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- Author or Editor: George C. Holzworth x
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Abstract
This paper presents time cross-sections of vertical temperature structure during the 1966 Thanksgiving week air pollution episode in New York City, based on 6-hourly soundings at Kennedy Airport. The analyses depict numerous inversions in the lower 10,000 ft of the atmosphere, including an interesting sequence of surface-based inversions and an outstanding inversion aloft. Diurnal and daily variations in the height of the mixing layer can also be seen. Some possible influences of the vertical temperature structure on SO2 concentrations in Manhattan are discussed, and it is suggested that exceptional peak SO2 concentrations were largely due to the fumigation process.
Abstract
This paper presents time cross-sections of vertical temperature structure during the 1966 Thanksgiving week air pollution episode in New York City, based on 6-hourly soundings at Kennedy Airport. The analyses depict numerous inversions in the lower 10,000 ft of the atmosphere, including an interesting sequence of surface-based inversions and an outstanding inversion aloft. Diurnal and daily variations in the height of the mixing layer can also be seen. Some possible influences of the vertical temperature structure on SO2 concentrations in Manhattan are discussed, and it is suggested that exceptional peak SO2 concentrations were largely due to the fumigation process.
Abstract
The climatological occurrence of meteorological conditions associated with extensive and persistent arms of high air pollution potential over the western United States is presented. The most likely large-scale synoptic feature conducive to poor air quality is found to be the quasi-stationary anticyclone. A typical episode of high pollution potential is described. The forecasting of such episodes, including some inherent difficulites, is discussed.
Abstract
The climatological occurrence of meteorological conditions associated with extensive and persistent arms of high air pollution potential over the western United States is presented. The most likely large-scale synoptic feature conducive to poor air quality is found to be the quasi-stationary anticyclone. A typical episode of high pollution potential is described. The forecasting of such episodes, including some inherent difficulites, is discussed.
Abstract
The plume rise equations of Briggs (1975) for variable vertical profiles of temperature and wind speed are described and applied for hypothetical short and very tall chimneys at five National Weather Service rawinsonde stations across the United States. Annual average effective chimney heights are presented and from other available data additional information on plume behavior is deduced. For example, based on the 0515 CST soundings at Nashville, 61% of the effective plume heights for 50 m chimneys were in a temperature inversion, but only 21% of the plumes for 400 m chimneys were so constrained. Ordinarily, such plumes would be in a fanning configuration. Most of the plumes from tall chimneys (60%) were above an inversion, practically isolated from the ground. Overall, 98% of the short-chimney plumes were reached by the afternoon mixing height, but only 85% of the tall-chimney plumes were reached. Such information supports the obvious presumption that the effluent from tall chimneys remains airborne longer than that from short chimneys, is transported over greater distances, and has more opportunity to undergo chemical transformations before reaching the ground.
Abstract
The plume rise equations of Briggs (1975) for variable vertical profiles of temperature and wind speed are described and applied for hypothetical short and very tall chimneys at five National Weather Service rawinsonde stations across the United States. Annual average effective chimney heights are presented and from other available data additional information on plume behavior is deduced. For example, based on the 0515 CST soundings at Nashville, 61% of the effective plume heights for 50 m chimneys were in a temperature inversion, but only 21% of the plumes for 400 m chimneys were so constrained. Ordinarily, such plumes would be in a fanning configuration. Most of the plumes from tall chimneys (60%) were above an inversion, practically isolated from the ground. Overall, 98% of the short-chimney plumes were reached by the afternoon mixing height, but only 85% of the tall-chimney plumes were reached. Such information supports the obvious presumption that the effluent from tall chimneys remains airborne longer than that from short chimneys, is transported over greater distances, and has more opportunity to undergo chemical transformations before reaching the ground.
Abstract
The chemical analyses of particulate samples obtained by high-volume air-sampling instruments at remote sites near the California coast are shown to be related to trajectories of the sampled air. In particular, high-chloride concentrations are associated with nearby heavy-surf conditions. Background concentrations of materials analyzed are shown to agree reasonably well among the various sites.
Measurements of oxidant concentrations at rural sites are given and compared with previously observed background concentrations. The occurrence of relatively high oxidant concentrations at a site 70 mi from the nearest most-likely source area is discussed with respect to trajectory computations.
Abstract
The chemical analyses of particulate samples obtained by high-volume air-sampling instruments at remote sites near the California coast are shown to be related to trajectories of the sampled air. In particular, high-chloride concentrations are associated with nearby heavy-surf conditions. Background concentrations of materials analyzed are shown to agree reasonably well among the various sites.
Measurements of oxidant concentrations at rural sites are given and compared with previously observed background concentrations. The occurrence of relatively high oxidant concentrations at a site 70 mi from the nearest most-likely source area is discussed with respect to trajectory computations.
Abstract
Daily estimates of morning and afternoon mixing depths and average wind speeds through the mixing layers were calculated and summarized for seven locations in several climatic regions of the contiguous United States. Mixing depth and wind speed estimates were based on regular surface (airways) and upper air (rawinsonde) observations of the Weather Bureau and on the assumption of a dry-adiabatic lapse rate in the mixing layer. Monthly averages of morning and afternoon mixing depth and wind speed are presented graphically. The frequency of occurrence of various combinations of mixing depth and wind speed classes were used in an urban diffusion model to calculate theoretical values of relative pollutant concentration for four major cities. These relative pollutant concentrations, which also depend upon city size, are compared among the cities on the bases of their current sizes and a common size.
