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

Results from Test-flight Series

PNNL NASA Ames NASA GSFC

B. Schmid S. Dunagan S. Sinyuk

C. Flynn R. Johnson

E. Kassianov P. Russell

C. Kluzek J. Redemann

M. Segal-Rosenheimer

Y. Shinozuka

M. Kacenelenbogen

J. Livingston

A collaboration involving:

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

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

4STAR: AATS-like capability:

AOD at 13 wavelengths H2O

horizontally and vertically resolved

Meet the family…

4STAR(2012-

AATS-6(1985-2001)

AATS-14(1996-

4STAR Integration on PNNL/Battelle G-1

Anticipated 4STAR data products:

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

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

Angularly-resolved sky radiance inversionsScattering phase function, asymmetry parameterAerosol size distributions, fine/coarse mode fractionAerosol sphericityAerosol 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.)

Ground Prototype Heads (4STAR-G)

4STAR-Ground

AERONET Cimel

Jens Redemann

Roy Johnson

-40 -20 0 20 40 60 80 100 120

100

101

102

scattering angle (deg)

uW/(

cm2 .s

r.nm

)4STAR and Aeronet principal plane scans on 2007-04-30, SZA=43.8 deg

Independently calibrated at NASA Ames and NASA GSFC

+ 4STARo Aeronet

440.8 nm

673.6 nm869.3 nm

1005.6 nm

Sun Photometer Inter-Comparison Experiment Mauna Loa, Aug. 24 - Sep. 2 2008

4STAR

PredeAATS-14

3 AERONET Cimels

Mauna Loa (August 2008) AOD Intercomparison

400 500 600 700 800 900 10000.002

0.005

0.008

0.01

0.014

0.02

0.04

wavelength [nm]

AO

D

2008-08-26 average AOD UT=16.5-18.5

4STAR (residual AOD)AATS-14AERONET

Mauna Loa (August 2008) Water Vapor Intercomparison

16.5 17 17.5 18 18.5 19 19.5 200.05

0.06

0.07

0.08

0.09

0.1

0.11

0.12

0.13

0.14

time [UT hour]

CW

V [

cm]

2008-08-26

AATS CWV4STAR average 940 (5 nm width) bandAERONET CWV

12

3 flights in Sep 2010:

1.Pilots only: Airworthiness certification2.Science ops: Pasco, WA to San Jose, CA3.Science ops: San Jose local

2 flights in April 2011: Pasco - Eastern WA, Idaho

max alt 5.7 km

Vertical profile of optical depth(normalized to top of layer)

13

l (nm)9/28/2010SJC ~10 am

Final flight series (late Aug 2011)

14

max alt 5.7 km

TestCapability

FORJCTesting

LangleyCalibration

ScienceExample

Airborne Langley Plot (Aug 30, 2011)

15

16

AODs during Airborne Langley Plot (Aug 30, 2011)

400 500 600 700 800 90010

-3

10-2

10-1 AE (linear fit)= 0.42963

10 20 30 40 50 60 70 80 90 100 110

10-10

10-9

10-8

scattering angle [degrees]

sky

radi

ance

4STAR data file:20110831_042_VIS_SKYP.datElapsed time: 76 sec over 7815 m at 585 m above MSL

4STAR 400 nm

4STAR 500 nm4STAR 675 nm

4STAR 870 nm

10 20 30 40 50 60 70 80 90 100 110

10-10

10-9

10-8

scattering angle [degrees]

sky

radi

ance

4STAR data file:20110831_030_VIS_SKYP.datElapsed time: 71 sec over 7814 m at 2974 m above MSL

4STAR 400 nm

4STAR 500 nm4STAR 675 nm

4STAR 870 nm

10 20 30 40 50 60 70 80

10-9

10-8

10-7

scattering angle [degrees]

sky

radi

ance

4STAR data file:20110831_029_VIS_SKYA.datElapsed time: 72 sec over 8042 m at 2971 m above MSL

4STAR 400 nm

4STAR 500 nm4STAR 675 nm

4STAR 870 nm

10 20 30 40 50 60 70 80

10-9

10-8

10-7

scattering angle [degrees]

sky

radi

ance

4STAR data file:20110831_041_VIS_SKYA.datElapsed time: 74 sec over 7551 m at 583 m above MSL

4STAR 400 nm

4STAR 500 nm4STAR 675 nm

4STAR 870 nm

Stray light rejection close to Sun

Sensitivity of retrievals to stray light close to sun (3-6°)

15%

20%

Sensitivity of retrievals to stray light close to sun (3-6°)

Poster A11H-0196, Kassianov et al.

Next steps…

FY12: bring 4STAR to full science capabilityImprove FOV uniformity of sun optics

Improve scattering isolation of sky optics

Apply correction of stray light inside spectrometer

Hardening and retrieval algorithms

DOE/ARM Mission on G-1, Cape Cod, July 2012 & Feb 2013

Possible Mission on NASA DC-8,(SEAC4RS, Asia), Aug-Sep 2012

Funding: NASA, DOE ARM, BMI, PNNL