Kippzonen Brewer MkIII Manuel d'utilisateur télécharger pdf (Page 114)

MKIII OPERATOR’S MANUAL

111

These airmass calculations are imbedded within the "equation of time" computations.

A second path-lengthening factor, M2, is also calculated. This airmass corresponds to a layer

height of 22 km.

COMPUTING SINGLE AND DOUBLE RATIOS

At this point the count rates Fi have been corrected and compensated for deadtime, temperature,

and (if applicable) Rayleigh scattering. Four sets of single ratios are formed (recall that these count

rates are in logarithm units, hence a "ratio" is formed by computing the difference):

254

FFMS −←

(includes effects of O

and SO

)

355

FFMS −←

456

FFMS −←

(affected predominantly by O

)

567

FFMS −←

Only the shortest of the five observation wavelengths (306.3 nm, count rate F( 2 )) is significantly

affected by SO

column amounts, so ratios MS( 5) , MS( 6 ), MS( 7 ) will be largely independent of

effects.

Two higher-order ratios are formed:

748

2.3 MSMSMS ⋅−←

7659

7.15.0 MSMSMSMS ⋅−⋅−←

Both of these functions have weightings which remove the effects of absorption which are linear

with wavelength. In addition, they are stabilized with respect to small wavelength calibration errors.

The second function is weighted to remove SO

absorption effects

These ratios are written to disk and printer.

DETERMINING O

AND SO

FROM DIRECT-SUN DATA

The O

amount, MS11, is determined from the logarithms of the count rates for the four longer

wavelengths :

BMS

⋅

−

←

where

MS9 is the double ratio described in the previous section

B1 is the extra-terrestrial coefficient for the O3 wavelength combination (instrument-

dependent)

A1 is the differential O3 absorption coefficient for the O3 wavelength combination

(instrument-dependent)

M2 is the path-lengthening factor for an ozone layer of height 22 km.

APPENDIX G PRELIMINARY DATA REDUCTION

1 2 ... 109 110 111 112 113 114 115 116 117 118 119 ... 135 136

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Kippzonen Brewer MkIII Manuel d'utilisateur Page 114

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