VISIBILITY DEGRADATION AND METEOROLOGY IN THE BOULDER VALLEY by George M. Mathews, Jr. AKTHim LAKES LÏB1A1Y COlOmDO gC’JOOL oi MINES nOLDSN. COLORADO 80*01 ProQuest Number: 10783590 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a com plete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest ProQuest 10783590 Published by ProQuest LLO (2018). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States C ode Microform Edition © ProQuest LLO. ProQuest LLO. 789 East Eisenhower Parkway P.Q. Box 1346 Ann Arbor, Ml 48106- 1346 T-3870 À thesis submitted to the Faculty and the Board of Trustees of the Colorado School of Mines in partial fulfillment of the requirements for the degree of Master of Science, Mineral Resources Ecology. Golden, Colorado Date ^I 11^0 Signed: ITI eorge M. Mathews, Jr. Approved: :dward A. Howard, Ph.D. Thesis Advisor Golden, Color^o Date JohnVAC Cordes Department Head Dq^rtment of Environmental Sciences and Engineering Ecology 11 T-3870 ABSTRACT This study demonstrated significant differences in the micrometeorologic conditions associated with different types of poor visual air quality events and that these differences were linked with mesoscale and synoptic weather features. For the study period December 1988 through January 1989, 51 identified poor visual air quality events in Boulder, Colorado were categorized into two groups, those caused by transported pollution and those caused by locally generated pollution. The classification procedure was based on the ratio of the peak particle light scattering coefficient during an event to the mean coefficient of the 4 preceding hours. Periods of acceptably clear visibility, 10 for each month, were randomly selected from the remaining time spans. The classification procedure was more applicable to the December 1988 group than to the January 1989 group. Nonparametric and parametric statistical tests were applied to seven météorologie variables for the three visibility groups. Significant differences were found among the wind speeds, wind directions, relative humidities, inversion heights, and event timings in relation to a diurnal wind shift associated with the three groups. No significant differences were detected for the net radiation and snow iii T-3870 cover associated with the two types of poor visual air quality events. A brief comparison of poor visibility events and high carbon monoxide periods was conducted. This project suggested that meteorology was a major factor governing the levels of fine particulates, but not of carbon monoxide, in instances of pollution transport. In contrast, during local pollution events meteorology played a minor role in the different temporal patterns of the two pollutants. Three case study days, one each to represent acceptable visibility, transport pollution, and local pollution were examined in detail. Regional changes in the pressure gradient along the lee side of the mountains, because of movement of a synoptic low pressure trough, were seen as the driving force behind transport of a polluted air mass. IV T-3870 TABLE OF CONTENTS Page ABSTRACT iii LIST OF FIGURES vii LIST OF TABLES ix ACKNOWLEDGMENTS x INTRODUCTION 1 Visibility Theory 1 State of Colorado Visibility Standard 5 Previous Visibility Studies in the Denver Metro Area 6 Project Objectives 11 AVAILABLE DATA SET 12 METHODS 17 ANALYSIS AND RESULTS 21 Interpretation of a Poor Visibility Event 21 Determination of a Threshold b 21 Frequency Distributions of Nephelometer Data 29 Effect of Relative Humidity 29 Definition of a Poor Visibility Event 38 Identification of Poor Visibility Events 39 Classification of Poor Visibility Events 44 Statistical Methods 49 Météorologie Variables 49 Wind speed 49 Wind direction 51 Relative humidity 51 Inversion height 53 Time of event start in relation to a diurnal wind shift 56 Net radiation 63 Snow cover 63 Discussion 66 Relationships Between Poor VAQ Events and High Carbon Monoxide Periods 71 T-3870 TABLE OF CONTENTS (continued) Page Phenomenological Descriptions of Selected Case Days 74 Acceptable Visibility Period: December 03, 1988 74 Transport Poor VAQ Event: December 29, 1988 80 Locally Generated Poor VAQ Event: December 30, 1988 89 CONCLUSIONS 95 REFERENCES CITED 98 Appendix A. Visual Air Quality Events of December 1988 104 Appendix B. Visual Air Quality Events of January 1989 110 VI T-3870 LIST OF FIGURES No. Title Page 1. Boulder Air Quality Study, Winter of 1988-1989, Monitoring Sites. 13 2. PROFS Mesonet Monitoring Sites. 16 3. Heated Nephelometer, SCT. December 1988. 27 4-a. Frequency Distribution of Unheated Nephelometer, SCT. Dec 1988. 3 0 4-b. Frequency Distribution of Heated Nephelometer, SCT. Dec 1988. 31 4-c. Frequency Distribution of Unheated Nephelometer, SCT. Jan 1989. 32 4-d. Frequency Distribution of Heated Nephelometer, SCT. Jan 1989. 33 5. Field and Calculated Unheated Nephelometers, SCT. Dec 1988. 