Pollutant Transport Analyses

Definitions
Investigate Air Quality Characteristics and Transport in a Region
Useful Data for 3-D Analyses
Pollutant Transport Issues
Approaches to Quantifying Transport
Investigate Boundary Layer Structure and Evolution
Case Studies
Constructing A Case Study
Transport into and within the Lake Michigan Air Quality Region on July 18, 1991
Isentropic Analysis
Analysis of Ventilation and Recirculation
Performing Trajectory Analyses
Trajectory Analyses of Surface and Aloft Transport
Other Tasks for Case Study Analyses
Investigate Other Available Data
Methods for Estimating Relative Emission Contributions
Summary
References

• Investigate surface meteorology and air quality data, especially including diurnal patterns during times of maximum ozone concentrations.
• Investigate aloft meteorology and air quality including cross sections, nocturnal jet, sea breeze, satellite photos, isentropic analyses, etc.
• Develop hypotheses concerning transport and evaluate them against data.

PAMS Data

• PAMS requirements are for one upper-air station per PAMS network with four soundings per day of winds and temperature. Instruments that provide these are rawinsondes, radar wind profilers with radio acoustic sounding systems (RASS), and sodars with RASS.

Radar wind profilers with RASS provide hourly averaged vertical profiles of winds, virtual temperature, and related quantities such as the radar reflectivity structure parameter, which can be used to estimate mixing depth.

Non-PAMS Data

• Aircraft instrumented to measure ozone, NO, NO_y, hydrocarbons, carbonyl compounds, SO₂, CO, meteorological observables, position, and altitude.
• Satellite photographs.
• Tethersondes and ozonesondes measurements of ozone concentrations as a function of altitude.

• Definition of boundaries (and scale)
• Pollutants: O₃ and precursors
• Continuing reaction to form ozone
• Transport versus carryover (recirculation)
• Aloft and surface
  - Air Quality
  - Winds
• Transport time
• Characteristics along transport path
• Where (origin, route)?
• When?
• How frequent?
• How much?
• How to compare with 'local'?

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• Boundary measurements
• Estimate flux (e.g. mass/time)
• Ventilation
• Compare with 'local' ozone and/or total ozone
• Compare with 'local' precursor and/or total precursors
• Trajectories
• Indicator criteria
• Air-mass age
• Tracers
• Grid modeling

Boundary Layer Features

• Nocturnal boundary layer
• Evolution of the convective boundary layer
• Low-level jet
• Mixing

Analyses

• Investigate typical profiler/RASS data during episodes, investigate the frequency of the nocturnal jet; investigate the spatial occurrence of the nocturnal jet.
• Analyze tethersonde and ozonesonde data; compare with early-morning aircraft data and profiler/RASS data; investigate overnight pollutant and meteorological data.

• A case study is the in-depth analysis of the meteorology and air quality experienced during a selected high ozone concentration episode. A case study links individual analyses into a coherent picture. 

Analysis Objectives

• To integrate the meteorology and air quality and develop a conceptual model of the important meteorological factors and air quality, which help to produce high ozone concentrations in a region.

• Select an episode(s). Base selection on the occurrence of high ozone concentrations and the availability of meteorological and air quality data (including upper-air meteorological measurements).
• Assess air quality conditions including the extent and timing of peak ozone concentrations and assessing the background ozone concentrations.
• Assess the meteorological conditions including the synoptic pattern and prevailing surface conditions.
• Assess the origin of pollutants by coupling the meteorology and the patterns of ozone and precursor concentrations.
• Assess transport of ozone and precursors beginning with the morning conditions and proceeding throughout the episode.
• Perform isentropic analyses and analysis of air quality data collected by aircraft and by surface monitoring sites to understand how ozone and ozone precursors are horizontally and vertically transported.

