HR: 11:50h
AN: G21E-06    [PDF]
TI: Ocean-Atmosphere interaction observed from comparison of the ENSO signatures in the time series of J$_{2}$ and the Earth's spin rate
AU: * Fang, M
EM: fang@chandler.mit.edu
AF: Department of Earth Atmospheric & Planetary Sciences, MIT, 77 Mass. Ave., Cambridge, MA 02139 United States
AU: Zang, X
EM: xiaoyun@ocean.mit.edu
AF: Department of Earth Atmospheric & Planetary Sciences, MIT, 77 Mass. Ave., Cambridge, MA 02139 United States
AU: Zheng, D
EM:
AF: Shanghai Observatory, Chinese Academy of Sciences, Nandan Road, Shanghai, 200030 China
AU: Hager, B H
EM:
AF: Department of Earth Atmospheric & Planetary Sciences, MIT, 77 Mass. Ave., Cambridge, MA 02139 United States
AU: Wunsch, C
EM:
AF: Department of Earth Atmospheric & Planetary Sciences, MIT, 77 Mass. Ave., Cambridge, MA 02139 United States
AU: Ding, X
EM:
AF: Department of Surveying & Geo-informatics, Hong Kong Polytechnic University, Hong Horn Kowtoon, Hong Kong, 033333 Hong Kong
AB: Significant interannual variations have been observed from the multi-satillite SLR solutions of the Earth's oblateness, known as the J$_{2}$ time series, by the Texas CSR group (Cheng \& Tapley, submitted) with a time span from 1975 to the present, as well as by our independent analysis of the Godard series (courtesy of Ben Chao for the data) with a time span from 1979 to the present. These variations are closely related to the ENSO events as evidenced by their apparent correlation, not perfect though, with the Southern Oscillation Index. Our preliminary analysis shows that the ENSO signature in the atmospheric circulation is not adequate to account for up to 50% of the interannuals in the J$_{2}$ series. In contrast, the atmosphere contributes better than 80% of the observed time variation of the Earth's rotation rate i.e. the length of day (LOD) at the ENSO time scale, mostly from the thermally driven eastward wind fields (e.g. Zheng et al, 2003). We normalize the LOD and J$_{2}$ series by making the maxima in both data sets units, and make a comparison. A strong correlation is found between the LOD and J$_{2}$. It is apparently due to a common cause from the ENSO. At the same time, noticeable differences are observed, especially with the phases. These differences are ultimately attributed to the ocean-atmosphere interaction during the ENSO events. As a preliminary study, we calculate the oceanic contribution to the interannuals of LOD and J$_{2}$ by running a high-resolution state-of-art self-consistent and volume conserving ocean numerical model with realistic atmospheric forcing. A simple model for the ocean-atmospheric interaction will be employed to calculate the changes in the wind and pressure fields. Solid Earth deformation induced by the bottom pressure change is also considered in the modeling. Correlation analysis are conducted between the "fully model" ENSO driven LOD and J$_{2}$. Comparisons between the observed and modeled correltions will be presented.
DE: 1200 GEODESY AND GRAVITY
DE: 1724 Ocean sciences
DE: 3010 Gravity
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
DE: 4200 OCEANOGRAPHY: GENERAL
SC: Geodesy [G]
MN: 2003 Fall Meeting