| Popis: |
Radiative heating of clouds, particularly those in the upper troposphere, alters temperature gradients in the atmosphere, affecting circulation and precipitation in today's and future climates. However, the response of cloud radiative heating to global warming remains largely unknown. We study changes to cloud radiative heating profiles in a warmer climate, identify physical mechanisms responsible for these changes, and develop a theory based on well-understood physics to predict them. Our approach involves a stepwise procedure that builds upon a simple hypothesis of an upward shift in cloud radiative heating at constant temperature, gradually incorporating additional physical effects. We find that cloud radiative heating intensifies as clouds move upward, despite minimal changes in cloud properties and temperatures. We attribute this intensification to a decrease in air density, which often overcompensates the decrease in high cloud fraction with warming in idealized multi-model simulations in radiative-convective equilibrium. Furthermore, this mechanism is confirmed in a 15-year satellite-derived dataset. The density-mediated increment in cloud radiative heating may increase the role of high clouds in controlling atmospheric flows in a warmer climate. Moreover, a narrowing of the spread in model-simulated cloud radiative heating highlight an actionable path to reduce uncertainties in regional climate change projections. |
