AERONET Quarterly

Brent Holben September 25, 2001

Following is a brief informal status of the AERONET program. This report will be available on the AERONET website (http://aeronet.gsfc.nasa.gov) under “AERONET Papers” as are previous quarterly reports.

The tragic events of Sept. 11, I believe, have given us all an increased appreciation that we are privileged to be living comfortably and safely, enjoying our work with the great fortune to collect and analyze data for a greater understanding of our world. Let us continue forward.

The issues: Staff changes, Lab news, programming news, research news, new collaborators, instrument load and program growth, acknowledgement.

Staff Changes:

Dave Giles-software development, operational processing system management

Don Ho-Technical and engineering, replaced Twan Tran

Amy Scully-replaced Dedrie Jones as our Administrative Assistant.

Ross Nelson no longer supports AERONET. Technical issues should be directed to Wayne Newcomb and shipping to Amy Scully.

AERONET Staff

Tom Eck-tom@aeronet.gsfc.nasa.gov

Ilya Slutsker-ilya@aeronet.gsfc.nasa.gov

Wayne Newcomb-wayne@aeronet.gsfc.nasa.gov

Alexander Smirnov-asmirnov@aeronet.gsfc.nasa.gov

Brent Holben-brent@aeronet.gsfc.nasa.gov

Oleg Dubovik-dubovik@aeronet.gsfc.nasa.gov

Joel Schafer-joel@aeronet.gsfc.nasa.gov

Anne Vermeulen-anne@aeronet.gsfc.nasa.gov

Mikhail Sorokine-msorokin@aeronet.gsfc.nasa.gov

Dave Giles-dave@aeronet.gsfc.nasa.gov

Don Ho-anho@aeronet.gsfc.nasa.gov

Amy Scully-amy@aeronet.gsfc.nasa.gov

Lab News

The Goddard 6 ft integrating sphere will be repainted and calibrated in Nov. It is projected to be down for a week but could easily take 2 or 3 weeks before the system is back on line. Some delays in our calibration should be expected. The lab is operating efficiently requiring approximately 4 to 6 weeks to turn a field instrument around. We typically have between 20 and 30 instruments here for calibration but this varies by season, weather and our staff travel load. Please note our website for any updates regarding shipping which may change daily as a result of current events affecting both air and ground transportation and Goddard security.

Programming News

GMS is now fully operational to our program. For the past two years, we have had to manually retrieve data from our receive site in Hawaii. A new operating system was installed by our vendor that Ilya quickly adapted to our automatic processing. The system is now more advanced than either our GOES or METEOSAT links. Data from Asia are updated and processed hourly.

Few people have been able to take advantage of the Dubovik retrievals as they are presented on the homepage without a thorough knowledge of the constraints placed on those retrievals (Dubovik et al., 2000). There has been no QA on these data available through the website. Beginning September 25, 2001, the retrieval data set will be QA’d through and available under DATA “level 1.5”. These data are linked to cloud cleared AOD (level 1.5 with measurements immediately before and after almucantar observations), thresholds of optical depth (t_a>0.4 @ 440 nm for w_o and complex index of refraction only), required scattering angles (>20 angles used in retrieval) and zenith angles (qo >15 degrees nominal and qo>45 degrees for w_o and complex index of refraction) and retrieval residual errors (<10%). We believe that this will eliminate confusion over which retrievals are good and which are suspect. In some cases eliminate good retrieval products but overall should give users a “default” data set to work with that will eliminate hours and days of screening and potential misrepresentation of the data. The unscreened data set will continue to be available under level 1.0.

Access to the database is an ongoing development process. We anticipate new products to be available in the coming months delivered on with a new web interface.

