Landcover status and dynamics have a direct feedback on the climate system by determining the boundary conditions of the exchange of momentum, energy and mass between the atmosphere and the land.
To represent landcover in models of the climate system, it must first be parameterized with respect to albedo, aerodynamic roughness, and surface resistance to evaporation, among others. These biophysical characteristics are functions of vegetation structure, e.g. height, canopy closure, and leaf-area index (LAI), and composition, that are poorly know for most biomes, even as estimated using the best passive remote sensing techniques. Lidar (light detection and ranging) remote sensing recently has been used to observe the three-dimensional structure of the Earth's surface from various airborne and space-based platforms. Lidar provides direct measurements of canopy height, canopy vertical and spatial structure, as well as sub-canopy topography, all of which are critical for land surface modeling. In this paper we explore the potential of lidar for improved land surface parameterization. We give examples from NASA airborne and space platforms such as the Laser Vegetation Imaging Sensor (LVIS) and the Shuttle Laser Altimeter (SLA). Lastly, we summarize the data sets that will be available from the Vegetation Canopy Lidar (VCL), a two year NASA space mission scheduled for launch in spring of 2000.