Radial winds from insects detected by four operational weather radars were assimilated using three-dimensional variational data assimilation (3D-Var) into a 1.5-km resolution version of the Met Office Unified Model.

The Met Office’s Unified Model (nonhydrostatic) version 7.3 was used with no convective parameterization. The domain covered the southern part of England and Wales (Fig. 1). The model had a fixed horizontal resolution of 2883360 cell grid with 0.0368 spacing (approximately 1.5 km). The vertical coordinates consisted of 70 terrain-following levels that were closely spaced near the ground. The upper boundary was 40 km MSL. The initial conditions (ICs) used to initialize the runs were derived from archived output of runs from a 4-km resolution, whole U.K. version of the Unified Model.Thereafter the 1.5-km model was run with hourly assimilation cycling to produce updated analyses. The boundary conditions (BCs) used during the forecasts were supplied from the same U.K. 4-km runs.