Tracing water and energy fluxes and reflectance in an arid ecosystem using the integrated model SCOPE

Transpiration plays a critical role in the water cycle of terrestrial ecosystems, especially for arid ecosystems in which water availability is typically the main constraint for plant growth. Although remote sensing has provided insights into transpiration across different temporal and spatial scales, its potential has not been fully exploited. This is due to a lack of synchronous observations of fluxes and reflectance. Only a few models have attempted to incorporate both radiative transfer and physiological processes. In this study, we calibrated the newly developed Soil, Canopy Observation, Photochemistry and Energy fluxes (SCOPE) model to trace synchronous fluxes of water, energy and reflectance, and thus, their interplays, in a typical arid ecosystem dominated by Haloxylon ammodendron based on long-term continuous field measurements. An initial global sensitivity analysis is conducted to identify parameters that have the greatest impact on model output before subsequent calibration with field data. The resulting calibrated model gives insight into the interplay between reflectance, energy and water fluxes in an arid ecosystem. The calibrated model is thus a useful tool to understand land surface fluxes and radiative transfer processes theoretically, from which additional reflectance information can be exploited to trace the physiological status of ecosystems.