Average optical depths are total optical depths from Langley analyses for each morning and/or afternoon on which a successful analysis was obtained. Each value is the slope of a regression of ln(voltage) on airmass, as described in Harrison and Michalsky (1994). Time periods included in the analyses are limited to specific airmass ranges which vary by wavelength: 1.5-3.0 for 332 and 368nm; 2.0-6.0 for 415-870nm.


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.