Hristo Chipilski-April 6

Impact of Assimilating PECAN Field Campaign Observations on the Numerical Prediction of Bores and Bore-Initiated Convection

The Plains Elevated Convection at Night Field Campaign (PECAN) provided a unique set of in-situ and remote sensing observations of the lower troposphere. Throughout this presentation, we will try to understand whether the incorporation of these new observations in convection-allowing numerical models is able to improve the forecasts of a bore-initiated convection event that took place on 6 July 2015 (IOP20 mission). The focus of this study on bore-initiated convection is driven by its important role in the maintenance of nocturnal mesoscale convective systems (MCSs) as well as the challenges it poses to current numerical weather prediction (NWP) models. In order to address the multi-scale nature of the studied phenomenon, results from this talk will be presented separately with respect to the bore, its environment and the subsequent bore-initiated convection.

The diverse observations from the IOP20 mission are assimilated with a GSI-based ensemble data assimilation system and include the Atmospheric Emitted Radiance Interferometer (AERI), aircraft, surface, lidar, wind profiler and sounding instruments. The relative impact of the PECAN observations is assessed through a data addition framework, whereby each of the aforementioned instruments is added to a baseline experiment, in which only conventional and radar data are assimilated. Results from the data addition experiments reveal that different PECAN observations can constructively improve the simulated bore environment, with the largest contributions coming from the AERI, aircraft and wind profiler instruments. By contrast, the skill of the forecasted bore-initiated convection is increased only after assimilating AERI data. Finally, it appears that the positive impact from the data addition experiments is relatively short-lived, which has important implications on the inherent predictability of nocturnal convection.