Stratospheric Wind Tracing from Aerosols: Comparison of Geostationary and Polar-Orbiting Satellites Using the Hunga Tonga Plume

Uncertainties in tropical wind analyses exist in both the troposphere and the stratosphere. One contributing factor is the scarcity of direct wind observations, which makes retrieving wind information from atmospheric tracers particularly attractive. Long-lived sulfate aerosols in the tropical and subtropical lower stratosphere following the Hunga Tonga–Hunga Ha'apai (HTHH) volcanic eruption provide a unique opportunity to investigate this possibility. In this study, we use the HTHH case to examine factors affecting stratospheric wind retrieval in four-dimensional variational data assimilation (4D-Var). We perform observing system simulation experiments (OSSEs) to compare wind analyses produced with 12-hour and 24-hour assimilation windows and explore the effects of tracer observation and background errors. This dataset contains the truth and background states at the initial time, as well as the analysis fields at all times within the assimilation window for the conducted OSSEs. All experiments were performed using the MADDAM model (Zaplotnik et al., 2020).