Aeronet Quarterly and Annual Summary
Aeronet Quarterly and Annual Summary FY 98
http://spamer.gsfc.nasa.gov
Summary
AERONET has four research staff, four technical staff and a half time office
manager. Everyone participates in operational activities including the
research staff which dedicates about 50% of their time on operational issues
such a calibration, deployment, and problem solving. This past fiscal year we
have reached some semblance of operational stability that we can more easily
determine what we can and cannot do. The repair and calibration load has
increased as the larger federated community has relied more heavily on us to
repair instruments, supply parts as needed and check real time field data. The
procedures for checking instruments, on site repairs, swapping out instruments
is pretty well established between our staff and the site managers. A quality
assured/cloud screened data base was implemented in January by Alexander
Smirnov and is available on our homepage. Oleg Dubovik has made great strides
developing the sky radiance inversion code. AERONET has been given
authorization to broadcast on the DCS international channels which will allow
data collection over Asia. This will probably be operational around February
1999. AERONET's goal of ±0.01 accuracy in AOD is achieved in the visible
and NIR channels and is ~ ±0.02 in the UV thanks largely to the strict
requirements of Tom Eck and Alexander Smirnov and the diligence of Nader
Abuhassen. The absolute accuracy of the sky calibration is still probably in
the ±5% range owing to the uncertainty of the GSFC sphere calibration
facility. Efforts to shift the polarization calibration to GSFC should
facilitate a much more rapid turnaround for those instruments. The Goddard
polarizer should be available around December 1. Goddards integrating sphere
was repainted in August and came back on line in late September. We are
awaiting the new calibration coefficients, probably available in late October.
Further modification is required delaying full operational status until
December 1999. All data affected by this delay will be reprocessed immediately
upon receipt of the new coefficients. We continue to participate in various
field campaigns including, SCAR-B, TARFOX, INDOEX, LBA and ACE-2. Recent
military contacts are expected to help develop an ocean network particularly
working through SIMBIOS. The AERONET network paper was published in Remote
Sensing of Environment. A new computer "AERONET" was received which should
come on line in late October. Our processing capability and on line storage is
greatly expanded. More detailed information follows.
HOMEPAGE: The homepage, although not particularly fancy, is functional.
All processed data can be visualized (AOD) and downloaded with acceptance that
the PI is notified. Raw data is available only through the program
`demonstrat' for which PI's have access. A cloud screened and quality assured
AOD data base is available through demonstrat. Other operational information
is posted on the homepage as well as papers that directly pertain to the
program such as the "Network' and `cloud screening' papers. Three versions of
the homepage are planned. Considering that some sites have a very slow
internet connection, a scaled back version will drop all pictures and only list
a table of sites to which the usual down load procedures may be applied. The
second version is the current homepage. A third level will have GIS capability
which should facilitate EOS validation research and help address the difficult
problem of spatial homogeneity.
In order to protect the PI's that contribute their data to this federated
network, we require any user to accept the following announcement when
downloading data from the homepage:
NOTICE TO NON-AERONET INVESTIGATORS : To maintain the integrity of the data
base and fairness to the individuals who have contributed, use of these data
for publication requires an offer of authorship to the AERONET PI(s).
AERONET has a new computer called `AERONET' giving us much needed disc space,
much faster processing and I hope improved access to the data base. The
homepage should be on AERONET by the end of October.
Deployment:
The AERONET system had a deployment goal of 60 instruments world wide by the
end of July to support the Launch of EOS-AM1. The actual number was
approximately 40 by the end of Sept. This number may drop slightly again due
to the return of some seasonal instruments during the northern hemisphere's
winter. Several EOS validation sites and campaigns have been supported
(Howland, Maine; flux tower), Beltsville BRDF (EOS validation program), CAMEX,
and U of Miami dust exp. and Safari 2000 (Mongu, Zambia, Skakuza (S. African
Low Veld) and Johannesburg). The swap out campaign is beginning in earnest
with swap outs occurring in the Maldives (INDOEX), Barbados, Bermuda, Lanai,
Dry Tortugas and San Nicholas Island. The calibration of the network
instruments depends on our ability to swap out the instruments for freshly
calibrated units.
The entire French PHOTON network (19 instruments) was sent to GSFC and has not
yet been redeployed. The instruments suffered from repair and calibration
issues which combined with grouped returns as required by the import/export
declarations has resulted in slow progress. Nine instruments were crated by
October 20. We are waiting for customs documentation.
