Instantaneous optical depths total or (aerosol + cloud) are given at 3-minute intervals. Total optical depths are calculated using the standard Beer's Law approach, (ln(V0) - ln(V))/airmass. Rayleigh and ozone optical depths are subtracted from total optical depths to give aerosol optical depths. V0 for each wavelength and requested date is determined from a time series of Langley-generated voltage intercepts for morning periods. The Langley method is described in Harrison and Michalsky (1994).


Graphs of the data are available for a time selection of a month or less. The graphs will be displayed along with a tabular view of the data used to create the graph. We also provide a feature to export the data to a file on your local computer in a comma delimited(CSV) format.


For any time duration greater than a month, use the end date option below. This will generate a data file that you can download to your local computer. Keep in mind a year's worth of data is about 14 megabytes and will take almost a minute to generate.