Naval Research Laboratory Preliminary Results from AR RECON 2018

The US Naval Research Laboratory Marine Meteorology Division participated in the 2018 Atmospheric River (AR) Reconnaissance Program by providing adjoint-based sensitivity information used in the flight-track planning process, as well as forecasting support. The adjoint, tangent linear, and nonlinear models for the atmospheric portion of the nonhydrostatic Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPS) were used to provide adjoint-based sensitivity fields of west coast precipitation to changes in the initial state four times per day with lead times of one, two and three days. Examples of the sensitivity products for the AR RECON IOPs and their relationship to atmospheric features of interest will be shown. Consistent with previous findings, the adjoint sensitivity results underscore the importance of the low- and mid-level moisture distribution, particularly in filaments of the water vapor fields embedded in ARs, as well as middle-tropospheric regions of dynamic importance (e.g., regions of large potential vorticity gradients). Subsequent examination of the dropwindsonde impact in the Navy Global Environmental Model (NAVGEM)-NRL Variational Data Assimilation System Accelerated Representer (NAVDAS-AR) hybrid 4DVAR system using the Forecast Sensitivity Observation Impact (FSOI) will also be described. Preliminary FSOI results indicate a larger impact per observation from the dropwindsondes than from radiosondes in reducing the 24-h forecast error (measured in terms of global moist total energy). For moisture, observations in the middle-lower troposphere have the largest impact, while temperature and wind observations have comparable impacts through the depth of the troposphere.