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Titolo:
OZONE PRODUCTION DURING AN URBAN AIR STAGNATION EPISODE OVER NASHVILLE, TENNESSEE
Autore:
VALENTE RJ; IMHOFF RE; TANNER RL; MEAGHER JF; DAUM PH; HARDESTY RM; BANTA RM; ALVAREZ RJ; MCNIDER RT; GILLANI NV;
Indirizzi:
TENNESSEE VALLEY AUTHOR,ATMOSPHER SCI & ENVIRONM ASSESSMENTS,CEB2A,POB 1010 MUSCLE SHOALS AL 35662 NOAA,ENVIRONM TECHNOL LAB BOULDER CO 80303 UNIV ALABAMA,EARTH SYST SCI LAB HUNTSVILLE AL 35899 BROOKHAVEN NATL LAB,ENVIRONM CHEM DIV UPTON NY 11973
Titolo Testata:
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
fascicolo: D17, volume: 103, anno: 1998,
pagine: 22555 - 22568
Fonte:
ISI
Lingua:
ENG
Soggetto:
UNITED-STATES; RURAL SITE; DEPOSITION; ATLANTA;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Science Citation Index Expanded
Science Citation Index Expanded
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
19
Recensione:
Indirizzi per estratti:
Citazione:
R.J. Valente et al., "OZONE PRODUCTION DURING AN URBAN AIR STAGNATION EPISODE OVER NASHVILLE, TENNESSEE", J GEO RES-A, 103(D17), 1998, pp. 22555-22568

Abstract

The highest O-3 levels observed during the 1995 Southern Oxidants Study in middle Tennessee occurred during a period of air stagnation fromJuly 11 through July 15. Extensive airborne (two fixed wing and one helicopter) and ground-based measurements of the chemistry and meteorology of this episode near Nashville, Tennessee, are presented. In situ airborne measurements include O-3, NOy, NO, NO2, SO2, CO, nitrate, hydrocarbons, and aldehydes. Airborne LIDAR O-3 measurements are also utilized to map the vertical and horizontal extent of the urban plume. The use of multiple instrumented research aircraft permitted highly detailed mapping of the plume chemistry in the vertical and horizontal dimensions. Interactions between the urban Nashville plume (primarily a NOx and hydrocarbon source) and the Gallatin coal-fired power plant plume (primarily a NOx and SO2 source) are also documented, and comparisons of ozone formation in the isolated and mixed urban and power plant plume are presented. The data suggest that during this episode the background air and the edges of the urban plume are NOx sensitive and thecore of the urban plume is hydrocarbon sensitive. Under these worst case meteorological conditions, ambient O-3 levels well over the level of the new National Ambient Air Quality Standard (NAAQS) for ozone (80ppb) were observed over and just downwind of Nashville. For example, on July 12, the boundary layer air upwind of Nashville showed 60 to 70ppb O-3, while just downwind of the city the urban plume maximum was over 140 ppb O-3. With a revised ozone standard set at 80 ppb (8 hour average) and upwind levels already within 10 or 20 ppb of the standard, only a slight increase in ozone from the urban area will cause difficulty in attaining the standard at monitors near the care of the urbanplume during this type of episode. The helicopter mapping and LIDAR aircraft data clearly illustrate that high O-3 levels can occur during stagnation episodes within a few kilometers of and even within the urban area. The extremely light boundary layer winds (1-3 m s(-1)) contributed to the creation of an ozone dome or blob which stayed very near to the city rather than an elongated plume. The small spatial scale ofthe zone of high O-3 concentrations is mapped in detail demonstratingthat the regulatory monitoring network failed to document the maximumO-3 concentrations. Modelers using such regulatory data to test photochemical algorithms need to bear in mind that magnitude and frequency of urban ozone may be underestimated by monitoring networks, especially in medium-sized urban areas under slow transport conditions. Finally, this effort shows the value of collaborative field measurements frommultiple platforms in developing a more complete picture of the chemistry and transport of photochemical O-3.

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Documento generato il 04/04/20 alle ore 02:08:58