H093-03
Exploring Surface Temperature, Evapotranspiration, and Downwelling Longwave Radiation Heterogeneity in High-Altitude Complex Terrain with ECOSTRESS
Thursday, 10 December 2020: 05:36
Virtual
Matthew Worden1, Daniel Feldman2, P. James Dennedy-Frank2, Nicola Falco2, Baptiste Dafflon2, Jiancong Chen3, Haruko M Wainwright2 and Alexandra G. Konings4, (1)Lawrence Berkeley National Laboratory, Climate Sciences, Berkeley, CA, United States, (2)Lawrence Berkeley National Laboratory, Berkeley, CA, United States, (3)University of California Berkeley, Berkeley, CA, United States, (4)Stanford University, Department of Earth System Science, Stanford, CA, United States
Abstract:
Increasing evapotranspiration (ET) in the Colorado River Basin has recently been identified as the dominant contributor to the observed -9.3 %/°C negative trend in discharge from the river [Milly and Dunne, Science, 2020]. However, this ET change has been inferred indirectly from proxies and model simulations, and the underlying assumptions of process representations in those calculations need to be tested with data. We develop a detailed picture of the surface radiative environment in the Upper Colorado River with a particular focus on the East River Watershed near Crested Butte, Colorado with recent observations of land-surface temperature from ECOSTRESS. We characterize the spatiotemporal variability in surface temperature, ET, and downwelling longwave radiation with mosaics of ECOSTRESS observations at different local-times.
We show that the diurnal cycle of surface temperature, which is driven by the radiative environment, is highly modulated by vegetation and the presence of snow and surface water in complex terrain. While numerous assumptions underlie the retrieval of evapotranspiration from surface temperature observations, this finding suggests a relatively direct relationship between the surface temperature observable and ET. Despite the spatial variability of ET in complex terrain, ECOSTRESS observations show that the temperature modulation is consistent across the East River and 3 adjacent watersheds covering a 300 km2 area. These findings support the use of ECOSTRESS observations as a consistent measure of ET in high-altitude complex terrain and to characterize the processes governing ET variability in the Upper Colorado River.
