Seasonal and extended-range predictability of atmospheric rivers and their associated precipitation
This project will create a new high quality catalog of landfalling atmospheric rivers (ARs) covering a time period of at least 1948 to present. Using this catalog, the follwing will be explored: (1) climate signals driving the variability of landfalling ARs and (2) AR-related precipitation and its contribution to seasonal total precipitation along the West Coast. Leveraging these analyses, development of seasonal forecasting models for AR frequency and intensity statistics will be explored. Further, the extended-range statistical predictability of landfalling ARs will be researched.
Need and Benefit
West Coast precipitation is extremely variable from synoptic to multi-decade time scales, in response to Pacific climate variability (Gershunov et al. 1999, 2000, Gershunov and Cayan 2003). In particular, PDO, ENSO and intraseasonal variability have a strong influence on the track and intensity of winter storms and the amount of precipitation. The number and intensity of relatively infrequent heavy precipitation events during a given year in California has an extraordinarily strong influence upon the amount of water that is delivered to the State (Dettinger 2011, 2013) as well as whether floods may occur (Ralph 2006, 2012, 2014). A large portion of the heavy precipitation that occurs has been attributed to Atmospheric Rivers (ARs). These extreme precipitation events, by far mostly AR-related, have recently been shown to account for 85% of the interannual variability in annual precipitation in Northern California (Dettinger and Cayan 2014). Recognizing this, the ability to better understand and subsequently predict these events would be a considerable benefit to water management.
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