Evaluating the Impact of Dropsonde Data from the 2023-2024 Atmospheric River Reconnaissance on NCEP Operational GFS Forecasts

Atmospheric Rivers (ARs) are essential to global weather patterns, transporting water vapor horizontally beyond the tropics and serving as a primary source of precipitation and water supply for the U.S. West Coast. Since the winter of 2020, observations from AR Reconnaissance (AR Recon) have been incorporated into the U.S. National Winter Season Operations Plan (NWSOP) as a key operational component.

During the winter of 2023-2024, the AR Recon campaign conducted 40 intensive observing periods (IOPs). These periods have significantly enhanced traditional data by incorporating dropsonde observations and high-density flight level data, which have provided detailed atmospheric profiles of water vapor, temperature, and wind within and around ARs. Near real-time data impact experiments were conducted during the AR Recon period using the NCEP operational Global Forecast System (GFS) version 16 (GFSv16) to evaluate the influence of dropsonde data on GFS forecasts, with a focus on landfalling ARs and associated precipitation. Our analysis of the 2023-2024 AR Recon data shows that integrating dropsonde data improved GFS initial conditions, enhancing precipitation forecast accuracy along the U.S. West Coast. Additionally, improvements were noted across the Pacific North American region (180E-320E, 20N-75N) due to better GFS analysis. Specifically, there was roughly a 1% increase in 5-day anomaly correlation for 500hPa geopotential height over the North Pacific (140E-240E, 10N-50N), along with a 4% reduction in root-mean-square error. We plan to provide a detailed analysis of how dropsonde data has impacted GFS forecasts based on the AR Recon missions of 2023-2024.