Dipole Structure of Interannual Variations in Summertime Tropical Cyclone Activity over East Asia

Abstract

The present study examines variations in summertime (July–September) tropical cyclone (TC) activity over East Asia during the period 1951–2003. To represent TC activity, a total of 853 TC best tracks for the period were converted to TC passage frequencies (TPFs) within 5° × 5° latitude–longitude grids; TPFs are defined as the percentage values obtained by dividing the number of TC appearances in each grid box by the total number of TCs each year. Empirical orthogonal function analysis of the TPF showed three leading modes: two tropical modes that represent the long-term trend and the relationship with ENSO and one midlatitude mode that oscillates between south of Korea and southeast of Japan with an interannual time scale. The latter proved to be the most remarkable climatic fluctuation of summertime TC activity in the midlatitudes and is referred to as the East Asian dipole pattern (EADP) in this paper. Anomalous atmospheric flows directly connected to the EADP are an enhanced anticyclonic (cyclonic) circulation centering around Japan when the TPF is high south of Korea (southeast of Japan), thereby showing an equivalent barotropic structure in the entire troposphere. This regional circulation anomaly varies in conjunction with the zonally oriented quasi-stationary Rossby wave train in the upper troposphere. This wave train is meridionally trapped in the vicinity of the summer-mean jet stream; therefore, the mean jet stream alters its internal meandering structure according to the phase of the wave train.

Relationship between Tropospheric Circulation over the Western North Pacific and Tropical Cyclone Approach/Landfall on Japan

“…In this study, first we identify the years with higher and lower frequency of TC landfall on Japan, and then extract the dominant modes of atmospheric circulation fields over the western North Pacific. To what extent our dominant modes are comparable with the modes identified by Kim et al (2005) will also be examined. Finally, the relationship between the dominant modes is investigated for years with higher and lower frequency of TC landfall.…”

“…Similarly, Wang and Chan (2002) showed the relationship between ENSO episodes and TC genesis, but the relationship between ENSO episodes and TC landfall on Japan is to be examined. Recently Kim et al (2005) computed the TC passage frequency at 5 Â 5 grid resolution, and applied the empirical orthogonal function (EOF) analysis to extract the dominant modes of the TC passage. They found that there are three dominant modes; two tropical modes, and a Korea-Japan dipole mode as a third mode, which they referred to as 'East Asian dipole pattern' (EADP).…”

Modulation of North Pacific Tropical Cyclone Activity by Three Phases of ENSO

“…The La Niñ a phase induces a reversed situation. The difference in the location of genesis in the different phases of ENSO has been explained in terms of large-scale ocean-atmosphere interaction associated with regional changes in sea surface temperature (SST), a vertical wind shear, an extension of the monsoon trough, and relative vorticity anomalies induced by wind anomalies in the lower troposphere (Chen et al 1998;Chan 2000;Chia and Ropelewski 2002;Wang and Chan 2002;Wu et al 2004;Kim et al 2005;Camargo et al 2007b). …”

A Physical Basis for the Probabilistic Prediction of the Accumulated Tropical Cyclone Kinetic Energy in the Western North Pacific

“…Therefore, in strong El Niño years, TSs tend to have a higher potential to become generally more intense and long lived because of their formation nearer to the equator than in normal years, allowing a longer period within a warm SST environment (Wang and Chan 2002;Camargo and Sobel 2005;Camargo et al 2007b). These characteristics are induced by large-scale oceanatmosphere interactions associated with regional changes in SST, vertical wind shear, the extension of the monsoon trough, and lower-tropospheric relative vorticity anomalies (Chen et al 1998;Chan 2000;Chia and Ropelewski 2002;Wang and Chan 2002;Wu et al 2004;Kim et al 2005;Camargo et al 2007b;Kim et al 2011). Because of the strong influence of ENSO on TS activity described above, ENSO is generally considered to be the main predictor in seasonal statistical TS prediction models (Chan et al 1998;Chan et al 2001;Wang and Chan 2002;Chan 2003, Lea andSaunders 2006).…”