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R. P. Cebula, H. Park, and D. F. Heath

Abstract

Precise knowledge of in-orbit sensitivity change is critical for the successful monitoring of stratosphere ozone by satellite-based remote sensors. This paper evaluates those aspects of the in-flight operation that influence the long-term stability of the upper stratosphere ozone measurements made by the Nimbus-7 SBUV spectroradiometer and chronicles methods used to maintain the long-term albedo calibration of this UV sensor. It is shown that the instrument's calibration for the ozone measurement, the albedo calibration, has been maintained over the first 6 yr of operation to an accuracy of approximately ±2%. The instrument's wavelength calibration is shown to drift linearly with time. Knowledge of the SBUV wavelength assignment is maintained to a 0.02 mm precision.

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S. E. Frederick, R. P. Cebula, and D. F. Heath

Abstract

The scientific objective of unambiguously detecting subtle global trends in upper stratospheric ozone requires that one maintain a thorough understanding of the satellite-based remote sensors intended for this task. The instrument now in use for long term ozone monitoring is the SBUV/2 being flown on NOAA operational satellite. A critical activity in the data interpretation involves separating small changes in measurement sensitivity from true atmospheric variability. This is the goal of the instrument characterization task, and of necessity it involves examining numerous details of SBUV/2 hardware operation. By defining the specific issues that must be addressed and presenting results derived early in the mission of the first SBUV/2 flight model, this work serves as a guide to the instrument investigations that an essential in the attempt to detect long-tem changes in the ozone layer.

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A. J. Miller, R. M. Nagatani, T. G. Rogers, A. J. Fleig, and D. F. Heath

Abstract

The most long-lived satellite set of ozone observations, to date, is that derived from the Backscatter Ultraviolet (BUV) ozone sensor on Nimbus 4 and extends from April 1970 through 1976. Unfortunately, this experiment suffered spacecraft power limitations which limited the spatial and temporal coverage and also appears to have suffered from long-term drifts which may be associated with changes in the instrument characteristics or the incident solar flux. We have developed techniques to account for these problems and our purpose here is to present results of the BUV total ozone variations and compare them with those from ground-based observations, specifically the computations of Angell and Korshover (1978).

After adjustments for the spatial gaps and comparison with concurrent Dobson ground-based observations, no significant trend was found in the BUV data over the years 1970-74. This finding is in contrast to a general decrease of ∼2% during the same period appearing in the data of Angell and Korshover. The difference in these results is discussed in terms of the geographic sampling and the methods of hemispheric integration.

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J. E. Frederick, P. B. Hays, B. W. Guenther, and D. F. Heath

Abstract

Backscatter ultraviolet data obtained by the Explorer E satellite imply very large ozone column abundances above 56 km in the tropics during mid-day. The number of molecules in a vertical column decays by a factor of 2–3 after the solar zenith angle exceeds 75° in the evening. An increase of similar magnitude occurs after sunrise. Such behavior implies the presence of a greater source of odd oxygen than is included in current photochemical theories. Ozone profiles deduced between altitudes of 50 and 62 km when the solar zenith angle exceeds 80° are in reasonable agreement with past rocket results.

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