Based on the temperature and humidity data measured at 14 observation sites in Nanjing during July 27 and 28

2008

the diurnal variation of surface temperature

air temperature and humidity at 80 cm above ground were analyzed.The intensity of UHI and urban dry island（UDI） in three distinct zones

i.e.urban zone

rural zone and Xuanwu Lake zone

and the effect of typical surface covers（cement and grass） were discussed.The results show that:（1） the near-surface UHI effect is evident in Nanjing city

the maximum diurnal average temperature difference between urban zone and rural zone is 3.1°C on cement cover

1.9°C in air and 1.2°C on grass cover;（2） the UHI effect in Xuanwu Lake zone is evident on cement cover

but insignificant in air and on grass cover;（3） The UDI effect in urban zone is evident

the humidity in urban zone is much lower than rural zone and the difference reaches-14.1% on cement cover;（4） the diurnal variation of the humidity is contrary to that of temperature and significantly depends on temperature;（5） it is observed that

in urban zone

Yuhuatai

Xinjiekou

Nanqi and Confucius temple areas show relative high UHI intensity.The city lake and grass cover play an important role in reducing the UHI effect

while the cement cover can intensify the UHI effect.The Yangtze River located in the west of Nanjing can reduce the UHI effect in Hexi area.