| For the purpose to research the influence of urban heterogeneity on urban meteorological characters, dividing the city into 3 types according to the building density data of landsat satellite:Commercial, Hi-dens Res（High intensity residential）, Low-dens Res（Low intensity residential）. Several numeric experiments were made to make simulations of Nanjing by using the WRF.The results showed that:among different types of cities, there are significant differences in urban meteorological characteristics,the spatial and annual average of commercial, high -density, low-density are 135.0W/m2,101.1W/m2,51.9W/m2; annual average latent heat are 5.4W/m2,9.7 W/m2,44.6 W/m2; annual average net shortwave radiation are 390.6 W/m2,386.9 W/m2,376.9 W/m2; annual average net longwave radiation are 80.5 W/m2,78.1 W/m2,67.1W/m2; annual average heat island intensity are 2.26℃,1.88℃,1.02℃; annual average dry island intensity are-11.33%,-9.44%,-5.75%; The annual average reduction of wind speed are -2.37m /s,-2.1m/s,-1.48m/s.After considering the urban heterogeneity, it will improve the simulations of wind and precipitation. In urban areas, the temperature, the heat island, the relative humidity, the wind speed, the sensible heat, the latent heat, the albedo, the net shortwave radiation and the net longwave radiation distribution exhibit more complex spatial distribution. Between the scheme of considering the urban heterogeneity and the scheme of not onsidering the urban heterogeneity, their urban net longwave radiation variances of spatial distribution are 33.03 and 0.26; their urban net shortwave radiation variances of the spatial distribution are 35.91 and 6.51; their urban temperature variances of the spatial distribution are 0.39 and 0.15; their wind speeds variances of the spatial distribution are 0.15 and 0.02. After considering the urban heterogeneity, the average urban heat island, dry island,wind reduction, sensible heat,latent heat, net shortwave radiation, net the longwave radiation have reduced compared to uniform urban scheme, for example, the heat island, wind reduction, sensible heat, net shortwave radiation, net longwave radiation are reduced by 0.18℃,0.14m/s,9.27 W/m2,1.86 W/m2.84 W/m2.Along the vertical direction, the impaction’s maximum height of heat island’s effect, dry island’s effect and the effect of wind are 160m,320m and 560m, the reduction of wind will lead to a smaller and thinner zone of low-level jet stream.Urbanization will lead to more precipitation and bigger intensity of precipitation, while considering the urban heterogeneity this impaction will strength further.The urban heterogeneity has a bigger influence in precipitation of summer than other seasons. And the scheme of urban heterogeneity leads to better results of precipitation compared with data of observation. There are significant differences of diurnal variation among those schemes. In the morning, the precipitation of urban heterogeneity is lowest; and in the afternoon, it is the highest. The results of convective precipitation will be improved by the scheme of urban heterogeneity, and the diunal variation is more consistent compared with the observation. The urban heterogeneity havs a more locally impact on the energy balance and urban heat island, but the impact on precipitation is not. Although the average height of city decreases, but the total precipitation will increase. |
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