The Impact of Additional Surface Pressure Observations over the Northeast Pacific Ocean on the Data Assimilated Analysis and Forecast of Atmospheric Rivers During Feb – Apr 2019

Abstract:

Atmosphere River Reconnaissance (AR Recon) is an interagency, international collaborative project to collect unique dropsonde and other in-situ observations in and around ARs off the U.S. West Coast to improve AR landfall forecasts and associated weather during the winter. These observations are now officially called for in the U.S. National Winter Season Operations Plan. Global modeling centers (U.S. National Centers for Environmental Prediction, U.S. Navy, European Centre for Medium-Range Weather Forecasts (ECMWF)) that assimilate these data in near real-time have developed a research and operations partnership to assess impacts and improve outcomes. Beginning in 2019, the group partnered with the Global Drifter Program to explore the potential of drifting ocean buoys with surface pressure sensors, in concert with dropsondes and data assimilation efforts, to support the project’s forecast improvement objectives. The hypothesis was that adding surface pressure observations to the data-sparse Northeast Pacific Ocean can improve the representation of large-scale circulations in global weather prediction models, which is essential for accurate AR landfall forecasts. This presentation will focus on the impact of these additional sea level pressure measurements on the ECMWF Integrated Forecast System data assimilated analysis and forecasts using data denial runs from 28 January – 30 April 2019. Verification metrics for mean sea level pressure and relevant surface variables, along with integrated water vapor- a key quantity for ARs, will be presented. Drifter deployments in 2020 and future planned efforts to support robust ocean surface observations as a critical component of AR Recon will be described.