The Diagnostic Analysis On The Causes Of The Anomalous Typhoon Phenomena In Northwest Pacific Ocean In2013

In order to fix out the reason of tropical cyclones abnormalities in the frequency,intensity, period abnormalities in Northwest Pacific in2013, this article did diagnosticanalysis using the ERA reanalysis data from ECMWF, and Outgoing LongwaveRadiation (OLR) data of NOAA-CIRES. And analyzed the rapidly intensify reasonsof the special Super-Typhoon Haiyan before its first landing.The study found that the main reasons for the typhoon frequency large, occurredlate in2013are here as follows:(1) In July and August the Southern Hemisphere coldair mainly located in the Western Hemisphere, as Southeast Pacific-SouthwestAtlantic, which makes high surface temperature in the Australian region, smallcross-equator current at Low-levels, weak Intertropical Convergence Zone (ITCZ)appeared. convection at the region of135°E-175°E in Northwest Pacific Ocean isweak. All these are not conducive to the formation and development of thedisturbance. However, in September and October the Southern Hemisphere cold airlocated in the Eastern Hemisphere, as Southern Indian Ocean-South-West Pacificregion, so the Australian areas are affected by strong cold air, and abnormalanticyclonic circulation enhanced. All those strengthen cross-equator current of100°E-155°E, and leading to increased ITCZ strength of140°E-160°E.(2) Allsummer and autumn season in2013, subtropical waters of the Northwest Pacificremained high sea surface temperature (SST), thick warm-water, which illustrateshigh ocean heat content high, especially in October and November.(3) In NorthIndian Ocean, SST remained low, so the convection turned weak. Sub-tropicalupdrafts of the Pacific Northwest become strong. When it came to Autumn, theconvection in the northwest Pacific Ocean enhanced and range eastward, which alsoled to enhanced ITCZ in the autumn.(4)200hPa divergence at upper atmosphere wasstrong zonal wind shear typhoon to small. The average zonal vertical-wind-shear at total originating region of typhoon is too small.2013Super Typhoon outbreak in the fall is mainly due to:(1) In autumn ITCZposition biased towards the south. The westward typhoon track was more thanNorthwest ones. The total originating region of Super Typhoon was located in the eastof130°E, so the Super Typhoon track was path through the high ocean heat contentarea, and maintained over time over the warm water;(2) Because of that the totaloriginating region of Super Typhoon was in ITCZ, and in autumn the southernhemisphere cold air activities which made cross-equatorial current enhanced, leadingto ITCZ strength enhancement, the super typhoon absorb more energy from the oceanduring the development process.Super Typhoon Haiyan increased rapidly before landing, mainly because of theseas follows: high ocean heat content in the Sub-tropical Northwest Pacific, stronglatent heat transport from the ocean, little vertical wind shear, strong upperatmosphere divergence. And came to the energy absorption, the south and the northwind of ITCZ superimposed with typhoon wind field, that strengthen the latent heatflux of the north and south sides of Typhoon from the ocean. The south side wind oftyphoon superimposed with cross-equatorial current strengthened the latent heatabsorption of that farm. These factors play important roles in intensity of Haiyan.