A New Formulation and Code to Compute Aerodynamic Roughness Length for Gridded Geometry—Tested on Lidar-Derived Snow Surfaces
Year: 2025
Type: article
Abstract: The roughness of the Earth’s surface dictates the nature of air flow across it. During some parts of the year, a large portion of the Earth’s surface is snow covered, and the roughness of the snow surface varies over the snow season and over space. Detailed meteorological data that are necessary to access the aerodynamic roughness (z0) are not widely collected and as such the geometry of a surface can be used to estimate z0. Here we present a formulation and the corresponding computer code to compute z0 based on the Lettau (1969) geometric approach. We apply it to three snow surface datasets, each at different phases of the snowpack (and each at two resolutions): fresh snow accumulation (1 m2 at 1 and 10 mm), peak accumulation (1 km2 at 1 and 10 m) and ablation sun cups (25 m2 at 5 and 50 mm). The new code produces a mean z0, as well as a histogram of all z0 values for each individual roughness element (10s of thousand for the 1000 x 1000 grids), as well as directional z0 diagrams, which can be matches with the wind rose for the location. The formulation includes two parameters that may optionally be applied to smooth the surface before calculating z0. By calculating z0 as a function of these two parameters, we demonstrate the sensitivity of the z0 value to these parameter choices.
Source: Remote Sensing
DOI: 10.3390/rs17121984
Language: English
Subfield: Atmospheric Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,258
OpenAlex ID: W4411142529