The Cross-Equatorial Hadley Circulation of the Eastern Pacific

The intertropical convergence zone (ITCZ) in the eastern Pacific ocean forms the rising branch of a cross-equatorial Hadley circulation. On a time averaged sense, the ITCZ is located in the northern hemisphere close to the equator, with strong subsidence observed south of the equator. However, the strength and position of the ITCZ varies greatly on a day to day basis, for reasons still not understood.

The coupling of the cross-equatorial Hadley circulation with the ITCZ is investigated by studying the correlation between meridional winds at the Galapagos Islands and the presence of deep convection in the ITCZ to the north of the Galapagos. We found that northward mid-level winds at equatorial latitudes are indeed correlated with the presence of deep convective activity in the ITCZ. However, fluctuations in the intensity of the summertime low level meridional jet at the Galapagos were not correlated with ITCZ convection. Instead, these appeared to be a function primarily of the cross-equatorial SST gradient.