Data-denial and adjoint-based forecast impact experiments during T-PARC/TCS-08

This presentation will describe a set of experiments to measure the impact of supplemental in-situ and satellite observations on medium-range track forecasts of typhoons Sinlaku and Jangmai during the TCS-08 (THORPEX Tropical Cyclone Structure-08) West-Pacific field campaign. The study is performed using the Navy Operational Global Atmospheric Prediction System (NOGAPS) and the NRL Atmospheric Variational Data Assimilation System - Accelerated Representer (NAVDAS-AR). Data-denial experiments with satellite observations include 3-hourly, hourly, and rapid-scan atmospheric motion vectors (AMVs). Experiments with in-situ observations include dropsondes deployed from aircraft and drifting stratospheric balloons (driftsondes). In addition, an adjoint-based method is used to quantify and compare the impact of ALL assimilated observations on short-range forecast error. Results suggest that AMVs assimilated over a large regional area can improve typhoon track forecasts and their impact is larger on the medium range (3 to 5 days) than the short range (0 to 3 days). Targeted dropsondes can improve typhoon track forecasts, however their impacts are smaller on average and tend to be less consistent than the effects of the satellite wind observations