AERONET Quarterly-Winter 2004


Dear Colleagues:


Happy New Year!


AERONET with the collaboration of PHOTONS and many other partners has grown rapidly in geographic distribution and importance to the scientific community due to improved data access to more and better product types during the last five years.  Our web tracking statistics showed there were 26,740 unique visitors to the AERONET website last year.  Congratulations to everyone for making the federated network such a valuable resource for the research community and the planet.   This Quarterly reviews the following headlines:


AERONET/PHOTONS workshop planned for May 10-14, 2004 in Spain

New instrument models are functioning well

Inversion Corner Review and Update

Inversion QA

New Inversion release anticipated in April

New AOT Version to be released 

Tracking status of instruments, the new relational data base

Lab notes

Calibration-The network has two official calibration sites

Database Integration-BAMGOMAS

Publications and Research



AERONET workshop:

I feel that to keep the network innovative and relevant that we need a two-way communication between the AERONET and PHOTONS staff and our research and operational community.  I’d like to announce an AERONET/PHOTONS workshop to be held in El Arenesillo, Spain from May 10 to May 14, 2004.  The workshop will be hosted by the University of Vallidolid and INRA through the capable efforts of Drs. Angel de Frutos and Victoria Cachorro.  Sessions will be run by AERONET and PHOTONS staff but will only be useful with the active participation of the attendees.  Our experience has shown that data quality and quantity is driven by integrating research needs with operational understanding thus this workshop is unique in that we want all aspects of the program represented during the course of the week.



  • Day 1: a program overview AERONET/PHOTONS staff
  • Days two and three:  Research issues, invited and solicited talks and poster session.  
  • Days 4 and 5:  Operational issues such as instrument maintenance, AERONET webpage surfing, data products, database management, etc.  I want to particularly emphasize the importance for site managers to attend.
  • I invite you to submit an abstract for a science talk (which we’re emphasizing integrated aerosol research that may or may not involve AERONET data) or a poster session that will emphasize AERONET/PHOTONS activities.  If you are interested in providing a talk or poster please send a short abstract to Amy Scully. 
  • If you want to attend, please also let Amy know as soon as you can so we can get a head count. 
  • Please see the AERONET homepage ( for more details including the agenda and logistics.  


More Current matters:


Weather/calibration:  Despite having nearly 2 meters of rain equivalent this past year at Goddard we managed to catch up on our intercomparison/calibration backlog this fall.  We currently have 39 instruments in the calibration/maintenance queue at Goddard and 15 at the PHOTONS facilities.  More tend to come in during this season due to darkness and poor weather at the higher northern latitudes.


New instrument models are functioning well: 

The new model instruments featuring the 1.64 mm channels are operating well however a few minor issues persist including rare periodic negative spikes (~1/day) in the AOD that are screened by the cloud screening algorithm. Not all corrections are applied to this channel thus it cannot be raised to level 2 status as yet (see New version section).  The tracking, symmetry about the aureole, stray light rejection and dynamic range all appear to be as good or better than the old instruments.  We had anticipated two 1020 nm AOD retrievals (Si detector and InGAS detector) however the InGAS is significantly more noisy so it is not displayed nor downloadable on the website.  The new version polarization instrument appears to function as expected. 

The SeaPRISM model is accepted into the network for assessing atmospheric parameters as well as estimating ocean leaving radiances (Zibordi et al., 2004, submitted to IEEE Trans.).  This instrument makes selected ocean radiance observations.  We currently provide the radiance observations but the ocean leaving radiance products are planned for mid-year.


Cimel does provide upgrades of old instruments that that AERONET and PHOTONS staff will install if the instrument owner chooses to purchase the kit.  Please contact Cimel for details.  Considering the condition of some instruments particularly those located near marine aerosols, I feel this is should be considered.


Inversion Corner-Review and Update:

Inversions are operationally computed using the 1996 Nakajima Code, the Dubovik spherical model and the new Dubovik spheroid model for almucantars.  PP inversions are currently being processed for the Dubovik spherical and spheroid models but the current analysis shows them to be less stable than almucantars.  Currently only the Nakajima and Dubovik spherical  and spheroid models (almucantars only) are available from the AERONET download tool.  


Inversion QA:

Level 1:  Does not apply to Inversions.


Level 1.5:  Inversions produced from predeployment calibrations using cloud screened AOT data.


