Impact of Assimilating the THINICE2022 Continuous Windborne Observations inside a TPV on the Predictability of an Arctic Cyclone

A case study of a weak Arctic Cyclone (AC) during the THINICE2022 field campaign was used to understand the impact of assimilating continuous observations inside a tropopause polar vortex (TPV) on the predictability of the AC. Windbornes, which are weather balloons with dynamic altitude control and 7-day long average flight time, were released at various locations inside the Arctic Cyclone during the field campaign. Two windbornes were flying into the TPV superimposed with the selected AC for two continuous days. A data assimilation (DA) experiment was designed assimilating the two windbornes with in-situ conventional observations for one cycle, one day, and two days. The baseline experiment without assimilating windbornes underpredicted the intensity of both the AC and the TPV, and it predicted the cyclone location to the north compared to the verifying analysis at the 2-day forecast lead time. Windbornes demonstrated the potential to reduce the forecast error as several of the TPV vertical profiles sampled showed that the TPV intruded into lower altitude compared to the baseline analysis. Assimilating one cycle of windborne resulted in stronger predicted AC intensity and less predicted track error prediction. Preliminary results suggest that continuous assimilation over a one-day period was not as beneficial as assimilating just the observation of the above critical forecast error. Further experiments aimed at optimizing the continuous assimilation of windborne observations, and understanding the impact of the specific features targeted by the windbornes for this case study are ongoing and will also be presented.