AERONET growth temporally suspended:

AERONET at last count had 162 numbered instruments and 102 sites sending data, 21 on the AERONET calibration platform, 5 in the lab for maintenance and the rest in transit or not transmitting. There are more instruments coming on line in N. America and Western Europe. We are growing where there is money not where we need site coverage such as high latitude oceans, Eastern Europe, central Africa and Asia. Core funding from NASA supports EOS satellite validation and aerosol characterization. CNES support for PHOTON (French contribution of AERONET) is also for satellite validation and surface based atmospheric linear polarization observations. AEROCAN for aerosol characterization in Canada, SIMBIOS for marine aerosol model development and atmospheric correction, AEROBRASIL for aerosol characterization in Brazil’s Amazon, New sites have been established in Yulin, China, Moscow, Russia, Holland, Santiago, Chile, Cheju Is., South Korea, Austria, Munich, Germany. In the near term we expect the Galapagos Is., Ecuador, Morocco, Algeria and UCLA to come on line. Other groups and individual PIs have deployment plans as well.

Given the current world events and the exceptional growth in the number of field instruments straining AERONET staff to support them, no additional new instruments will be accepted into the program until further notice. All commitments to this point will be honored but new requests will be denied. This should be considered temporary until we evaluate the impact of heightened security on our operation and can account for the full impact of existing commitments on our AERONET staff resources.

Research Activities

Several new papers have been published within and outside the group and are listed below.

Dubovik has made great progress addressing the influence of non-spherical particles that confound dust size distribution retrievals and the real refractive index. Using spheroids with a fixed aspect ratio for dust aerosols, the 440 nm real refractive index is reasonable and the non-physical but mathematically necessary accumulation mode is greatly reduced. Both new results are more physical and reasonable. For spherical particles all aspects of the retrievals are unchanged. I feel this is another important step forward in the retrievals.

Participation in field campaigns: Tom Eck and Brent Holben have participated in the SAFARI2000 program that has recently convened several workshops. Eck is investigating biomass burning aerosol properties variability in southern Africa (SAFARI 2000) with emphasis on the seasonal and spectral variability of aerosol single scattering albedo. Analysis of the data have shown the single scattering albedo to be regionally lower than the geographically equivalent areas subject to biomass burning in Brazil. A significant seasonal dependence is apparent in the data record. Additional participation in ACE-Asia and PRIDE last year and CLAMS, Pacific2001, EO-1 validation, MODLAND and ESPO1 this year will provide many research opportunities both within and outside of AERONET.

Holben is heading work on a new aerosol climatology paper that uses the Dubovik retrievals. Although we have an extensive record, the limitations on the retrievals are often severe. The results should assist other users interpretation of the retrievals from the home page as well as providing a baseline observation record.

Smirnov is examining the diurnal characteristics at some of the globally distributed sites and is working with the SIMBIOS staff to established improved marine aerosol models.

Vermeulen is examining the polarization data at a few sites. The results obtained confirm that the calibration is good and the instruments are working properly. Efforts are especially directed toward the development and testing of an algorithm using polarization to retrieve the aerosol polarizing properties.

I also note that more modelers are using the AERONET data set to validate their predictions.

Acknowledgements

It is with a great deal of embarrassment that I bring this subject up. It was pointed out to me that two papers have appeared in print with me as a senior and junior author that did not properly acknowledge the PI or program that collected some of the data used in the analysis. Points to remember:

Acknowledging AERONET does not imply an acknowledgement of all the rest of the contributors to the program
Authorship with a contributor does not necessarily satisfy the requirement to acknowledge the program.
Although this is a public domain database, it is an honor system. Each PI associated with the data set must be offered authorship that in most cases can be reduced to an acknowledgement.
All data sets used must be acknowledged. I suggest the following model for acknowledgment: "We thank the (Project/PI) for its effort in establishing and maintaining (site name(s)) sites". Site and data ownership can be complicated at times so it is particularly important to be aware that this strengthens the concept of a cooperative data-base.

Cheers,

Brent Holben

Recently Published Papers

Chin, M., P. Ginoux, S. Kinne, O. Torres, B. N. Holben, B. N. Duncan, R. V. Martin, J. A. Logan, A. Higurashi, and T. Nakajima, Tropospheric aerosol optical thickness

From the GOCART model and comparisons with satellite and sunphotometer measurements, J. Atmos. Sci., special issue of Global Aerosol Climatology, accepted,

2001.