The SIMBIOS (ocean color network) has developed good contacts with the Naval
Research Laboratory through AERONET resulting in an instrument at Bahrain and
the potential for others in South Korea, Iceland, and the Azores and TBD sites.
The ocean deployment has also been slow due to the hardening upgrade required
for the marine environment. Half of the instruments have now been hardened.
The Brazilian deployment has also been on hold due to the extremely slow
progress of the LBA MOU required for NASA instruments. Word on the street is
for a late October signing.
FY 99 deployment plan (new sites) :
Oceans: South Korea (SIMBIOS), Iceland (SIMBIOS), Azores (SIMBIOS),
Turkey (SIMBIOS), Nauru (SIMBIOS/ARM), Tahiti (SIMBIOS), Robins Carusoe
(SIMBIOS), TBD (SIMBIOS)
Asia: Beijing (AERONET), IMGRASS NE China (AERONET), NEPAL (AERONET),
Australia, Darwin (CSIRO), SIBERIA (MODIS), Israel (MODIS Atmosphere), India
(PHOTON)
Urban: Mexico City (AERONET), Beijing (AERONET), NYC (AERONET)
South America: Tapajos (LBA), Manaus (LBA), Ji-Parana (LBA), Brasilia
(LBA), 3 TBD (USP), Buenos Aires (AERONET)
Europe: Paris network (Photon?), Gotland Island (Sweden), Mianz
(Photon), Hungary (AERONET)
Africa: Mozambique (SAVE), Etosha Pan (AERONET), Okavango Delta
(PHOTON), Mt. Kenya (AERONET)
AERONET federated sites: Current and anticipated distribution by Launch of
AM-1, June 1999.
Calibration:
The following table shows the stability of Vo (Vo % change=
((t1-t2)/t1))*100) based on MLO revisits for
two of our reference instruments during the last four months. All filters are
BARR IAD from the same batch.
Inst.
101 April-Aug. 98
|
|
Inst
27 May-Sept 98
|
|
Wavelength
|
%
change in Vo
|
|
Wavelength
|
%
change in Vo
|
|
1020
|
-0.64%
|
|
1020
|
0.43%
|
|
870
|
-0.46%
|
|
870
|
0.90%
|
|
670
|
1.94%
|
|
670
|
0.29%
|
|
500
|
0.07%
|
|
500
|
0.54%
|
|
440
|
0.32%
|
|
440
|
1.69%
|
|
380
|
0.69%
|
|
380
|
1.56%
|
|
340
|
-2.23%
|
|
340
|
1.57%
|
|
940
|
2.04%
|
|
940
|
-0.50%
|
|
Inst.
37 Feb.-July. 98
|
|
Inst.
37 July-Sept. 98
|
|
1020
|
-0.47%
|
|
1020
|
-0.45%
|
|
870
|
-0.15%
|
|
870
|
0.22%
|
|
670
|
-1.38%
|
|
670
|
New
Filter
|
|
500
|
-0.23%
|
|
500
|
-1.92%
|
|
440
|
-0.27%
|
|
440
|
-1.96%
|
|
380
|
0.12%
|
|
380
|
-1.29%
|
|
340
|
1.26%
|
|
340
|
0.12%
|
|
940
|
-1.57%
|
|
940
|
-1.51%
|
|
# 101: Negative denotes higher Vo in Aug. The only significant changes in Vo
(larger than Vo uncertainty as defined by MLO repeatability) occurred for the
670 and 340 nm filters. All other filters were, in a statistical sense, stable.
Note that Langley Vo value variability for the 940 nm filter is much greater
than other filters, so the change of 2.04% is not statistically significant,
given the Vo coefficient of variation for the 940 filter is ~2.5%.
#27: Therefore the only significant changes in Vo (larger than Vo uncertainty
as defined by MLO repeatability) occurred for the 440, 380, and 340 nm filters.
All other filters were, in a statistical sense, stable, with the 870 filter
perhaps showing some slight change.
#37: Note that the 675 nm filter was changed in #37 before being sent to MLO
in
Sept. 1998, therefore no percentage changes were computed for that channel.
Also the changes in the 440 and 500 nm (and probably 380 nm) channels were
caused by changes which occurred as a result of the sensor head being opened
up and the 675 nm filter replaced.
The only significant changes in Vo (larger than Vo uncertainty as defined by
MLO repeatability) occurred for the 440, 500 and 380 nm filters. All other
filters were, in a statistical sense, stable. Note that Langley Vo value
variability for the 940 nm filter
is much greater than other filters, so the change of -1.57% is not
statistically significant, given the Vo coefficient of variation for the 940
filter is ~2.5%.
