The Pacific Meridional Mode and the Occurrence of Tropical 1 Cyclones in the Western North Pacific
نویسندگان
چکیده
30 This study investigates the association between the Pacific Meridional Mode (PMM) 31 and tropical cyclone (TC) activity in the western North Pacific (WNP). It is found that 32 the positive PMM phase favors the occurrence of TCs in the WNP while the negative 33 PMM phase inhibits the occurrence of TCs there. Observed relationships are 34 consistent with those from a long-term preindustrial control experiment (1000 years) 35 of a high-resolution TC-resolving Geophysical Fluid Dynamics Laboratory (GFDL) 36 Forecast-oriented Low Ocean Resolution (FLOR) coupled climate model. The 37 diagnostic relationship between the PMM and TCs in observations and the model is 38 further supported by sensitivity experiments with FLOR. The modulation of TC 39 genesis by the PMM is primarily through the anomalous zonal vertical wind shear 40 (ZVWS) changes in the WNP, especially in the southeastern WNP. The anomalous 41 ZVWS can be attributed to the responses of the atmosphere to the anomalous 42 warming in the northwestern part of the PMM in the positive PMM phase, which 43 resembles a classic Matsuno-Gill pattern. Such influences on TC genesis are 44 strengthened by a cyclonic flow over the WNP. The significant relationship between 45 TCs and the PMM identified here may provide a useful reference for seasonal 46 forecasting of TCs and interpreting changes in TC activity in the WNP. 47
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