HR: 1340h
AN: G33B-1246    [Abstracts]
TI: Thermal Wind Forcing, Atmospheric Angular Momentum and Earth Rotation: Origin of the Earth's Delayed Response to ENSO
AU: * Dickey, J O
EM: jean.dickey@jpl.nasa.gov
AF: Jet Proplusion Laboratory, California Institute of Technology, MS 238-600, 4800 Oak Grove Dr., Pasadena, CA 91109-8099, United States
AU: Marcus, S L
EM: steven.marcus@jpl.nasa.gov
AF: Jet Proplusion Laboratory, California Institute of Technology, MS 238-600, 4800 Oak Grove Dr., Pasadena, CA 91109-8099, United States
AU: Chin, T M
EM: toshio.m.chin@jpl.nasa.gov
AF: Jet Proplusion Laboratory, California Institute of Technology, MS 238-600, 4800 Oak Grove Dr., Pasadena, CA 91109-8099, United States
AB: Interannual length-of-day variations and ENSO indices such as the Southern Oscillation Index (SOI) and Nino 3.4 SST are well correlated as a consequence of angular momentum conservation. During an El Nino event, the westerly winds increase, which raises the atmospheric angular momentum (AAM); as a result, the solid Earth must slow down, which increases the duration of the day (length-of-day: LOD). However, a lag has been observed with the SOI and Nino 3.4 SST leading the LOD and AAM series by one – two months; to date no dynamical explanation has been offered. The dominant excitation mechanism of interannual LOD is the wind term driven largely by thermal winds arising from the poleward gradient of tropical temperature (TT). We show that the TT gradient (TTG), which peaks 1-2 months after the Nino 3.4 SST anomaly, is the source of the thermal winds that drive the LOD anomaly and account for this well-known ENSO-Earth rotation lag. This work serves to underscore the global signature of climate processes such as ENSO, and highlights the utility of geodetic methods for studying both natural and anthropogenic climate variations and their interactions with broader aspects of the Earth system.
DE: 0350 Pressure, density, and temperature
DE: 1223 Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions (0762, 1218, 3319, 4550)
DE: 1239 Earth rotation variations
DE: 4522 ENSO (4922)
SC: Geodesy [G]
MN: 2007 Fall Meeting