EMD-WRF On-Demand ICING

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Introduction

EMD-WRF OD ICING is the name of EMD’s icing model. The model is driven by an icing configuration of the standard EMD WRF [1] On-Demand service [2]. The model is run with a spatial resolution of 3x3 km with an hourly temporal resolution and using the ERA-5 reanalysis data from ECMWF as global boundary data [3]. The Thompson microphysics scheme is used for parameterization of the cloud physics and the MYJ scheme for the planetary boundary layer physics [4], [5]. The median volume diameter (MVD) by [6] is used, with a constant droplet concentration (Nc) of (default) 100 cm-3 and the liquid water content (LWC) in kg/m3 [7]. The atmospheric data feeds into the standard cylinder-based model [8], [9] including melting and shedding [10]. The WRF grid point (latitude, longitude) closest to the at mast location or site location is used as a default. The grid point holds a certain elevation above sea level and icing is modelled as a default for 15 heights in the vertical direction above ground level (agl.).

The modelled ice load (kg) is used to identify hours of instrumental icing based on the industry standard thresholds of 10 g [11]. And similar from the modelled ice accretion rate (g/h), hours of meteorological icing [12] is found using the threshold of 10 g/h [9]. The final step of EMD’s modelling chain, is an estimate of the expected production loss of a site which is found by using the IEA Ice Classification system seen in Table 1.

TABLE HERE