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
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.)
-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
Final flight series (late Aug 2011)
14
max alt 5.7 km
TestCapability
FORJCTesting
LangleyCalibration
ScienceExample
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
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