Impact of GPS radio occultation data on the analysis and prediction of an intense synoptic-scale storm over the Southern Ocean near the Antarctic Peninsula

The West Antarctic Ice Sheet (WAIS) is a key location in the global climate change. Recent observation shows a dramatic warming and rapid reduction of ice mass over the area, alarming the scientific community with subsequent sea level rise and positive feedback to the warming. During the recent decade, West Antarctica showed thinning of ice. One of major sources of water mass that can counterbalance the recent ice loss is precipitation, which is a likely explanation for the recent ice gain over East Antarctica. Among all precipitating mechanisms, synoptic-scale storms can bring significant amount of moisture to the area because of their large spatial and time scales. Therefore, changes in the track and intensity of the storms responding to regional climate change could be a key factor in understanding and predicting future mass balance over the Antarctica. Improvements in the analysis and forecast of the synoptic-scale storms over the area are necessary to reduce the uncertainty in the future climate projection. The structure and developing mechanism of the synoptic-scale storms over the Southern Ocean are little known compared to other areas on the globe due to scarcity of observation. GPS Radio Occultation (RO) data could be a vital source of information over the Antarctic area. Although the potential GPS RO data over the Antarctica has been well demonstrated, practical data assimilations towards optimal use of the data is not straightforward. In this study, we have performed many assimilation experiments pertinent to the GPS RO data. As we needed to conduct a large number of experiments, WRF 3D-Var has been used because of its low computational cost. We investigated the impact of GPS RO data on an intense Antarctic storm. It is found that the data impact depends on many factors from model configuration, initial condition, assimilation period, and the way the data are used. Despite all the uncertainties, it is very clear that GPS RO data is very useful in better understanding the structure and developing mechanism of the storm, and improving the storm prediction.