Global Climatologies of Vegetation Aerodynamic Roughness for Momentum: A Fusion of MODIS and ICESat‐2 Observations

This paper presents global climatology fields of vegetation aerodynamic roughness for momentum based on 17 years of MODIS data. The approach combines MODIS‐derived leaf‐area index and ICESat‐2 canopy heights with a previously developed representation of the roughness sublayer to generate data products for both the vegetation roughness length for momentum (z0m) and the zero‐plane displacement height (d0). The principal products consist of a mean seasonal cycle of the two roughness parameters at 500‐m spatial resolution based on a nominal 8‐day time step. The second, derivative data set removes seasonality while maintaining spatial information by assigning temporal averages of the underlying 8‐day data to each 500‐m pixel. A third data set includes global spatial and temporal averages for a range of MODIS land cover types, analogous to the look‐up tables employed in land surface modeling. Comparison to field data indicates that satellite‐derived maps of vegetation height produce more favorable roughness results than generic land class‐aggregated values published in the literature, although land cover classification mismatches between field and satellite footprints make validation challenging. The resulting roughness length and displacement‐height fields possess internal consistency, with small differences overall as compared to static, cover‐type dependent estimates, making them a realistic alternative for incorporation into regional and global‐scale earth science models that benefit from improved representation of land‐atmosphere interactions.