Figure 7. Monthly temperature from station observation, temperature biases from default (DEF) and wetland scheme (WS) simulations, and the cooling effect induced by the WS in the summer (May-August) for three-year simulations.
In the summer of 2006, a record-breaking heatwave hit the major part of the U.S. and Southern Canada. The extreme heat conditions can be represented by the number of “hot days” during the summer, with the daily maximum temperature exceeding the 90th percentile of the 30-year climatology. We summed the number of hot days from May to August in 2006 from two simulations and the results are shown in Figure 8. Through these four months, the hottest region is in the southeast of the domain in Nebraska, Iowa, Kansas and Missouri – with more than 40 hot days – while in the Northern Great Plains and Canadian Prairies, the hot days are about 10~20 days. The WS simulation shows that wetlands could effectively reduce the number of hot days by about 10 days in the entire domain. Two regions receive greater impacts from wetlands, including southern Manitoba and the area between Nebraska and Iowa. This result manifests the important role of wetlands in mitigating climate change, especially in extreme heat events.