Evaluation of weather conditions for methyl bromide ambient air monitoring in Monterey, Santa Cruz, and Kern Counties in the year 2000

Weather condition is one of the most important factors affecting spatial and temporal distributions of air pollutants, especially for short-term air dispersion. Abnormal weather conditions might lead to higher or lower ambient air concentrations than they would be under normal weather conditions. Therefore, testing for normality of weather conditions during the air monitoring period is an essential step for evaluating ambient air monitoring results. In this paper, a distance method was used to select a most representative weather station from the available candidates. An array of meteorological elements were identified that affect air dispersion and transportation. A statistical method was used to determine whether the weather conditions during the air monitoring period were significantly different from that of previous years. Using methyl bromide ambient air monitoring as a case study, this paper documents the methods, procedures, and results of weather analysis for Monterey, Santa Cruz, and Kern Counties during ambient air monitoring periods for methyl bromide in the year 2000. With a few exceptions, the meteorological elements and atmospheric stability factors, such as wind speeds, wind directions, and stability classes, during the monitoring period were in the normal range. Although there were higher frequencies of stable atmospheric conditions in Monterey/Santa Cruz Counties than in Kern County, weather conditions during the monitoring period were not significantly different from normal local weather conditions of previous years. Consequently, the subchronic air concentrations observed during the ambient air monitoring periods for methyl bromide in the year 2000 was taken under typical weather conditions of those areas at that time of the year.     

Visibility in California

A comprehensive study is conducted of visibility in California using prevailing visibility measurements at 67 weather stations in conjunction with data on particulate concentrations and meteorology. The weather station visibility data, when handled with special techniques that account for the nature of visibility reporting practices, prove to be of very good quality for the purposes of most of the analyses that are attempted. It is found that the most important meteorological parameters with respect to visibility are relative humidity, temperature, and special weather events (especially fog). A detailed isopleth map of visibility within California, when compared with earlier work on nationwide visibility, reveals that California experiences far more severe and complex spatial gradients in visibility than those observed anywhere else in the U.S. Two major pockets of heavy man-made visibility impact in California are the Los Angeles basin and the San Joaquin Valley. The spatial, seasonal, and diurnal patterns of visibility are found to be readily explainable in terms of corresponding patterns in emissions, air quality, and meteorology. Regression analyses relating visibility to relative humidity and aerosol concentrations produce high levels of correlation and physically reasonable regression coefficients; these analyses indicate that secondary aerosols are major contributors to visibility reduction in California. An analysis of long-term visibility trends from 1949 to 1976 reveals several interesting features in historical visibility changes for California.     

Trends and Relationships of O3, NOx and HC in the South Coast Air Basin of California

A basin-wide air quality trend analysis for the South Coast Air Basin of California is conducted for hydrocarbons (HC), NO_x, O₃ and CO using multi-station composite daily maximum-hour average ambient concentrations for the third quarter (July, August and September) from 1968 to 1985. Emissions and air quality trends are compared for the period 1968-1984. Ambient HC and NOX trends are somewhat different from estimated emission trends of HC and NO_x, while a definite, downward trend of ambient CO is consistent with vehicular emission control measures. Basin-wide ambient HC, NO_x and O₃ appear to show downward trends for the period 1970-1985, but because of high fluctuations it is difficult to delineate trends for shorter periods. The meteorology (850 mb temperature)-adjusted O₃ shows a more consistent downward trend than does unadjusted O₃. Polynomial and multiplicative regression models for basin-wide empirical O₃-HC-NO_x relationships Indicate that the O₃ variation is explained largely by the meteorological variable (850 mb temperature) although model estimations are improved by adding HC and NO_x concentration terms.     

