Modelling winds in Lancaster sound and Northwestern Baffin Bay

Abstract

A one‐level primitive equations mesoscale wind model is applied to the area of Petro‐Canada's oil explorations in eastern Lancaster Sound and northwestern Baffin Bay. The model includes effects of orographic channelling, land‐water roughness contrasts, and thermal circulations such as land‐ and sea‐breezes and anabatic and katabatic winds. The grid sizeislO’ latitude by 40’ longitude (approximately 19 km by 20 km). The model is verified with ship winds in the 1978 and 1979 seasons and with Seasat satellite winds in September 1978. Two versions of the model have been investigated. In the first, termed model A, the geostrophic wind was set equal to the analysed Canadian Meteorological Centre (CMC) wind ata = p/p_s = 0.94. Herep is pressure and p_s is surface pressure. In the second version, model B, the geostrophic wind is obtained from sea‐level pressures manually abstracted from surface charts. The latter had been reanalysed after Petro‐Canada and delayed ship reports had been plotted. The improvement of model B over model A is significant. The mean underestimate in speed has decreased from 12.0 to 7.8 km h⁻¹ for the ship winds and from 22.6 to 11.2 km h⁻¹ for the Seasat winds. Fifty per cent of the angle errors now lie between ‐ 31 and 49° for the ship winds and between ‐11 and 31° for the Seasat winds. The corresponding figures for model A are ‐54 and 71° for the ship winds and ‐14 and 47° for the Seasat winds. The model is also run with prognostic CMC input data. In general, errors grow slowly with time from 0 to 36 h.