Our weekly network assessments of in situ measurements has revealed a tendency
for the 675 and 340 nm channels to be more unstable than other channels. As
instruments are recalibrated we will develop statistics for these. So far we
feel that a 6 to 9 month recalibration is adequate to maintain our AOD accuracy
of ±0.01 for the vis and nir channels and 0.02 for the UV.
The Goddard 6 foot sphere was painted in August brought on line in September
but calibration and substrate stability has been problematic. We will use with
the lower output hemisphere until the 6 foot sphere becomes fully operational.
AERONET and the calibration facility is scheduled for a move to the new Earth
System Science Building (affectionately known as Bldg. 33) in March 99 so some
disruption in all phases of the AERONET program is likely.
Quality Assurance-How is the AOD data raised to Level 2?
After the postfield calibration is applied we examine the data set in order to
evaluate the admissibility of aerosol optical depth spectral dependence. If
some channels show crossovers in spectral optical depth we try to determine if
the pattern is random or systematic. We evaluate the consistency in Angstrom
parameters estimated through the full spectral range (340-1020 nm) and the 440
through 870 nm. If we conclude that a certain channel (or channels) does not
preserve the calibration owing to filter degradation (or any other reason),
aerosol optical depths will not show up on the homepage QA data base. From sky
measurements, we evaluate the consistency of the signals measured in the sun
and sky collimators in order to determine if our calibration might be
compromised by obstructions in the sun collimator. Consideration of the sky
data may give a good indication when certain abnormalities started to appear
(if any) and went undetected. We also check for optical depth diurnal
variations that might be associated with the poor sun tracking. After that the
cloud screening procedure is applied and the data are available on the homepage
". This is not an absolute guarantee that the data are perfectly calibrated or
free from errors and cloud contamination but we believe the level 2 is very
good. Regardless the user must also carefully examine these data before using
them in any analysis.
GMS-Measurements in Asia:
NOAA has given AERONET 10 of 80 international assignments which we will use on
GMS. The next step is acquiring the data from GMS. Global Transmission System
(GTS) is the standard method however it requires encoding the data at JMA and
subsequent decoding. The authorization for GTS transmission is a bottleneck
requiring months to years for each site. In it's place, we will install a
receive station in Hawaii to be operated by NOAA.
International Agreements: International agreements between NASA and the
host countries is absolutely required for deployment of all NASA instruments.
This process is very slow however compromises have been made on the part of
NASA HQ and encouragement on our collaborating hosts is resulting in more
completed agreements. Approximately 10 have been completed and another 10 are
pending. Basically they contain a statement of collaboration, expedition of
equipment through customs and agreeing that NASA will not be liable for any
injuries resulting from use of this equipment.
Network size:
Little comment was received regarding size limits of the network nor it's
collaborative management with other networks. John Ogren suggested that a
closer collaboration be made with GAW. Contact has been made but GAW is
limited. Discussions will continue.
A recent meeting at GISS for assessment of the current state of ground based
optical depth measurements clearly showed several other important and related
activities that I hope will foster collaboration with AERONET. Those
activities are linked on our homepage which we'll try to keep current.
Research:
The cloud screening algothrim developed by Alexander Smirnov has been presented
at several conferences and informal meetings and a paper submitted to JGR.
Dubovik is making rapid progress on the sky radiance inversion code and
associated products. He's currently working on a comprehensive sensitive study
with a seminar planned for November at GSFC.
Progress has been made on an aerosol climatology paper and several
presentations have been made by Smirnov and Holben at various conferences. The
poster is on the AERONET homepage http://spamer.gsfc.nasa.gov.
The AERONET paper was finally published!
Publications in FY `98
Journal articles:
Holben B.N., T.F.Eck, I.Slutsker, D.Tanre, J.P.Buis, A.Setzer, E.Vermote,
J.A.Reagan, Y.Kaufman, T.Nakajima, F.Lavenu, I.Jankowiak, and A.Smirnov, 1998.
AERONET - A federated instrument network and data archive for aerosol
characterization. Remote Sensing of Environment, 66: 1-16.
Dubovik, O. V, T. Yokota and Y .Sasano. Improved technique for data inversion
and its application to the retrieval algorithm for ADEOS/ILAS. Advances in
Space Research, 21,N3, 397-403 (1998).
Dubovik, O., B.N. Holben, Y. Kaufman, M. Yamasoe, A. Smirnov, D. Tanre, I.
Slutsker. Single-scattering albedo retrieval from the sky-radiance measured by
ground based sun-photometer. Accepted to J. Geophys. Res.
