Impact of Assimilating PECAN IOP 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 observations within the lower troposphere. Their importance for numerical weather prediction (NWP) was tested within a GSI-based convection-allowing ensemble data assimilation system. In particular, this study examined the impact of assimilating PECAN observations from 5-6 July 2015 on the forecast skill of bore-induced convection, which is deemed to be an important mechanism for the maintenance of nocturnal mesoscale convective systems (MCSs). This impact was investigated separately with respect to the bore, its environment and the subsequent bore-induced convection in order to address the multi-sale nature of the studied phenomenon.

To understand the effect of assimilating different PECAN observations on the forecast quality of the bore and the bore-induced convection, several data addition experiments were performed. The latter included observations from the Atmospheric Emitted Radiance Interferometer (AERI), aircraft, surface, lidar, wind profiler and sounding instruments. The majority of these observation types exerted positive impact on the bore forecast, especially with respect to the environmental conditions in which the bore developed. On the other hand, improvements to the convective part of the forecast were only evident in the numerical simulations utilizing AERI data. The impact of PECAN observations in this case study was shown to be relatively short-term, which has some important implications for the predictability of the studied phenomenon. This aim of this presentation is to not only overview the subjective and objective aspects of the aforementioned results, but also to further explain how the PECAN observations were able to improve the forecast results from both dynamic and thermodynamic points of view.