Sources of Subseasonal‐To‐Seasonal Predictability of Atmospheric Rivers and Precipitation in the Western United States

Atmospheric rivers (ARs) account for a large portion of winter precipitation in the western US. To evaluate sources AR and predictability at subseasonal-to-seasonal timescales, we examine relationships between two climate modes, El Niño/Southern Oscillation (ENSO) Madden-Julian oscillation (MJO), hydroclimate Our analysis uses ensemble Weather Research Forecast (WRF) model simulations from 1981 to 2017, facilitating assessment uncertainty mode-AR relationship due variability short length observations. Over North Pacific basin, find ENSO-related latitudinal shifts ARs, but ENSO has little effect on basin-wide averaged frequency. US, there is some ENSO-AR connection impacts indices datasets. However, extreme Niño events defined by longitude index are consistently linked increased landfalling activity. The MJO can lead significantly enhanced or suppressed activity large-ensembles, depending phase time lag, while observations too robustly show this signal. substantially modulates MJO-AR relationship, triggering variegated responses ARs La Niña years. findings highlight need concurrent effects different modes precipitation, may shed light path toward more accurate prediction over