, and frequency). We demonstrate that spatial hotspots for thirstwaves are quite distinct than how regions are perceived for mean evaporative demand. Finally, we will present how thirstwaves have changed in the recent past and their possible implications for agricultural and water stress management. Although all characteristics worsened over CONUS, increase in total number of thirstwave days (frequency) was the most widespread. The likelihood of no thirstwaves detected in the season has significantly decreased. Distinct spatial patterns were revealed for extreme thirst exposure that had little in common with those observed for total ETo. Spatially, hotspots of high extreme thirst exposure were co-located with the Midwest and High Plains aquifer regions, that account for 64% of total acreage and 28% of irrigated acreage nationally, respectively. We find that evaporative demand occurring during thirstwaves in CONUS has increased by 5.1 percentage points during 1981-2021.
