A. Sarkissian et al., OZONE AND NO2 AIR-MASS FACTORS FOR ZENITH-SKY SPECTROMETERS - INTERCOMPARISON OF CALCULATIONS WITH DIFFERENT RADIATIVE-TRANSFER MODELS, Geophysical research letters, 22(9), 1995, pp. 1113-1116
Calculations of air-mass factors (AMFs) for ground-based zenith-sky UV
-visible spectrometers are now well developed in laboratories where st
ratospheric constituents are measured with this technique. An intercom
parison between results from the different radiative transfer models u
sed to calculate AMFs at twilight is presented here. The comparison wa
s made for ozone AMFs at 510 nm and for NO2 AMFs at 440 nm. Vertical p
rofiles were specified. Results are presented firstly for calculations
in a pure Rayleigh atmosphere, then including background aerosols. Re
lative differences between calculated AMFs from different models cause
relative errors in vertical columns of ozone and NO2 measured by zeni
th-sky spectrometers. For commonly used averages over solar zenith ang
les, these relative errors are +/-2.3% in the vertical column of ozone
and +/-1.1% in the vertical column of NO2. Refinements to the calcula
tions, suggested by the intercomparison, should reduce these errors to
+/-1.0% for ozone and +/-0.5% for NO2.