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Changes in Organized Deep Convection Motivation Cloud Regimes Regime Trends Future Changes Conclusions

Observed Changes in Organized Tropical Deep Convection as Identified by Cloud Regime Analysis

Jackson Tan 3rd April 2014

Changes in Organized Deep Convection Motivation Cloud Regimes Regime Trends Future Changes Conclusions

Motivation: Changes in Org. Deep Conv.

Motivation

Organized deep convection has a critical impact on the climate system, but we know little about how it has changed globally in the past and will change in a warming climate. GCMs cannot properly represent organized deep convection lack of observations that are both global and sufficiently long

Changes in Organized Deep Convection Motivation Cloud Regimes Regime Trends Future Changes Conclusions

• Org. Deep Conv. Has Increased by 20%

(Tselioudis et al., 2010)

Changes in Organized Deep Convection Motivation Cloud Regimes Regime Trends Future Changes Conclusions

How do they represent organized deep convection?

Changes in Organized Deep Convection Motivation Cloud Regimes Regime Trends Future Changes Conclusions

Representing Org. Deep Conv. with Cloud Regime

by cloud regimes (or weather states) classification of the convective state of the atmosphere

• ne regime in particular characterizes an environment of
• rganised deep convection

Changes in Organized Deep Convection Motivation Cloud Regimes Regime Trends Future Changes Conclusions

Aims: Changes in this Regime and Other Regimes

Aims

• 1. how has this organized deep convective regime changed

internally?

• 2. how have other regimes of less organized deep

convection changed?

Changes in Organized Deep Convection Motivation Cloud Regimes Regime Trends Future Changes Conclusions

Cloud Regimes as Convective Indicators

first proposed by Jakob and Tselioudis (2003) classification of cloud fields by k-means clustering of joint-histograms of CTP and τ 280 km × 280 km, daily time resolution, 35◦N/S indicators of the convective state of the atmosphere

Changes in Organized Deep Convection Motivation Cloud Regimes Regime Trends Future Changes Conclusions

Three Regimes Describe Deep Convection

1000 800 680 560 440 310 180 10 CR1 5.5% . 2 1 . 3 3 . 6 9 . 4 2 3 6 1 1000 800 680 560 440 310 180 10 CR2 8.4% . 2 1 . 3 3 . 6 9 . 4 2 3 6 1 CR3 14.2% 0.0 0.2 1.0 2.0 3.0 4.0 6.0 8.0 10.0 15.0 20.0 (%) τ CTP (hPa)

Changes in Organized Deep Convection Motivation Cloud Regimes Regime Trends Future Changes Conclusions

Re-clustering CR1 Gives Two Sub-Regimes

1000 800 680 560 440 310 180 10 CR1a 1.4% CR1b 4.1% . 2 1 . 3 3 . 6 9 . 4 2 3 6 1 1000 800 680 560 440 310 180 10 CR2 8.4% . 2 1 . 3 3 . 6 9 . 4 2 3 6 1 CR3 14.2% 0.0 0.2 1.0 2.0 3.0 4.0 6.0 8.0 10.0 15.0 20.0 (%) τ CTP (hPa)

Changes in Organized Deep Convection Motivation Cloud Regimes Regime Trends Future Changes Conclusions

Caution in Using ISCCP in Trend Studies!

Changes in Organized Deep Convection Motivation Cloud Regimes Regime Trends Future Changes Conclusions

Minimize Artifacts by Zenith Angle Filter

• ne main source of satellite artifacts due to high satellite

zenith angles µ generally affects the threshold detection of optically thin clouds set zenith angle filter µ > 30◦ to minimize such artifacts

METEOSAT INSAT GMS GOES-WEST GOES-EAST METEOSAT

Changes in Organized Deep Convection Motivation Cloud Regimes Regime Trends Future Changes Conclusions

How does our approach compare with Tselioudis et al. (2010)?

Changes in Organized Deep Convection Motivation Cloud Regimes Regime Trends Future Changes Conclusions

Result Consistent with Tselioudis et al. (2010)

1980 1985 1990 1995 2000 2005 2010 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 CR1 ( 15.8 ± 5.7)%

Changes in Organized Deep Convection Motivation Cloud Regimes Regime Trends Future Changes Conclusions

How has CR1a changed?

Changes in Organized Deep Convection Motivation Cloud Regimes Regime Trends Future Changes Conclusions

CR1a Increasing in Every Satellite Region

0.00 0.02 0.04 METEOSAT ( 55.4 ± 30.5)% 0.00 0.02 0.04 INSAT (110.4 ± 62.6)% 0.00 0.05 0.10 GMS ( 96.9 ± 15.0)% 0.00 0.02 0.04 GOES-WEST ( 60.8 ± 30.3)% 1980 1985 1990 1995 2000 2005 2010 0.00 0.02 0.04 GOES-EAST ( 82.8 ± 24.1)%

Changes in Organized Deep Convection Motivation Cloud Regimes Regime Trends Future Changes Conclusions

How has other regimes changed?

Changes in Organized Deep Convection Motivation Cloud Regimes Regime Trends Future Changes Conclusions

CR1a Increases But Convective Regimes Constant

0.00 0.02 0.04 CR1a ( 56.7 ± 9.8)% 0.00 0.05 0.10 CR1b ( 3.2 ± 6.6)% 0.0 0.1 CR2 (-13.9 ± 7.1)% 0.1 0.2 CR3 ( 11.9 ± 5.8)% 1980 1985 1990 1995 2000 2005 2010 0.2 0.4 Conv. ( 4.9 ± 4.5)%

Changes in Organized Deep Convection Motivation Cloud Regimes Regime Trends Future Changes Conclusions

Still an Increase when Jumps are Removed

0.00 0.02 0.04 CR1a ( 33.2 ± 11.1)% 0.00 0.05 0.10 CR1b ( 3.2 ± 6.6)% 0.0 0.1 CR2 (-13.9 ± 7.1)% 0.1 0.2 CR3 ( 11.9 ± 5.8)% 1980 1985 1990 1995 2000 2005 2010 0.2 0.4 Conv. ( 4.9 ± 4.5)%

Changes in Organized Deep Convection Motivation Cloud Regimes Regime Trends Future Changes Conclusions

How will organised deep convection change in the future?

Changes in Organized Deep Convection Motivation Cloud Regimes Regime Trends Future Changes Conclusions

CR1a/CR1 May Increase in a Warming Climate

13.8 14.0 14.2 14.4 14.6 14.8 15.0 global mean surface temperature (°C) 0.00 0.02 0.04 0.06 0.08 0.10 FOC

CR1 (corr = 0.240) CR1a (corr = 0.475)

Changes in Organized Deep Convection Motivation Cloud Regimes Regime Trends Future Changes Conclusions

Conclusions

Conclusions

• 1. increase in organized deep convection is due increase in

the more intense component

• 2. area of deep convection remained constant but has

intensified into more organized modes

• 3. a warmer climate may have more organised deep

convection

To Do

Address other sources of satellite artifacts, such as from polar-orbiting satellites