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The data file "daily_aod_metric_2009.dat" contains daily values of NSA (Barrow, AK) aerosol optical depth (AOD) at 500 nm and corresponding angstrom exponent.
The data file contains header rows preceded with %. The header rows are followed by title row of comma-separated column headings: yyyy, mm, dd, HH, doy, aod_500nm, angstrom_exponent_500_840nm
The header row is followed by 366 rows of data matching the column headings. Unavailable data values are indicated by "NaN".
Comment: The aod values are a composite of NIMFR measurements and an empirical regression of form:
AOD = a + b(Mean BL RH) + c(surface RH) + d(surface RH * ln(Total Humidified Scattering).
The angstrom exponent values are derived from NIMFR measurements at 415 nm and 870 nm and interpolated over data gaps.
The data values in the ASCII file are drawn directly from the netcdf file "daily_aod_metric_2009.cdf" which also contains all related surface and meteorological data relevant to the data product. In addition, hourly and 10-minutely data is available in data files named "hourly_aod_metric_2009.cdf" and "aod_metric_2009.cdf", respectively. In particular, the 10-minutely file contains flags permitting identification of data source (e.g., NIMFR measurement, interpolated, regressions, ...).
Additional information are available in the 4th Quarter 2009 science metric report at http://www.arm.gov/science/metrics.stm>.