ss with respect to 
                     meridional wind component in lowest model layer.
                     Units = kg/(m**2 s)

                dsens_datmos = derivative of surface sensible heat flux 
                     with respect to temperature in lowest model layer.
                     Units = W/(m**2 K)

                devap_datmos = derivative of surface flux of water vapor 
                     with respect to specific humidity in lowest model layer.
                     Units = kg/(m**2 s)

