Distortions of the Rain Distribution With Warming, With and Without Self-Aggregation.

Area of Science:

• Atmospheric Science
• Climate Science
• Hydrology

Background:

• Convective aggregation influences the hydrologic cycle's sensitivity to warming.
• Understanding rainfall distribution shifts is crucial for climate change impact assessments.

Purpose of the Study:

• To investigate how mesoscale circulations modulate the hydrologic cycle's response to warming.
• To quantify changes in rainfall distribution under varying convective organization and Sea Surface Temperature (SST).

Main Methods:

• Utilized a cloud-resolving model to simulate radiative-convective equilibrium states.
• Analyzed the full distribution of rainfall, distinguishing between disorganized and aggregated convective states.
• Examined the impact of Sea Surface Temperature (SST) and aggregation feedbacks on rainfall extremes.

Main Results:

• Increased rainfall extremes (20-30% heavier rain) observed with convection aggregation.
• Mean rainfall increase with warming is independent of convective organization.
• Nonlinear behaviors and amplified sporadic rainfall noted, with multiplicative effects of feedbacks on extremes.
• Identified alternating Clausius-Clapeyron and super-Clausius-Clapeyron regimes in extreme rainfall as a function of SST.

Conclusions:

• Mesoscale circulations can amplify the hydrologic cycle, but nonlinearities challenge idealized self-aggregation models.
• Further research is needed to link global energetics, aggregation feedbacks, and local convection.
• Systematic testing of model configurations is essential for accurate hydrologic cycle sensitivity studies.