The concept of drag partioning to parameterise the surface roughnessof sea ice is validated using topography data of regions with high sea iceconcentrations. The parameterised drag is compared to measurementsobtained by aircraft and ship. The form drag can well be expressed asa function of mean rigde heights and spacings averaged over flightlegs of at least 12, if an improved approximation for the coefficient ofresistance of a single ridge is used. We find a good agreement between theparameterised and observed drag coefficients. The highest sea iceroughness was encountered close to coastal regions and the lowest in thecentral Arctic.