Dubovik, O., B.N.Holben, T.F.Eck, A.Smirnov, Y.J.Kaufman, M.D.King, D.Tanre, and I.Slutsker, Variability of absorption and optical properties of key aerosol types observed in worldwide locations, J.Atm.Sci., 2001 (accepted).

Eck, T.F., B.N. Holben, O. Dubovik, A. Smirnov, I. Slutsker, J.M. Lobert, and V. Ramanathan, Column integrated aerosol optical properties over the Maldives during the NE Monsoon for 1998-2000, J. Geophys. Res., accepted, 2001.

Eck, T.F., B.N. Holben, D.E. Ward, O. Dubovik, J.S. Reid, A. Smirnov,; M.M. Mukelabai, N.C. Hsu, N.T. O'Neill, and I. Slutsker, Characterization of the optical properties of biomass burning aerosols in Zambia during the 1997 ZIBBEE field campaign, J. Geophys. Res., 106 , 3425-3448, 2001.

Ferrare, R. A., D. D. Turner, L. A. Heilman, W. F. Feltz, O. Dubovik, and T. P. Tooman, "Raman lidar measurements of aerosol extinction-to-backscatter ration over Southern Great Plains", J. Geophys. Res., 106, pp. 20,333 - 20,348, 2001.

Formeni, P., M.O. Andreae, L. Lange, G. Roberts, J. Cafmeyer, I. Rajta, W. Maenhaut, B.N. Holben, P. Artaxo, J. Lelieveld, Saharan dust in Brazil and Suriname during the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA) - Cooperative LBA Regional Experiment (CLAIRE) in March 1998, JGR, VOL. 106, NO. D14, PAGES 14,919-14,934, JULY 27, 2001.

Ginoux, P., M. Chin, I. Tegen, J. Prospero, B.N.Holben, O.Dubovik, and S.-J.Lin, "Sources and distributions of dust aerosols simulated with the GOCART model", J. Geophys. Res., 106, 20,255 - 20,274, 2001.

Holben, B.N., D.Tanre, A.Smirnov, T.F.Eck, I.Slutsker, N.Abuhassan, W.W.Newcomb, J.Schafer, B.Chatenet, F.Lavenue, Y.J.Kaufman, J.Vande Castle, A.Setzer, B.Markham, D.Clark, R.Frouin, R.Halthore, A.Karnieli, N.T.O'Neill, C.Pietras, R.T.Pinker, K.Voss, and G.Zibordi, An emerging ground-based aerosol climatology: Aerosol Optical Depth from AERONET, J. Geophys. Res., 106, 12,067-12,097, 2001.

Kaufman, Y.J. , Didier Tanre', O. Dubovik, A. Karnieli, L.A. Remer, Absorption of sunlight by dust as inferred from satellite and ground-based remote sensing

GRL, VOL. 28, NO. 8, PAGES 1479-1482, APRIL 15, 2001.

Kaufman, Y.J., A.Smirnov, B.N.Holben, and O.Dubovik, Baseline maritime aerosol: methodology to derive the optical thickness and scattering properties, Geoph.Res.Lett., 28, 3251-3254, 2001.

Kinne, S., B.N.Holben, T.F.Eck, A.Smirnov, O.Dubovik, I.Slutsker, U.Lohmann, S.Ghan, M.Chin, P.Ginoux, T.Takemura, R.Kahn, E.Vermote, D.Tanre, L.Stowe, O.Torres, and M.Mischenko, How well do aerosol retrievals from satellites and representation in global circulation models match ground-based AERONET aerosol statistics, in Remote Sensing and Climate Modelling: Synergies and Limitations (Advances in Global Change Research, vol. 7), edited by M.Beniston and M.M.Verstraete, Kluwer Academic Publishers, pp.103-158, 2001.

