The 1979-2001 ERA-40 monthly mean meridional winds are used to calculate the mass streamfunctions in the monsoon region (60-140° E) and Nio zone (160° E-120° W),with which the climate characteristics and intensity variation of the localized Hadley circulation (LHC) are analyzed over the two regions and the linkage of this LHC to Pacific SST is explored.Evidence suggests as follows.1) The climatological LHC is stronger in the monsoon than in the Nio zone,with its position in the former northward of the latter,especially in the summer half-year.The resulting difference is due mainly to the land-sea heterogeneous distribution and the existence of a cold pool in the equatorial eastern Pacific.2) The LHC experiences a distinct interannual variability in intensity and during 1979-2001 the LHC strength of the two regions changes broadly in an anti-phase manner.3) The LHC has its intensity associated closely with Pacific SST in such a way that its strength anomaly in the monsoon (Nio) band in January is correlated negatively (positively) with the SSTA over the all-Nio (1-4) zone (ANZ) in the equatorial middle and eastern Pacific but positively (negatively) correlated to SSTA in the C-shaped area that surrounds the ANZ.The pattern of July is in rough agreement with that of January,except for more feeble correlativity in July,especially over the monsoon region;4) The ENSO episode has different impacts on the LHC vigor in the two regions.With the occurrence of an El Nio,the LHC is weakened (strengthened) in the monsoon (Nio) region,and the reversal takes place during the La Nia year,with greater anomaly in the Nio area.
Based on the daily NCEP/NCAR reanalysis data,the position variation of the western Pacific subtropical high（WPSH） in June 2005 and its relation to the diabatic heating in the subtropical East Asia are analyzed using the complete vertical vorticity equation.The results show that the position variation of the WPSH is indeed associated with the diabatic heating in the subtropical East Asian areas.In comparison with June climatology,stronger heating on the north side of the WPSH and relatively weak ITCZ（intertropical convergence zone） convection on the south side of the WPSH occurred in June 2005.Along with the northward movement of the WPSH,the convective latent heating extended northward from the south side of the WPSH.The heating to the west of the WPSH was generally greater than that inside the WPSH,and each significant enhancement of the heating field corresponded to a subsequent westward extension of the WPSH.In the mid troposphere,the vertical variation of heating on the north of the WPSH was greater than the climatology,which is unfavorable for the northward movement of the WPSH.On the other hand,the vertical variation of heating south of the WPSH was largely smaller than the climatology,which is favorable for the anomalous increase of anticyclonic vorticity,leading to the southward retreat of the WPSH.Before the westward extension of the WPSH in late June 2005,the vertical variation of heating rates to（in） the west（east） of the WPSH was largely higher（lower） than the climatology,which is in favor of the increase of anticyclonic（cyclonic） vorticity to（in） the west（east） of the WPSH,inducing the subsequent westward extension of the WPSH.Similar features appeared in the lower troposphere.In a word,the heating on the north-south,east-west of the WPSH worked together,resulting in the WPSH extending more southward and westward in June 2005,which is favorable to the maintenance of the rainbelt in South China.
