ISSN 1006-9895

CN 11-1768/O4

Tropical Pacific-Indian Ocean Associated Mode and Its Climatic Impacts
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    Abstract:

    Based on observational data and simulation results by LICOM2.0 model, a synthetic introduction with regard to the existence, feature, evolution and impacts of the Pacific-Indian Ocean associated mode (PIOAM) are given in this paper. EOF analyses of SSTA both in the tropical Pacific-Indian Ocean and in the global ocean show that the EOF-1 pattern in the tropical Pacific-Indian Ocean is perfectly similar to the PIOAM, which indicates that the PIOAM is a very real mode of oceanic temperature anomalies in the tropical Pacific-Indian Ocean. Corresponding to positive and negative phases of the PIOAM, the wind field anomalies at 850 hPa over the tropical Pacific-Indian Ocean in the summer (JJA) are almost opposite, the Walker circulation at the lower troposphere and the Asian summer monsoon display different anomalous (close to opposite) features. In positive (negative) phase of the PIOAM, the South Asia high is located to the east (west) of its normal position. EOF analyses of subsurface oceanic temperature anomalies (SOTA) at the thermocline camber in the tropical Pacific-Indian Ocean reveals that the EOF-1 is a triangle mode similar to the PIOAM at the sea surface. This result suggests that the PIOAM also occurs in the oceanic subsurface. The numerical simulation by the high resolution oceanic circulation model LICOM2.0 shows that when the tropical central-western Indian Ocean and central-eastern Pacific are abnormally warmer/colder, the tropical eastern Indian Ocean and western Pacific are correspondingly colder/warmer. This result further confirms that the tropical PIOAM is an important mode that is significant in both sea surface temperature anomaly (SSTA) field and subsurface ocean temperature anomaly (SOTA) field. The positive and negative phases of the PIOAM not only affect the weather/climate in Asian and west Pacific regions, but also have impacts in south-north American and Africa regions. The influences of the PIOAM are different from that of ENSO and Indian Ocean Dipole (IOD).

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History
  • Received:October 17,2017
  • Revised:
  • Adopted:
  • Online: May 31,2018
  • Published: