Abstract/Summary

A mixed subgrid scheme for scalars and momentum fluxes in cloud‐resolving models which includes an extra subgrid vertical flux, referred to as “the Leonard term”, that accounts for the tilting of horizontal flux into the vertical by horizontal gradients in vertical velocity was proposed by Moeng. Here we describe the implementation of the Leonard term in the current subgrid mixing scheme used in kilometre‐scale versions of the Met Office's Unified Model. We present results that show that including this extra term in the Met Office's 1.5 km grid length UK model reduces the domain‐average precipitation by reducing the number of grid points with rainfall rates greater than 4 mm/hr‐1, which are over‐represented by the model. Increasing the magnitude of the Leonard terms further decreases the occurrence of the heaviest rainfall rates.