Note: Level 1.5 inversions will be post field calibrated if the instruments have been returned for post field calibration.


Level 2 inversion products:  The data have been post field calibrated and cloud screened, inversion screening criteria are applied to raise selected data to ‘Quality Assured’ status.


Note:  QA criteria for Level 2 was subsequently ‘slightly modified’ in September 03 to more adequately screen for unrealistic endpoints of the size distribution.


The Database is being upgraded again to accommodate the increased number of products from the various processing models and in anticipation of new processing strategies.  Our best chronological guess for availability through the AERONET website follows:


Nakajima (Level 1.5)-current

Dubovik spherical & spheroid 4 almucantars (Level 1.5 & 2)-current

Dubovik spherical & spheroid 4 PP (Level 1.5)-processed but not operationally available

Dubovik spherical & spheroid 6 almucantar–Proposed for April.

Dubovik spherical & spheroid , 6 PP (Level 1.5)- processed for April but not operationally available


% Polarization from PP @ 870 nm (Level 1)-Current (No QA strategy formulated)


New Inversion release anticipated in April:

A new more computationally efficient inversion is currently being tested that will facilitate processing of variable spectral inversions from almucantars, PP, polarization and combination of such measurements.  This also has enhancements to the PP inversion module.   Implementation of this will require reprocessing of the entire data base likely in April this year.  Current product types will be maintained with the exception of the Nakajima retrievals.  This new database will be designated as ‘Version 2I’(I=inversion) to replace the current ‘Version 1I’.


New AOT Version to be released: 

Over the years small improvements to the various AOT algorithms have been published and accepted by the community.  We plan to release ‘Version 2A’ (A=AOT) in March that will include the latest enhancements.  At that time the entire data base will have been reprocessed.  The improvements include:


Water Vapor retrievals (Hitran database and line by line radiative transfer mthd)

1020 nm water vapor correction

1640 nm water vapor, CO2 and CH4 corrections

            Air pressure measurements from web and or modeled sources for Rayleigh correction where appropriate

            Rayleigh algorithm upgrade

Ozone LUT correction based on TOMS monthly climatology (1 deg X 1 deg)

AOT fine and coarse fractions based on O’Neil (2003)


Tracking status of instruments, the new relational data base:

We track many parameters of an instrument and it’s location, including maintenance, filters, calibration status and coefficients, site manager coordinates and photos, site location etc in web-based  ‘FileMaker’ a relational data base that has proven extremely useful for asking questions like: What field instruments are due for calibration?  The answer is immediate and has made our operation much more efficient.  The calibration status is posted daily on the AERONET website under ‘Operation’ if you want to track the status of your instruments calibration.  Site manager list, site photo page etc. are all part of the relational database. 


Lab notes:

Site managers, please track the health of your instruments at least weekly on the AERONET website.  Low sun and cold in the northern hemisphere can cause power problems.  Often times tilting the solar panels toward the low sun solves the problem. 


We’ve noted that the 340, 380 and 1,610 nm filters provided by Cimel (Spectragon) cannot be used in the project due to inadequate blocking and/or spectral mismatches.  Other standard IAD Spectragon filters will be accepted at this time as long as we have the measured filter function. We don’t have information on the long term stability of these filters however.  If the stability is shown to be poor, they will be dropped from network use.



The network has two official calibration sites, Goddard and Lille/Carpentras.  Lille handles approximately 30 instruments per year and Goddard the remaining 170 or so thus requiring we cycle out about 1instrument every 2 days.  Ross Mitchell is ramping up as a calibration site at CSIRO in Australia and will handle mainly instruments from that region.  AEROCAN is also considering this as a possibility for a growing Canadian network as is Frank Wagner in Munich. The distributed calibration procedures and protocols and intercomparisons are being carefully plotted out to insure that all instruments are referenced to the same standards with well established uncertainties. 


New Sites and Field campaigns:

New sites were established in the UAE, Algeria, Thailand, 5 in N. America, 6 in Europe, 1 in Antarctica, 1 in the South Indian ocean and only 2 in Asia during the last 6 months.  Until new calibration sites are established both Lille and GSFC calibration sites are not accepting new North American or European participants.  An independent cimel network (20 + sites) is in operation in northern China.  Formal and informal field campaigns are difficult to define and track.  The AEROENT team has developed a SE Asia network of five sites from last year’s field campaign.  AERONET stations participated in the GLAS validation campaign.


