Enhancing Vegetation Aerodynamic Roughness for Momentum with ICESat-2 Data Products: Early Results

Abstract:

Land surface model (LSM) parameterizations include information about vegetation roughness in order to characterize fluxes of momentum, heat, and other scalars between the surface and atmosphere. Normally, it is assumed that roughness is a constant value, or within a discrete range, for all members of a given land cover class. These “look-up” values are typically derived from a limited number of field data sets published in the literature. Such approaches have obvious caveats, including validity of the assumed values, unaccounted for within-class variability, and uncertainty in the class labels.

Here, we compare satellite derived estimates of vegetation aerodynamic roughness for momentum using MODIS leaf-area-index and ICESat-2 vegetation height products with literature-derived look-up values. The primary motivation is to evaluate the utility of such satellite-derived roughnesses for assimilation into an LSM. A secondary motivation is to understand better the within-class variability of vertical vegetation structure as characterized by ICESat-2 products. Preliminary results indicate that the satellite-based estimates compare favorably in aggregate with the literature-derived values, while capturing realistic within-class variability – a feature that look-up approaches cannot provide.