Start day Create SWEEP input file? CALL saeinp calc. wind facing ridge spacing snow depth > 20mm No Erosion CALL sbzo aerodynamic rough CALL sbsfdi aggregate mass < 0.84mm wind interval time steps CALL sbwus friction velocity CALL sbwust threshold friction velocity max(friction vel/ threshold friction vel) ratio next wind interval time step max ratio > 1 No Erosion CALL sbinit grid initialization wind interval time steps next wind interval time step ratio < 1 or wind vel < min vel friction vel/ threshold friction vel ratio calc. substep interval substep interval steps next substep interval step CALL sbwind update all friction velocities on grid ratio > 1 CALL sberod erosion flux and surface update on grid End day yes no yes no no yes yes no no yes