The state-of-art Computational Fluid Dynamics (CFD) codes FLUENT is applied in a fine-scale simulation of the wind field over a complex terrain. Several numerical tests are performed to validate the capability of FLUENT on describing the wind field details over a complex terrain. The results of the numerical tests show that FLUENT can simulate the wind field over extremely complex terrain, which cannot be simulated by mesoscale models. The reason why FLUENT can cope with extremely complex terrain, which can not be coped with by mesoscale models, relies on some particular techniques adopted by FLUENT, such as computer-aided design (CAD) technique, unstructured grid technique and finite volume method. Compared with mesoscale models, FLUENT can describe terrain in much more accurate details and can provide wind simulation results with higher resolution and more accuracy.
Lei LiLiJie ZhangNing ZhangFei HuYin JiangWeiMei Jiang
By means of the regional boundary layer model (RBLM),a study on the influences of the urban planning and construction on the summer urban heat island (UHI) in the metropolis of Shenzhen is performed.In the study,the current summer UHI distribution,the influences of the increasing high-density construction and the energy consumption on the summer air temperature distribution,and the influences of the urban ventilation corridor on the summer air temperature distribution are numerically analyzed.Some conclusions are drawn in the light of the study:(1) The summer UHI is more obvious in day time than that in night time in the summer of Shenzhen,and the maximum values of UHI intensity in the day time appear in the areas with high-density construction,which are located in Nanshan,Futian and Luohu and western Bao'an districts.(2) The increase of construction density and energy consumption in the urban area will lead to the increase of temperature near the ground,and the increase of temperature at nighttime is more obvious than that at daytime.(3) The ventilation corridor can effectively reduce the UHI intensity and can be taken as a method to eliminate the negative climatic effect caused by the increase of high-density construction and energy consumption in the future.
Characteristics of the spatiotemporal distributions of precipitation anomalies in the reaches of the Yangtze River and Huaihe River (YHR) were studied using EOF method. Four main precipitation pat-terns for the YHR in summer identified by the first two modes: a region-wide flood over the entire YHR (RWF); a region-wide drought over the entire YHR (RWD); a flood in the south with a drought in the northern region of the Yangtze River (FS-DN); and a drought in the south with a flood in the northern region of the Yangtze River (DS-FN). Based on the first two modes and the actual precipitation departure percentage, a new precipitation index is defined in this paper. The typical flood/drought years associated with the various rainfall patterns defined by this precipitation index are more representative and closer to reality compared to some existing precipitation indexes which just use the area-mean precipitation or the EOF time components individually. The characteristics of atmospheric circulation in summer corresponding to the four main precipitation patterns over the YHR in summer show the features of atmospheric circulation differ in different precipitation pattern years. Although the different patterns share a common main influential circulation system, such as the blocking high over northeastern Asia, the low trough of westerly flows in the mid latitudes, the West Pacific Subtropical High (WPSH), and the high ridge over the Tibet Plateau, the difference in location and intensity of these systems can lead to different distributions of precipitation anomalies.
