Precipitation extreme changes exceeding moisture content increases in MIROC and IPCC climate models

Area of Science:

• Atmospheric Science
• Climate Modeling
• Extreme Weather Events

Background:

• Precipitation extreme changes are often linked to atmospheric moisture content.
• Observed deviations in the tropics suggest other factors influence precipitation extremes.

Purpose of the Study:

• To investigate why tropical precipitation extremes deviate from moisture-scaling assumptions.
• To identify the key drivers of these deviations in climate models.

Main Methods:

• Analyzed precipitation extreme changes across twelve Intergovernmental Panel on Climate Change (IPCC) models.
• Decomposed precipitation changes to isolate the role of atmospheric dynamics, specifically upward velocity.
• Evaluated a new scaling method incorporating dynamical effects.

Main Results:

• Half of the IPCC models showed tropical precipitation extremes increasing faster than precipitable water.
• Model variations were primarily attributed to differences in upward velocity (vertical motion).
• A new scaling incorporating dynamics accurately captured precipitation changes in tropics and midlatitudes.

Conclusions:

• Atmospheric dynamics, particularly upward velocity, play a crucial role in modulating tropical precipitation extremes.
• Precipitation extremes can intensify beyond moisture increases, as suggested by models like MIROC.
• Future tropical disturbances may lead to more extreme precipitation events than solely predicted by moisture content.