Selection of the Episode

• Highest ozone concentrations of episode on July 18
• Nine sites with ozone concentrations over 125 ppb
• Speciated hydrocarbon data available
• Aloft air quality data available
• Upper-air meteorological data available
• Boundary air quality data available

Examples

• Air quality conditions
• Meteorological conditions
• Transport of ozone and ozone precursors

• Refers to locating surfaces of constant potential temperature and examining their structure, their relationships to other meteorological features present in the domain, and the implications of their relationships.
• Analysis along constant potential temperature surfaces (called isentropes); computed from upper-air temperature, relative humidity, and pressure data.
• Air parcels flow along isentropes because potential temperature is conserved during adiabatic motion.
• Use isentropic cross sections for diagnosing the evolution of the boundary layer structure and winds to help evaluate pollutant transport.

Contour of maximum ozone concentrations (ppb) in the southeast Texas region on August 19, 1993. The locations and concentrations of all exceedances are shown. (SAI et al., 1995)

P Maximum ozone concentrations observed in southeast Texas during the GMAQS project; the black bars indicate days on which a sea/land breeze circulation formed that produced an onshore-offshore flow reversal in the region. (SAI et al., 1995)

Wind profiles measured by the 915MHz radar profiler at Galveston, TX (GAL) August 10, 1993. Solid lines
indicate sea breeze (SB), land breeze (LB); dashed line indicates a convergence zone (CZ) that formed at the
onset of the land breeze. The first level of winds was measured by the surface station that was collocated with
the profiler (SAI et al., 1995).

Twelve-hour resultant wind vectors for radar profiler sites in the northeastern United States from
1900 EST on July 31 through 0700 EST on August 1, 1995 (Ray et al., 1997). Note that vectors
are based only on data from the end-points and that the 10 m agl levels at Gettysburg and
Holbrook, PA were less than 20 km.

Tethersonde ozone and wind speed data collected at Gettysburg, PA from 1815 EST on July 31 through 0630 EST on August 1, 1995 (Ray et al., 1997).

• Used to investigate transport conditions aloft.
• Procedure based on integral quantities computed from the profiler data following the work of Allwine and Whiteman (1994).
• Parameters include:

S Scalar wind run (km)
L Resultant (vector) transport distance (km)
Q Resultant wind directions in degrees from true N adjusted to the proper quadrant
R Recirculation factor (L/S)

• Recirculation Factor:

R = 1     Straight-line, steady transport occurred during integration period
R = 0     No net transport
R » 1      Good ventilation conditions (for L = few hundred km)
R small   Stagnation for small S (i.e., low winds)
              Recirculation for low L (i.e., < 50 km)

Conceptual model of the six stages of the onshore-offshore-onshore flow reversal in southeast Texas on episode days (SAI et al., 1995).

Time series plot of mixing depths estimated from C_n² and virtual temperature data for the profiler sites in southeast Texas located at Southeast Houston (SHE), Galveston (GAL), Beaumont (JCA), and offshore at the High Island Platform (HIP) on August 19, 1993. Note that T_v-derived mixing depths should be used from about 1800 to 0900 CST (SAI et al., 1995).

• Assemble required data: hourly surface and upper-air meteorology (wind speed and wind direction).
• Determine physical barriers to airflow.
• Prepare 3-D wind fields for selected periods using the selected wind field model.
• Run the 3-D trajectory model.
• Assess results with respect to other analyses and data.

Analysis Objectives

• Diagnose important surface and aloft transport pathways and examine and evaluate key source-receptor relationships in a region.
• Evaluate the potential for long-range transport overnight, and estimate the contribution of aloft carryover of ozone and precursors to regional background concentrations.
• Characterize periods when surface and aloft transport are coupled (typically during the daytime in the convective boundary layer) versus periods when aloft transport is decoupled from near-surface processes (such as occurs at night as the stable NBL develops).
• Examine the relative roles of same-day transport versus multi-day transport of ozone and precursors to key receptors where exceedances were observed.
• Help develop recommendations for future aloft meteorological and air quality measurement strategies in the region.

