Interannual Variability of the Climate System

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Tsay, Jenq-Dar
Major Professor
Tsing-Chang Chen
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Geological and Atmospheric Sciences

Research on short-wave teleconnection (SWT) patterns appeared much later and less often compared to the planetary-scale waves. Recent studies show the SWT is significant during the La Nina, but the impact of the SWT on the weather was not explored yet. This study attempt to explore the impacts of the SWT on the weather during the summer and boreal winter. The main results are: 1) During boreal summer, anomalous shortwaves in the Arctic can reduce or increase the wator vapor transported from tropics/midlatitude to the Arctic region, which has an impact on the wet/drought and concurrency of wildfire in boreal forests; 2) During boreal winter, the cross-Pacific SWT can fill/reduce the upper level trough place in the coast of the East Asia. It has an effect in the storm genesis of East Aian. The flip of anomalous circulation can modulate the esat-west distribution of storm activity in the middle path of the short wave train. In the down stream of the SWT, the SWT can modulate the intensity of the blocking in the northeast Pacific; it affects the occurrence of blizzard and cold air outbreak in North America.

The problem of "midwinter suppression" has been reconized for two decades without a full explanation. This study uses existing knowledge about the semiannual cycle to explain the impact of the semiannual on "midwinter suppression". The result shows that the semiannual oscillation (SAO) mode is made not only from the dynamic processes of the monthly-mean mode, but also by the feedback interaction from the modulated transient activity. The feedback interaction of the modulated transient activity affects not only the development of the SAO of the atmospheric circulation, but also the SAO of divergent circulation and its hydrological cycle.

The proposed future works extended from this study are 1) The interaction between Muchurian monsoons and wet/drought in the Arctic needs to be understood. The interannual variation of wet/drought in the polar region might be caused by eastward propagation of anomalous circulation in the polar region are need more studying. 2) The winter time north Pacific short wave train is driven by the anomalous sea surface temperature (SST) in the western Pacific, since this SST has decadal change, Pacific Decadal Oscillation might be modulated by the short wave train. 3) Explore whether the semiannual cyclone causes suppression on synoptic weather system in tropics and South Hemisphere.

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Sun Jan 01 00:00:00 UTC 2012