Changes in Diurnal Patterns Related to Changes in Ozone Levels

Ozone is an ubiquitous air pollutant that affects both human health and vegetation. There is concern about the number of hours human populations in nonattainment areas in the United States are exposed to levels of 03 at which effects have been observed. As improvement in air quality is achieved, it is possible that 03 control strategies may produce distributions of 1-h 03 concentrations that result in different diurnal profiles that produce greater potential exposures to 03 at known effects levels for multiple hours of the day. These concerns have prompted new analysis of aerometric data. In this analysis, the change in the seasonally averaged diurnal pattern was investigated as changes in 03 levels occurred. For the data used in this analysis, 25 of the 36 sites that changed compliance status across years showed no statistically significant change in the shape of the average diurnal profile (averaged by 03 season). For 71 percent (10 out of 14) of the sites in southern California and Dallas-Fort Worth, Texas, that showed improvement in O3 levels (i.e., reductions in the number of exceedances over the years), but still remained in nonattainment, a statistically significant change in the shape of the seasonally averaged diurnal profile occurred. Based on the results obtained in this study, the evaluation of diurnal patterns may be useful for identifying the influence of changes in emission levels versus meteorological variation on attainment status. Using data from the southern California and Dallas-Fort Worth sites, which showed improvements in 03 levels, changes were observed in the seasonally averaged diurnal profiles. On the other hand, for the sites moving between attainment and nonattainment status, such a change in shape was generally not observed and it was possible that meteorology played a more important role than changes in emission levels relative to attainment status.     

Assessment of the nested grid model estimates for driving regional visibility models in the southwestern United States

The Nested Grid Model (NGM) is a primitive-equation meteorological model that is routinely exercised over North America for forecasting purposes by the National Meteorological Center. While prognostic meteorological models are being increasingly used to drive air quality models, their use in conducting annual simulations requires significant resources. NGM estimates of wind fields and other meteorological variables provide an attractive alternative since they are typically archived and readily available for an entire year. Preliminary evaluation of NGM winds during the summer of 1992 for application to the region surrounding the Grand Canyon National Park showed serious shortcomings. The NGM winds along the borders between California, Arizona and Mexico tend to be northwesterly with a speed of about 6 m/sec, while the observed flow is predominantly southerly at about 2-5 m/sec. The mesoscale effect of a thermal low pressure area over the highly heated Southern California and western Arizona deserts does not appear to be represented by the NGM because of its coarse resolution and the use of sparse observations in that region. Tracer simulations and statistical evaluation against special high resolution observations of winds in the southwest United States clearly demonstrate the northwest bias in NGM winds and its adverse effect on predictions of an air quality model. The "enhanced" NGM winds, in which selected wind observations are incorporated in the NGM winds using a diagnostic meteorological model provide additional confirmation on the primary cause of the northwest bias. This study has demonstrated that in situations where limited resources prevent the use of prognostic meteorological models, previously archived coarse resolution wind fields in which additional observations are incorporated to correct known biases provide an attractive option.     

Haze trends over the United States, 1980–1995

The patterns and trends of haze over the United States for the period of 1980–1995 are presented. Haze measurements are based on human visual range observations at 298 synoptic meteorological stations operated by the United States Weather Service. There was a significant (∼10%) decline in haziness over the 15-yr period. The reductions were evident throughout the eastern United States as well as over the hazy air basins of California. During the same period, in the eastern United States sulfur emissions also declined by about 10%. However, a causality for the reductions has not been established. This report is an update of an earlier survey of haze patterns and trends from 1950 to 1980.     

Long-range transport of polycyclic aromatic hydrocarbons from China to Japan

Airborne particulate matter was collected at Wajima, on the Noto Peninsula, Ishikawa, Japan by a high-volume air sampler with a quartz filter every week from 17 September 2004 to 16 September 2005. Polycyclic aromatic hydrocarbons (PAHs) extracted from filters were analyzed by HPLC with fluorescence detection. The atmospheric concentrations of PAHs at Wajima were higher during the heating period of China (when coal is burned for heat) than during the no-heating period. A meteorological analysis indicated that the air samples collected in that heating period at Wajima were transported mainly from Northeast China over the Japan Sea. Principal component analysis of nine PAHs indicated a Chinese origin of the PAHs. These results strongly suggest that the high-level PAHs detected at Wajima were the result of long-range transport from China.     

