Intercomparison of the Surface Energy Partitioning in CMIP5 Simulations

Abstract

The warming climate significantly modifies the global water cycle. Global evapotranspiration has increased over the past decades, yet climate models agree on the drying trend of land surface. In this study, we conducted an intercomparison analysis of the surface energy partitioning across Coupled Model Intercomparison Phase 5 (CMIP5) simulations and evaluated its behaviour with surface temperature and soil moisture anomalies, against the theoretically derived thermodynamic formula. Different responses over land and sea surfaces to elevated greenhouse gas emissions were found. Under the Representative Concentration Pathway of +8.5 W m−2 (RCP8.5) warming scenario, the multi-model mean relative efficiency anomaly from CMIP5 simulations is 3.83 and −0.12 over global sea and land, respectively. The significant anomaly over sea was captured by the thermodynamic solution based on the principle of maximum entropy production, with a mean relative error of 14.6%. The declining trend over land was also reproduced, but an accurate prediction of its small anomaly will require the inclusions of complex physical processes in future work. Despite increased potential evapotranspiration under rising temperatures, both CMIP5 simulations and thermodynamic principles suggest that the soil moisture-temperature feedback cannot support long-term enhanced evapotranspiration at the global scale. The dissipation of radiative forcing eventually shifts towards sensible heat flux and accelerates the warming over land, especially over South America and Europe.

A benchmark dataset of diurnal- and seasonal-scale radiation, heat and CO<sub>2</sub> fluxes in a typical East Asian monsoon region

“…Land-atmosphere interaction processes, which control the surface-atmosphere exchanges of water, energy, and atmospheric carbon dioxide (CO 2 ) across the atmospheric boundary layer, play a key role in ecosystem processes, hydrologic and biogeochemical cycles, and even in weather and climate (You et al, 2017;Yang et al, 2019). Previous studies have shown that climate simulations are especially sensitive to seasonal and diurnal variations in the surface energy partitioning of available energy into sensible heat (H ) and latent heat (λE) fluxes in numerical models (Gao et al, 2004), where considerable uncertainties still remain in the land-surface parameters (Sun et al, 2013).…”

Critical transitions in the hydrological system: Early-warning signals and network analysis

“…However, as compared to temperature shifts, changes in global hydrological cycle (e.g. precipitation) are relatively less wellunderstood, despite the strong coupling between energy and water transport (Allen and Ingram, 2002;Marvel and Bonfils, 2013;Yang et al, 2019). Andrews et al (2010) pointed out that the precipitation response to climate change can be roughly split into a fast response part strongly correlated with radiative forcing absorbed by the atmosphere and a relatively slow response to global surface temperature change.…”