典型河谷型城市春季温湿场特征及其生态环境效应

Characteristics of temperature field,humidity field and their eco-environmental effects in spring in the typical valley-city

快速的城市化对城市气候要素产生了重要的影响,城市温度场、湿度场的分布格局和结构特征强烈的影响着城市生态系统的物流、能流,产生了一系列生态环境效应。应用城市气候流动观测、定点观测、GIS空间分析和遥感反演等方法,模拟分析了典型河谷型城市——兰州市的春季温湿场特征和演变规律,结果表明:一日中14:30和20:30温度场的分布格局较为类似,高值区主要位于火车站、第二热电厂、五里铺十字、盘旋路围成的高惯高耗区域;8:30温度场的热中心位于西关十字至胜利宾馆开发程度较高的商贸区附近;一日中8:30和20:30的湿度场分布格局较为相似,湿度场强度较大的区域主要位于城区北部的徐家山森林公园、雁滩村、高滩村等开发程度较弱的绿地区和低惯低耗区,高湿度区分布与高植被覆盖率区域基本一致。利用景观生态学理论,热场空间分布结合NDVI分布,进行了热力景观空间格局分析和热力景观类型的划分,城区不同热力景观格局的形成与能耗、人口、建筑、下垫面类型之间存在显著的因果关系,NDVI>0.5的区域对应湿度场强度高值区、热场强度低值区。利用城、郊气象站观测数据,分析了近50年城区热岛效应和干岛效应强度的变化规律,近50年城区热岛强度和干岛强度呈现逐渐增强的趋势,热岛强度的线性趋势达到0.31℃/10a,干岛强度的线性趋势达到-2.1%/10a,20世纪70年代之后急剧增强。城市热岛强度和干岛强度作为人类活动对城市生态系统影响的一种量度,与各时段城市化发展水平、城市建设规模、城市下垫面性质的改变等因素是密切联系的。

Rapid urbanization has a significant impact on temperature and humidity, the distribution patterns and structure characteristics of temperature field and humidity field profoundly affect the ecosystems energy flow and material cycle, and further result in a series of eco-environmental problems. In recent years, contribution of the urban heat island effect to the global warming has been widely concerned by people. Distribution characteristics and causes of temperature field and humidity field in typical valley-city were researched widely, there are practical significance on urban eco-environmental construction, city planning, urban architecture design, urban energy usage and the health of residents for the typical valley- city. Lanzhou is a typical valley-city in western China; the level of urbanization is higher than average level of China; and urban area increased rapidly in last 50 years; in addition, air pollution is very serious for natural and anthropogenic reasons. So the urban climate effect is unique in Lanzhou. Based on methods of climate mobile observation, fixed-point observation, GIS spatial analysis and remote sensing, distribution pattern and its evolution of temperature and humidity fieldin a spring day are simulated in the typical valley-city. The results show that distribution pattern of temperature field is more similar in 14：30 and 20：30, high-value areas are mainly located in the train station, the second thermal power station, the Wulipu cross and Panxuan road area. Thermal centers are mainly concentrated in the Xiguan cross to victory hotel in 8：30. Distribution pattern of humidity field is similar in 8 ： 30 and 20 ： 30, and the large area mainly locates in Xujia mountain forest park, Yantan village and Gaotan village with high vegetation coverage. Using the theory of landscape ecology, and combining distribution of thermal field and humidity field with NDVI map, thermal landscape distribution is analyzed and thermal landscape types are divided. Results show fox, nation of urban thermal landscape pattern has a significant relationship with energy consumption, population, building, underlying surface types, and regions while NDVI 〉 0.5 are corresponding to higher value in humidity field and lower value in thermal field, so the reasonable planning of green belt is very important in eco-city or low-carbon city construction. Finally, using the observation data from urban and suburb weather stations, and analyzing variation of urban heat island effect and dry island effect in the past 50 years. Both urban heat island intensity and dry island intensity are gradually increasing in the past 50 years, the linear trend of urban heat island intensity is 0.31℃ per 10 years, and the linear trend of dry island intensity is -2.1% per 10 years, the trends are dramatically enhanced after the 1970s. The urban heat island intensity in the recent 10 years average to 3.6 ℃ and dry island effect intensity is 11%. Urban heat island intensity and dry island intensity were affected obviously by the level of urbanization, scale of urban construction, characteristics of urban underground and human activities. Urban heat island intensity and dry island intensity also can be a measure of the impact of human activities on the urban ecosystem.