The influence of vegetation cover on air temperatures was received more concerning recently. Air temperatures of above, under canopy and top of a concrete pavement building have been monitored for investigating the effects of tree canopy on air temperature. Results indicated that the yearly temperature difference between above and under canopy is about 0.42℃ and monthly highest temperature difference can be up to 0.93℃ during the summer season. The difference temperatures between above and under canopy showed no significant difference when temperature of above canopy below 27.2℃. The yearly difference temperatures between top of cement paved building and above canopy were 0.55℃ and showed no significant difference when the above canopy temperature below 24.3℃.
This study also used the Landsat-8 thermal images to estimate air temperatures of the entire Taipei metropolitan area through converting infrared wavelength to radiation intensity and calculating brightness temperature (TB). The obtained air temperature distribution map showed that the heat island effects can cause temperature of the urban area of Taipei city reaching up to 5.0 °C and temperature above vegetated zones showed a relatively lower temperature. These results also proved that vegetation coverages have a cooling effect to mitigate the effect of urban heat island (UHI) and provide a better understanding of the effects of vegetation cover on land surface temperature in the Taipei metropolitan area.
Key Words: air temperature, urban heat island effects, brightness temperature, thermal images