Vegetation cooling effects can effectively improve the outdoor microclimate. To explore the potential of vegetation transpiration cooling, we validated the feasibility of a new coupled porous medium and solar radiation model to simulate the interactions between vegetation transpiration and other physical processes in CFD. To emphasize the spatial extent of vegetation's influence, we compared and quantified the flow-adjustment distances(LFA) for wind speed, the temperature difference between simulated temperature and background temperature(ΔT(°C)), and water vapor mass fraction(ΔMw(g/kg)) between shrub(100m) and tree(200m) canopies: 1)For both vegetations, the LFA required for ΔT and ΔMw exceeds that of wind speed achieve fully-developed, indicating the momentum adjustment occurs more rapidly than energy and mass transport processes. 2)Vegetation drag effect depends on both leaf area density and vegetation canopy's height and width.3)Vegetation exhibits a significantly higher transpiration cooling effect under ambient relative humidity(RH)=0% than RH=60%(the mean value of ΔT, ΔTfd), for the tree(z=1.5m): ΔT fd is -5.4°C (-1.4∼-1.5°C) at RH=0%/60%. 4)At RH=60%, both shrubs and trees exhibit a notable warming phenomenon near the vegetation canopies tops(ΔTMax=1.3°C/0.9°C for shrubs/trees). This study provides and confirms a reliable numerical method for simulating the interactions of vegetation transpiration and other physical processes in urban or rural areas.