A one-dimensional boundary-layer model for Mars is described, and its results are compared with Viking data. The model equations are similar to Earth boundary-layer models in that they include contributions from Coriolis, pressure gradient, and frictional forces for momentum; and radiation, sensible heat flux convergence, and advection for heat. Turbulent fluxes are computed from the level-2 second-order closure theory of Mellor and Yamada with similarity relations employed for boundary conditions. The pressure gradient force can be specified or computed from a simple slope model. Radiative heating is due to the absorption of solar and infrared radiation by CO2 gas and suspended dust particles. Ground temperatures are computed by solving a surface heat budget using an accurate treatment of conduction into the Martian soil. The data used for comparison were obtained by the Viking 1 and 2 landers for early northern summer. At each site, these data include a single profile of wind and temperature be... Abstract A one-dimensional boundary-layer model for Mars is described, and its results are compared with Viking data. The model equations are similar to Earth boundary-layer models in that they include contributions from Coriolis, pressure gradient, and frictional forces for momentum; and radiation, sensible heat flux convergence, and advection for heat. Turbulent fluxes are computed from the level-2 second-order closure theory of Mellor and Yamada with similarity relations employed for boundary conditions. The pressure gradient force can be specified or computed from a simple slope model. Radiative heating is due to the absorption of solar and infrared radiation by CO2 gas and suspended dust particles. Ground temperatures are computed by solving a surface heat budget using an accurate treatment of conduction into the Martian soil. The data used for comparison were obtained by the Viking 1 and 2 landers for early northern summer. At each site, these data include a single profile of wind and temperature be...