Fig. 5. A vertical scan showing the water vapor concentration in a vertical plane above the corn canopy during SMEX02. The day was strongly convective. Red colors represent areas of high water vapor concentration, while blue colors represent lower concentrations. The intense red color at the bottom is a result of the attenuation of the laser beam by the ground or canopy (in this case, corn). The change in the lidar signal as it reaches the canopy top enables determination of the shape and orientation of the surface.