Research On The Relations Between Climatic Change Of Typhoon And ITCZ Or Warm Water Over Northwest Pacific

The statistical features of the intensity and position of ITCZ over the northwestern Pacific ocean, the influence of Elnino on ITCZ, and the interaction among the members of east Asia monsoon circulation have been studied in this paper, in the last part of which, numerical experiments on affections of ITCZ, cross Equator stream and the Australia High to typhoon over Northwestern Pacific with 9 level Atmospheric General Circulation Model (IAP9L-AGCM).Location of ITCZ will be calculated with an index of the latitudes where there is maximum value of the zonal wind shear.Another index of ITCZ strength was presented by the zonal wind speed difference at latitudes south and north of the ITCZ:I_ITCZ=U₈₅₀[E_ITCZ,N_ITCZ-2.5]- U850[E_ITCZ,N_ITCZ+2.5],E_ITCZ is the longitude and NITCZ is the latitude where ITCZ is located. Larger value of I_ITCZ corresponds to stronger ITCZ and small value of I_ITCZ corresponds to weaker ITCZ.Remarkable correlation between the typhoon's number and ITCZ location on 33 different longitudes indicates that the position of ITCZ has more impact on typhoon producing process in this region.It was found that strong ITCZ was located near equator that in other years. Spectrum analysis showed that, the strength of ITCZ oscillated with about 3 years at about 130°E, with 5 years at 160°E. The location of ITCZ oscillated with 3-5 years at 105 - 112.5°E,with 3 years at 125-145°E and with 5 years at 152-157°E, Similar with the ENSO cycle.Study on the east Asia monsoon circulation like cross-equator stream and cold high over Australia on typhoon showed that the intensity of ITCZ was more affected than that of location. The cross-equator stream and the Australia High affected the ITCZ intensity in a common way: ITCZ located at east of 130°E was easily affected that at other place, and the affections diminished eastward. Numerical experiment with IAP9L model also confirms this conclusion.