LOCALIZED HADLEY CIRCULATION AND ITS LINKAGE TO PACIFIC SSTA

The 1979-2001 ERA-40 monthly mean meridional winds are used to calculate the mass streamfunctions in the monsoon region (60-140° E) and Ni(n)o 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 Ni(n)o 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 (Ni(n)o) band in January is correlated negatively (positively) with the SSTA over the all-Ni(n)o (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 E1 Ni(n)o,the LHC is weakened (strengthened) in the monsoon (Ni(n)o) region,and the reversal takes place during the La Ni(n)a year,with greater anomaly in the Ni(n)o area.