Dubovik O., B.N.Holben, Y.Kaufman, M.Yamasoe, A.Smirnov, D.Tanre, and
I.Slutsker. 1998 (accepted, in press, paper 98JD02276). Single-scattering
albedo retrieval from the sky-radiance measured by ground based sunphotometer.
Journal of Geophysical Research.
Eck, T. F., Holben, B.N, Slutsker, I., and Setzer, A. Measurements of
irradiance attenuation and estimation of aerosol single scattering albedo for
biomass burning aerosols in Amazonia. Accepted by Journal of Geophysical
Research for the SCAR-B special issue.
Reid, J.S., Hobbs, P.V., Liousse, C., Martins, J.V., Weiss, R.E., and Eck, T.F.
Comparisons of techniques for measuring shortwave absorption and black carbon
content of aerosols from biomass-burning in Brazil. Accepted by Journal of
Geophysical Research for the SCAR-B special issue.
Smirnov A., B.N.Holben, T.F.Eck, O.Dubovik, I.Slutsker. 1998 (submitted). Cloud
screening and quality control algorithms for the AERONET data base. Remote
Sensing of Environment,.
Smirnov A., B.N.Holben, I.Slutsker, E.J.Welton, and P.Formenti. (accepted, in
press, paper 98JD01930). Optical properties of Saharan dust during ACE-2,
Journal of Geophysical Research, 1998.
Tanre D., L.R.Remer, Y.J.Kaufman, S.Mattoo, P.V.Hobbs, J.M.Livingston,
P.B.Russell, and A.Smirnov. 1998. Retrieval of aerosol optical thickness and
size distribution over ocean from the MODIS airborne simulator during TARFOX.
Journal of Geophysical Research, 1998.
Yamasoe, M.A., Y.J. Kaufman, O. Dubovik, L.A. Remer, B.N. Holben and P.
Artaxo. Retrieval of the real part of the refractive index of aerosols from
sun/sky radiometers during SCAR-B. Accepted to J. Geophys. Res.
Yokota, T., M. Suzuki, O. Dubovik and Y. Sasano. ILAS (Improved Limb
Atmospheric Spectrometer)/ADEOS data retrieval algorithms. Advances in Space
Research, 21,N3, 393-396 (1998).
Articles in preparation:
Christopher, S.A., Li, X., Welch, R. M, Hobbs, P.V., Reid, J.S., Eck, T. F.,
and Holben, B.N. Estimation of downward shortwave irradiances in biomass
burning regions during SCAR-B. Submitted to Journal of Geophysical
Research.
Dubovik, O., B.N.Holben, M.D.King, A.Smirnov, T.F.Eck, S.Kinne, and I.Slutsker.
A flexible inversion algorithm for retrieval of aerosol optical properties from
Sun and sky radiance measurements.
Holben, B.N., D. Tanre, A. Smirnov, and T.E. Eck. and TBD, An emerging
aerosol optical depth climatology from ground based sunphotometry.
Satheesh, S.K., B.N. Holben, Xu Li-Jones, J.M. Lobert, I. Podgorny, J.M.
Prospero, and V. Ramanathan. A model for the natural and anthropogenic
aerosols over the tropical Indian Ocean derived from INDOEX data.
Tarasova, T. A., Nobre, C.A., Holben, B.N,. and Eck, T. F. Long-term
observations of surface solar irradiance in Brazil's Amazonia and modeling of
gaseous, aerosol and cloudiness effects on it. Submitted to Journal of
Geophysical Research.
Meetings, proceedings, reports and abstracts:
Dubovik O., B.N.Holben, Y.Kaufman, M.Yamasoe, A.Smirnov, D.Tanre, and
I.Slutsker. Single-scattering albedo retrieval from the sky-radiance measured
by ground based sunphotometer, AGU Fall Meeting, San Francisco, CA, December
8-12, 1997.
Dubovik, O., B.N. Holben, Y. Kaufman, M. Yamasoe, A. Smirnov, D. Tanre, I.
Slutsker, "Single-scattering albedo retrieval from the sky-radiance measured by
ground based sun-photometer",AGU Fall Meeting, San Francisco, CA, December
8-12, 1997.
Dubovik, O., B.N.Holben, M.D.King, A.Smirnov, T.F.Eck, S.Kinne, and I.Slutsker,
A flexible inversion algorithm for retrieval of aerosol optical properties from
Sun and sky radiance measurements, submited to International Symposium Ocean
color, Land surfaces, radiation and clouds, Aerosols: the contribution of
POLDER and new generation spaceborne sensors to global climate studies,
Meribel, France, January 18-22, 1999.
