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Atmospheric Warming and the Amplification of Precipitation Extremes. Brian Soden University of Miami Richard Allan University of Reading. We Expect an Increase in Heavy Precipitation. Changes in Column Water Vapor During ENSO. La Nina (cold). El Nino (warm). El Nino. La Nina. - PowerPoint PPT Presentation
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Atmospheric Warming and the Atmospheric Warming and the Amplification of Precipitation Amplification of Precipitation ExtremesExtremes
Brian SodenUniversity of Miami
Richard AllanUniversity of Reading
We Expect an Increase in Heavy Precipitation
El
Nin
o(w
arm
)
La
Nin
a(c
old
)
El
Nin
o
La
Nin
a
Changes in Column Water Vapor During ENSO
Response of Precipitation Extremes to ENSO
9
6
3
-3
-6
-9(%)
Heavy
Light
Extreme precipitation increases as atmosphere warms and moistens.
Allan and Soden (2008)
Response of Precipitation Extremes to ENSO: Observations vs GCMs
• Heavy rain events increase in frequency during warm/moist periods.
Warm (El Nino)Cold (La Nina)
• Heavy rain events decrease in frequency during cold/dry periods.• Qualitatively supports GCM projections of increased precipitation extremes.
Allan and Soden (2008)
Sensitivity of Precipitation Changes to SST
• On average, models underpredict sensitivity of heaviest rain events to SST
• There is a large intermodel spread in the responses of heaviest rain events
Allan et al. (2010)
Change in Daily Upward Vertical Velocity (500 )IPCC AR4 Models
Strongest updrafts become less common
Weakest updrafts become more common
2100-2080 minus 2020-2000
Gastineau and Soden 2009
• Heavy rainfall events increase despite weaker “updrafts”
Summary Points Observations and GCM simulations (AMIP3) both show an increase
in heavy precipitation events associated with warmer and moister conditions during El Nino.
The observed suggest a larger sensitivity to SST than ensemble mean GCM simulations or Clausius Clapeyron scaling.
The GCM response to SST is highly varied, and increased heavy rain events are associated with weaker ‘dynamics’ in the model.
The general tendency for weaker precipitation sensitivity is qualitatively consistent with other findings.
Tropical-mean Precipitation Trends: Ascending vs. Descending Regimes
All
Ascending
Descending
Allan and Soden (2009)
Extra Slides
Global Tropical Extra-tropical
Model Projected Change in Daily Upward 500: IPCC AR4 Models
• Reduction in intensity of strongest “updrafts” is a robust projection of AR4 models.
• Heavy rainfall events increase despite weaker “updrafts”.
Gastineau and Soden (2009)
2100-2095 minus 2000-1995
Model Projected Change in Most Intense “Updrafts”: IPCC AR4 Models
Multi Model Ensemble-Mean
Reduction in strongest “updrafts” occurs everywhere except central and eastern Pacific.
Gastineau and Soden 2009
Global Tropical Extra-tropical
Model Projected Change in Precipitation and Upward 500 : IPCC AR4 Models
Gastineau and Soden 2009
Upward 500
Precipitation
Precipitation Variability: Changes in Extremes
Extreme precipitation increases as atmosphere warms and moistens.
