Start
April 17, 2024 - 3:30 pm
End
Categories
Weather and Climate SystemsWeather and Climate Systems
Zhihong Chen
Impact of assimilating WindBorne observations following different parts of a TPV on the predictability of an Arctic Cyclone during THINICE
Wednesday, April 17th, 2024
3:30 pm
NWC 1350
If unable to attend in person, please join us via Zoom: https://oklahoma.zoom.us/j/94741626909?from=addon
Abstract: The impact of assimilating in situ observations inside a TPV from a novel weather balloon system, the WindBorne, on the predictability of the TPV and the coupled Arctic Cyclone is investigated using an AC case in the 2022 THINICE filed campaign. Two WindBornes continuously sampled inside and near the center of the TPV at various vertical levels for 27 hours before the cyclogenesis. The 27 hours were divided into three phases based on the different vertical levels the WindBornes sampled. The RMSE of the forecasted cyclone at the tropopause, mid troposphere, and surface is reduced as more phases of Windborne assimilated from 12-hour to 36-hour forecast lead time, during which the surface cyclone became superimposed with the TPV and rapidly deepened. Comparing the experiment with three phases of WindBorne observations assimilated versus the control group with no WindBorne assimilated, the surface cyclone expands southwestwards towards the TPV and forms a stronger coupled structure. Three mechanisms leading to the improved TPV and coupled AC predictability are revealed. First, a lowered tropopause is observed by WindBorne compared to the background analysis, leading to TPV intensity increasing. Second, a stronger circulation at and below the tropopause of the TPV is observed, leading to stronger coupling between the TPV and the surface cyclone. Third, WindBorne observing the jet stream associated with the TPV results in a jet streak location shift, leading to the southeastward expansion of the surface cyclone and earlier coupling with the TPV. The sensitivity of forecast performance to horizontal localization parameter of the WindBorne observations is also studied. Larger localization parameters (2000 km and 3000 km) results in larger RMSE reduction compared to smaller values (500 km and 1000 km).