| Summary: | application/pdf In 2010, the Northern Hemisphere, in particular Russia, Europe and Japan, experienced an abnormally hot summer characterized by record-breaking warm temperatures and associated with a strongly positive Arctic Oscillation (AO), that is, low pressure in the Arctic and high pressure in the midlatitudes. In contrast, in winter 2009/2010, just a half-year earlier, Eurasian continent suffered from anomalously cold weather associated with are cord-breaking negative AO, indicating that AO index abruptly changed from strong negative to strong positive. The abrupt change of AO index in 2010 corresponded to the change from the abnormally cold winter of 2009/2010 to the abnormally hot summer of 2010. The AO polarity reversal that began in summer 2010 can explain the abnormally hot summer. The winter sea surface temperatures (SST) in the North Atlantic Ocean showed a tripolar anomaly pattern-warm SST anomalies over the tropics and high latitudes and cold SST anomalies over the midlatitudes-under the influence of the negative AO. The warm SST anomalies continued into summer 2010 because of the large oceanic heat capacity. A AGCM(atmospheric general circulation model) simulation strongly suggested that the AO related summertime North Atlantic warm SST anomalies remotely caused the occurrence of the positive summertime AO. Thus, a possible cause of the AO polarity reversal can be the ‘‘memory’’ of the negative winter AO in the North Atlantic Ocean. An interseasonal linkage of the AO probably induces a positive AO in the following summer. Understanding of this interseasonal linkage can aid in the long term prediction of such abnormal summer events. 三重大学大学院生物資源学研究科博士前期課程共生環境学専攻 34 thesis
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