Ambient Air Measurements of Petroleum Refinery Emissions

An ambient air monitoring program to characterize airborne emissions from the Exxon petroleum refinery at Benicia, California was conducted during September 8–22, 1975. Ground level sampling facilities and an instrumented aircraft provided an integrated, three-dimensional monitoring network. Measurements made during the study included ozone, oxides of nitrogen, methane, carbon monoxide, individual C₂-C₆ hydrocarbons, halocarbons, condensation nuclei, visual distance and various meteorological parameters. The study focused on three major areas: (1) the characterization of gaseous components within the refinery effluent, especially non-methane hydrocarbons and ozone, (2) natural sunlight bag irradiation experiments to determine the ozone forming potential of refinery emissions, and (3) an investigation of changes in plume chemistry as refinery emissions were transported downwind.     

Assessment of the Nested Grid Model Estimates for Driving Regional Visibility Models in the Southwestern United States

ABSTRACT

The Nested Grid Model (NGM) is a primitive-equation meteorological model that is routinely exercised over North America for forecasting purposes by the National Meteorological Center. While prognostic meteorological models are being increasingly used to drive air quality models, their use in conducting annual simulations requires significant resources. NGM estimates of wind fields and other meteorological variables provide an attractive alternative since they are typically archived and readily available for an entire year. Preliminary evaluation of NGM winds during the summer of 1992 for application to the region surrounding the Grand Canyon National Park showed serious shortcomings. The NGM winds along the borders between California, Arizona and Mexico tend to be northwesterly with a speed of about 6 m/sec, while the observed flow is predominantly southerly at about 2-5 m/sec. The mesoscale effect of a thermal low pressure area over the highly heated Southern California and western Arizona deserts does not appear to be represented by the NGM because of its coarse resolution and the use of sparse observations in that region. Tracer simulations and statistical evaluation against special high resolution observations of winds in the southwest United States clearly demonstrate the northwest bias in NGM winds and its adverse effect on predictions of an air quality model. The “enhanced” NGM winds, in which selected wind observations are incorporated in the NGM winds using a diagnostic meteorological model provide additional confirmation on the primary cause of the northwest bias. This study has demonstrated that in situations where limited resources prevent the use of prognostic meteorological models, previously archived coarse resolution wind fields in which additional observations are incorporated to correct known biases provide an attractive option.     

Seasonal source-receptor relationships in a petrochemical industrial district over northern Taiwan

This study investigated the relationships between meteorological data, pollution sources, and receptors over northern Taiwan. During the intensive sampling period in summer 1992, the weather was controlled predominantly by a Pacific subtropical high and by Typhoon Mark. During the other intensive sampling period in winter 1993, while a cold frontal system approached Taiwan, the northeasterly winds prevailed most of the time. The local circulation such as land-sea breeze only developed under weak synoptic environment. Particle concentrations and element composition in winter were higher than in summer. This can be attributed to the high convection of air mass, which leads to the vertical dispersion of pollutants in summer. In addition to the subtropical high pressure, typhoons are frequently accompanied with high-wind speeds and unstable weather conditions that also dilute and eliminate the pollutants. In winter, the prevailing northeasterlies might carry pollutants from Midland China. Furthermore, the anticyclone system develops a stagnant condition that easily leads to pollutant accumulation. In this case, the wind direction affected the source contribution of the receptor and the PM10 displays a higher correlation with coarse and fine particulate than meteorological parameters in summer. In addition, the mixing height shows a high correlation with PM10 in winter.     

