Effects of sub-seasonal variability on seasonal-to-interannual Indian Ocean meridional heat transport

摘要

Numerical experiments using the Hybrid Coordinate Ocean Model are performed to examine atmospheric intraseasonal oscillation (ISO) effects on seasonal-to-interannual meridional heat transport (Q(v)) in the tropical Indian Ocean. Analysis focuses on the equator and 14.5 degrees S, latitudes associated with the cross-equatorial and southern subtropical meridional cells. ISOs alter seasonal Q(v) anomaly (Q(v)*) at these latitudes by a-few-hundredths PW up to 2 - 3 tenths PW. On interannual timescales, heat transport anomaly (Q(v)') induced by ISOs tends to reinforce (correlates positively with) the total Q(v)' signal. ISO winds can induce interannual Q(v)' up to 0.15 PW, comparable to the maximum amplitude of the Q(v)' signal. Net effects of atmospheric ISOs can account for similar to 30% of Q(v)' in some years; in others, ISO contributions are insignificant. Wind stress ( via momentum flux) and wind speed ( via turbulent heat fluxes and vertical mixing) play notable roles in ISO effects on Q(v)* and in some years on Q(v)'.