AERONET Quarterly 10/02

1. Inversion products QA’d

2. Download tool

3. Spheroid Inversion

4. Network remains closed to new sites

5. Distributed Calibration sites

6. New Instruments-under evaluation

7. Polarization status

8. Ancillary products (demonstration)

9. Amy has a baby girl; Terry Aquino subs for Amy

10. AERONET related Research papers

Greetings Everyone.

1. Our Goddard team has decided upon and implemented a strategy to quality assure the ‘Dubovik’ inversion products that we’ve been using these past several years. The strategy follows the recommendations of the Dubovik et al, 2001 sensitivity paper and divides the level 2 products into spherical and non-spherical particles. We’ve eliminated the non-physical accumulation mode of the size distribution for non-spherical aerosols. The attached figures summarize the approach (Figures - PDF). We are open to suggestions or modifications. The approach required reprocessing of the entire data archive that was completed in May. The new processing also includes fine and coarse mode AOD, SSA, Reff, Rv and Cv. All retrievals are available through level 1.5 and you have the option of using your own criteria for screening the inversion retrievals (see 2 below).

2. The level 2 data are available through the new download tool found on the website under “DATA.” The tool allows creation of a compressed file of the AOD products or Level 2 products for any time period in question, one site at a time. Note that under level 2.0 you may use our ‘recommended’ level 2 data or establish you own criteria ‘advanced’ in which several criteria options become available. Under level 2, ‘Recommended,’ you may choose all retrievals that fit our ‘spherical’ criteria or those that fall under non-spherical conditions. Almucantars can be retrieved singularly or as daily averages. All raw data can also be retrieved. All of these retrievals are derived using Dubovik’s spherical model.

3. A spherical model is not the final answer. Oleg recently published the results from his inversion using randomly oriented spheroids (see reference below). In principle the spheroid model is a more general case. The results clearly demonstrate realistic accumulation modes for known non-spherical particles (dust). The results for assumed spherical cases match the spherical inversion results usually very well. We are now reprocessing the entire database with the non-spherical inversion. Completion will likely be in December at which time the download tool will have that option.

Inversion products will be available from PP measurements in a few months and using both together sometime after that.

Note that the AOD monthly climatology under ‘DATA’ on the web site is automatically updated when level 2 data become available.

4. The network is still closed to new sites unless the candidate is located in Asia, the southern Oceans, Africa or high latitudes. New sites are still coming on line from prior commitments. The Goddard facility has very little capacity to expand its operations. So the question may be posed: How does the network grow?

5. We are proposing a distributed calibration network, that is, calibration will be preformed at a few collaborating sites. Goddard will insure that procedures and reference standard instruments are used and all calibrations are traceable back to the Goddard master instruments. Should this system work, the network will have the ability to handle more field instruments. This will be a slow process; we are currently implementing it at Lille with the PHOTON instruments.

6. Given the possibility for expansion, Cimel has developed a prototype extended wavelength (1.6mm) instrument which is currently being evaluated for inclusion into the network. So far this instrument is not ready for AERONET nor is AERONET ready for it. The prospect of constraining the non-spherical retrievals is very interesting.

7. Polarization: Cimel modified their polarization instrument because the polarization filters are no longer commercially available. The redesign has not yet been evaluated for AERONET but in principle will protect the polarizers from excessive exposure to sunlight and require much less polarizer material.

8. If you visit the AERONET website and know where to look, you will see some new data sets available under the daily AOD window. We’re working with several groups to more easily provide complimentary data to the user. Please note that these are only a demonstration so far.

Dr. Anne Thompson who runs the SHADOZ ozone monitoring program makes extensive use of back trajectories. She is now providing twice daily kenematic back trajectories at 4 pressure levels for twenty-two AEROENT sites. This began in February and is currently running about 3 months behind real time. (http://hyperion.gsfc.nasa.gov/Data_services/aeronet/index.html)

Dr. Judd Welton is operating the Micro Pulse Lidar Network (MPLNET). AERONET sites are co-located with most permanent MPLNET sites and many field campaigns. Files are updated every four hours, A raw backscatter (24hr) image is provided and shortly extinction profile will be added during each AEROENT observation. (http://mplnet.gsfc.nasa.gov/)

Jacques Descloitres has developed the highly regarded MODIS Land Rapid Response site. MODIS true color imagery over selected AEROENT sites is provided at 250m, 500m and 2000m resolution. (http://rapidfire.sci.gsfc.nasa.gov/)

The intention is to provide these three products for all AEROENT sites in near real time visually on the same page with AERONET retrievals. Links to the host site will allow digital acquisition. New ancillary data contributors are sought to develop this capability.

9. Amy Scully our Administrative Assistant is on maternity leave with her baby daughter born Sept. 23^rd. All is well. She will be out for at least 4 weeks more and is replaced by Terry Aquino. Anne Vermeulen is also out on maternity leave in anticipation of her second child. She’ll be handling polarization issues from home for a while.

Those of you maintaining instruments, please be mindful of spider webs in the collimators, check that your wet sensors work, the clocks are accurate and the instruments are tracking. A quick check of the web page (OPERATIONS) will let you know how your instrument is performing.

10. Recent Papers:

Kaufman, Y.J., D. Tanré and O. Boucher , A satellite view of aerosols in the climate system, Nature, 419, 215-223. (Provides a synergistic view of AERONET, satellites & models)

Dubovik, O., B.N.Holben,T. Lapyonok, A.Sinyuk, M. I. Mishchenko, P. Yang, and I.Slutsker, 2002: Non-spherical aerosol retrieval method employing light scattering by spheroids, Geophys. Res. Lett., 29, 54-1 - 54-4. (Provides a glimpse of improved retrievals we may expect in a few months)

Cheers,

Brent