Meteorology, Energy, and Air Quality
In theory the energy and air quality implications of climate and meteorological changes are relatively well established. Climate fluctuations on spatial and temporal scales have significant impacts on energy use, emission of pollutants, atmospheric chemical reactions, and other parameters such as diffusion, transport, and deposition of airborne pollutants.
The Heat Island Group's objective is to understand the relationship between energy and air quality with a focus on the role of urban meteorology. Urban areas are known to generate their own weather patterns, urban heat islands, convective clouds, and precipitation. Urban heat islands also induce increased emission of pollutants. The Heat Island Group performs meteorological and air quality modeling to understand and quantify these relationships from the perspective of developing mitigation strategies, such as urban heat island control.
Producing better meteorological forecasts and modeling capabilities is useful for improving the prediction of energy needs and the related distribution of electricity and gas. The energy crisis in California serves as a reminder that such forecast models and quantification tools may become even more important in the future.
During the past 15 years, Heat Island Group modeling has assessed the implications of local, short-term meteorological effects (e.g., urban heat islands) and long-term climatic fluctuations (e.g., some aspects of climate change). Several U.S. areas and airsheds were examined—those in non-attainment status for ozone or in climate types that require significant energy use (cooling or heating). The modeling served as a basis for formal or informal inclusion of heat island control strategies in State Implementation Plans (SIPs) or related air quality regulations. Atlanta, GA, Los Angeles, CA, San Francisco, CA, Salt Lake City, UT, Houston, TX, Chicago, IL, and Baton Rouge, LA, are considering including heat island control in some aspects of their air quality-improvement strategies. The South Coast Air Quality Management District and the City of Los Angeles have formally encouraged urban heat island control as an air quality-improvement strategy. The City of Houston and the Texas Natural Resources Conservation Commission are eager to include these strategies in their SIP and mid-course adjustment to the SIP, if modeling shows air quality benefits from heat island control in that region.
The heightened attention to heat island reduction and the modeling work for Houston are a result of the air quality situation in that region.
Southern Texas was recently examined for inclusion in the modeling work by the Heat Island Group. Using the PSU/NCAR MM5 (meteorological) and the UAM-V/CAMx (photochemical) models, We have simulated the greater Houston region's baseline meteorological and air quality conditions, as well as those in cases with "implemented" heat island reduction strategies. The simulations of a 7-day summer episode in Texas suggest that the daytime urban heat island in Houston can grow up to 3° Kelvin (K). Heat island reduction via increased urban albedo and forest can have a potential offset effect of 5K in air temperature near the surface. Higher above ground, for example at 20m, the offset is smaller (up to 3K) but still significant. Of course there are also negative effects from heat island reduction: downwind of modified areas there is a potential increase in air temperature of 2 to 3K near the surface and up to 2K at 20m above ground.
In terms of ozone air quality, in some areas ozone concentrations decrease and in others, they increase as a result of heat island reduction. Just like the response in meteorological parameters, the signal in ozone concentrations (increases or decreases) also varies from one day to another during the modeled episode. The range of changes in ozone at the peak time of the day (e.g., 1600 local time) is on the order of 10 to 20% reduction or increases, amounting to anywhere between 5 to 25 parts per billion (ppb).
Modeling work to date suggests that the impacts of heat island reduction in the Houston region are relatively larger than in other regions we have previously simulated, such as Salt Lake City, Sacramento, or Baton Rouge. In these other regions, the impacts on air temperature were smaller than 2K and the impacts on ozone air quality were smaller than 8 ppb in general.
We are also working on preliminary assessments of the possible air quality implications of meteorological and emissions changes in California that could be brought on by long-term climate change. Although this work is relatively more recent than the urban heat island effort, the preliminary results show significant potential impacts on ozone air quality, should climate change (global warming) occur. Using future-year controlled emission scenarios for the Sacramento Valley and the Los Angeles Basin, we used output from the Canadian and Hadley (UK) GCMs to prepare meteorological and emission data and used them in a photochemical model (Urban Airshed Model). The simulations of specific episodes in the Sacramento Valley and the Los Angeles Basin show that both regions will be in non-attainment status by 2050 and after. In the Los Angeles basin, the overall sensitivity to temperature is about 4.6 ppb/K whereas in the Sacramento valley, it is up to 2 ppb/K. Of course, the dependence is larger if non-controlled (present-day) emissions are used in the simulations.
For more information, contact:
- Haider Taha
- (510) 486-7338; fax (510) 486-4673
Haider Taha leads the meteorological and air quality-modeling activities in the Heat Island Group (HIG) of EETD.