Impact/Purpose:

To understand and characterize the factors, including optical transmission properties of aerosols, which affect the intensity of UV-B radiation measured at the earth's surface in order to improve our estimates of ecosystem and human exposures to UV-B radiation; to understand the relationship between UV radiation and total column ozone; to model UV-B exposures at different locations, conditions, and times in order to estimate UV-B exposures throughout the US. This objective is achieved by maintaining a strict quality assurance program for both the Brewer Spectrophotometers in the network and the UV data obtained from the Brewers.

Description:

Because exposure to ultraviolet (UV) radiation is an ecosystem stressor and poses a human health risk, the National Exposure Research Laboratory (NERL) has undertaken a research program to measure the intensity of UV-B radiation at various locations throughout the U.S. In September 1996, the National Park Service (NPS) and the Environmental Protection Agency (EPA) signed an interagency agreement (IAG) to cooperate on a program of long-term monitoring of environmental stressors at various sites throughout the U.S., and to undertake research on the effects of those stressors on ecosystems and human health. The EPA UV monitoring network is composed of 21 Brewer spectrophotometers deployed throughout the United States to measure full sky UV irradiances. Each site is comprised of a Brewer spectrophotometer mounted on a tracker and tripod unit which is controlled by a desktop computer running the Disk Operating System (DOS) and GW Basic Brewer software. The sites come under the joint EPA/NPS Park Research and Intensive Monitoring of Ecosystems Network (PRIMENet) [formerly Demonstration Intensive Site Project (DISPro)] network. Fourteen of the Brewer sites are located in U.S. National Parks, and seven of the Brewer sites are located in urban settings. Data from those 21 sites are being run through a quality assurance program to properly characterize UV radiation intensities at the earth's surface.

NERL has undertaken this UV radiation research program in two separate, but related research tasks: Task 3900 (this research task) - a process-oriented research program designed: a) to improve our understanding and description of the nature and intensity of UV-B radiation reaching the earth's surface; b) to characterize the physical and chemical parameters that modify and control the UV radiation flux; and c) to use our enhanced understanding of UV radiation in improving radiative transfer models to obtain better estimates of UV exposures at different times, locations and meterological conditions; Task 9423 - a quality-assurance/quality control program responsible for: maintenance of the Brewer Spectrophotometer instruments; collecting the UV data from each of the 21 PRIMENet sites on a daily basis; providing Level 1 data correction to the raw UV data collected from the Brewer Spectrophotometers; development of wavelength intensity standards traceable to NIST standards (for the horizontal position to correlate with the Brewer's input optics); characterization of the Brewers for slit width, wavelength dependency for stray light, cosine response function for the input optics.

This task covers: operation of the UV measurement site at Research Triangle Park (RTP), NC; technical collaboration / interaction and data exchange with other researchers in the UV measurement field (including application of UV radiation standards and devices and intercomparison protocols); analysis of the UV-B data collected at the 21 PRIMENet sites; and research to understand and characterize the critical factors that affect the nature and intensity of the UV-B radiation measured at the earth's surface.

Record Details:

Record Type:PROJECT

Start Date:01/01/1996

Completion Date:09/01/2004

Record ID: 56142

Show Additional Record Data

Project Information:

Progress :This research provides accurate measurements of UV radiation of known quality to assess effectiveness of Agency's stratospheric ozone policies; provides data and methods to evaluate the "climatology" of UV stress to the environment; and by incorporating the improved understanding of aerosol effects on UV into the "UV Index" and other models, the Agency will be able to better inform the public of potential harmful effects of increased UV radiation and will be better able to model the magnitude of the stress to ecosystems from UV radiation.

During independent quality assurance audits, including UV calibrations completed at network sites, indications are that calibrations are repeatable within about 2% but are subject to annual drifts averaging about 7%. Routine audits of the Brewer Spectrophotometer sites continue to ensure that Brewer data are subject to quality control. In March 2002, UGA completed the detailed QC and data correction program on all archived Brewer data, allowing researcher access to the final UV data base. All data are available on UGA's FTP site and EPA's publicly accessible website. All corrected data are transferred to EPA, and the corrected data from the network is posted to an EPA web site accessible to the general public. To access the (Level 1 corrected) UV data collected at all of the PRIMENet sites on the Internet, you must go to the following web page: http://www.epa.gov/uvnet/access.html . The UV data for each site is provided to EPA on CD-ROMs by the contractor (UGA). The structure of the UV data displayed on the public web page (and files, formats, etc.) and the content is exactly the same as that on the CD-ROMs.

ABSTRACT/ORAL: Date Cleared: 11-APR-00

Godar, D.E., Wengraitis, S.P., Shreffler, J.H., and Sliney, D. Average annual solar UV dose of the continental US citizen. 13th

International Congress on Photobiology, San Francisco, CA, July 2-6, 2000.

ABSTRACT/ORAL: Date Cleared: 15-MAY-00

Shreffler, J.H. Data from EPA's UV monitoring network. Abstract presented at: 13th International Contress on Photobiology, San Francisco, CA, July 2-6, 2000

15-MAY-00 Shreffler, J.H. Data from EPA's UV monitoring network. Abstract presented at: 13th International Congress on Photobiology, San Francisco, CA, July 2-6, 2000.

ORAL PRESENTATION: Date Cleared: 25-FEB-03

Hall, E.S. The UV Monitoring Research Program. Presented at: US Global Change Research Program Seminar (videoteleconference), Washington D.C., February 24, 2003



Relevance :The "UV Index" was developed by EPA in conjunction with the National Weather Service in 1993-1994. The algorithms currently being used for UV predictions for the following day have only been developed to include a limited set of parameters. One of the parameters which is felt to have a major impact on the UV radiation at the earth's surface and has yet to be utilized effectively in the UV Index predictions, is aerosols. This is especially true in urban areas. However, the UV radiation community has not fully characterized the absorption of UV radiation by aerosols due to lack of proper instrumentation and funding. It is also believed that the amount of aerosols has had a dramatic effect on the ratio of direct to indirect UV radiation. This is why a key objective of the research is to understand the effects of clouds, haze, and aerosols on the amount of UV radiation reaching the earth's surface.

NERL installed 21 regionally dispersed UV monitoring sites in the United States. The sites, 14 in National Parks (PRIMENet) and 7 in urban areas, provide spectrally resolved UV-B and UV-A radiation data, on a daily basis, that is traceable to National Institute for Standards and Technology (NIST) standards and accepted as being of high quality and defensible by the international research community. The data is suitable for research into fundamental processes for understanding UV flux to enable us to describe and model exposures of ecosystems and human beings to UV radiation. Additionally, the research program will enable the Agency to specify the actual levels of ultraviolet radiation as a stressor in the environment and to identify long-term trends in UV flux, as appropriate.

This research is important to help protect the public against increased UV radiation associated with decreasing stratospheric ozone concentrations.

Clients :NERL (Sharon Harper), NRMRL (Mark Mason), NCSU (Bill Barnard), OAR (Terry Keating), ERD (Richard Zepp)

Project IDs:

ID Code :3900

Project type :OMIS