lmd_Li1996_abstracts.html

1996 .

Z. X. Li. Correlation of the astrometric latitude residuals at Mizusawa and Tokyo with the southern oscillation index on an interannual time scale. Astronomy Astrophysics, 309:313-316, May 1996. [ bib | ADS link ]

The El Nino/southern oscillation (ENSO) is the most prominent interannual fluctuation in the atmosphere-oceanic system. A single index SOI (Southern Oscillation Index), based on the sea level pressure difference between Tahiti and Darvin, is conventionally used to describe the ENSO phenomenon. Its linkage to other geophysical phenomena is being studied now. The paper studies the correlation of SOI with the latitude residuals by means of cross correlation in using the latitude observational data of the six astrometric instruments at Mizusawa and Tokyo: the Zenith Telescope (1900-1978), the Photographic Zenith Tube No. 1 and No. 2 (1962-1975; 1975-1992), the Floating Zenith Telescope(1967-1984) and the astrolabe (1966-1984) at Mizusawa; the Photographic Zenith Tube at Tokyo (1966-1988). It appears that the latitude residuals at Mizusawa and Tokyo have a significant correlation at interannual time scale with the SOI, the SOI leading latitude residual of about 2-3years.

M. Collins, S. R. Lewis, P. L. Read, and F. Hourdin. Baroclinic Wave Transitions in the Martian Atmosphere. Icarus, 120:344-357, April 1996. [ bib | DOI | ADS link ]

Surface pressure data from the Viking Lander mission and from GCM simulations of the martian atmosphere have been analyzed using singular systems analysis. Very regular oscillations are found with frequencies that are distributed bimodally with peaks corresponding to periods of approximately 2-4 days and 5-7 days, respectively. Reconstructions of the amplitudes of the two oscillations are often negatively correlated; i.e., when the amplitude of one oscillation is large, that of the other is small. The GCM simulations show that the negative correlation in the amplitudes of the two oscillations can be explained as a flipping between two different wavenumber modes. In the absence of diurnal forcing in the model, transition from an unrealistically regular high frequency mode to a similarly unrealistic regular low frequency mode occurs at most once during the northern winter season. The diurnal cycle in the model, however, acts in a non-linear sense to stimulate the transitions between the two wavenumbers and thus increases the frequency of mode flipping events. The corresponding simulations bear a closer resemblance to the observations.