Dissertation Abstract
The impact of sea surface thermal status anomalies on the interannual variability of tropical Northwestern Pacific climate
minghong, zhang 2013
Institute of Atmospheric Physics, Chinese Academy of Sciences (China), 137 pp.
The impact of sea surface thermal status anomalies on the interannual variability of tropical Northwestern Pacific climate is investigated in this thesis. First, the impact of global sea surface temperatures (SSTs) is studied through evaluating the simulations in 12 atmospheric general circulation models (AGCMs) which attended the AMIP II experiments. Then, the impacts of different oceanic regional SST, particularly in the tropical central eastern Pacific and the Indian Ocean, are focused. Followed is a further analysis on the impacts of different regional thermal anomalies through so-called pacemaker experiments, in which the observed heat flux is prescribed into a coupled AGCM-slab mixed-layer ocean model. The results are summarized as follows.
1. The skills in simulating interannual variability of northwestern Pacific (NWP) summer climate in twelve AMIP II AGCMs show a wide range, which is related with the simulated teleconnection of NWP summer climate with sea surface temperatures (SSTs) in the tropical Pacific and Indian oceans. These results also highlight the key roles of model’s background climatology in Walker Cell and diabatic heating for the difference, thus providing important clues to improving model’s ability.
2. Through observational analyses, AGCM and diagnostic linear model experiments, it is shown that in the decaying phase of CP-El Niño, the northwestern Pacific anticyclone (WNPAC) is induced by the cooling SSTA in the central eastern Pacific and enhanced by the suppressed convection in the northwestern Pacific. The latter may be induced by the enhanced convection over the maritime continent.
3. The different effects of Indian Ocean Basin-scale Mode (IOBM) on northwestern Pacific in three seasons (winter, spring and summer) are investigated by using the sensitive AGCM experiments, and the results show the key role of seasonal transition of Indian monsoon circulation.
4. Through the pacemaker experiments in a coupled AGCM-slab mixed-layer oceanic model and the sensitive experiments in AGCM with prescribed SSTA, it is found that oceanic forcing from the deep tropical eastern Pacific (DTEP) can instigate the Pacific-East Asia teleconnection and WNPAC, and the associated air-sea interaction is essential for the realization of the teleconnection. The sensitive experiments also show the oceanic forcing over the west Pacific and South China Sea can exert significant influences on the northwestern Pacific-East Asian climate, but the forcing over the tropical Indian Ocean is negligible. Due to a lack of ocean dynamic couple processes, the predictability of northwestern Pacific SST in the slab mixed-layer AGCM is not high.
1. The skills in simulating interannual variability of northwestern Pacific (NWP) summer climate in twelve AMIP II AGCMs show a wide range, which is related with the simulated teleconnection of NWP summer climate with sea surface temperatures (SSTs) in the tropical Pacific and Indian oceans. These results also highlight the key roles of model’s background climatology in Walker Cell and diabatic heating for the difference, thus providing important clues to improving model’s ability.
2. Through observational analyses, AGCM and diagnostic linear model experiments, it is shown that in the decaying phase of CP-El Niño, the northwestern Pacific anticyclone (WNPAC) is induced by the cooling SSTA in the central eastern Pacific and enhanced by the suppressed convection in the northwestern Pacific. The latter may be induced by the enhanced convection over the maritime continent.
3. The different effects of Indian Ocean Basin-scale Mode (IOBM) on northwestern Pacific in three seasons (winter, spring and summer) are investigated by using the sensitive AGCM experiments, and the results show the key role of seasonal transition of Indian monsoon circulation.
4. Through the pacemaker experiments in a coupled AGCM-slab mixed-layer oceanic model and the sensitive experiments in AGCM with prescribed SSTA, it is found that oceanic forcing from the deep tropical eastern Pacific (DTEP) can instigate the Pacific-East Asia teleconnection and WNPAC, and the associated air-sea interaction is essential for the realization of the teleconnection. The sensitive experiments also show the oceanic forcing over the west Pacific and South China Sea can exert significant influences on the northwestern Pacific-East Asian climate, but the forcing over the tropical Indian Ocean is negligible. Due to a lack of ocean dynamic couple processes, the predictability of northwestern Pacific SST in the slab mixed-layer AGCM is not high.