Regional precipitation simulations for the mid-1970s shift and early-2000s hiatus

It has been demonstrated that climate models initialized with observations produce better simulations of Pacific sea surface temperature (SST) patterns than uninitialized simulations for the two major climate regime changes of the last 40 years, the mid-1970s climate shift and early-2000s hiatus. A fundamental feature of these hindcasts is the simulation of the SST anomalies associated with the phase of the Interdecadal Pacific Oscillation (IPO). Since regional precipitation patterns over selected land areas in south Asia, Australia, and North America are known to be affected by SST patterns over the Pacific, it is shown that the initialized climate model simulations produce qualitatively better agreement with observations for regional precipitation anomalies in those regions compared to uninitialized climate models. Though the signals are small, the anomalies are consistent with our physical process-based understanding of precipitation responses over certain land areas during different IPO phases.