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A synoptic climatology of rural ozone pollution at three forest sites in Pennsylvania
Abstract An analysis reveals strong relationships between ozone (O3) concentratins at three rural forest sites in north-central Pennsylvania and the synoptic-scale atmospheric circulation. To identify these associations, a synoptic classification scheme is applied to daily maximum 1-h ambient surface O3 measurements for the growing seasons of 1988, 1989 and 1990. The results cover five aspects of the atmospheric circulation-rural O3 relationship: overall conditions, O3 extremes, key weather sequences, the seasonal cycle and interannual differences. Overall, high rural O3 concentrations occur with southwesterly transport conditions on the western sides of anticyclones, while low values are found in post-frontal and cyclonic conditions. While slow-moving or stagnant anticyclones are occasionally associated with high-O3 episodes, these situations are most frequent in the same southwesterly transport regime. This behavior is the inverse of that found in Pittsburgh in a closely related study by Comrie and Yarnal (Atmospheric Environment, 26B, No. 3, pp. 301–312, 1992). Unlike urban environments where air mass stagnation leads to an episode, an episode in a non-urban environment requires transport of a polluted air mass from a source region. In this latter scenario, forest O3 levels are critically dependent on the air mass history and trajectory. Key weather pattern sequences show that the southwesterly transport must be preceded by stagnation of the air mass over an upwind polluted region, with stagnation and transport each lasting 1–2 d. The relative importance of these complementary mechanisms in the O3 climatology remains the same through the growing season. The unusually hot and dry conditions of the summer 1988 were more favorable for O3 formation across all synoptic patterns, as compared to 1989 and 1990.
A synoptic climatology of rural ozone pollution at three forest sites in Pennsylvania
Abstract An analysis reveals strong relationships between ozone (O3) concentratins at three rural forest sites in north-central Pennsylvania and the synoptic-scale atmospheric circulation. To identify these associations, a synoptic classification scheme is applied to daily maximum 1-h ambient surface O3 measurements for the growing seasons of 1988, 1989 and 1990. The results cover five aspects of the atmospheric circulation-rural O3 relationship: overall conditions, O3 extremes, key weather sequences, the seasonal cycle and interannual differences. Overall, high rural O3 concentrations occur with southwesterly transport conditions on the western sides of anticyclones, while low values are found in post-frontal and cyclonic conditions. While slow-moving or stagnant anticyclones are occasionally associated with high-O3 episodes, these situations are most frequent in the same southwesterly transport regime. This behavior is the inverse of that found in Pittsburgh in a closely related study by Comrie and Yarnal (Atmospheric Environment, 26B, No. 3, pp. 301–312, 1992). Unlike urban environments where air mass stagnation leads to an episode, an episode in a non-urban environment requires transport of a polluted air mass from a source region. In this latter scenario, forest O3 levels are critically dependent on the air mass history and trajectory. Key weather pattern sequences show that the southwesterly transport must be preceded by stagnation of the air mass over an upwind polluted region, with stagnation and transport each lasting 1–2 d. The relative importance of these complementary mechanisms in the O3 climatology remains the same through the growing season. The unusually hot and dry conditions of the summer 1988 were more favorable for O3 formation across all synoptic patterns, as compared to 1989 and 1990.
A synoptic climatology of rural ozone pollution at three forest sites in Pennsylvania
Comrie, Andrew C. (author)
1993-12-10
14 pages
Article (Journal)
Electronic Resource
English
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