Based On Modis And Glas Data Inversion Sequence China Epicontinental Vegetation Aerodynamic Roughness

Aerodynamic roughness length is an important parameterization in "land surface atmosphere" models, including the momentum flux, sensible heat flux and latent heat flux. The vegetation is a significant part of terrestrial ecosystem; and it is very important to estimate the vegetation aerodynamic roughness length. At present, it is usually estimated through establishing the empirical relationship between aerodynamic roughness length and surface biophysical parameters in most land surface-atmosphere models, or establishing the roughness length look-up table of different land cover/use types. These approaches have some shortcomings in quantifying the roughness characteristics of vegetation underlying surface.Land surface parameters retrieving from laser radar and optical remote sensing data can well describe the changes of the structural features and phenology of the vegetation, so it is more appropriate to quantify vegetation aerodynamic roughness length with these parameters. In this paper, the target is to retrieve and map the vegetation aerodynamic roughness length of China’s land-surface using multi-temporal remote sensing data and analyze and compare its annual variation impacted by the vegetation canopy composition and structure. Firstly, the vegetation canopy area index was estimated from MODIS data, specifically using the leaf area index (LAI) data product and land cover data product. Secondly, normalized zero-plane displacement and normalized aerodynamic roughness length are estimated through Raupach’s aerodynamic roughness model, which is established on the basis of the drag coefficient and the geometry of the roughness element and can describe the roughness length changes affected by the land surface phenology in a better way. Then the changes of normalized zero-plane displacement and normalized aerodynamic roughness length were analyzed with the canopy area index. Finally, the vegetation mean canopy height of China’s land-surface was retrieved from the GLAS data (including GLA01and GLA14products) in2008; and the results were quantitatively analyzed.The results are shown as follows:(1) The normalized zero-plane displacement increases with canopy area index; but the normalized aerodynamic roughness length increases with canopy area index Λ until Λ max, after which the normalized aerodynamic roughness length decreases with further increases in canopy area index.(2) There is a seasonal change in normalized zero plane displacement height, with higher normalized zero plane displacement heights during the growing season and lower values in the non-growing season. But when the canopy area index is high, the normalized aerodynamic roughness length tends to be low.(3) The aerodynamic roughness zo of evergreen needle-leaved forests are the highest in seven vegetation cover types, and it ranges from1.43to1.53. But the deciduous needle-leaved forests are lowest, which ranges from0.51to0.77, followed by the open shrub lands which ranges from0.86to0.89.