Mitigation Strategies

The user may select a vegetation, albedo, or combined mitigation strategy to model. In all cases the mitigation level represents a fractional increase over the entire city, and the distribution of the change is assumed to be uniform over all urban areas. For example, suppose the city surface is 40% rooftop, 30% paved surface, and 30% vegetated surface. If the user specifies an increase of 0.1 in vegetative fraction this corresponds to the assumption that the total vegetative cover of the city increases uniformly from 30% to 40%. Likewise a specified increase of 0.10 in city albedo is assumed to be applied uniformly over the entire city. In practice, of course, this could be accomplished in many ways. For example, consider the case where we desire to increase the city albedo by 0.10 by modifying ONLY rooftops. Since rooftops account for only 40% of the surface area one would need to increase rooftop albedo by 0.25 to affect a city-wide increase of albedo of 0.10 (ie., 0.25*0.40= 0.10). The MIST code is not capable of discerning spatial differences in application of either mitigation strategy, however, so all mitigation is assumed uniform over the city.

 

The MIST code limits the range of changes in either albedo or vegetation to -0.5 < D < 0.5. This is primarily to limit the chance of entry errors (e.g., 10 rather than 0.10). Positive values correspond to an increase in albedo or vegetation. Negative values are allowed so the user can explore issues such as urban deforestation.

 

In either case the level of mitigation specified by the user is converted directly to projected changes in near-surface air temperatures using results from mesoscale atmospheric modeling studies which are discussed in the Meteorological Impacts section of this help file.

 

Alternatively the user may simply input a uniform temperature change. This option directly affects a change in near-surface air temperature which is assumed uniform in space and time.

 

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.