Measuring Urban Microclimates and Vertical Temperature Profiles in Portland, Oregon for Analyzing Energy Budgets and Air Pollution Sources

Abstract:

Major goals of this study included 1) making new measurements and analyses of microclimates in an urban area for applications to energy conservation, and 2) assessment of local air pollution sources. The study site in Portland, Oregon features complex natural topography, tall buildings, a major river, significant variations in vegetation types and coverage, heavy industry emitting several kinds of airborne pollutants, a major shipyard, a rail line, bus lines, and a high population density. Methods centered on installing a dense network of remote automated weather stations in contrasting microclimates spanning a range of 70 m in the vertical from the lowest to highest station altitude within an area of only 0.25 km². Station measurements included air temperatures and humidities at multiple heights per station, wind speed, wind direction, wind gusts, incoming solar radiation in several spectral ranges, direct-diffuse ratios of incoming radiation, precipitation, air pressure, leaf wetness, soil moisture, thermal-infrared radiant temperatures, surface kinetic temperatures, boundary layer fluxes, and photovoltaic performance. Novel tethersonde sampling methods conducted in coordination with the ground-based stations provided complimentary high-resolution data on vertical profiles of air temperatures, winds, and humidities within the boundary layer. Results show frequent, strong, low-level temperature inversions following consistent diurnal patterns, with important implications for local air pollution concentrations and circulation. Other results demonstrate some avoidable cool-season heating losses from the buildings within the study area, especially through building rooftops. Applications include improving air quality and reducing heating and cooling costs to take advantage of diurnal patterns and anomalies in response to various synoptic fluctuations.