Destination Earth On-demand Extremes case studies: results, challenges and lessons learnt at DMI

The on-demand Digital Twin Extreme (DTE) is part of the European Destination Earth initiative which, during phase 1 of the project (2022-2024), has involved the cooperation of a large number of European National Weather Centers. The goal of the on-demand DTE is to provide a technical framework which is capable of running different flavours of the ACCORD forecast models (e.g. HARMONIE-AROME, AROME and ALARO) at very high resolution. The forecast predictions are expected to be triggered on demand for high-impact weather events within a regional domain (the so-called Limited Area Model) at subkilometre scale (e.g. horizontal resolutions of 750, 500 or 200 metres). In this poster, we will present some case studies which were explored at the Danish Meteorological Institute (DMI) in the contest of DTE phase 1. We will provide an overview of the challenges we faced looking at different weather events (such as flooding, extreme winds and precipitation) when the high resolution forecast model is initialised by lateral boundary conditions which can be from either the operational ECMWF Integrated Forecasting System (about 9 km resolution) or the Global Continuous Extreme Digital Twin (about 4.5 km resolution). Development and testing of data assimilation within the high resolution domain were not considered in the phase 1 of the project. Hence, in the case studies we focused on exploring the benefits and limitations of the LAM high resolution forecasts when the system is simply initialised with one of the ECMWF global systems. Overall, we will show the predictability capacity of the on-demand DTE and the added value of the increased model horizontal resolution.