• Perform case studies of several ozone episodes.
• Compare episode characteristics and the conceptual model with past year episodes.
• Make recommendations for future modeling efforts such as:

- Selection of episodes to model and why these episodes are important.
- Selection of data which should be used for boundary and initial conditions.
- Selection of data which should be used for data assimilation.
- Selection of data which should be used for model evaluation.
- Examples of meteorological and air quality phenomenon which should be represented in the models (for model   development and evaluation).

 Satellite Images

• Use visible and infrared images to understand weather phenomena that affect air quality conditions. These weather events include:

- Land/sea breeze circulation.
- Thunderstorms, squall lines, rain showers, etc.
- General cloud cover (clear/cumulus/overcast).
- Synoptic weather features (cold fronts, warm fronts, high pressure systems).

The following satellite image was used to aid in analyses for the Gulf of Mexico Air Quality Study.

• Simple ratio of precursor emissions in upwind air basin to those in downwind air basin
• Simple ratio of precursor emissions in a portion of the upwind air basin (that portion most connected by geography and wind patterns to the downwind area) to those in the downwind area
• Ratio of upwind to downwind emissions, with emissions accumulated along a typical trajectory path
• Ratio of upwind to downwind emissions using meteorological and photochemical models

Allwine K.J. and Whiteman C.D. (1994) Single-station integral measures of atmospheric stagnation, recirculation, and ventilation. Atmos. Environ. 28, 713-721.

Blumenthal D.L., Lurmann F.W., Roberts P.T., Main H.H., MacDonald C.P., Knuth W.R., and Niccum E.M. (1997) Three-dimensional distribution and transport analyses for SJVAQS/AUSPEX. Draft report prepared for the San Joaquin Valleywide Air Pollution Study Agency, California Air Resources Board, Sacramento, CA by Sonoma Technology, Inc., Santa Rosa, CA, STI-91060-1705-DFR, February.

Chang J.C. and Hanna S.R. (1993) Trajectory calculation for selected LMOS periods. Report prepared for Sonoma Technology, Inc., Santa Rosa, CA by Sigma Research Corp., Concord, MA, Report No. 1197-600, May.

Dye T.S., Lindsey C.G., and Anderson J.A. (1995a) Estimates of mixing depths from "boundary layer" profilers. In Preprints of the 9th Symposium on Meteorological Observations and Instrumentation, Charlotte, NC, March 27-31, STI-94212-1451.

Dye T.S., Roberts P.T., and Korc M.E. (1995b) Observations of transport processes for ozone and ozone precursors during the 1991 Lake Michigan Ozone Study. J. Appl. Meteorol. 34, 1877-1889. (STI-1384).

Hanna S.R. and Chang J.C. (1993) Representativeness of 1991 LMOS ozone episodes and relations between ozone episodes and meteorological variables in the Lake Michigan area. Report prepared for Sonoma Technology, Inc., Santa Rosa, CA by Sigma Research Corp., Concord, MA, Report No. 1197-407/411, January.

Lindsey C.G., Dye T.S., Blumenthal D.L., Ray S.E., and Arthur M. (1995a) Meteorological aspects of summertime ozone episodes in the Northeast. Paper FA 5.8 to be presented at the 9th Joint Conference on the Applications of Air Pollution Meteorology at the 76th AMS Annual Meeting, Atlanta, GA, January 28-February 2, 1996, (STI-1549).

Lindsey C.G., Dye T.S., Roberts P.T., Anderson J.A., and Ray S.E. (1995b) Meteorological aspects of ozone episodes in southeast Texas. Paper No. 95-WP96.02 presented at the 88th Air & Waste Management Association Annual Meeting, San Antonio, TX, June 18-23.

Lu Z. and Fujita E.M. (1995) Volatile organic compound source apportionment for the coastal oxidant assessment for Southeast Texas Study. Final report prepared for Texas Natural Resource Conservation Commission, Austin TX by Desert Research Institute, Reno, NV.