Abstract
Daily estimates of morning and afternoon mixing depths and average wind speeds through the mixing layers were calculated and summarized for seven locations in several climatic regions of the contiguous United States. Mixing depth and wind speed estimates were based on regular surface (airways) and upper air (rawinsonde) observations of the Weather Bureau and on the assumption of a dry-adiabatic lapse rate in the mixing layer. Monthly averages of morning and afternoon mixing depth and wind speed are presented graphically. The frequency of occurrence of various combinations of mixing depth and wind speed classes were used in an urban diffusion model to calculate theoretical values of relative pollutant concentration for four major cities. These relative pollutant concentrations, which also depend upon city size, are compared among the cities on the bases of their current sizes and a common size.
Abstract
Hourly surface wind-speed observations recorded over 2 yrs, at 16 Weather Bureau Airport Stations were studied to establish relationships between average daily speeds and the frequencies of individual hourly speeds. Only days with no precipitation were considered. Although the results of the study are intended for use in air pollution meteorology, they are of general interest to synoptic meteorologists.
Abstract
Hourly surface wind-speed observations recorded over 2 yrs, at 16 Weather Bureau Airport Stations were studied to establish relationships between average daily speeds and the frequencies of individual hourly speeds. Only days with no precipitation were considered. Although the results of the study are intended for use in air pollution meteorology, they are of general interest to synoptic meteorologists.
Abstract
Mean radiosonde observations and normal maximum surface temperatures are used with the assumption of a dry adiabatic lapse rate to estimate monthly mean maximum mixing depths (MMD's) for 45 stations in the contiguous United States. From these data isopleth analyses of mean MMD's are presented for each mouth. Deviation from the assumption of a dry adiabatic lapse rate is discussed. Sixteen of the available 45 radiosonde stations are selected as generally representative of the United States and are subjected to further considerations. These considerations are (1) the relationship between monthly mean MMD's computed from mean observations and from individual observations, (2) comparison of monthly mean MMD's based on observations for 1 year with those based on observations for 10 years, and (3) the standard deviations of daily MMD's.
Abstract
Mean radiosonde observations and normal maximum surface temperatures are used with the assumption of a dry adiabatic lapse rate to estimate monthly mean maximum mixing depths (MMD's) for 45 stations in the contiguous United States. From these data isopleth analyses of mean MMD's are presented for each mouth. Deviation from the assumption of a dry adiabatic lapse rate is discussed. Sixteen of the available 45 radiosonde stations are selected as generally representative of the United States and are subjected to further considerations. These considerations are (1) the relationship between monthly mean MMD's computed from mean observations and from individual observations, (2) comparison of monthly mean MMD's based on observations for 1 year with those based on observations for 10 years, and (3) the standard deviations of daily MMD's.
Abstract
Daylight visibility observations at the Sacramento Municipal Airport were used to investigate the possibility that visibility in the area has been declining due to rising levels of air pollution. Those visibility observations made with naturally occurring fog (defined as relative humidity greater than 90 percent) and/or precipitation were eliminated from the data. Observations for July, a warm, dry month with relatively slight climatic differences from year to year, and November, a cool month that often exhibits it considerable annual variation of climate, were tabulated for the three 4-year periods, 1935–38, 1945–48, and 1953–56. The results show that for July the percent frequency of poor visibilities steadily increased, and of good visibilities steadily decreased over the last 20-odd years. Such a trend is consistent with the Sacramento population increase. For November the trend was irregular. This is believed to be due to variations in the occurrence of meteorological factors, important to atmospheric dispersion. It is likely that such irregularities are characteristic of other months and areas where there are large annual climatic variations.
From concurrent surface wind observations, the preferred wind conditions for various visibility ranges were determined. These data indicate that poor visibilities at the airport, on the southern edge of the city, occurred most frequently with light winds from over the nearby Sacramento urban area. Good visibilities were favored by moderate winds from rural directions. Visibilities were reduced when the wind speed became strong enough for loose materials to be picked up from the ground.
Abstract
Daylight visibility observations at the Sacramento Municipal Airport were used to investigate the possibility that visibility in the area has been declining due to rising levels of air pollution. Those visibility observations made with naturally occurring fog (defined as relative humidity greater than 90 percent) and/or precipitation were eliminated from the data. Observations for July, a warm, dry month with relatively slight climatic differences from year to year, and November, a cool month that often exhibits it considerable annual variation of climate, were tabulated for the three 4-year periods, 1935–38, 1945–48, and 1953–56. The results show that for July the percent frequency of poor visibilities steadily increased, and of good visibilities steadily decreased over the last 20-odd years. Such a trend is consistent with the Sacramento population increase. For November the trend was irregular. This is believed to be due to variations in the occurrence of meteorological factors, important to atmospheric dispersion. It is likely that such irregularities are characteristic of other months and areas where there are large annual climatic variations.
From concurrent surface wind observations, the preferred wind conditions for various visibility ranges were determined. These data indicate that poor visibilities at the airport, on the southern edge of the city, occurred most frequently with light winds from over the nearby Sacramento urban area. Good visibilities were favored by moderate winds from rural directions. Visibilities were reduced when the wind speed became strong enough for loose materials to be picked up from the ground.
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