SOLAR ACTIVITY AND EARTH ROTATION VARIABILITY

Abstract

The analysis of variability in Atmospheric Angular Momentum (AAM) and Length of day (LOD) of Abarca del Rio et al. [Ann. Geophys. 18 (2000) 347] is extended to investigate a possible connection with solar activity fluctuations from interannual to secular time scales. The southern oscillation index and records of sea surface temperature are used as proxy series in this analysis during the era prior to the availability of AAM analyses. At interannual times scales, the variability in AAM and LOD agrees with that in solar activity with regard to the decadal cycle in the stratospheric quasi biennial oscillation and solar activity but whose phases are slowly shifting from one another with time, while the stratospheric quasi biennial cycle agrees with the solar quasi biennial cycle, though led by 6 years. At decadal times scales, AAM varies statistically with the solar decadal cycle over much of the last century since 1930–1940. The decadal mode in AAM is suggested here to be generated by upward propagation of surface atmospheric modes, from the surface throughout the troposphere through the stratosphere. Equatorial Sea Surface Temperature (SST) variability may be considered a proxy index for AAM variability because of the relationship to the El Nino/Southern Oscillation; its analysis over the last three centuries (1730–2000) and that of LOD since 1830 confirm the agreement found over the last part of the 20th century, as well as the general disagreement before.