More Frequent and Persistent Heatwaves Due To Increased Temperature Skewness Projected by a High-Resolution Earth System Model

Heatwaves are strongly associated with temperature distributions, but the mechanisms by which distributions are influenced by climate change remains unclear. Comparing simulations from a high-spatial resolution Community Earth System Model (CESM-HR) with those from low-resolution models, we identify substantial improvements by CESM-HR in reproducing observed Northern Hemisphere summer temperature skewness, as well as the frequency, intensity, persistence, and total heatwave days. Temperature skewness is strongly linked to land-atmosphere interactions and atmospheric circulation. Under global warming projections, some regions exhibit enhanced temperature skewness, along with more frequent and persistent heatwaves of greater intensity. We find that in energy-limited regimes, such as India, negative skewness in latent heat flux facilitates large positive skewness in sensible heat flux, which modulates near-surface air temperatures. Skewness differences of latent and sensible heat fluxes are amplified under global warming, increasing the temperature skewness. We find that this contrasting flux mechanism is active in several heatwave-prone regions. Heatwaves have occurred frequently in the recent decades, exerting substantial impacts on human health. While it is well known that mean warming can induce more frequent heatwaves, how higher order characteristics of the temperature distribution like skewness influence extreme hot events has received less focus. Using a high-resolution global climate model to simulate the response to future anthropogenic climate forcing, we find that regions with increasing positive temperature skewness tend to experience more frequent, persistent and intensified heatwaves. We also find that surface soil moisture and energy partitioning can significantly alter the shape of near surface air temperature distribution, and hence heatwaves. Striking improvements in simulating temperature skewness and heatwave days are achieved by a high-resolution Earth system modelRegions with enhanced temperature skewness in a warming climate tend to suffer more frequent, persistent and intense heatwavesOver energy-limited regions, temperature distribution is affected by negatively skewed latent and positively skewed sensible heat fluxes

Automated summary

Heatwaves are strongly associated with temperature distributions, and a high-resolution climate model can better simulate temperature distribution characteristics. Surface soil moisture and energy partitioning can alter the intensity and persistence of heatwaves.