Semiperiodic variations in CO 2 abundance on Venus
Abstract
Photoelectric spectral scans of the P branch of the 8689 Å CO 2 band on Venus were made using the 107-inch coude scanner during seven observing periods in the past 2 years. The relative CO 2 line strength was determined for each scan, then normalized to remove the spatial variations leaving only temporal variations. The 4-day periodicity in the relative CO 2 line strength noted by Young et al. (1973) is not unique; we do confirm their 4-day periodicity in August 1973. Four other observing periods rule out a 4-day periodicity. A definite North-South asymmetry in the relative CO 2 line strength is noted during 1973, in most cases with the same periodicity present in both hemispheres. When the slit positions are referred to the equator of Venus, particularly near inferior conjunction, the large asymmetrics between the slit positions can be explained by a greater CO 2 line strength over the polar regions and weaker over the equatorial latitudes. The amplitude of variation of each position on the crescent is much greater near inferior conjunction either because we are sampling a smaller area on the planet or because the upper atmospheric abundance is more sensitive to the mechanism causing the variation in the smaller regions sampled at inferior conjunction. Simultaneous H 2O measurementsduring several of the observing runs indicate a lack of correlation in the relative CO 2 line strengths and the H 2O abundance.
- Publication:
-
Icarus
- Pub Date:
- June 1975
- DOI:
- 10.1016/0019-1035(75)90024-X
- Bibcode:
- 1975Icar...25..282B
- Keywords:
-
- Abundance;
- Atmospheric Composition;
- Carbon Dioxide Concentration;
- Infrared Spectra;
- Venus Atmosphere;
- Near Infrared Radiation;
- Spectral Line Width;
- Spectrum Analysis