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.     

The length of growing season and adult sex ratio affect sexual size dimorphism in moose

While factors affecting body growth have been extensively studied, very little is known about the factors likely to affect the sexual size dimorphism (SSD) in polygynous mammals. Based on the carcass mass of 24420 male and female moose recorded in 14 Norwegian populations, we examine three hypotheses to explain geographical variation in SSD. First, SSD is expected to decrease when the relative density of animals (for a given habitat quality) increases, because resource limitation at high population densities is assumed to affect body growth of males more than females. Second, because males are selected to invest in growth more than females, environmental seasonality and related improvement of the forage quality during the short and intense growing season are expected to increase SSD. Third, by decreasing the proportion of adult males in the population, resulting in start of rutting earlier in life, hunting may decrease the SSD by increasing the reproductive cost of young males. We found that males grew faster and for a longer time of their life than did females and thus were heavier (-24%) when they reached adulthood. Sexual size dimorphism was independent of density but was higher in areas with short growing seasons. The low SSD in populations with largely adult female-biased sex ratios (males per female) shows that male body growth decreases with a decreasing proportion of adult males in the population. Our results indicate that geographical variation in moose SSD is influenced by divergent responses in the sexes to ecological factors affecting body growth.     

Safety-culture in a Norwegian shipping company

Problem: Although there has been considerable interest in safety culture and safety climate in many industries, little attention has been given to safety culture in one of the world's riskiest industries, shipping. Method: Using both self developed items and items from published research on safety culture, safety climate, and quality and management style, a 40-item safety culture questionnaire was developed. The questionnaire was distributed in a self-administered form to sailors onboard 20 vessels and to officers attending a seminar in Manila. A total of 349 questionnaires were collected (total response rate, 60%). Results, discussion and impact on industry: Principal component analysis (PCA) revealed 11 factors when the Kaiser eigenvalue rule was used and four factors when the scree test criterion was used. The factor structure in the material confirmed structures found in other industries. The relative importance of the factors from the factor analysis on “level of safety” measures was tested by canonical correlation analysis and regression analysis. The results confirmed previous research and showed that the most important factors were influential across industries. To determine weather differences existed between nationalities, occupations, and vessels the factors from the PCA was subjected to Multiple Discriminant Analysis. Significant differences between occupations, nations, and vessels were found on one or more of the factors from the PCA.     

Safety culture aboard fishing vessels

Safety at sea is a serious issue for the commercial fishing industry. Injury and fatality rates are between 25 and 40 times the national average in many European counties, Australia and the USA. A 50-item safety culture questionnaire was developed, using items from published research combined with some original items. The questionnaire was distributed to fishermen who completed the responses. A total of 209 questionnaires were collected. Principal Component Analysis (PCA) revealed nine factors, all with a Cronbach’s Alpha higher than 0.68. The factors were tested using ANOVA, t-tests, correlations and regression analysis.The findings indicate significant differences between age groups, vessel types, occupations, and whether or not a close family member is a fisherman. It was also found that the safety attitude of management had a strong influence on a company’s safety policy. Fishermen who had sought medical attention during the preceding year as a result of an accident showed a significantly less positive attitude to rules and regulations and had a less positive safety attitude in general. Fishermen who had been involved in a serious accident/incident showed a significantly more positive attitude to rules and regulations.     

Natural background visibility and regional haze goals in the Southeastern United States

The goal of the regional haze mitigation program in the United States is to attain "natural conditions" in national parks and wilderness areas by 2064. Results of research investigations on background concentrations of sea salt and biogenic organic matter, of episodic Saharan and Asian dust, and of carbon from natural fires were reviewed to provide a basis for making site-specific estimates of what the concentrations of atmospheric fine particulate matter components might be under natural conditions in the Southeastern United States. Based on this review, rough estimates were made of potential contributions of these aerosol components to natural background visibility. Natural organic particles were the dominant influence on the rate of visibility improvement required to reach natural conditions at an inland, mountainous location, and organic particles and sea salt were the dominant influences on the rate at a coastal location. African dust also had a large episodic effect, but the current regulatory approach is not designed to address episodic background variations. Insufficient data exist to quantify the contributions of wildfires with any detail, although global air pollution modeling provides insight, and their emissions can be locally dominant. Conservative regional refinements to the default natural background estimates do not greatly alter the region-wide rates of reduction of ambient particulate matter concentrations that will be needed to accomplish the first phase of the regional haze program. However, refinements at specific Class I areas may have considerable influence on defining the nature (magnitude and spatial and temporal distribution) of local emission reduction efforts there.     