Adapting air quality management for a changing climate: Survey of local districts in California

Air quality can be affected by weather and thus is sensitive to a changing climate. Wildfire (influenced by weather), consecutive high temperature summer days, and other extreme events are projected to become more severe and frequent with climate change. These may create challenging conditions for managing air quality despite policy targets to reduce precursor and pollutant emissions. Although extreme events are becoming more intense and interest in climate adaptation is increasing among public health practitioners, little attention in scholarly literature and policy covers climate adaptation for air quality governance. Understanding the management and managers’ perspectives at the local level provides insight about the needs for climate adaptation, including their adaptation status, perspectives, responsibilities, and roles. This study explores local manager perspectives and experiences of managing air quality within a changing climate as one puzzle piece to understand the gap in climate adaptation within the air quality sector. A broader goal is to contribute to the discussion of developing a multi-jurisdictional vision for reducing the impacts of air quality in a changing climate. In 2016 local air quality district managers in California were invited to participate in an online survey of 39 questions focused on extreme event impacts on air quality. The questionnaire focused on present air quality threats and extreme event challenges, adaptation status and strategies, adaptive capacities, perceived barriers to adaptation, and jurisdictional responsibilities and roles. Over 85 percent of the 35 local air districts in California participated in the survey, which represents 80 percent of the state’s population. High awareness and knowledge of climate change among local managers indicates they are ready to adopt and take action on policies that would support climate adaptation, but barriers reported suggests they may need policies and adequate funding to take action and make necessary changes.

Implications: Downscaled global climate models project an increasing severity and frequency of extreme events. In the southwestern United States, these include wildfire, heat events, and dry periods, among others, all of which can place an extra burden on air quality managers and emitters to achieve air quality standards even as they reduce emissions. Despite climate change presenting increasing challenges to meet air quality standards, in the southwestern United States, policy and action to mitigate these impacts have been surprisingly absent. California presents a valuable case study on the topic because of its historic leadership in air quality management for the United States and also because of its initiatives in combating climate change. Yet still we found that adaptation has not been incorporated into air quality management thus far, but local managers seem sufficiently knowledgeable and willing.     

An assessment of source contributions to the ozone concentrations in southern Ontario, 1979–1985

Source contributions to the surface O₃ concentrations in southern Ontario were assessed for the 1979–1985 period. Ozone episode analyses indicate a frequency of about nine episodes per year (15 episode-days). These occur primarily in the summer months and are generally manifestations of the northern extent of the O₃ problem in eastern North America. Widespread elevated O₃ levels tend to occur under weather classes indicative of back or centre of the high pressure situations and associated flow/trajectory from areas south/southwest of the lower Great Lakes. These episodes vary considerably from year-to-year. Local impacts on O₃ levels are generally small.A study of O₃ levels during cloud-free summer days for the period 1981–1985 gave local ‘background’ O₃ levels of about 20–30 ppb daily and 30–50 ppb hourly maxima. The O₃ contributions from the U.S. to southern Canada (assuming local ‘background’ O₃ levels to be independent of wind direction) were estimated to be 30–35 ppb daily and 30–50 ppb hourly maxima. These results indicate an overall O₃ contribution of about 50–60% from the U.S. to southern Ontario. For episode-days, the U.S. contribution is even more significant.     

Atmospheric Aerosol Composition and Concentration as a Function of Particle Size and of Time

As a step toward better understanding the reactive Los Angeles air basin atmosphere, a study was undertaken at the University of California—Riverside Campus, to determine the composition and concentration of atmospheric particulate matter as a function of particle size and time. The study involved developing a method for obtaining size-classified, time-fractionated aerosol samples amenable to chemical and physical (including microscopic) analysis. During a 15-day period, samples were obtained over 4-hr periods and subsequently analyzed for nitrate, sulfate, iron, and lead. Concentration of six gaseous pollutantsj total aerosol light-scattering, and several meteorological measurements were simultaneously recorded and averaged over the 4-hr intervals. This data was presented graphically to show the diurnal variation in and relationship between gaseous, particulate, and meteorological measurements. A strong relationship between gaseous peroxyacetyl nitrate, particulate nitrate, and aerosol light-scattering was found. High concentrations of ammonium nitrate particles, mainly in the 0.5-2μ, diameter size range, were found in the atmospheric particulate samples collected on days of very high smog (very limited visibility).     

