Numerical simulations of effects on urban PBL characters with landuse categeories modification
Journal of East China Normal University(Natural Sc
2011, 2011 (4):
ENVI, IDL, GIS and aerial photographs were used to modify landuse data in ARW-WRF within Shanghai area. Firstly, grids were gained with GIS into the same resolution with the input data in WRF, which is too old for present landuse situation in Shanghai. Secondly, irrigated cropland and pasture, grassland, shrubland, loamy sand and silt were partly changed into urban and built-up land grid by grid, so as to be more closer to real situation, and the distribution of buildings was gained, helping to reach more accurate roughness value in UCM according to the 24 landuse categories defined in WRF model. Lastly, both modified and original data were input into WRF in case simulations. The wind field, temperature, and other characters of PBL in spring of Shanghai were gained in the simulation results. It shows that because of landuse types modification, horizontal wind velocity decreases obviously, displaying the urban dragging effects. Meanwhile, the vertical wind velocity increases, being greatly affected by surface warming effects. The higher temperature centers appear in the downwind direction by the effects of surface wind fields. Surface temperature and PBL height are both closer to observation values. The results lead us to discuss the importance of landuse categories input in models, and some other possible reasons causing the difference were mentioned.
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