3 5 6. Field and Calculated Nephelometers, SCT. Dec 15, 1988. 36 7. Field and Calculated Nephelometers, SCT. Dec 24-25, 1988. 37 8. Heated Nephelometer, SCT. Dec 6-7, 1988. 41 9. Heated Nephelometer, SCT. Dec 15, 1988. 42 10. Heated Nephelometer, SCT. Dec 27, 1988. 43 11. Frequency Distribution of Peak/Mean Ratios of 28 Poor VAQ Events, Dec 1988. 47 12. Frequency Distribution of Diurnal Wind Shift Times, 47 Observations, Dec 1988-Jan 1989. 57 Vll T-3870 LIST OF FIGURES (continued) No. Title Page 13. Frequency Distribution of the Times of Event Peaks, 51 Poor VAQ Events, Dec 1988-Jan 1989. 58 14. Frequency Distribution of the Times of Event Starts, 51 Poor VAQ Events, Dec 1988-Jan. 1989. 59 15. Heated Nephelometer, SCT vs CO, XRD. Dec. 1988. 72 16. Dec 03, 1988. Wind Direction and Speed. SCT. 76 17. Dec 03, 1988. Pressure Differential: PROFS Erie - Boulder. 77 18. Dec 03, 1988. Heated Nephelometer, SCT. CO, XRD. 79 19-a.Dec 29, 1988, llOOMST. Surface Pressures. 82 19-b.Dec 29, 1988, 1400MST. Surface Pressures. 83 19-c.Dec 29, 1988, 1700MST. Surface Pressures. 84 20-a.Dec 29, 1988. Heated Nephelometer, SCT. Wind Direction, XRD. 85 20-b.Dec 29, 1988. CO and Wind Direction, XRD. 85 21. Dec 29, 1988, 1300hr. Vertical Temperature Profile, XRD. 86 22. Dec 29, 1988. Pressure Differential: PROFS Erie - Boulder. 88 23. Dec 30, 1988. Wind Direction, XRD. Wind Speed, SCT. 90 24. Dec 30, 1988. Heated Nephelometer, SCT. Carbon Monoxide, XRD. 91 25. Dec. 3, 1988. Pressure Differential: PROFS Erie - Bouler. 94 viii T-3870 LIST OF TABLES No. Title Page 1. Statistics and Test Results for Wind Speed. 50 2. Statistics and Test Results for Wind Direction. 52 3. Statistics and Test Results for Relative Humidity. 54 4. Statistics and Test Results for Inversion Height. 55 5. Statistics and Test Results for Time of Event Start in Relation to a Diurnal Wind Shift. 61 6. Statistics and Test Results for Net Radiation. 64 7. Statistics and Test Results for Snow Cover. 65 8. Summary of Statistical Test Results for Météorologie Variables. 68 IX T-3870 ACKNOWLEDGMENTS I am grateful to my advisor Dr. Edward A. (Al) Howard for the optimism and encouragement that he extended to me from my initial inquiries about the environmental science programs at the Colorado School of Mines through the research and writing of this thesis project. I also want to recognize the other faculty members of my advisory committee. Dr. Ronald R. Cohen and Dr. Bruce Van Haveren, for their thoughtful suggestions, advice, and enthusiastic participation. To the secretary of the Department of Environmental Sciences and Engineering Ecology, Juanita Chuven, I extend a heartfelt thanks for her energy and dedication to the students of the department. I am deeply indebted to the staff of the National Oceanic and Atmospheric Administration, Wave Propagation Laboratory, in Boulder, Colorado. I am especially thankful to John E. Gaynor for giving me day to day guidance and teaching on this project, and for sharing his office for many months. Without his active interest and participation in these endeavors, this project could not have been accomplished. I am also grateful to David C. Welsh, Leslie K. Lewis, and Vivian LeFebvre for their patient instruction T-3870 in computer science, and to Daniel E. Wolfe, Richard B. Fritz, Clark W. King, Herman Sievering, Barry A. Bodhaine, and Amy S. Wyngaard for their technical support. Finally, I want to thank the Boulder County Health Department staff, especially Tom Douville, Environmental Health Program Manager, for allowing me the scheduling flexibility to pursue my educational goals. XI T-3870 INTRODUCTION Like many communities along the Front Range of Colora­ do, the City of Boulder endures days and longer periods of visibility degrading pollution during the winter months. While the influence of meteorology on visual air quality in nearby Denver and the South Platte River basin has been investigated in several studies, research into relationships between meteorology and air pollution of the Boulder Valley has only recently commenced. To date, examination into these relationships has addressed primarily carbon monoxide and only incidentally visibility degrading particulates. A detailed analysis of micrometeorologies, with related meso­ scale and synoptic weather patterns, that lead to episodes of poor visual air quality in the upper Boulder Valley has not yet been presented. This project used statistical analysis and descriptive phenomenology to investigate the relationships among micrometeorologic variables to two types of poor visual air quality (VAQ) events, those caused by pollution transport and those produced by local sources. Visibilitv Theory Visibility has historically been defined in terms of the greatest distance at which an observer can just distin­ guish a black object contrasted against the horizon sky T-3870 (Malm, 1983).