Urbanization Effect on Average and Extreme Temperature Warming in Tianjin during the last 60 Years

The trend changes of average and extreme temperatures in Tianjin during 1959–2000, 1959–2005, 1959–2012, and 1959–2017 were analyzed based on the homogenized daily mean, minimum, and maximum temperature data and the classification of urban and rural area derived from the hourly integrated temperature data at automatic stations. Results indicate a warming change in Tianjin, which is evident from the annual mean temperatures increasing by 1.35°C, 1.65°C, 1.71°C, and 2.05°C of the four-time periods, respectively. The annual mean temperatures for the four-time periods are observed to be largest in winter with increases of 2.45°C, 2.82°C, 2.55°C, and 2.86°C, respectively. The annual mean temperature warming caused by Tianjin's urbanization increases yearly with the warming contributions of 3.73%, 3.71%, 4.73%, and 5.17% of the four-time periods to the whole region, separately. However, the warming amplitude in the rural area during winter is significantly larger than that in the urban area, as revealed from the annual and seasonal extreme cold events (TN10p and TX10p) and extreme minimum temperature events (TNn). Therefore, the urbanization effect on the average and extreme temperature warming in Tianjin is still significant on the time scale. Furthermore, urbanization in rural areas is more prominent than that in urban areas.