Oxalic acid in PM2.5 particulate matter in California

Ambient air monitoring for organic acids in PM2.5 was conducted at several locations in California. During the study, it was found that oxalic acid (ethanedioc acid) was the most abundant organic acid found in the PM2.5 fraction. Samples from Azuza (in southern California), San Jose (in the San Francisco Bay area), and Fresno (in central California), a PM2.5 Super Site, were collected in 1999 and analyzed. The results for oxalic acid concentrations during this monitoring effort are presented.     

meteorological program for limiting power plant stack emission

This paper is directed to those individuals concerned with preserving the local air quality in areas affected by power plant operations. A meteorological forecast and field measurement program has been developed by the Tennessee Valley Authority for limiting stack emissions at the Paradise Steam Plant to preserve the air quality during adverse atmospheric dispersion conditions. Meteorological and plume dispersion criteria, developed from analysis of prior experience, govern the program. The criteria values are designed for limiting surface sulfur dioxide (SO₂) concentrations below an established threshold level.

Daily forecasts of vertical wind and temperature distribution, maximum surface temperature, and sky condition are issued each afternoon by the National Oceanic and Atmospheric Administration National Weather Service, Knoxville, Tennessee. Through use of power plant computer facilities, the forecast data are processed to determine quantitative criteria values. If the values indicate that the threshold level may be exceeded, an Air Pollution Control Notice (APCN) is issued that afternoon for the period 0900–1400 CST the following day, which is the expected period of maximum SO₂, surface concentrations. The APCN specifies the allowable SO₂ emission rate, in terms of megawatt load generation, which should prevent surface SO₂ concentrations from exceeding the established threshold level. Confirmation or cancellation of the APCN is made the following morning, based on plant-site meteorological field measurements taken at 0700–0730 CST. If confirmed, plant load generation is reduced to the designated level by 0900 CST and is continued no later than 1400 CST during the expected period of maximum SO2 surface concentrations.

The APCN conditions identified with the newer and larger TV A power plants with high stacks are associated with one principal regional weather pattern—a large surface high-pressure system, with weak-to-moderate anticyclonic circulation and pronounced stability throughout the lowest few thousand meters. With the limited mixing layer, or sometimes referred to as trapping- or capping-type dispersion associated with this weather condition, relatively high surface concentrations may persist 2–5 hours between 0900–1400 CST.     

Modeling Short Range Air Dispersion from Area Sources of Non-buoyant Toxics

A model based on K-theory has been developed for describing the short range air dispersion from area sources of non-buoyant toxics. Model parameter estimation is via boundary layer theory. Lateral dispersion by plume meander is considered but ail other sources of horizontal dispersion are neglected. The model can be applied on and near area sources and it can be adapted for predictions of downwind concentrations with a wide variety of meteorological Inputs.

The model has been evaluated by simulating the data obtained during atmospheric tracer studies and by comparison to vinyl chloride concentrations near the BKK landfill in southern California. The model appears to represent a useful and accurate tool for regulatory planning and risk assessment close to area sources of toxics.     

Synoptic weather patterns and their relationship to high ozone concentrations in the Taichung Basin

Frequent high ozone days (defined as daily maximum ozone concentration ⩾80 ppb) during recent years in the Taichung Basin have caused much concern. High ozone days occur mainly during autumn and spring. Statistically, there is no clear linear relationship between a single meteorological variable and ozone concentration. In this study, data from 1996–2000 has shown that high ozone concentrations occur during two types of synoptic weather patterns. The first type is a continental cyclone emanating from mainland China, the southern part of it swept towards Taiwan by easterly winds. The second pattern is a tropical depression moving northwards toward the region, the northern part of it affecting Taiwan via easterly winds. Both types cover Taiwan with easterly winds, which are blocked by the Central Mountain Ranges (altitude of 2000–3000 m). The ranges create lee cyclogenesis to the west, which is unfavorable for pollutant dispersion and leads to serious air pollution episodes.The statistical results of the synoptic weather patterns in relation to ozone concentrations are based on the 5 yr data (1996–2000). This was obtained from a network of air-pollution monitoring sites in the study area, while the vertical data come from two 3-day tethersonde experimental campaigns conducted during March and October 2000, measuring air pressure, air temperature, relative humidity, wind speed and direction, non-methane hydrocarbons, NO_x and O₃.     

