Findings

1
Comparison of Airborne Sunphotometer and OMI
Retrievals of Aerosol Optical Depth during
MILAGRO/INTEX-B and ARCTAS J. Livingston1, J.
Redemann2, Y. Shinozuka3, P. Russell3, O.
Torres4, B. Veihelmann5, R. Braak5, R. Johnson3,
S. Ramachandran3,6, L. Remer7, R. Levy7,8, A.
Smirnov7,8, B. Holben7, C. McNaughton9, Q.
Zhang2, S. Ramirez2 1SRI International, Menlo
Park, CA, 2Bay Area Environmental Research
Institute, Sonoma, CA, 3NASA Ames Research
Center, Moffett Field, CA, 4Center for
Atmospheric Sciences, Hampton University,
Hampton, VA, USA, 5Royal Netherlands
Meteorological Institute (KNMI), DeBilt, The
Netherlands, 6Physical Research Laboratory,
Ahmedabad, India, 7NASA Goddard Space Flight
Center, Greenbelt, MD, USA, 8Science Systems and
Applications, Inc., Lanham, MD USA, 9University
of Hawaii, Honolulu, HI USA
MILAGRO (March 2006)4 AATS/OMI Coincidences
ARCTAS (Summer 2008) 3 AATS/OMI Coincidences
Abstract
During the fall 2007 Aura Science Team Meeting,
we presented comparisons of aerosol optical
depths retrieved from spatially and temporally
near-coincident measurements acquired during
March 2006 during MILAGRO/INTEX-B (Megacity
Initiative-Local And Global Research
Observations/Phase B of the Intercontinental
Chemical Transport Experiment) by the NASA Ames
Airborne Tracking Sunphotometer (AATS) and by
Aura OMI. Results were shown for three AATS/OMI
coincidences over the Gulf of Mexico, two of
which also included Aqua MODIS AOD retrievals,
and one over the Mexico City area. We showed
OMAERUV results derived from the OMI Collection
002 radiances, and preliminary OMAERO results
derived from the Collection 003 radiances. In
this presentation, we update those comparisons
using the final archived OMAERO and OMAERUV
retrievals derived from the Collection 003
radiances. In addition, we show a preliminary
comparison of AATS, OMI, and MODIS AOD retrievals
from measurements acquired over the boreal
forests of Canada during the summer 2008 Arctic
Research of the Composition of the Troposphere
from Aircraft and Satellites (ARCTAS) field
deployment. During ARCTAS, AATS was flown aboard
the NASA P-3B research aircraft together with a
variety of other remotely sensing atmospheric
radiation instruments and in situ particle and
gas sensors. Data were obtained in clear air and
through forest fire smoke plumes directly over
and at various distances downwind of boreal
forest fires.
10 March 2006
30 June 2008 PRELIMINARY RESULTS
3 March 2006
17 March 2006
AATS and MODIS AOD Spectra
19 March 2006
Findings (1) OMI and AATS AOD retrievals have
been analyzed for four spatially and temporally
near-coincident events during MILAGRO/INTEX-B
three over the Gulf of Mexico and one over the
Mexico City metropolitan area. (2) For the March
10 coincidence, the OMAERO algorithm retrieves a
biomass burning aerosol and the corresponding AOD
retrievals significantly exceed AATS and MODIS
values in all 7 OMI grid cells, of which at least
4 were cloud-free. When the retrieval was
restricted to weakly absorbing (sulfate) aerosol
models, AODs decreased and the agreement with
AATS and MODIS improved significantly. (3) The
OMAERUV algorithm retrieves a non-absorbing
sulfate aerosol model for all 3 over-water
events, and AOD retrievals significantly
underestimate AATS values for all cloud-free grid
cells on March 10. (4) On March 19, AATS
measured a wide range of AOD at altitudes 480 m
above the T2 site 70 km NE of the Mexico City
metropolitan area. AATS spectra were flat,
indicative of dust. Corresponding OMAERUV AOD
retrievals agree with AERONET AOD spectra, which
exceed the AATS values that were not corrected
for AOD below the J31 aircraft. OMAERO AOD
spectra significantly exceed the sunphotometer
and OMAERUV values. (5) AATS AOD spectra 420 m
above the T0 site near the heart of Mexico City
agree with AERONET measurements and exhibit a
steeper wavelength dependence (a0.6-0.7).
OMAERUV retrievals slightly exceed and OMAERO
retrievals significantly exceed the AATS and
AERONET AODs. (6) Preliminary analysis of
measurements acquired on June 30, 2008 during
ARCTAS indicate that the AATS, OMI, and MODIS AOD
retrievals appear to paint a consistent picture
through the smoke plume, despite differences in
the retrieved OMI aerosol models and in retrieved
AODs outside the smoke.
T2
T0