Grantee Research Project Results
2004 Progress Report: The Urban Data Analysis and Modeling Project
EPA Grant Number: CR830890C002Subproject: this is subproject number R830890C002 , established and managed by the Center Director under grant CR830890
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: Solutions for Energy, AiR, Climate and Health Center (SEARCH)
Center Director: Bell, Michelle L.
Title: The Urban Data Analysis and Modeling Project
Investigators: Frederick, John , Kotamarthi, V. Rao
Institution: University of Chicago , Argonne National Laboratory
EPA Project Officer: Chung, Serena
Project Period: July 1, 2003 through June 30, 2004 (Extended to June 30, 2005)
Project Period Covered by this Report: July 1, 2003 through June 30, 2004
RFA: Targeted Research Center (2003) Recipients Lists
Research Category: Targeted Research
Objective:
The objective of this research project is to define the role of specific urban characteristics (altered air quality, altered surface properties, and vertical structure) on the chemical and physical environments to which large populations are exposed. The approach involves analysis of measurements from the Chicago area combined with mechanistic models.
Progress Summary:
The Ph.D. research of former graduate student Shelby Winiecki focused on the interpretation of solar ultraviolet spectral irradiances and ground-level ozone measured at the University of Chicago. The primary dataset was obtained by a Brewer spectrophotometer that resided on campus prior to establishment of the Urban Atmosphere Observatory (UAO). The initial goal of the effort was to examine the influences of cloudiness and degraded urban air quality on ground-level ultraviolet irradiance. As the research progressed, it became apparent that these two influences are coupled in a manner unrecognized previously. Ms. Winiecki completed her dissertation and received her degree in August 2004.
To examine the issues identified above, each measured irradiance was expressed as a fraction of the irradiance that would have existed under clear skies for the total column ozone amount at the time of data collection. The column ozone value came from satellite-based measurements that were not sensitive to the contribution from the boundary layer. The analysis considered irradiances in two wavelength bands centered on 305 nm and 345 nm that were 5 nm and 10 nm wide respectively. Irradiances in the shorter wavelength band are sensitive to the ozone abundance, whereas absorption by ozone is negligible at the longer wavelengths. The computed fractions are referred to as the “transmission ratios” at 305 nm and 345 nm respectively. This method of presentation highlights attenuation provided by cloudy skies and boundary layer ozone that is not implicit in the calculated clear-sky irradiances
The spectroradiometer data for the period May through September revealed a smaller average transmission ratio at 305 nm than at 345 nm. Furthermore, in a monthly averaged sense, the percent difference in transmission ratios at the two wavelengths increased with local time from 9:00 to 15:00 hours. This behavior suggests a link to urban ozone, which typically builds over the course of a day. To examine the role of ozone in the urban boundary layer, a series of radiative transfer calculations varied ozone amounts in the lowest 2 km of the atmosphere for a range of cloudiness, although the clouds themselves contained no ozone. The results showed that altered boundary layer ozone alone was unable to account for the observed percent difference in transmission ratios at 305 nm and 345 nm.
A more detailed model in which ozone is present in the interstitial air of a cloud produced transmission ratios in excellent agreement with those derived from the spectroradiometer measurements. The mechanism is straightforward but apparently has not been recognized previously. As clouds become optically thick in scattering, a beam of light takes a long geometrical path through the medium as radiation experiences multiple scattering by droplets. When ozone is present in the interstitial air of the cloud, enhanced absorption takes place at 305 nm compared to what occurs in a clear atmosphere. The result is a smaller transmission ratio at 305 nm than at 345 nm, where the percent difference increases from morning to afternoon as urban ozone amounts grow. This mechanism constitutes a coupling between tropospheric air quality and the optical properties of clouds in the ultraviolet.
Future Activities:
An undergraduate student, Bradley Grams, will begin analyzing data on atmospheric extinction provided by particulate matter, including the contribution from black carbon. Studies of the attenuation of visible and ultraviolet sunlight by clouds and particles will be extended using new data acquired at UAO by the Multifilter Rotating Shadowband Radiometer and the Robertson-Berger UV meter.
Journal Articles:
No journal articles submitted with this report: View all 1 publications for this subprojectSupplemental Keywords:
urbanization, solar radiation, particulate matter, air quality, air, atmosphere, modeling, monitoring, Chicago, IL, Illinois,, RFA, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Monitoring/Modeling, Environmental Monitoring, Urban and Regional Planning, community-based data, urban air quality, ecosystem management model, land use model, urban planning, air quality model, environmental impact, ecological models, urban environment, air qualityRelevant Websites:
http://www.atmos.anl.gov/CES/ Exit
Progress and Final Reports:
Original AbstractMain Center Abstract and Reports:
CR830890 Solutions for Energy, AiR, Climate and Health Center (SEARCH) Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
CR830890C001 The Urban Measurements Project—The Urban Atmosphere Observatory
CR830890C002 The Urban Data Analysis and Modeling Project
CR830890C003 Attenuation of Ultraviolet Solar Radiation by Cloudy Skies: Links to Urban Air Quality
CR830890C004 Measurements of Black Carbon in Chicago: Implications for Controls on Diesel Emissions
CR830890C005 Attenuation of Visible Sunlight by Limited Visibility and Cloudiness
CR830890C006 The Energy Balance of Urban Microclimates
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.
Project Research Results
Main Center: CR830890
9 publications for this center
1 journal articles for this center