Heat wave vulnerability and mitigation in urban ecosystems

Background/Question/Methods

Urban surface temperatures vary greatly in space and time. This variation is in part regulated by impervious surface characteristics, vegetation, water availability, and regional climate changes. The effects of urban surface temperature variation can influence distributions of urban risks and when moderated by potential coping can lead to drastically different vulnerabilities. To better understand present and future vulnerabilities we conducted two analyses focused on the Phoenix, AZ metropolitan region. First, we examined micro-scale variation in surface temperature patterns and compared these with parcel level variation for a subset of more than 30 neighborhoods. The second study used recently developed relationships between vegetation, meteorology, and land surface temperature with future scenarios of climate, land cover, and socioeconomic variation. Combining micro-scale patterns of urban temperature with future projections of high heat events provides a basis for understanding patterns of heat vulnerability and can help direct activities to mitigation of heat induced stresses.

Results/Conclusions

Within neighborhoods, temperatures of each parcel and different land covers within the parcel were compared within and across neighborhoods.  These fine scale patterns are showing strong relationships between neighborhood and parcel landscape variation in land cover and surface temperature patterns. Parcel building temperature was negatively correlated with the area of vegetation within the individual parcel.  Future scenarios suggest Phoenix will have longer lasting and more intense heat waves and that neighborhood characteristics will either moderate or magnify their effects.  These scenarios suggest different future trajectories of land surface temperature depending on interactive changes in these dominant drivers.  Future vulnerability will be dictated by both these changes to environmental riskscapes and also changes in potential coping strategy. Together these studies highlight both the microscale determinants of urban climate variation and potential future variation in vulnerability to extreme surface temperature in hot arid metropolitan regions.