Hybrid fine scale climatology and microphysics of in-cloud icing: From 32 km reanalysis to 5 km mesoscale modeling

Abstract

In-cloud icing can impose safety concerns and economic challenges for various industries. Icing climate representations proved beneficial for optimal designs and careful planning. The current study investigates in-cloud icing, its related cloud microphysics and introduces a 15-year time period climatology of icing events. The model was initially driven by reanalysis data from North American Regional Reanalysis and downscaled through a two-level nesting of 10km and 5km, using a limited-area version of the Global Environment Multiscale Model of the Canadian Meteorological Center. In addition, a hybrid approach is used to reduce time consuming calculations. The simulation realized exclusively on significant icing days, was combined with non-significant icing days as represented by data from NARR. A proof of concept is presented here for a 1000km area around Gaspé during January for those 15years.An increase in the number and intensity of icing events has been identified during the last 15years. From GEM-LAM simulations and within the atmospheric layer between 10m and 200m AGL, supercooled liquid water contents indicated a maximum of 0.4gm−3, and 50% of the values are less than 0.05gm−3. All values of median volume diameters (MVD) are approximately capped by 70μm and the typical values are around 15μm. Supercooled Large Droplets represent approximately 5%. The vertical profile of icing climatology demonstrates a steady duration of icing events until the level of 60m. The altitudes of 60m and 100m indicate substantial icing intensification toward higher elevations. GEM-LAM demonstrated a substantial improvement in the calculation of in-cloud icing, reducing significantly the challenge posed by complex terrains.