Dubovik, O., B.N.Holben, M.D.King, A.Smirnov, T.F.Eck, S.Kinne, and I.Slutsker,
A flexible inversion algorithm for retrieval of aerosol optical properties from
Sun and sky radiance measurements. International Symposium Ocean color, Land
surfaces, radiation and clouds, Aerosols: the contribution of POLDER and new
generation spaceborne sensors to global climate studies, Meribel, France,
January 18-22, 1999.
Eck, T.F., Holben, B.N., and Slutsker, I., Estimation of aerosol single
scattering albedo from irradiance and aerosol optical properites maesurements
for biomass burning smoke and urban haze, IGAC 1998 Symposium, Seattle,
Washington, August 20-25, 1998.
Eck, T.F., B. N. Holben, A. Smirnov, and I. Slutsker. Interannual and Regional
Variations of Biomass Burning Aerosol Optical Properties in Amazonia and
South-Central Africa. Abstract submitted to Fall AGU special session on
Atmospheric Effects of Large Fires.
Holben B.N., D.Ward, T.F.Eck, M.Mukelobai, I.Slutsker, A.Smirnov, O.Dubovik,
Interannual variability of biomass burning aerosol optical properties measured
in Zambian source regions. Fifth Scientific Conference of the International
Global Atmospheric Chemistry, Seattle, Washington, USA, August 19-25, 1998.
Holben B.N., D.Tanre, A.Smirnov, T.Eck, I.Slutsker, A.Setzer, B.Markham, J.Van
de Castle, D.Ward, Y.Kaufman, T.Nakajima, and N.T.O'Neill,. Aerosol
climatology measured from the globally distributed ground-based AERONET system,
Fifth Scientific Conference of the International Global Atmospheric Chemistry,
Seattle, Washington, USA, August 19-25, 1998.
Holben B.N., A.Smirnov, T.Eck, and N.Abuhassan, Instrumental problems in
sunphotometry,. Sunphotometer Workshop, Goddard Institute for Space Studies,
New York City, New York, USA, August 10-11, 1998.
Holben B.N., D.Ward, T.F.Eck, M.Mukelobai, I.Slutsker, A.Smirnov, O.Dubovik,
Interannual variability of biomass burning aerosol optical properties measured
in Zambian source regions, Fifth Scientific Conference of the International
Global Atmospheric Chemistry, Seattle, Washington, USA, August 19-25, 1998.
Holben B.N., D.Tanre, Y.Kaufman, A.Smirnov, T.Eck I.Slutsker, O.Dubovik,
B.Markham, and N.Abuhassan, Atmospheric aerosol optical properties measured
through the NASA Aerosol Robotic Network (AERONET), International Aerosol
Symposium, St.Petersburg, Russia, July 6-9, 1998.
Holben B.N., D.Tanre, Y.Kaufman, A.Smirnov, T.Eck I.Slutsker, O.Dubovik,
B.Markham, and N.Abuhassan. Atmospheric aerosol optical properties measured
through the NASA Aerosol Robotic Network (AERONET), International Aerosol
Symposium, St.Petersburg, Russia, July 6-9, 1998.
Remer L., R.G.Kleidman, Y.Kaufman, B.N.Holben, and A.Smirnov. Aerosol physical
and optical properties from AERONET data at TARFOX, AGU Spring Meeting,
Baltimore, MD, May 26-29, 1997.
Smirnov A., B.N.Holben, I.Slutsker, and E.J.Welton. Optical properties of
Saharan dust during ACE-2, AGU Fall Meeting, San Francisco, CA, December 8-12,
1997.
Smirnov A., B.N.Holben, L.Remer, and I.Slutsker. Measurement of atmospheric
optical parameters during TARFOX, TARFOX Data Workshop, San Francisco,
California, December 8-12, 1997.
Smirnov A., B.N.Holben, L.Remer, and I.Slutsker. Measurement of atmospheric
optical parameters on East coast sites, ships and Bermuda, AGU Spring Meeting,
Baltimore, MD, May 26-29, 1997.
Smirnov A., B.N.Holben, L.Remer, and I.Slutsker. Measurement of atmospheric
optical parameters during TARFOX, TARFOX Data Workshop, Monterey, California,
January 29-31, 1997.
Yamasoe M. A.,Y. Kaufman, P. Artaxo, L. Remer, O. Dubovik and B. Holben.
Determination of the real part of the index of refraction for aerosol particles
at the SCAR-B and TARFOX experiments