Cooling effects of wetlands in an urban region: The case of Beijing

The cooling effects of wetlands, which form “urban cooling islands” (UCIs), are important for mitigating urban heat island effects. Ten reservoirs/lakes and five rivers in Beijing are selected to investigate UCI intensity using ASTER images. The UCI intensity is quantified by the temperature difference and gradient between the wetland and surrounding landscapes. The results indicate that: (1) the UCI intensity is correlated with the landscape shape index (LSI) of the wetlands, and the Spearman Rho is 0.679 between LSI and temperature difference, and 0.568 between LSI and temperature gradient; and (2) the UCI intensity is also determined by the wetland location in relation to the downtown, and the correlation coefficient is 0.691 between the location and temperature difference, and 0.706 between the location and temperature gradient. Our results suggest that wetland shape and location are significant indicators influencing the UCI intensity in an urban region, and are important to consider in quantifying the microclimate regulation services of wetlands as well as in designing urban landscape to mitigate UHI effects.