What controls early or late onset of tropical North Atlantic hurricane season?
The occurrence of first hurricane in early summer signifies the onset of an active Atlantic hurricane season. The interannual variation of this hurricane onset date is examined for the period 1979-2013. It is found that the onset date has a marked interannual variation. The standard deviation of the interannual variation of the onset day is 17.5 days, with the climatological mean onset happening on July 23.
A diagnosis of tropical cyclone (TC) genesis potential index (GPI) indicates that the major difference between an early and a late onset group lies in the maximum potential intensity (MPI). A further diagnosis of the MPI shows that it is primarily controlled by the local SST anomaly (SSTA). Besides the SSTA, vertical shear and mid-tropospheric relative humidity anomalies also contribute significantly to the GPI difference between the early and late onset groups.
It is found that the anomalous warm (cold) SST over the tropical Atlantic, while uncorrelated with the Niño3 index, persists from the preceding winter to concurrent summer in the early (late) onset group. The net surface heat flux anomaly always tends to damp the SSTA, which suggests that ocean dynamics may play a role in maintaining the SSTA in the tropical Atlantic. The SSTA pattern with a maximum center in northeastern tropical Atlantic appears responsible for generating the observed wind and moisture anomalies over the main TC development region. A further study is needed to understand the initiation mechanism of the SSTA in the Atlantic.
Key wordsonset of a hurricane season genesis potential index TC maximum potential intensity
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- Cai Ninghao, Xu Xin, Song Lili, et al., 2014: Dynamic impact of the vertical shear of gradient wind on the tropical cyclone boundary layer wind field. J. Meteor. Res., 28, 127–138.Google Scholar
- Chu Huiyun and Wu Rongsheng, 2013: Environmental influences on the intensity change of tropical cyclones in the western North Pacific. J. Meteor. Res., 27, 335–343.Google Scholar
- Emanuel, K. A., and D. S. Nolan, 2004: Tropical cyclone activity and global climate. Preprints, 26th Conf. on Hurricanes and Tropical Meteorology, Miami, FL, Amer. Meteor. Soc., 240–241.Google Scholar
- Ge, X. Y., T. Li, and X. Q. Zhou, 2007: Tropical cyclone energy dispersion under vertical shears. Geophys. Res. Lett., 34, L23807, doi: 10.1029/2007GL031867.Google Scholar
- Gray, W. M., 1979: Hurricanes: Their formation, structure and likely role in the tropical circulation. Meteorology over the Tropical Oceans. James Glaisher House, 155–218.Google Scholar
- Li, T., 2012: Synoptic and climatic aspects of tropical cyclogenesis in western North Pacific. Cyclones: Formation, Triggers, and Control. Oouchi, K., and H. Fudeyasu, Eds. Nova Science Publishers, Inc., 61–94.Google Scholar
- Liebmann, B., and C. Smith, 1996: Description of a complete (interpolated) outgoing longwave radiation dataset. Bull. Amer. Meteor. Soc., 77, 1275–1277.Google Scholar
- Wing, A. A., A. H. Sobel, and S. J. Camargo, 2007: Relationship between the potential and actual intensities of tropical cyclones on interannual timescales. Geophys. Res. Lett., 34, L08810.Google Scholar
- Yu, L., X. Jin, and R. A. Weller, 2008: Multidecade Global Flux Datasets from the Objectively Analyzed Air-sea Fluxes (OAFlux) Project: Latent and Sensible Heat Fluxes, Ocean Evaporation, and Related Surface Meteorological Variables. OAFlux Project Technical Report OA-2008-01, Woods Hole Oceanographic Institution, Massachusetts, 64 pp.Google Scholar