| Popis: |
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 field in 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 formation 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. |
