Delayed influence of the Indian Ocean Dipole mode on the East Asia-West Pacific monsoon: possible mechanism

作者：Kripalani R H^*; Oh J H; Chaudhari H S

来源：International Journal of Climatology, 2010, 30(2): 197-209.

DOI：10.1002/joc.1890

• Indian Ocean
• Eurasia
• East Asia-West Pacific

This study investigates the possible physical processes for the delayed response of the East Asia-West Pacific summer monsoon to the Indian Ocean Dipole Mode (IODM) through the Eurasian continent based oil composite and correlation analyses. The media carrying the memory for this delayed response is identified.
Results reveal that the peak positive phase of the dipole during autumn could suppress the following summer monsoon activity over East Asia three seasons later, in particular over the Korea-Japan sector, South China and the adjacent West Pacific region. Composite and correlation analysis Suggests that the autumn positive phase of the dipole could induce heavy snow over Eastern Eurasia, north of the Korea-Japan (EENKJ) peninsula, during the following winter and spring seasons. This could increase the temperature gradient conducive to transport cold and dry air from the north towards South over the warmer East Asia-West Pacific domain during the following summer. The sea surface temperature (SST) reveals that the positive phase of the dipole mode during autumn is associated with the warm phase (El Nino) of the El Nino Southern Oscillation (ENSO) over the Pacific. As the seasons progress through to summer, the warm phase over the Pacific transforms to a developing cold phase (La Nina) with warmer SSTs over the West Pacific. Both the anomalous northerly winds due to heavy snow and the anomalous warm SST over the West Pacific due to La Nina displace the North Pacific Subtropical High (NPSH) eastwards, resulting in a weak cross-equatorial flow and a weak low-level jet. This could inhibit moisture supply from the Pacific leading to Subdued rainfall activity. The footprints of the IODM for delayed response, three seasons later, could be carried by the snow distribution over Eastern Eurasia by the northern route. Furthermore, correlation analysis suggests that the relationships with IODM are slighter stronger than with the ENSO phenomenon. However, partial correlation analysis probably Suggests that both the IODM and ENSO work cooperatively for the summer monsoon rainfall anomalies over East Asia-West Pacific region.

• 出版日期2010-2