Cigarette smoking and nickel exposure

The tobacco plant contains nickel and several other toxic metals, most probably absorbed from the soil, fertilizing products or from pesticides. It has been stated that nickel in a burning cigarette might form the volatile, gaseous compound, nickel tetracarbonyl, and thereby be introduced into the respiratory tract. Accordingly, the main objective of the present study was to find out if nickel content in inhaled smoke from ordinary cigarettes and nickel-contaminated cigarettes handmade by nickel process workers might be a supplementary source of nickel exposure to cigarette smoking process workers leading to additional risk of occupational respiratory cancer in these workers. Blood and urine samples from 318 randomly selected employees from Falconbridge Nickel Refinery in Kristiansand, Norway, allocated to 197 smokers and 121 non-smokers, were analysed for nickel content. Nickel quantities in tobacco from various cigarette brands, from nickel-contaminated cigarettes made by process workers or from cigarettes added known amounts of various nickel salts were analysed before being smoked. The cigarettes were smoked in a smoking machine device applying an electrostatic filter. Blood and urine, tobacco, ash and precipitates in the filter from the main stream smoke of the cigarettes were analysed for nickel quantities by atomic absorption spectrometry methods as previously described by the authors. The nickel concentrations in blood plasma and urine were quite similar among smokers and non-smokers, 6.2 and 48.1 microg L(-1) in smokers, and 6.4 and 50.5 microg L(-1) in non-smokers respectively. We recovered 1.1% or even less of nickel in the mainstream smoke after smoking the entire cigarettes without leaving any butt. Most of the tobacco nickel was recovered in the ash. We conclude that the inhaled nickel in the working atmosphere is probably the main source of the nickel exposure to the respiratory tract in these workers. It remains to be determined why cigarette smoking still seems to be a decisive cofactor in the development of respiratory tract cancer in nickel workers.     

An Analysis of Visual Range in the Eastern United States Under Different Meteorological Regimes

ABSTRACT

The issue of fine particle (PM₂₅) exposures and their potential health effects is a focus of scientific research because of the recently promulgated National Ambient Air Quality Standard for PM_{2 5}. Before final implementation, the health and exposure basis for the standard will be reviewed by the U.S. Environmental Protection Agency within the next five years. As part of this process, it is necessary to understand total particle exposure issues and to determine the relative importance of the origin of PM_{2 5} exposure in various micro-environments. The results presented in this study examine emissions of fine particles from a previously uncharacterized indoor source: the residential vacuum cleaner. Eleven standard vacuum cleaners were tested for the emission rate of fine particles by their individual motors and for their efficiency in collecting laboratory-generated fine particles. An aerosol generator was used to introduce fine potassium chloride (KC1) particles into the vacuum cleaner inlet for the collection efficiency tests. Measurements of the motor emissions, which include carbon, and the KCl aerosol were made using a continuous HIAC/Royco 5130A light-scattering particle detector. All tests were conducted in a metal chamber specifically designed to completely contain the vacuum cleaner and operate it in a stationary position. For the tested vacuum cleaners, fine particle motor emissions ranged from 9.6 x 10⁴ to 3.34 x 10⁸ particles/min, which were estimated to be 0.028 to 176 mg/min for mass emissions, respectively. The vast majority of particles released were in the range of 0.3-0.5 mm in diameter. The lowest particle emission rate was obtained for a vacuum cleaner that had a high efficiency (HEPA) filter placed after the vacuum cleaner bag and the motor within a sealed exhaust system. This vacuum cleaner removed the KC1particles that escaped the vacuum cleaner bag and the particles emitted by the motor. Results obtained for the KC1 collection efficiency tests show >99% of the fine particles were captured by the two vacuum cleaners that used a HEPA filter. A series of tests conducted on two vacuum cleaners found that the motors also emitted ultra-fine particles above 0.01 mm in diameter at rates of greater than 10⁸ ultra-fine particles/CF of air. The model that had the best collection efficiency for fine particles also reduced the ultra-fine particle emissions by a factor of 1 x 10³.     

Thermodynamic analysis on post-combustion CO2 capture of natural-gas-fired power plant

A chemical absorption, post-combustion CO₂ capture unit is simulated and an exergy analysis has been conducted, including irreversibility calculations for all process units. By pinpointing major irreversibilities, new proposals for efficient energy integrated chemical absorption process are suggested. Further, a natural-gas combined-cycle power plant with a CO₂ capture unit has been analyzed on an exergetic basis. By defining exergy balances and black-box models for plant units, investigation has been made to determine effect of each unit on the overall exergy efficiency. Simulation of the chemical absorption plant was done using UniSim Design software with Amines Property Package. For natural-gas combined-cycle design, GT PRO software (Thermoflow, Inc.) has been used. For exergy calculations, spreadsheets are created with Microsoft Excel by importing data from UniSim and GT PRO. Results show the exergy efficiency of 21.2% for the chemical absorption CO₂ capture unit and 67% for the CO₂ compression unit. The total exergy efficiency of CO₂ capture and compression unit is 31.6%.