Abstract
Abstract. This paper presents a framework to estimate aerodynamic roughness over specific height (zo/H) and zero plane displacement (d/H) over various landscapes in Kelantan State using airborne LiDAR data. The study begins with the filtering of airborne LiDAR, which produced ground and non-ground points. The ground points were used to generate digital terrain model (DTM) while the non-ground points were used for digital surface model (DSM) generation. Canopy height model (CHM) was generated by subtracting DTM from DSM. Individual trees in the study area were delineated by applying the Inverse Watershed segmentation method on the CHM. Forest structural parameters including tree height, height to crown base (HCB) and diameter at breast height (DBH) were estimated using existing allometric equations. The airborne LiDAR data was divided into smaller areas, which correspond to the size of the zo/H and d/H maps i.e. 50 m and 100 m. For each area individual tree were reconstructed based on the tree properties, which accounts overlapping between crowns and trunks. The individual tree models were used to estimate individual tree frontal area and the total frontal area over a specific ground surface. Finally, three roughness models were used to estimate zo/H and d/H for different wind directions, which were assumed from North/South and East/West directions. The results were shows good agreements with previous studies that based on the wind tunnel experiments.
Highlights
The information related to energy and mass transfer between land surface and the atmosphere is really important for both numerical weather prediction and climate studies (Su, et al, 2001)
Monin-Obukhov similarity (MOS) theory serves an effective tool for turbulence statistics prediction in the horizontally-uniform surface layer for applying MOS formulation to relate surface fluxes of momentum, heat and water vapour to meteorological variables (Wood et al, 2010). zo/H can be defined as the height at which the wind speed become zero (Lefsky et al, 2002) while d/H can be explained such that: “When some roughness elements are closely arranged, there will be a higher surface formed by them, equivalent to which is the distance by which the height moves up, and this distance is called zero-plane displacement (d/H)” (Hu et al, 2015)
The data is used in the pre-processing stage where generation of canopy height model (CHM) is performed with 3 m spatial resolution which similar to digital terrain model (DTM) and digital surface model (DSM)
Summary
The information related to energy and mass transfer between land surface and the atmosphere is really important for both numerical weather prediction and climate studies (Su, et al, 2001). Experimental-based method employed vertical wind profiles and micrometeorological theory provides locally estimated values (Schaudt and Dickinson, 2000). This type of measurements consumes high cost of implementation, which limits its implementation over greater spatial scale (PaulLimoges et al, 2013). This method provided zo/H values for the local surface features, which lead to the limited zo/H data in energy and water-heat exchange (Hu et al, 2015). Remote sensing method can be utilized to portray the vegetation structures with their spatial variation (Hu et al, 2015)
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