The East Pacific Inter-Tropical Convergence Zone (ITCZ) is a critical phenomenon in tropical climate, coupled ocean atmosphere interactions and Central and South American meteorology. Primarily, its seasonal variation involves a subtle evolution of the cross equatorial flow and the broader lower tropospheric momentum budget. This region is subject to one of the most pervasive biases in coupled earth system models; the double ITCZ problem. Its origin, even after decades of research, remains elusive, partly due to the paucity of in-situ observations. A myriad of reasons may underlie this bias including coupling of boundary layer dynamics with sea surface temperature (SST) gradients, interaction with the equatorial upwelling cold bias, diabatic heating profiles and large-scale overturning circulations. Challenges also exist across scales with the interplay of stratocumulus and trade wind cumulus clouds, the free tropospheric response to instability and the role played by the Madden Julian Oscillation (MJO) and convectively coupled waves.

• AMS: American Meteorological Society -