Assessing the Vertical Velocity of the East Pacific ITCZ

Abstract

AbstractReanalysis and satellite data sets disagree on the vertical structure of the meridional overturning circulation over the East Pacific (EP) intertropical convergence zone (ITCZ). Recent observations from the Organization of Tropical East Pacific Convection (OTREC) 2019 field campaign show a meridional slope of vertical motion with a shallow mode from 3° to 7°N, over a strong meridional sea surface temperature (SST) gradient, and a deeper mode from 7° to 10.5°N, where the SST is predominantly warm. However, reanalysis fields from the OTREC period show a predominant shallow mode from 3° to 9°N unless OTREC dropsondes are assimilated; then a weak deep mode is found at 8°N. Vertical motion over the OTREC region derived from Global Precipitation Measurement (GPM) precipitation radar latent heating retrievals has the opposite problem in that the deep mode is predominant from 3° to 10°N. A shallow mode is present with the addition of cloud radar data.