Urban heat island effects can be captured in computer models used to simulate meteorological and air chemistry activities. Likewise, changes accomplished through heat island actions, such as cool roofing and adding trees, can be modeled to show the air quality, energy and other impacts.
Air quality modeling of heat island effects have shown both a potential to reduce ozone and urban temperatures, but the results also have uncertainties. Many of these uncertainties in Houston are associated with the difficulty of modeling meteorology and the fact that urban heat island effects occur at higher resolution scales than air quality modeling.
Urban heat island mitigation involves changing the characteristics of the surface of the area by (1) increasing the reflectivity of surfaces such as rooftops and paving and (2) increasing the extent, volume and location of vegetation. Such changes can produce the following effects in air quality modeling: changes in wind speeds and possibly direction, changes in the boundary conditions in which mixing of pollutants occurs, effects on day and night time temperatures, changes in rainfall patterns, changes in the deposition of ozone through vegetation activity.
The intent is literally to change the weather of cities. When cities are built, the weather is changed significantly. The intent of heat island mitigation is simply to partially reverse these effects.
Houston Heat Island Research
Research studies have measured the extent of Houston's heat island and also demonstrated improved heat island modeling.
Modeling the Effects of Land-Use/Land-Cover Modifications on the Urban Heat Island Phenomena in Houston, Texas ( 3.28 MB)
Robert Bornstein and Rochelle Balmori, San Jose State University, May 2006
The current study used the Martilli-Dupont urbanization scheme within MM5 (uMM5) to investigate Houston urban heat island (UHI) conditions during an August TexAQS 2000 O3-episode. The resulting uMM5 model was used only in the (innermost) fifth domain (1-km grid spacing). Projected changes in vegetative cover for 2010, which showed areas of urban reforestation and rural deforestation, were also simulated by uMM5. Results showed that input NNRP fields correctly captured the observed largescale forcing and that the regular MM5 correctly captured the observed sequence of Bay, Gulf, and urban breeze effects on O3-transport. uMM5 better reproduced observed UHI magnitudes and urban impacts on regional flows: roughness-induced deceleration, building-barrier divergence, and UHI-induced convergence. Effects from the use of a higher resolution domain, uMM5, and/or urban reforestation showed that the first two generally increased daytime UHIs, while reforestation decreased them by an average of 2.8 K and by a maximum (at noon) of 3.3 K.
A Remote Sensing Study of the Urban Heat Island of Houston, Texas ( 442 KB)
David R. Streutker, Department of Physics and Astronomy, Rice University, American Geophysical Union, Fall Meeting 2001
Radiative surface temperature maps of Houston, Texas were derived from satellite sensor data acquired at approximately 0400 LST on 27 separate occasions over a two year period. Urban-rural temperature differences were determined for 21 of these cases by modelling the urban heat island as a two-dimensional Gaussian surface superimposed on a planar rural background. The purpose of this study was to characterise the complete urban heat island in magnitude and spatial extent without the use of in situ measurements and to determine whether a correlation exists between heat island magnitude and rural temperature. The urban heat island magnitude was found to be inversely correlated with rural temperature, while the spatial extent was found to be independent of both heat island magnitude and rural temperature.
Satellite-measured growth of the urban heat island of Houston, Texas ( 1.98 MB)
David R. Streutker, Remote sensing of environment, 2003
Growth of the surface temperature urban heat island (UHI) of Houston, TX is determined by comparing two sets of heat island measurements taken 12 years apart. Individual heat island characteristics are calculated from radiative temperature maps obtained using the split-window infrared channels of the Advanced Very High Resolution Radiometer (AVHRR) on board National Oceanic and Atmospheric Administration polar-orbiting satellites. Eighty-two nighttime scenes taken between 1985 and 1987 are compared to 125 nighttime scenes taken between 1999 and 2001. Analysis of the UHI characteristics from these two intervals reveals a mean growth in magnitude of 0.8 K, or 35%. The growth of the mean area of the UHI is found to range between 170 and 650 km[2], or from 38% to 88%, depending on the method of analysis.
Houston Cool and Green! ( 810 KB)
A workshop on climate variability in the Houston region
The Houston Cool and Green workshop (May 1999) was one of several such events that were part of the Southern Great Plains regional assessment of the U.S. Global Change Research Program, mandated by Congress in 1990 ( P.L. 101-606). These workshops linked research by scientists to the needs of stakeholders in each region. They provided planners, managers, organizations, and the public with information to cope with climate change, shaped to fit the unique priorities within each region.
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