Urban Climate And Its Influence On Urban Planning In Lishui City

Initiative situations of urban climate in Lishui city was studied through the analyses of some major meteorological factors as temperature, precipitation and winds in 8 meteorological auto-stations in the city area, as well as the characters of climate in Lishui city. The body comfort index of climate in urban area of this place is also analyzed. Based on these, three issues of urban climate which should be considered in urban planning of Lishui are put forward and the city design strategy to settle these problems during the urban planning are also presented accordingly.The result of research shows that (1) the annual variations of average temperature and precipitation in Lishui are the same with those in Zhejiang province, and the temperature appears increasing while the variation of the precipitation is not so apparent. These two factors appears some periodicity in theft change. The urban regions of Lishui city keep calm in most of days of all year around, and its major wind direction is easterly from April to August and changes to northeast by east wind in the other months. (2) The distribution of constant temperature line is inconsistent with the borderline of the city, and the peak of which appears in the centre of the urban districts and minimum appears in Fu Mountains suburbs. Comparatively intensive heat island effect exists in urban districts and has apparent daily change, which is intensive during the night and weak during the daytime. The daily change of the strength of heat island effect in sunny days is more intensive than that in rainy days, and it is stronger in dry season than in wet season. The strength of heat island effect has an significant negative correlation with the cloudage and rainfall, while has significant positive correlation with daylight.(3) evident dry island effect also exists in urban districts of Lishui city, and the horizontal distribution of constant vapor pressure line and constant relative moisture line is inconsistent with the borderline of the city, which minimum appears in the districts along the city centre to the agriculture science institution, and its peak appears in Fu Mountains. The strength of dry island effect is more intensive in daytime than in the night, and the daily change of it in sunny days is more intensive than that in rainy days; alternate change of dry island and wet island would happen in the sunny day of January, April and October while the wet island will seldom appear in rainy days. The development of wet island should be attributed to some weather phenomena as dew, thin fog, freeze, frost and rain, etc. the most intensive dry island effect appears in August and October while the minimum appears in January and February. (4) The urban regions of Lishui city keep calm in most of days of all year around, and this kind of weather is more likely to happen in winter and autumn rather than in spring and summer. Besides the calm, prevailing wind direction is easterly in urban regions and northerly in Fu Mountains suburbs and the flood protection dike near Daxi. The maximum of wind speed appears in February and the minimum appears in September to November. The wind speed decreases from the river bank in the southern place to the north of the urban districts, the further the weaker. Besides the constraint of flow field in larger scale, the wind field in the urban districts is also influenced heavily by the city underlying surface like constructions, streets, rivers, etc. (5) the rainy days of Lishui city also decreases from the south of the city to the center. The rainfall centre concentrate in the downwind place and its maximum appears in the city centre, and the phenomena of rain island also exist there. (6) with the temperature change, the surface temperature of abbertite has the largest changing amplitude, while moorstone, ceramic tile and cement plate take the second place, and the changing amplitude of nudation is larger than grassland. Different colors on the same building material would bring different changing amplitude of the surface temperatures, and materials in red and green has larger temperature changing than the yellow ones. (7)According to the estimate to the climate of Lishui with techniques of fuzzy synthetic discriminate, the climate comfort status of Lishui is not ideal, except April and July. (8)Base on the climate character of Lishui, two problem which is faced on the city planning have be put forward, that is: slowing down the summer high temperature, aeration problem of the city and draining water-logged of the city. Then, the measure to slowing down these two problems and the design strategy in the city planning has been set up.