O'Neill, N.T. , T.F. Eck, B.N. Holben, A. Smirnov, O. Dubovik, A. Royer

Bimodal size distribution influences on the variation of Angstrom derivatives in spectral and optical depth space, JGR, VOL. 106, NO. D9, PAGES 9787-9806, MAY 16, 2001.

O'Neill, N.T., O. Dubovik, O., and T.F. Eck, "A modified Angstrom coefficient for the characterization of sub-micron aerosols", Applied Optics., 40: (15) 2368-2375, 2001.

Pandithurai, G., R. T. Pinker, O. Dubovik, B. N. Holben , and T. O. Aro, "Remote sensing of dust optical characteristics in Sub-Sahel, West Africa", J. Geophys. Res., in press, 2001.

Pinker, R. T., G. Pandithurai, B. N. Holben, O. Dubovik, and T. O. Aro, "Observing Dust Aerosol Properties in Real Time: A Near-Future Prospect?", J. Geophys. Res., in press, 2001.

Reid, J.S., H.H.Jonsson, M.H.Smith, and A.Smirnov, Evolution of the vertical profile and flux of large sea-salt particles in a coastal zone, J. Geophys. Res., 106, 12,039-12,054, 2001.

Remer, L.A., D.Tanre, Y.J.Kaufman, Ch.Ichoku, S.Mattoo, R.Levy, D.A.Chu, B.N. Holben, O.Dubovik, Z.Ahmad, A.Smirnov, J.V.Martins, R.Li, Validation of MODIS aerosol retrieval over ocean, Geophys.Res.Lett., 2001 (accepted).

Schmid B., J.J. Michalsky, D.W. Slater, J.C. Barnard, R.N. Halthore,

J.C. Liljegren, B.N. Holben, T.F. Eck, J.M. Livingston, P.B. Russell, T.

Ingold, and I. Slutsker. Comparison of columnar water-vapor measurements

from solar transmittance methods. Applied Optics, Vol. 40, No. 12,

1886-1896 2001.

Smirnov, A., B.N.Holben, Y.J.Kaufman, O.Dubovik, T.F.Eck, I.Slutsker, C.Pietras, and R.Halthore, Optical properties of atmospheric aerosol in maritime environments, J.Atm.Sci., 2001 (accepted).

Smirnov, A., B.N.Holben, O.Dubovik, N.T.O'Neill, T.F.Eck, D.L.Westphal, A.K.Goroch, C.Pietras, and I.Slutsker, Atmospheric aerosol optical properties in the Persian Gulf region, J. Atm. Sci., 2001 (accepted).

Takemura T., T. Nakajima, O. Dubovik, B. N. Holben and S. Kinne, "Single scattering albedo and radiative forcing of various aerosol species with a global three-dimensional model", J. Climate, in press, 2001.

Tanre, D., Y.J.Kaufman, B.N.Holben, B.Chatenet, A.Karnieli, F.Lavenu, L.Blarel, O.Dubovik, L.A.Remer, and A.Smirnov, Climatology of dust aerosol size distribution and optical properties derived from remotely sensed data in the solar spectrum, J. Geoph. Res., 106, 18,205-18,218, 2001.

Torres, O. , P.K. Bhartia, J.R.Herman, A.Sinyuk, Paul Ginoux and Brent Holben, A long-term record of aerosol optical depth from TOMS observations and comparison to AERONET measurements, J.Atm.Sci., 2001 (accepted).

Zhang, J., Sundar A. Christopher, Brent N. Holben, Intercomparison of smoke aerosol optical thickness derived from GOES 8 imager and ground-based Sun photometers, JGR, VOL. 106, NO. D7, PAGES 7387-7397, APRIL 16, 2001.

Zhao, T.X.-P., L.L.Stowe, A,Smirnov, D.Crosby, J.Sapper, and C.R.McClain, Development of a global validation package for satellite oceanic aerosol retrieval based on AERONET sunphotometer observations and its application to NOAA/NESDIS operational aerosol retrievals, J.Atm.Sci., 2001 (accepted).