Seasonal Source-Receptor Relationships in a Petrochemical Industrial District over Northern Taiwan

Abstract

This study investigated the relationships between meteorological data, pollution sources, and receptors over northern Taiwan. During the intensive sampling period in summer 1992, the weather was controlled predominantly by a Pacific subtropical high and by Typhoon Mark. During the other intensive sampling period in winter 1993, while a cold frontal system approached Taiwan, the northeasterly winds prevailed most of the time. The local circulation such as land-sea breeze only developed under weak synoptic environment. Particle concentrations and element composition in winter were higher than in summer. This can be attributed to the high convection of air mass, which leads to the vertical dispersion of pollutants in summer. In addition to the subtropical high pressure, typhoons are frequently accompanied with high-wind speeds and unstable weather conditions that also dilute and eliminate the pollutants. In winter, the prevailing northeasterlies might carry pollutants from Midland China. Furthermore, the anticyclone system develops a stagnant condition that easily leads to pollutant accumulation. In this case, the wind direction affected the source contribution of the receptor and the PM₁₀ displays a higher correlation with coarse and fine particulate than meteorological parameters in summer. In addition, the mixing height shows a high correlation with PM₁₀ in winter.     

Air pollution characteristics associated with mesoscale atmospheric patterns in northwest continental Europe

An impact related daily air quality index (DAQx), calculated for 15 air quality monitoring stations (traffic, background, and industry) in Belgium, France, Germany and Luxembourg, was compared to mesoscale atmospheric patterns between 2001 and 2007. Meteorological conditions were described by the Hess and Brezowsky synoptic weather classification system and gridded data of the EU FP6 ENSEMBLES project of total precipitation and mean surface temperature. DAQx values indicate sufficient to poor air quality in the urban area of Brussels and at urban traffic stations, as well as satisfactory air quality at the background stations. The air quality index refers to more than 90% to the presence of high PM₁₀, O₃ and NO₂ concentrations. SO₂ and CO play only a minor role. The investigation of weather regimes indicates that zonal and mixed cyclonic circulation regimes are associated with better air quality than meridional and anticyclonic weather regimes. In general, weather regimes with high daily precipitation lead to better air quality than dryer air masses because of lower contribution of PM₁₀ to the air quality index. A trend analysis of weather regimes from 1978 to 2007 shows significant (α = 0.05) positive trends for weather classes associated with lower PM₁₀ concentrations. The results of a case study at a German station examining the relationship between PM₁₀ concentrations and local meteorological quantities (wind speed and precipitation) confirm the results of the regional analysis.     

Environmental specimen bank samples of Pleurozium schreberi and Hylocomium splendens as indicators of the radiation environment at the surface

Pleurozium schreberi (Brid.) Mitt. and Hylocomium splendens (Hedw.) Schimp. samples from the Finnish Environmental Specimen Bank were used to study the UV-B-absorbing compounds as potential screens of the past radiation environment. The first series from southern and central Finland consisted of samples collected from 18 P. schreberi or H. splendens dominated sites in 1985 and 1995. The second series from four H. splendens dominated sites (two in southern and two in northern Finland) and two P. schreberi dominated sites (one southern and one northern) were from the years 1985, 1990, 1995 and 2000. In the first series, the moss surface area of the analyzed specimens (5 +/- 0.2 mg DW) was smaller in 1995 (40% of both species collected in June) than in 1985 (40% of P. schreberi and 55% of H. splendens collected in September). The methanol-extractable UV-B-absorbing compounds of P. schreberi in 1985 and 1995 measured as absorbance at 10 nm intervals at 280-360 nm per mg DW revealed a negative correlation with reconstructed UV-radiation data. In the second series, the UV-B-absorbing compounds per specific surface area (surface area mm2 per DW) showed significant differences between the years. The highest values in both species were obtained in 1990. In H. splendens, a difference between the southern and northern samples was observed. The preliminary study encouraged the use of environmental specimen bank samples to indicate changes in surface radiation conditions.