Influence of the North Pacific Victoria mode on the Pacific ITCZ summer precipitation

Our analysis shows that strong positive VM cases are followed by positive precipitation anomalies over the central-eastern Pacific ITCZ region, in association with negative precipitation anomalies over the ITCZ regions of the tropical western Pacific and eastern North Pacific.

The hypothesized physical mechanism through which the spring VM induces the Pacific ITCZ summer precipitation is similar to but slightly different from the seasonal footprinting mechanism. During strong positive VM cases, SSTAs in the subtropics associated with the spring VM persist until summer and develop toward the equator, where low-level convergence and divergence caused by SSTA gradients give rise to enhanced precipitation over the central-eastern Pacific ITCZ region and to reduced precipitation over the ITCZ regions of the tropical western Pacific and eastern North Pacific.