| The dissertation focuses on the linkage between Asian summer monsoon and El Niño/Southern Oscillation (ENSO)—the two global-scale climate systems. The impact of the Asian summer monsoon—ENSO feedback on ENSO is investigated through numerical experiments with the modified Cane-Zebiak (CZ) coupled ocean-atmosphere dynamical model. To better achieve this objective, the spatio-temporal structure of ocean-atmosphere interannual variability associated with ENSO is comprehensively described using COADS observations, ECMWF and NCEP reanalyses (including diagnosed 3D heating), and ocean data-assimilation products.; The ENSO deep heating anomalies are in general agreement, with ECMWF deep-heating to be most consistent with the Xie-Arkin precipitation anomaly structure. The RPCA of band-pass filtered surface and subsurface observations has lead to the finding that the LF mode's transition phase in SST closely resembles the well-known ‘North Pacific’ mode.; Analysis of the 95,000-year long model integrations conducted with and without the interactive Asian-sector heating anomalies reveals that their influence on the Pacific surface winds leads to increased ENSO occurrence—an extra ENSO event every 20 years or so. An examination of the ENSO event distribution w.r.t. the peak SST-anomaly in the eastern equatorial Pacific shows a population-shift due to the strengthening of weak El Niño events in the monsoon run; this finding attests to the positive feedback between the two phenomena. The interaction of ENSO-related Asian summer monsoon heating with the CZ model's ocean-atmosphere also results in a wider period-distribution of ENSO variability, but with the El Niño peak-phase remaining seasonally locked with the Northern winter months. (Abstract shortened by UMI.)... |
