Heat release from rooftops during rainstorms in the Minneapolis/St. Paul Metropolitan Area, USA
Article first published online: 1 FEB 2011
Copyright © 2011 John Wiley & Sons, Ltd.
Volume 25, Issue 13, pages 2018–2031, 30 June 2011
How to Cite
Janke, B. D., Mohseni, O., Herb, W. R. and Stefan, H. G. (2011), Heat release from rooftops during rainstorms in the Minneapolis/St. Paul Metropolitan Area, USA. Hydrol. Process., 25: 2018–2031. doi: 10.1002/hyp.7954
- Issue published online: 16 JUN 2011
- Article first published online: 1 FEB 2011
- Manuscript Accepted: 4 NOV 2010
- Manuscript Received: 3 MAR 2010
- surface runoff;
- thermal pollution
In the modeling of urban storm water runoff temperatures, the contribution of rooftops to the heating of rainfall runoff is usually neglected or not mentioned in the literature. In this paper we examine the accuracy of this assumption (a) by analyzing temperature data that we recorded on a residential rooftop, a commercial rooftop, and a concrete driveway, and (b) by simulating temperature profiles within rooftops and pavements, and estimating heat transfer amounts from these surfaces to rainfall runoff (‘heat export’). Analysis of both wet- and dry-weather temperature data recorded in the Minneapolis/St. Paul metropolitan area (north-central USA) over periods of several months leads to the conclusion that (a) a concrete driveway has a far greater capacity for heat storage and release than a shingled residential rooftop, and (b) an insulated commercial rooftop is able to store and release more heat than the residential rooftop. Unexpectedly, the rainfall events with the highest dew point (rainfall) and surface temperatures often occurred during late night or early morning hours, and not during daylight hours. The analysis of three rainfall events showed that the heat export from the commercial rooftop was roughly three times that of the residential rooftop, but only 30%–90% of the heat export from a concrete driveway. Maximum (potential) heat export was significantly higher for the driveway than for either rooftop. In conclusion, the results of the data analysis and heat export simulations support the assumption that residential rooftops contribute very little heating to runoff from rainfall, while commercial rooftops may have a thermal impact on rainfall runoff because of their greater thermal storage capacity. Commercial rooftops, in addition to asphalt and concrete pavements, should be considered when estimating water temperature of rainfall runoff from urbanized areas and the associated impact on the thermal regime of streams and fish habitat. Copyright © 2011 John Wiley & Sons, Ltd.