The Temporal-Spatial Variations Of Accumulated Cyclone Energy Of Tropical Cyclones Over The Western North Pacific

The best track data of tropical cyclones (TC) provided by the Shanghai TyphoonInstitute (STI) over the western North Pacific including the South China Sea from1949to2011are employed to analyze the basic features of tropical cyclones,including source distribution of TC, space distribution of observing frequency, thecharacteristics of the duration, the temporal-spatial of accumulated cyclone energy(ACE) in different levels of TC, and the decadal variations of ACE. The mainconclusions are as follows:1. With increasing intensity of tropical cyclones, the positions of TC sourcecenters gradually move eastward and southward. Spatial distribution of TCobservation frequency has significant seasonal variations, which moves northwardfrom March to August, and southward from September. Total durations of differentlevels of TC have different trends, but the average duration of TC has commongrowth characteristics from1950s to1990s.2. TC intensity is proportional to the ACE. ACE and average ACE of differentlevels have different annual variations. ACE in August or September is the max inseasonal variations in different TC levels. Spatial distribution of ACE has twohigh-value centers, and the area east of Hainan Island is the center of TS, STS, TYand STY, and the area (125°E-135°E,15°N-to25°N) east of Philippines is the highvalue center of the SuperTY.3. ACE of Landfall TC shows a gradually annual decreasing variation, and ACEof different TC levels have different effects in different stages. Followed by the westNorth Pacific, South China Sea is the main area where TC is the most active. The highfrequency Center of landfall TC’s ACE is located in the South China Sea and the Pacific Northwest, and the SuperTY’s ACE Center is in the Pacific Northwest, andother levels of tropical cyclones regard the South China Sea as the center.4. Decadal variability of ACE about tropical cyclone over the western NorthPacific is mainly divided into the high-value period (1957-1967), transition period(1976-1986) and low value period (1998-2008). Severe tropical storm (STS),typhoon (TY) and super typhoon (SuperTY) are very important in dividing the years,and especially the SuperTY is the crucial composition. While the weak subtropicalhigh, small wind shear, eastward relative vorticity anomaly in low levels at lowlatitudes, and eastward sea surface temperature anomaly at low latitudes, all of thesedecadal features are favorable for the formation of the high-value period of ACE.