Variations in the 13 CM Opacity Below the Main Cloud Layer in the Atmosphere of Venus Inferred from Pioneer - Radio Occultation Studies, 1978-1987

Details Variations in the 13 CM Opacity Below the Main Cloud Layer in the Atmosphere of Venus Inferred from Pioneer - Radio Occultation Studies, 1978-1987 Variations in the 13 CM Opacity Below the Main Cloud Layer in the Atmosphere of Venus Inferred from Pioneer - Radio Occultation Studies, 1978-1987

Jan 1992

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992phdt........26j&link_type=abstract

Thesis (PH.D.)--GEORGIA INSTITUTE OF TECHNOLOGY, 1992.Source: Dissertation Abstracts International, Volume: 53-04, Section: B, p

Statistics

Computation

Radio Occultation

Scientific paper

Radio astronomical observations of Venus have suggested that the abundance and distribution of sulfur -bearing gases below the main cloud layer may vary significantly both in time and with position. Radio occultation studies may provide the only method for identifying and characterizing variations in the abundance and distribution of sulfuric acid vapor (H_2SO_4) during the period 1979 to 1986. In this research we reduced Pioneer Venus Orbiter Radio Occultation (PVORO) data from seasons 1 and 2 (1978-79) and season 10 (1986 -87) to obtain 13-cm absorptivity profiles and abundance profiles for sulfuric acid vapor. Reducing amplitude data from radio occultation experiments requires the computation of Inverse Abel Transforms (IAT) and derivatives of noisy data sets. These two operations tend to exacerbate the effects of measurement noise. The method used to reduce the data did not allow the variations in 13-cm absorptivity to be fully characterized, due to large error estimates. Software simulating the occultation experiment was developed to evaluate the performance of alternate methods for performing the IAT and numerically differentiating experimental data. Three approaches were investigated and tested using the simulation software: least squares polynomials, Kalman filtering, and Wiener filtering. We developed a method based on the Wiener filtering method of Anderssen and Bloomfield (1974a and 1974b) that performed 30% better on average than the old method with respect to root mean square error on synthetic data sets. The new technique was applied to several data sets from season 1, 2 and 10. The more accurate results support a decrease in the abundance of H_2 SO_4(g) from 1979 to 1986 at latitudes northward to 70^circ . This new technique holds potential for improving the results of other investigations involving radio occultation data.

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