Rapid urbanization effect on local climate: intercomparison of climate trends in Shenzhen and Hong Kong, 1968-2013

An intercomparison of climate trends between 2 adjacent large cities, Shenzhen and Hong Kong, in the past 46 yr (1968-2013) suggests that the rate of urbanization is clearly reflected in the rate of the change in local climate. Since becoming a special economic zone in 1980, Shenzhen has experienced a very rapid urbanization process. In only 30 yr, Shenzhen has transformed from a small town into a metropolis rivaling Hong Kong. The gross domestic product and urban built-up area in Shenzhen have increased rapidly. Climate data analysis over the last 46 yr showed a greater rate of change in climate in Shenzhen than in Hong Kong over the same period. In Shenzhen, average annual temperature warmed by 1.63 +/- 0.18 degrees C (similar to 0.35 +/- 0.04 degrees C per decade), average maximum temperature increased by 0.90 +/- 0.19 degrees C, average minimum temperature in creased by 2.09 +/- 0.23 degrees C and the diurnal temperature range (DTR) decreased by 1.18 +/- 0.23 degrees C. Over the same period in Hong Kong, average temperature increased by 0.47 +/- 0.20 degrees C (similar to 0.10 +/- 0.04 degrees C per decade), maximum temperature increased by 0.12 +/- 0.28 degrees C, minimum temperature in creased by 0.55 +/- 0.20 degrees C and DTR decreased by 0.43 +/- 0.27 degrees C. In addition, relative humidity in Shenzhen decreased by 13.13 +/- 1.78% in the last 46 yr, while there were no significant changes in Hong Kong. Finally, data analysis showed that urbanization has no significant effect on total rainfall for both cities.