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

massie@ucar.edu

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

Example : Vertical and Seasonal Variations

Example: HIRDLS and CALIPSO Cloud Fields

HIRDLS Cloud Frequency MLS RHI

January 2006, 100 hPa

Cloud Frequency Extinction

HIRDLS Cirrus Observations at 82 hPa

These patterns are very similar to the RHI patterns

Cloud Frequency Extinction

MLS RHI and HIRDLS Cirrus at 82 hPa

RHI > 100 %

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

CDC OLR (Proxy of Deep Convection)

Deep convection is present when OLR < 170 W / m2

(green colored regions)

Longitudesnear 100 are

overIndonesia

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 )

Lidar Observations of Cirrus andTemperature Waves

Green: ΔT between -1 and -4 KBoehm and Verlinde , GRL, v27, p3209, 2000

Equatorial Wave Temperatures

HIRDLS analyses courtesy of Joan Alexander, and COSMIC analyses courtesy of Bill Randel and Fei Wu

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)

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