Thermal Model
The Thermal Model can serve as a cost-effective tool for helping public officials develop mitigation strategies for the UHI effect without complicated numerical calculations and costly CPU time. Like all numerical codes this model must be used correctly with proper input data and input parameters. This simple model is driven by empirical data and hence is sensitive to improper usage.
A simple energy balance model is created for use in developing mitigation strategies for the Urban Heat Island effect. There are six primary contributions to the overall energy balance:
- incident solar radiation
- anthropogenic heat input
- conduction heat loss
- outgoing evapotranspiration
- outgoing convection
- outgoing emitted radiation
Meteorological data are input to the model, which then computes an urban characteristic temperature at a calculated time step for a specified time range.
Meteorological data are taken from a viable source, and include wind speed [m s-1], dry bulb air temperature [ºC], relative humidity [%], ambient air temperature [ºC], solar radiation [MJ m-2 hr-1)], four-inch soil temperature [ºC], and reference evapotranspiration [mm hr-1]. The above mentioned input data are linearly interpolated to two-minute increments from hourly input data. Anthropogenic data also needs to be taken from a credible source.
The last set of required input values is the thermophysical constants. This depends on how many cover classifications one wants to analyze and on their respective area percentage over the entire urban area.
The model is not intended to supplant more robust meteorological models such as MM5 and WRF, but rather to complement these efforts with a more user-friendly modeling scheme. For policy makers (non-scientists) to formulate mitigation strategies in an efficient manner they need access to a simple-to-use and already validated model that can be used effectively without extensive training. We regard the primary utility of this model to be geared towards predicting the average UHI effect on a daily basis and for general education, which can both direct policy and point the direction for additional research, using more comprehensive models. For example, this model will be available for use to include (but not limited to) warning urban dwellers about the potential health risks and possible excess in power usage during times of extreme heat.
