| Yangtze River Delta is the most rapidly growing city group inChina. Recently, urbanization has led to serious meteorologyical and environmental problems,such as increasing urban heat intensity and frequent appearance of haze. In this thesis, Nanjing University City Air Quality Prediction System (NJU-CAQPS) is used to study the impact of urbanization on urban meteorology and environment in Suzhou and Hangzhou area.In Suzhou area,19 days in Mid January, April, July and October are picked out, conclusions as following are made according to the simulations:(1) the urban heat island (UHI) intensity in Suzhou area reaches 1.2℃,RH in urban and suburban districts are 69.9% and 71.9%,respectively, while wind velocity are 3.2 m·s-1 and 3.8m·s-1.The downwind area of urban district is low-velocity zone.(2)PM10 and PM2.5 concentrations far exceed the standard levels in the northern suburb; high value zone of secondary pollutants located in the west of the urban district; PM10 and PM2.5 concentrations in urban district exceed that in suburb by 30%,while the concentrations of organic carbons and black carbons exceed that in suburb by 1-2 fold.(3)sensitivity tests are performed by changing those parameters of buildings and land cover types, and conclusions are drawn as following:the changes of buildings may lead to a decrease of wind velocity by 0.15-0.3 m·s-1, a decrease of visilibity by 0.1km in the urban district and an increase of PM2.5 concentration by 0.4-0.8μg·m-3(6-12μg·m-3 at most in local area of pollutant source);the expansion urban size may lead to a decrease of wind velocity by 0.6 m·s-1, a decrease of visilibity by 0.3-0.4km in the urban district and an increase of PM2.5 concentration by 3-4μg·m-3(25-32μg·m-3 at most in local area of pollutant source).Therefore,the impact of urbanization on the pollutants concentrations is more evident in local area of pollution source; the impact of urban expansion plays a more important role than buildings; the altitudes of muddy island and "haze line" are rising with urban development; the average haze hours increase 0.3-0.5h in the urban district,and the area suffering from haze increase by 170km2.In Hangzhou area,90 days between 2010 and 2012 are chosen to simulate, ventilation passages are figured out for different synoptic types and it is found that ventilation passages vary much. In order to study the impact of urbanization on ventilation passages, datasets of land cover and buildings in different ages are used. It is concluded that in urban district, wind velocity decrease by 1.1 m·s-1(2.9 m·s-1 at most and 0.1 m·s-1 at least); UHI intensity increase by 0.58 ℃ (1.3℃ at most and -0.1℃ at least); average RH decrease by 9.7%(17.9% at most and 3.6% at least).In Hangzhou area, it is heavily polluted in the juncture of Shangcheng District, Xiacheng District and Jianggan District. Urbanization may contribute to the rise of PM2.5 concentration and lead to a rise of haze line by 100-300m in these districts. Average NOx concentration in urban area increase by 2.1μg·m-3(3.3μg·m-3 at most and 1μg·m-3 at least); average PM2.5 concentration increase by 2.3μg·m-3(7.0μg·m-3 at most and 0.4μg·m-3 at least);average visibility decrease by 0.2km (0.4km at most and 0.1km at least); the average haze hours increase by 0.46h(1.2h at most and 0.1h at least). |
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