Cloud processes near the tropopause

CHEM Science Team March 2000

Cloud processes near the tropopause

• HIRDLS will measure cloud top altitude and aerosol concentrations:

• the limb view gives high sensitivity;

• geometry used to determine altitude with fine resolution

(200 m step size; 1 km IFOV)

• May benefit from formation flying partners

Aqua, PICASSO-CENA and CloudSat

to obtain very comprehensive near-simultaneous cloud measurements and for cross-validation

.

[STS047-54-018, 20 Sep 1992, 15.5 S, 158.5 E]

Silhouette of several thunderstorms with cirrus anvil tops spreading out against the tropopause, and Pinatubo aerosol layers appearing blue above.


Frequency of cirrus measured by HALOE

Relative frequency of occurrence of larger extinction values measured at 3.46 micron by the UARS HALOE instrument for 1993-1998.[S.Massie et al, submitted to J. Geophys. Res., 1999]


Variation of limb extinction

Frequency of limb

extinction at 3.46 micron

and 121 hPa tangent

pressure measured by

HALOE for different

years.

Data are for the Indian

Ocean to the Eastern

Pacific between 30oN and

30oS.

[S.Massie et al, ‘The Effect of the 1997 El Nino on the Distribution of UpperTropospheric Cirrus’, submitted to J. Geophys. Res., 1999]


Radiative transfer studies

HIRDLS will measure the radiation emitted in multiple spectral passbandsup to the thermosphere

Important for validating radiative transfer theory and undertaking basicresearch into radiative transfer


(Day-Night )/Night

radiance difference

measured by CRISTA

in 1490-1560 cm-1

spectral region

Daytime enhancement is due

to a combination of H2O non-

LTE emission and tidal activity increasing daytime temperature

Radiative transfer studies

[Figure from David Edwards]


Acquisition of atmospheric data in an extreme state

• Stratospheric chlorine levels are expected to peak during

the EOS-Chem mission.

• EOS-Chem data will be valuable for centuries into the future as

tests of model behaviour in this extreme high-chlorine state.

• Changes in ozone levels as chlorine declines and stratospheric

cooling accelerates will provide critical tests of model behaviour

and their ability to predict.


Growth of stratospheric chlorine according to various scenarios

(from Joe Waters)

Stratospheric Chlorine


HIRDLS Scientific Objectives

• Understand stratosphere-troposphere exchange of radiatively and chemically active constituents (including aerosols) down to small spatial scales

• Understand chemical processing, transports and mixing in the upper troposphere/lowermost stratosphere/lower overworld

• Understand budgets of quantities (momentum, energy, heat and potential vorticity) in the middle atmosphere that control stratosphere-troposphere exchange

• Determine upper tropospheric composition (with high vertical resolution)

• Provide data to improve and validate small scales in models

• Measure global distributions of aerosols and PSC’s and interannual variations


Major HIRDLS Emphases

Small scale dynamics and transports

Troposphere - stratosphere exchange

Polar vortex filamentation

Tropical barrier leakage

Upper troposphere - lower stratosphere chemistry

O3, H2O, CFC11, CFC12, HNO3, CH4, N2O

Aerosol amounts, distributions & properties

Trends & changes

Trends of 10 radiativity & chemically active species, T, PSCs

Continuation of LIMS, SAMS, UARS

Gravity wave distributions

Sources & distributions of gravity waves, and their roles in atmospheric dynamics


Summary of Measurement Requirements

Temperature <50 km 0.4 K precision 1 K absolute

>50 km 1 K precision 2 K absolute

Constituents O3, H2O, CH4, H2O, HNO3, NO2, N2O5, 1-5% precision

ClONO2, CF2Cl2, CFCl3, Aerosol 5-10% absolute

Geopotential height gradient 20 metres/500 km (vertical/horizontal)(Equivalent 60oN geostrophic wind) (3 m s-1)

Coverage:Horizontal - global 90oS to 90oN (must include polar night)Vertical - upper troposphere to mesopause (8-80 km)Temporal - long-term, continuous (5 years unbroken)

Resolution:Horizontal - profile spacing of 5o latitude x 5o longitude (approx 500 km)Vertical - 1-1.25 km

Temporal - complete field in 12 hours


IGSE

IGSE

Auxiliary Filter Bank

TGSE

HIRDLS

HIRDLS Cleanroom


Collimator/monochromator calibration equipment


Monochromator turretSeismic isolator

Clean room and vacuum chamber Chamber optical bench

HIRDLS Calibration Facility

Cloud processes near the tropopause

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