Prediction of Atmospheric Rivers in NMME

“Heavy winter precipitation in the western United States (US) is significantly affected by long narrow bands of water vapor transport from the tropical/subtropical North Pacific into mid-latitudes, termed “Atmospheric Rivers” (ARs). Because of strong water vapor transport, ARs can produce hazardous hydro-meteorological extremes (heavy precipitation, mountain snowpack), while ARs are also the main agent of water resources in the western US. Accurate prediction of ARs with lead times of month to season is urgent, since it can help people to mitigate potential damages from the natural hazards. However, assessment of potential predictability and actual prediction skill of ARs has not been attempted with climate models.

Although a large proportion of ARs activity is related directly to synoptic weather conditions, recent studies have explored the linkage between ARs activity and modes of large-scale climate variability, such as El Niño Southern Oscillation (ENSO). Knowing that the state-of-the-art climate models can properly predict ENSO for several months, we can expect that ARs activity can be predicted to a certain extent in monthly to seasonal timescales. The objective of the proposed research is to understand the predictability of Atmospheric Rivers in climate models. To achieve the objective, the main steps of the proposed work are: (1) to assess the ARs activity (water vapor transport, AR frequency and duration) in NMME phase-II hindcasts, (2) to evaluate actual prediction skill of ARs activity for months to seasons, (3) to investigate the source of ARs predictability by understanding the processes related to ENSO, and (4) to evaluate models’ capability in representing the ENSO-ARs processes.

This proposal directly addresses MAPP’s focus area “North American Multi-Model Ensemble system evaluation and application” as it evaluates the performance of NMME system predictions, in particular the ARs prediction by understanding the processes related to ENSO. The outcomes of this project support NOAA’s long-term goals and directly contributes to the NOAA’s NGSP by addressing its objective for “improved scientific understanding of the changing climate system and its impacts””.”

Climate Risk Area: Water Resources