hirdls – oxford open science meeting hirdls observations of cirrus near the tropopause based upon:...
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HIRDLS – Oxford Open Science Meeting
HIRDLS Observations of CirrusNear the Tropopause
Based upon:Spring 2008 AGU Joint Assembly
Ft. Lauderdale, Florida
Steven T. Massie,John Gille, John Barnett, Joan Alexander,
William Reed, Rashid Khosravi, Cheryl Craig,Bill Randel, Fei Wu
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Outline
Cirrus is produced in-situ by freezing of humid layersblow-off from deep convectioncold temperature perturbations of dynamical waves
The HIRDLS observations are correlated to RHI (relative humidity with respect to ice) OLR (outgoing longwave radiation)Wave temperature perturbations (Twave)
RHI - AURA Microwave Limb Sounder (MLS)OLR - Climate Diagnostics CenterTwave – HIRDLS and COSMIC (gps) temperature analyses
Focus is on the Tropics
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Example : Vertical and Seasonal Variations
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Example: HIRDLS and CALIPSO Cloud Fields
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HIRDLS Cloud Frequency MLS RHI
January 2006, 100 hPa
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Cloud Frequency Extinction
HIRDLS Cirrus Observations at 82 hPa
These patterns are very similar to the RHI patterns
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Cloud Frequency Extinction
MLS RHI and HIRDLS Cirrus at 82 hPa
RHI > 100 %
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Correlation of RHI and Extinction (β) at 100 hPa
1.0
1.5
2.0
2.5
3.0
20 40 60 80 100 120 140
January 2006 100 hPa E
xtin
cti
on
(10
-3 k
m-1
)
RHI
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CDC OLR (Proxy of Deep Convection)
Deep convection is present when OLR < 170 W / m2
(green colored regions)
Longitudesnear 100 are
overIndonesia
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Correlations of RHI and Extinction with OLR
Correlations are not as strong as RHI versus ExtinctionNot all Cirrus is directly related to deep convection
60
65
70
75
80
85
90
95
100
150 200 250 300
January 2006 100 hPa
RH
I
OLR ( watt / m2 )
1.6
1.8
2.0
2.2
2.4
150 200 250 300
January 2006 100 hPa
Ex
tin
cti
on
(1
0-3 k
m-1
)
OLR ( watt / m2 )
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Lidar Observations of Cirrus andTemperature Waves
Green: ΔT between -1 and -4 KBoehm and Verlinde , GRL, v27, p3209, 2000
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Equatorial Wave Temperatures
HIRDLS analyses courtesy of Joan Alexander, and COSMIC analyses courtesy of Bill Randel and Fei Wu
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COSMIC Temperature Wavesand HIRDLS Extinction
1.0 10-3
1.5 10-3
2.0 10-3
2.5 10-3
3.0 10-3
-3 -2 -1 0 1 2 3
Wave Temperature vs HIRDLS Extinction at 16 Km (110 hPa)
Ext
inc
tio
n (
km
-1)
Wave Temperature Perturbation (K)
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Discussion
HIRDLS vertical resolution ~ 1 Km, while MLS ~ several KmA 1 KM cirrus layer can be sandwiched bylow RHI air above and below the cloud structure,and clouds can be present for RHI < 100%
Largest correlations are between RHI and ExtinctionA consequence of thermodynamics !
Correlations of OLR and cirrus extinction are weak Not all cirrus is derived from convective blow-off
Negative temperature perturbations due to tropicaldynamical waves are correlated with larger cirrus extinction