NOAA/PMEL and NOAA/CMDL ACE 1, Legs 1 and 2 Aerosol Optical Depth (AOD)
As measured by CMDL’s handheld sunphotometers.

(P. Quinn, Feb. 25, 1997).

Column, heading
1, DOY (GMT)
2, Decimal Latitude
3, Decimal Longitude
4, AOD, 380 nm
5, AOD, 500 nm
6, AOD, 778 nm,
7, AOD, 862 nm
8, comments
9, AVHRR overpass

Notes on data reduction:

Calibration of the sunphotometers is based on Langley plots derived from measurements 
at Mauna Loa.   

The relative air mass, mr, was calculated using Kasten’s formula.

The total measured optical depth was used to calculate the aerosol optical depth by 
subtracting Rayleigh and ozone extinction, i.e.,

AOD = TotalOD - OD,Rayleigh - OD,ozone

where

OD, Rayleigh = P/Po x 0.00877l-4.05 + d(l)

and P = the atmospheric pressure during the observation, Po is standard atmospheric 
pressure (1013.25 mb), and d(l) is a time-dependent minor correction for a shift in the 
filter l.

OD,ozone = 0.01 at 500 nm and negligible at all other wavelengths.

The 380 nm channel displayed a severe drift after DOY 338.  Therefore, these data have been removed 
from the record.