Recent publications have investigated the interactions between the extratropical transitions （ETs） of tropical cyclones （TCs） and midlatitude circulations; however, studies of ET events have rarely considered the relationship between the storm and the nearby subtropical high. The TC best-track data provided by the Regional Specialized Meteorological Center-Tokyo Typhoon Center of the Japan Meteorology Agency are used in conjunction with the NCEP/NCAR reanalysis data to discuss the potential effects of the subtropical high on ETs over the western North Pacific basin. When the western Pacific subtropical high （WPSH） is weakened and withdrawn toward the east, more TCs follow recurving paths and the midlatitude trough activity is intensified. These changes lead to enhanced ET activity. By contrast, when the WPSH strengthens and extends westward, the number of TCs that follow direct westward paths increases and the midlatitude trough is relatively inactive. These conditions lead to reduced occurrences of ET cases. Abnormal activity of the WPSH should be considered as an important factor in determining ET activity.
Interannual variability of landfalling tropical cyclones(TCs) in China during 1960-2010 is investigated.By using the method of partial least squares regression(PLS-regression),canonical ENSO and ENSO Modoki are identified to be the factors that contribute to the interannual variability of landfalling TCs.El Ni o Modoki years are associated with a greater-than-average frequency of landfalling TCs in China,but reversed in canonical El Ni o years.Significant difference in genesis locations of landfalling TCs in China for the two kinds of El Ni o phases occurs dominantly in the northern tropical western North Pacific(WNP).The patterns of low-level circulation anomalies and outgoing longwave radiation(OLR) anomalies associated with landfalling TC genesis with different types of El Ni o phases are examined.During canonical El Ni o years,a broad zonal band of positive OLR anomalies dominates the tropical WNP,while the circulation anomalies exhibit a meridionally symmetrical dipole pattern with an anticyclonic anomaly in the subtropics and a cyclonic anomaly near the tropics.In El Ni o Modoki years,a vast region of negative OLR anomalies,roughly to the south of 25°N with a strong large-scale cyclonic anomaly over the tropical WNP,provides a more favorable condition for landfalling TC genesis compared to its counterpart during canonical El Ni o years.For more landfalling TCs formed in the northern tropical WNP in El Ni o Modoki years,there are more TCs making landfall on the northern coast of China in El Ni o Modoki years than in canonical El Ni o years.The number of landfalling TCs is slightly above normal in canonical La Ni a years.Enhanced convection is found in the South China Sea(SCS) and the west of the tropical WNP,which results in landfalling TCs forming more westward in canonical La Ni a years.During La Ni a Modoki years,the landfalling TC frequency are below normal,owing to an unfavorable condition for TC genesis persisting in a broad zonal band from 5°N to 25°N.Since the western North Pacific subtropical hig
