Increasing potential for intense tropical and subtropical thunderstorms under global warming

Area of Science:

• Atmospheric Science
• Climate Modeling
• Meteorology

Background:

• Intense thunderstorms are linked to destructive weather events.
• Convective Available Potential Energy (CAPE) is a key measure for thunderstorm potential.
• Climate models project increased mean CAPE in tropics/subtropics due to global warming, but mechanisms are uncertain.

Purpose of the Study:

• To investigate projected changes in CAPE extremes under global warming.
• To identify physical mechanisms driving increases in CAPE extremes.
• To validate a theoretical model for CAPE and its relationship with humidity.

Main Methods:

• Analysis of CAPE extremes from an ensemble of climate models.
• Utilizing a climate model with varied convective entrainment rates.
• Testing a theoretical model against simulations and observational data.

Main Results:

• High percentiles of CAPE (CAPE extremes) robustly increase with warming across tropics and subtropics.
• Increases in CAPE extremes are consistent with a theoretical model involving convective entrainment and lapse rates.
• The theoretical model successfully explains the relationship between CAPE and lower-tropospheric humidity.

Conclusions:

• Projected increases in CAPE extremes imply a higher frequency of environments conducive to intense thunderstorms.
• A theoretical framework provides a physical basis for understanding future increases in thunderstorm potential.
• Convective entrainment's influence on lapse rates is a key mechanism contributing to rising CAPE extremes.