A simple drag partition theory is developed for the classical problem of boundary layer flows over regular arrays of two- or three-dimensional roughness elements. The theoretical expression for the ratio of the form drag on these elements to the total drag is shown to be in good agreement with wind tunnel observations. It is used for determining the contribution of form drag on pressure ridges to the total wind stress on the arctic pack ice. The theory also leads to an expression for the large-scale roughness parameter as a function of mean ridge height, ridging intensity, small-scale or local roughness parameter, and an average form drag coefficient. It is required for determing the average wind stress over large areas of the Arctic on a routine basis, using the so-called geostrophic drag method, as envisaged in the Aidjex program.