Database Integration-BAMGOMAS:

You may have noticed that links to other data sets occasionally are available at some sites from the AERONET download tool.  These sites will be expanding and data links increasing as part of the BAMGOMAS integration effort that will provide backtrajectories, Lidar, MODIS imagery and aerosol products, model results for most of the AEROENT sites if the measurement is available.  Other data sets will be linked as appropriate and will be provided as an integrated website to facilitate analysis.  As AERONET users you will have the benefit of these links as they come on line although bear in mind you are the gunnea pigs during this development period.  It will not diminish access to AERONET data.


Publications and Research:

Research is our motivation and reason for existence of AERONET.  Without a substantial research component that is integrated into the daily operation of the project, the quality and quantity of the data would suffer.  Congratulations to Tom Eck and Alexander Smirnov in particular for providing that difficult task with such competency and still lead highly productive research lives.   Operational issues often overwhelm our research opportunities, so I note with awe and pride these senior authored papers published in 2003 by our staff.  Many junior author papers were also published by our staff.



  • Eck, T.F., B.N. Holben, J.S. Reid, N.T. O'Neill, J.S. Schafer, O. Dubovik, A. Smirnov, M.A. Yamasoe, and P. Artaxo, High aerosol optical depth biomass burning events: A comparison of optical properties for different source regions, Geophys. Res. Lett., 30(20), 2035, doi:10.1029/2003GL017861, 2003.
  • Eck, T. F., B. N. Holben, D. E. Ward, M. M. Mukelabai, O. Dubovik, A. Smirnov, J. S. Schafer, N. C. Hsu, S. J. Piketh, A. Queface, J. Le Roux, R. J. Swap, and I. Slutsker, 2003: Variability of biomass burning aerosol optical characteristics in southern Africa during the SAFARI 2000 dry season campaign and a comparison of single scattering albedo estimates from radiometric measurements, J. Geophys. Res., 108(D13), 8477, doi:10.1029/2002JD002321, 2003.
  • O'Neill, N.T., T.F.Eck, , A.Smirnov, B.N.Holben, and S.Thulasiraman, Spectral discrimination of coarse and fine mode optical depth, J. Geophys. Res., 108(D17), 4559, doi:10.1029/2002JD002975, 2003.
  • O'Neill, N. T., Strawbridge, K. B., Thulasiraman, S., Zhang, J. ,  Royer, A., Freemantle, J., Optical coherency of sunphotometry, sky radiometry and lidar measurements during the early phase of Pacific2001, accepted for publication in Atmospheric Environment, 2003.
  • Smirnov, A., B.N.Holben, T.F.Eck, O.Dubovik, and I.Slutsker, Effect of wind speed on columnar aerosol optical properties at Midway Island, J.Geophys.Res., 108(D24), 4802, doi:10.1029/2003JD003879, 2003.
  • Smirnov, A., B. N. Holben, O. Dubovik, R. Frouin, T. F. Eck, and I. Slutsker, 2003: Maritime component in aerosol optical models derived from Aerosol Robotic Network data, J. Geophys. Res., 108(D1), 4033, doi:10.1029/2002JD002701.


Our research activities include aerosol characterization, inversion development (that includes polarization, non-sphericity, UV wavelengths and satellite integration), validation and local, regional and global scale radiative forcing assessment in addition to participation in field campaigns.   Our research world is largely one of collaboration; because of the nature of the AERONET federated network, we all have this opportunity. 


Thanks again to everyone involved and I hope to see you in Spain.







Staff Contacts:


Brent Holben                              

Tom Eck                                    

Ilya Slutsker                               

Wayne Newcomb                      

Alexander Smirnov                     

Oleg Dubovik                             

Mikhail Sorokine                        

Anne Vermeulen                         

Don Ho                                      

Amy Scully                                 

Dave Giles                                  

Terry Aquino                              

Alexander Sinyuk                       



Philippe, Gouloub                       

Luc Blarel                                   

Thierry  Podvin                           

Damiri  Bahaiddin                       

Francois Lavenu (CESBIO)        

Bernadette Chatenet  (LISA)      


Note that Terry Aquino will be leaving the project for new adventures in Australia at the end of January.  Amy will be taking over the Site Photo duties from her.  Good luck down under!



Last Updated: 12 January 2004