This README file describes the format of the 6-channel Ames Airborne Tracking Sunphotometer (AATS-6) results obtained during ACE-Asia aboard the NCAR C-130.



The data are Q/A-ed and obstructions by clouds or aircraft structures have been removed. The current version (4.0) uses the RAF-distributed reference altitudes. 
For comparison with other investigators' data we recommend that their data be projected on the RAF reference altitudes as well. The curent version of AATS-6 data 
is also corrected for diffuse light entering AATS-6's field of view. For an explanation of these corrections, please see the statement posted at 
http://geo.arc.nasa.gov/sgg/ACE-Asia/Data_Plots/diffuse.html. 



We have computed fit coefficients for AOD and extinction that will allow you to interpolate the values to any desired wavelength in the range from 380 to 1021nm 
using a simple Angstrom law.



The fit is 



ln (tau_aero)=a0 + a1 * ln (lambda) 



where lambda has to be in units of micrometers. In the coefficient columns in the files the first column is a1, the second is a0. We highly recommend using this
interpolation in cases where the wavelengths don't match. Analogous fit parameters are given for extinction.


The exact format is described in the header of each file.



Note that:



AOD(5) and AOD_Error(5) expand to 5 variables (corresponding to the 5 wavelengths given in the header). Note that the 0.550 um data is not measured, but interpolated 
from the Angtsrom law fit above. It was added merely to save some of the in situ folks the individual efforts; analogous for extinction.





The retrieval algorithms are described in:



Russell, P. B., J. M. Livingston, E. G. Dutton, R. F. Puschel, J. A. Reagan,
T. E. Defoor, M. A. Box, D. Allen, P. Pilewski, B. M. Herman, S. A. Kinne, and 
D. J. Hofmann, 1993: "Pinatubo and Pre-Pinatubo Optical-Depth Spectra: Mauna Loa
Measurements, Comparisons, Inferred Particle Size Distributions, Radiative Effects,
and Relationsship to Lidar Data". Journal of Geophysical Research, Vol. 98, No. D12,
22'969-22'985.



Schmid B., C. Mätzler, A. Heimo, and N. Kämpfer, 1997: Retrieval of Optical Depth
and Size Distribution of Tropospheric and Stratospheric Aerosols by Means of Sun 
Photometry. IEEE Transactions on Geoscience and Remote Sensing, Vol 35, No. 1, 172-182.



Schmid, B., J. M. Livingston, P. B. Russell, P. A. Durkee, H. H. Jonsson, D. R. Collins,
R. C. Flagan, J. H. Seinfeld, S. Gassó, D. A. Hegg, E. Öström, K. J. Noone, E. J. Welton,
K. J. Voss, H. R. Gordon, P. Formenti, and M. O. Andreae, Clear sky closure studies of
lower tropospheric aerosol and water vapor during ACE 2 using airborne sunphotometer,
airborne in-situ, space-borne, and ground-based measurements, Tellus, B 52, 568-593, 2000.



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).







Point of contact:



Jens Redemann/Beat Schmid/Phil Russell/John Livingston
NASA Ames Research Center
MS 245-5
Moffett Field, CA 94035-1000
jredemann@mail.arc.nasa.go