4STAR: Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research

Results from TCAP Summer 2012 Flights A multi-agency collaboration involving:

• PNNL: Connor Flynn, J. Hubbe, E. Kassianov, B. Schmid

• NASA Ames: S. Dunagan, R. Johnson, M. Kacenelenbogen, J. Redemann, P. Russell, M. Segal Rozenhaimer, Y. Shinozuka, S. Ramachandran

• NASA GSFC: B. Holben, S. Sinyuk

Funding: NASA, DOE ARM, BMI, PNNL

Acknowledgments

AERONET: Tom Eck, Ilya Slutsker

ARM Cimel PI: Laurie Gregory, Rick Wagener

G1 facility support: Mike Hubbell, Bill Svancara, Dick Hone, Celine Kluzek, John Hubbe, Duli Chand, Jason Tomlinson, Gene Dukes

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Presentation Outline

What is 4STAR?

What measurements/science can it contribute?

4STAR TCAP Flights

4STAR TCAP Results

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So, what really is 4STAR? What does it measure?

4STAR: Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research

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AATS-like capability:

AOD at 13 wavelengths & H2O

horizontally and vertically resolved through airborne design and deployment

AATS-like capability:

AOD at 13 wavelengths & H2O

horizontally and vertically resolved through airborne design and deployment

AERONET-like capabilityGround-based direct beam + sky scanning yields column-integrated properties:• AOD• Size distributions• Single-scattering albedo • Asymmetry parameter • Aerosol shape / sphericity• Cloud OD

Airborne hyperspectral measurements of direct sunlight and angularly resolved sky radiance.

Anticipated 4STAR data products:

Solar Direct BeamAtmospheric TransmittanceAerosol Optical Depth and Ångstrom exponentAerosol Extinction (via aircraft vertical profiling)

Gases: H2O, O3, NO2, O4, CO2(?) (column and in profile)

Angularly-resolved sky radiance inversionsScattering phase function, asymmetry parameterAerosol size distributions, fine/coarse mode fraction, sphericityAerosol single scattering albedo, absorption

Zenith radiance cloud retrievals Cloudy/clear transition zone (Marshak, Chiu)Cloud Optical Depth, Droplet effective Radius (with auxilliary measurements, Barker et al.)Water vapor, liquid water, ice water fractionation (Daniels et al.)

Successful TCAP deployment

Operated successfully on ALL TCAP flightsFerry flight and 11 science flights

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AMF

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4STAR TCAP Operational Success:

Direct Sun Mode • AOD, Angstrom Exp.• Trace gases (H2O, O3, O4, NO2)

•AODs retrieved for all flights. •Gaseous retrievals in progress, prelim results for several days completed.

Typical TCAP 4STAR flight series

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4STAR Hyperspectral OD (column estimate) and AERONET Ground-based AOD

AOD comparisons with AERONET

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λ (nm) 380 440 500 675 870 1020 1640

RMSΔ 0.027 0.032 0.011 0.007 0.010 0.011 0.018

4STAR on G-1, n = 4AERONET at the Ground Site

4STAR on ground, n = 23AERONET at the Airport

λ (nm) 380 440 500 675 870 1020 1640

RMSΔ 0.010 0.012 0.012 0.010 0.012 0.014 0.015

Multicomponent Linear Regresssion of trace gases column amounts: O3, O4, NO2, H2O

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CWV retrieval from 940 nm band calibrated via “modified Langley”

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4STAR TCAP Sky Radiance Retrievals:• Sky Radiance Mode

• Size Distribution• phase function, asymmetry parameter• Index of refraction, SSA, absorption AOD

More challenging, dependent on sky conditions, flight conditions, and specification of surface conditions.

• Process scans of calibrated sky radiance vs scattering angle with AERONET aerosol intensive properties code.

• ~24 acceptable sky scans at surface, mid, and high alt.• Retrieval work is just beginning

Cloud effect

Airborne Sky Radiance Retrieval: July 22Altitude 605 m, SZA = 27 deg

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Preliminary!

First SSA and AAOD retrieval: July 22Altitude 605 m, SZA = 27 deg

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Preliminary! Preliminary!

Conclusions:

4STAR had an outstanding first deploymentComparisons of AOD with surface and in-situ aerosol optical properties look strong.Water and trace gas retrievals show good potential.First-ever hyperspectral airborne sky scans collected. Initial results are encouraging but much validation work remains.

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Layer AOD