Main H.H., Chinkin L.R., Haste T.L., Roberts P.T., and Reiss R. (1997) Shasta County ozone and ozone precursor transport quantification study. Final report prepared for the Shasta County Department of Resource Management, Redding, CA, STI-95180-1714-FR, March.

Ray S.E., Korc M.E., Byars M.S., Dye T.S., Lindsey C.G., Haste T.L., and Roberts P.T. (1997) Analysis of nocturnal low-level jets in the Northeastern United States during the summer of 1995. Final report prepared for U.S. Environmental Protection Agency, Research Triangle Park, NC by Sonoma Technology, Inc., Santa Rosa, CA, STI-996440-1706-FR, February.

Roberts P.T. and Main H.H. (1992a) Characterization of three-dimensional air quality during the SCAQS. In Southern California Air Quality Study Data Analysis. Proceedings from SCAQS Data Analysis Conference, University of California, Los Angeles, CA, July 21-23, Air & Waste Management Association, Pittsburgh, PA, (STI-1223), VIP-26.

Roberts P.T., Main H.H., Smith T.B., Lindsey C.G., and Korc M.E. (1992b) Analysis of 3-D air quality data and carbon, nitrogen, and sulfur species distributions during the Southern California Air Quality Study. Final report prepared for the Coordinating Research Council, Atlanta, GA by Sonoma Technology, Inc., Santa Rosa, CA, STI-99100-1213-FR, October.

Roberts P.T., Musarra S., Smith T.B., and Lurmann F.W. (1992c) A study to determine the nature and extent of ozone and ozone precursor transport in selected areas of California. Final report prepared for the California Air Resources Board, Sacramento, CA by Sonoma Technology, Inc., Santa Rosa, CA, STI-90060-1162-FR, December.

Roberts P.T., Main H.H., Lindsey C.G., and Korc M.E. (1993a) Ozone and particulate matter case study analysis for the Southern California Air Quality Study. Final report prepared for the California Air Resources Board, Sacramento, CA by Sonoma Technology, Inc., Santa Rosa, CA, STI-90020-1222-FR, May.

Roberts P.T., Main H.H., and Korc M.E. (1993b) Comparison of 3-D air quality data with model sensitivity runs for the South Coast Air Basin. Paper No. 93-WP-69B.05 presented at the Air & Waste Management Association Regional Photochemical Measurement and Modeling Studies Conference, San Diego, CA, November 8-12, STI-1244.

Roberts P.T., Main H.H., Chinkin L.R., Musarra S.F., and Stoeckenius T.E. (1993c) Methods development for quantification of ozone and ozone precursor transport in California. Final report prepared for the California Air Resources Board, Sacramento, CA by Sonoma Technology, Inc., Santa Rosa, CA, STI-90100-1233-FR, July.

Roberts P.T., Dye T.S., Korc M.E., and Main H.H. (1994) Air quality data analysis for the 1991 Lake Michigan Ozone Study. Final report prepared for Lake Michigan Air Directors Consortium, Des Plaines, IL by Sonoma Technology, Inc., Santa Rosa, CA, STI-92022-1410-FR.

Roberts P., Korc M., Blumenthal D., and Mueller P.K. (1995a) NARSTO-Northeast 1995 summer ozone study. Version 1. Report prepared for Electric Power Research Institute, Palo Alto, CA by Sonoma Technology, Inc., Santa Rosa, CA, STI-95135-1538-WD1; Research project EPRI WO9108-01.

Systems Applications International, Sonoma Technology Inc., Earth Tech, and Alpine Geophysics (1995) Gulf of Mexico Air Quality Study. Vol 1: Summary of data analysis and modeling. Draft final report prepared for U.S. Department of the Interior, Minerals Management Service, Gulf of Mexico OCS Region, New Orleans, LA, OCS Study, MMS 94-0046, SYSAPP-95/013d.

Tremback C.J. and Lyons W.A. (1993) Trajectory calculation derived from CALRAMS simulations. Report prepared for Lake Michigan Air Directors Consortium, Des Plaines, IL by ASTeR, Inc., Ft. Collins, CO, August.