Meteorological Impacts

Results from meteorological simulations in which the albedo and/or vegetation of cities was modified are used to provide estimates of the temperature impacts of surface characteristic modifications for the focus cities. Results for other cities were extrapolated from this set.

As weather patterns corresponding to representative bad air quality days were the focus of all meteorological modeling, the impacts on meteorology are inherently biased toward summer time impacts. The impacts for the small suite of simulations conducted for any individual city are then assumed to be uniform spatially and throughout the year.

For the ozone impacts analysis this assumption is considered reasonable as most ozone episodes are confined to summer months. For the year-round energy impacts analysis, however, this assumption is in error. Specifically, the temperature impacts of either mitigation strategy are likely to be smaller in winter when solar radiation plays a smaller role in the urban energy balance. By assuming that the temperature effects of mitigation are uniform throughout the year we essentially overestimate the wintertime cooling effect of the mitigation strategies. Hence, we overestimate the wintertime heating penalty associated with these mitigation strategies. As a result, the annualized energy savings presented by MIST may be considered to be a conservative estimate. In either case, however, it must be stressed that all simulations were conducted using a streamlined modeling approach, where the goal was to obtain rough estimates of the implications of heat island mitigation for urban air temperatures.

 

Advanced users seeking more detailed information on this and other topics related to the scientific and modeling underpinnings of the MIST software tool should read the detailed model description document that can be downloaded from the MIST website.