Two-day Fluctuations of Temperature and the Impacts of Urbanization in Shanghai during the Period 1873-2009
上海百余年来气温日间波动特征及城市化影响

Global average surface temperature has increased by 0.7°C over the 20th century and is projected to increase within the range of 2-6°C in the 21st century. Numerous studies indicated that the maximum and minimum temperature changes show obvious asymmetric characteristics of spatial distribution and the rate of linear increasing tendency. However, the two-day fluctuation of daily maximum and minimum temperature, which would have important impacts on municipal water supply, power supply, and human health, does not seem to be well investigated. Based on daily maximum and minimum temperature data of the Xujiahui station during the period 1873-2009, and those of 10 suburb stations during the period 1960-2009 in Shanghai, the characteristics of two-day fluctuation of daily maximum and minimum temperature and the impacts of urbanization on them were examined with climatologically statistical diagnosis methods. Results indicate that over the period 1873-2009, days with the two-day falling of daily maximum temperature increased gradually and those with the two-day rising decreased gradually. Days with the two-day falling of daily minimum temperature showed a more-less-more-less inter-annual variation, and days with the two-day rising of daily minimum temperature showed a less-more-less-more inter-annual variation. The two-day rising and falling range of daily maximum temperature, days with the two-day rising and falling of daily maximum temperature of no less than 5 °C, and the two-day falling range of daily minimum temperature and days with the two-day falling of daily minimum temperature of no less than 5 °C all increased firstly and then decreased during the period 1873-2007. However, the two-day rising range of daily minimum temperature, days with the two-day rising of daily minimum temperature of no less than 5 °C remained fairly invariant before the 1930s, and decreased obviously since the 1960s in Shanghai. Urbanization increased the two-day fluctuation range of daily maximum temperature and decreased the two-day fluctuation range of daily minimum temperature, which resulted in increases in days with the two-day rising of daily maximum temperature of no less than 5 °C and slower decreases in days with the two-day falling of daily maximum temperature of no less than 5 °C, and resulted in decreases in days with the two-day rising and falling of daily minimum temperature of no less than 5 °C in Shanghai.