Simulation Study On Impacts Of Urbanization And Roof Albedo On Urban Heat Island In Hangzhou

In recent years,with the acceleration of the urbanization process,the temperature rise in urban areas caused by the urban heat island effect has become increasingly severe,resulting in frequent occurrence of summer heat waves in many cities in China,which seriously endangers the health of urban residents and increases energy consumption.Hangzhou is a typical city with frequent high temperature in recent summers.Based on the WRF model,this paper uses different landuse data to study the historical evolution and development trend of Hangzhou's heat island effect in the urbanization process,along with measurement for the suppression of urban greening rate and high albedo to urban island effect.The results show that the urban heat island effect in Hangzhou is significant,and the intensity of the heat island is higher at night than during the day.Hangzhou Heat Island Intensity Center is located in Gongshu District and Xiacheng District,especially the downtown business district has higher thermal stress.The rapid urbanization since 2000 has caused the average daytime temperature in Hangzhou to increase by about 0.5°C and the heat island effect index UHII to increase by about0.75°C.For the urban area of Hangzhou,the probability that daytime temperature exceeds 35°C has increased by about 4%.The expanded urban area further increases the temperature and UHII in the central urban area.Expanding the urban greening rate is an effective measure to curb the increase in temperature and UHII caused by urbanization.When urban greening increases to 20%,the overall daytime temperature in Hangzhou decreases by approximately 0.3°C and UHII decreases by 0.2°C,which can better alleviate temperature rise effect from further urbanization.The roof with an albedo of 0.85 has an average temperature decrease of 0.45?during the day and 0.21?at night,which reduces the intensity of the urban heat island and alleviates the urban heat island effect;the air conditioning cooling load during the day decreases by 0.91W/m~2,which could save 5.3%of electricity expenditure for air conditioning systems in Hangzhou.