Vertical wind shear fundamentally influences changes in tropical cyclone （TC） intensity. The effects of vertical wind shear on tropical cyclogenesis and evolution in the western North Pacific basin are not .well und...Vertical wind shear fundamentally influences changes in tropical cyclone （TC） intensity. The effects of vertical wind shear on tropical cyclogenesis and evolution in the western North Pacific basin are not .well understood. We present a new statistical study of all named TCs in this region during the period 2000- 2006 using a second-generation partial least squares （PLS） regression technique. The results show that the lower-layer （between 850 hPa and 10 m above the sea surface） wind shear is more important than the commonly analyzed deep-layer shear （between 200 and 850 hPa） for changes in TC intensity during the TC intensification period. This relationship is particularly strong for westerly low-level shear. Downdrafts induced by the lower-layer shear bring low θe air into the boundary layer from above, significantly reducing values of θe in the TC inflow layer and weakening the TC. Large values of deep-layer shear over the ocean to the east of the Philippine Islands inhibit TC formation, while large values of lower-layer shear over the central and western North Pacific inhibit TC intensification. The critical value of deep-layer shear for TC formation is approximately 10 m s-1, and the critical value of lower-layer shear for TC intensification is approximately ±1.5 m s-1.展开更多
By performing a statistical change-point analysis of activities of the tropical cyclones(TCs)that have affected Korea(K-TCs),it was found that there was a signifi cant change between 1983 and 1984.During the period of...By performing a statistical change-point analysis of activities of the tropical cyclones(TCs)that have affected Korea(K-TCs),it was found that there was a signifi cant change between 1983 and 1984.During the period of 1984-2004(P2),more TCs migrated toward the west,recurved in the southwest,and affected Korea,compared to the period of 1965-1983(P1).These changes for P2 were related to the southwestward expansion of the subtropical western Pacifi c high(SWPH)and,simultaneously,elongation of its elliptical shape toward Korea.Because of these changes,the central pressure and lifetime of K-TC during P2 were deeper and longer,respectively,than fi gures for P1.This stronger K-TC intensity for P2 was related to the more southwestward genesis due to the southwestward expansion of the SWPH.The weaker vertical wind shear environment during P2 was more favorable for K-TC to maintain a strong intensity in the mid-latitudes of East Asia.展开更多
基金Supported by the National(Key)Basic Research and Development(973)Program of China(2009CB421502)China Meteorological Administration Special Public Welfare Research Fund(GYHY201006007)+2 种基金National Natural Science Foundation of China(40905020)State Key Laboratory of Severe Weather(2011LASW-B11)Funds for the Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutions
文摘Vertical wind shear fundamentally influences changes in tropical cyclone （TC） intensity. The effects of vertical wind shear on tropical cyclogenesis and evolution in the western North Pacific basin are not .well understood. We present a new statistical study of all named TCs in this region during the period 2000- 2006 using a second-generation partial least squares （PLS） regression technique. The results show that the lower-layer （between 850 hPa and 10 m above the sea surface） wind shear is more important than the commonly analyzed deep-layer shear （between 200 and 850 hPa） for changes in TC intensity during the TC intensification period. This relationship is particularly strong for westerly low-level shear. Downdrafts induced by the lower-layer shear bring low θe air into the boundary layer from above, significantly reducing values of θe in the TC inflow layer and weakening the TC. Large values of deep-layer shear over the ocean to the east of the Philippine Islands inhibit TC formation, while large values of lower-layer shear over the central and western North Pacific inhibit TC intensification. The critical value of deep-layer shear for TC formation is approximately 10 m s-1, and the critical value of lower-layer shear for TC intensification is approximately ±1.5 m s-1.
文摘By performing a statistical change-point analysis of activities of the tropical cyclones(TCs)that have affected Korea(K-TCs),it was found that there was a signifi cant change between 1983 and 1984.During the period of 1984-2004(P2),more TCs migrated toward the west,recurved in the southwest,and affected Korea,compared to the period of 1965-1983(P1).These changes for P2 were related to the southwestward expansion of the subtropical western Pacifi c high(SWPH)and,simultaneously,elongation of its elliptical shape toward Korea.Because of these changes,the central pressure and lifetime of K-TC during P2 were deeper and longer,respectively,than fi gures for P1.This stronger K-TC intensity for P2 was related to the more southwestward genesis due to the southwestward expansion of the SWPH.The weaker vertical wind shear environment during P2 was more favorable for K-TC to maintain a strong intensity in the mid-latitudes of East Asia.
