There is growing recognition within the subseasonal-to-seasonal (S2S) climate forecast community that the land surface state (i.e., soil moisture, soil temperature, snow, and vegetation) provides a significant source of S2S predictability. Potentially the largest source regions for land-forced climate variability are elevated regions, including the Tibetan Plateau and Rocky Mountain Cordillera. In these locations, the land provides thermal and dynamic forcing in the middle troposphere that can enforce and/or modulate a high-amplitude Rossby wave pattern over the North Pacific and North America. In fact, the recent international Impact of Initialized Land Temperature and Snowpack on Sub-seasonal to Seasonal Prediction Experiment (LS4P)-Phase 1 revealed that May surface heating anomalies over the Tibetan Plateau explain more June precipitation variability over the western U.S. than ocean sea-surface temperature anomalies. The Tibetan Plateau–North American teleconnection is strongest during April–May, before the North Pacific jet shifts poleward and the Pacific and Atlantic subtropical highs emerge. Collectively, these results imply that to fully harvest the potential S2S predictability embedded in the Tibetan Plateau–North American teleconnection, Earth system models must accurately represent spring–summer shoulder season land–atmosphere interactions.

This presentation describes an E3SMv2 modeling and model evaluation project to fully diagnose Tibetan Plateau and Rocky Mountain surface heating anomalies as sources of S2S climate predictability. In particular, we will motivate and describe planned E3SM modeling experiments to isolate the effects of the El Niño–Southern Oscillation, the Pacific Decadal Oscillation, and land surface heating anomalies over the Tibetan Plateau on climate and precipitation variability across the central U.S. Of particular interest will be the extent to which these thermal and dynamical forcings are communicated via the North Pacific jet stream towards North America where they can influence the frequency and magnitude of central U.S. synoptic-to-mesoscale precipitation events. Through our investigation, we will learn: 1) how dominant central U.S. precipitating event types are affected by remote Tibetan Plateau surface heating anomalies, 2) how local Rocky Mountain and remote Tibetan Plateau surface heating forcings interact and effect central U.S. precipitation, and 3) how accurately E3SMv2 represents the constituent multi-scale land–atmosphere interactions.   In addition, we will present preliminary E3SM results from the LS4P Phase 2 experiment.