Current State of Practice in Identifying and Forecasting Stratospheric Intrusion Events

Presented June 14, 2012, at the

Air Quality Applied Sciences Team 3rd Meeting (AQAST 3)

In Madison, Wisconsin

Patrick J. Reddy

Air Pollution Control Division

Colorado Department of Public Health & Environment

4300 Cherry Creek Drive South

Denver CO 80246

patrick.reddy@state.co.us

Brad Pierce NOAA/NESDIS

Stratospheric intrusions (SIs) are fairly common from late winter through late spring in the western U.S.

Stratospheric ozone intrusions lead to exceedances of the 8-hour ozone standards in western states.

These exceedances must be identified/documented by states with EPA concurrence as exceptional events or they will count towards attainment or nonattainment status.

Intrusions contribute to Policy Relevant Background (PRB) ozone.

Intrusions contribute to ozone episode background.

Intrusion effects on surface ozone are not typically reflected in CAMx and CMAQ photochemical model output.

Characteristics of and Diagnostic Indicators for Intrusion Events

Occur near intense surface and upper-level low pressure systems. Lowered tropopause heights or double tropopause in the region.

High Isentropic Potential Vorticity (IPV) in the troposphere – indicative of stratospheric air and tropopause folding.

High total column ozone in the region.

Deep vertical mixing in the planetary boundary layer (PBL) – can be accentuated by high terrain and lee wave processes. Dry stratospheric air in the PBL.

Post-frontal air mass change, frequently with high winds. Back trajectories lead to upper toposphere.

Sharp temporal changes in ozone concentrations, at any time of day, with elevated background often lasting 2 to 3 days.

Changes in trace species concentrations (CO, halocarbons, beryllium,

formaldehyde ?, NO2 ?).

Strong progressive upper level trough over the West. 500-mb geopotential heightsin meters and wind speeds in knots (right scale, only those above 60 knots areplotted) at 11:00 MST on May 24, 2010, from the 18Z initial analysis of the 18ZNAM12 model.

The intrusion ofMay 24, 2010,illustrates manyof the features ofa typical event.

NOAA’s TOAST Total O3 in Dobson Units (contours – from http://www.osdpd.noaa.gov/ml/air/toast.html)and surface low pressure for May 24, 2010, showing O3 of 400 to 450 Dobson Units in upper-level trough over western US.

NOAA’s TOAST Total O3 in Dobson Units (contours – from http://www.osdpd.noaa.gov/ml/air/toast.html),surface low pressure, and IPV in K m2 kg-1 s-1 at 320 K isentrope for May 24, 2010, showing intrusion into the troposphere over Colorado.

Surface low pressure and IPV in K m2 kg-1 s-1 at 320 K isentrope for May 24, 2010, showing intrusion into the troposphere over Colorado. Intrusion is behind cold front insouthwest quadrant of the surface low.

Surface low pressure, IPV in K m2 kg-1 s-1 at 320 K isentrope, and PBL in meters aboveground level for May 24, 2010, showing intrusion into the troposphere over Colorado. Intrusion is over elevated terrain and overlaps with region of deep mixing – only mixinggreater than 3 km above ground level is plotted.

Cross section of isentropic potential vorticity in potential vorticity units at 18ZMay 24, 2010, for latitude 39 degrees North across Colorado showing atropopause fold descending to about 5 kilometers (MSL) over central Colorado.From the 18Z analysis run of the NAM12 on may 24, 2010.

IPV in PVU units at the 310 K potential temperature surface or isentrope and one-hour ozone concentrations in ppb at 12:00 MST on May 24, 2010. The IPV values are from the 18Z run of GDAS 0.5 degree by 0.5 degree model for 12:00 MST May 24, 2010.

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Relationship Between Hourly O3 in ppb andIsentropic Potential Vorticity Units at 310 K

Potential Vorticity Units

O3 in

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R-squared = 0.711200 MST May 24, 2010

Linear regression between one-hour ozone concentrations and modeled GDAS IPVfor 12:00 MST for 27 surface ozone monitoring sites in Colorado on May 24, 2010.

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OMI Level 3 total column ozone in DobsonUnits for May 24, 2010, showing a band ofhigh ozone along the upper-level trough(only values above 350 Dobson Units areplotted).

Veefkind, J.P., J.F. de Haan, E.J. Brinksma, M. Kroon and P.F. Levelt(2006), Total ozone from the Ozone Monitoring Instrument (OMI)using the DOAS technique, IEEE Trans. Geo. Rem. Sens., 2006, 44,239-1244.

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GOME2 total column ozone in Dobson Unitsfor May 24, 2010, showing a band of highozone along the upper-level trough (source:http://www.osdpd.noaa.gov/ml/air/gome.html )

Contours of one-hour ozone concentrations in ppb over Colorado for the hour ending at12:00 MST, May 24, 2010.

Contours of surface dewpoint temperatures in degrees F between 11:45 and 12:00 MST onMay 24, 2010, from MesoWest web products (http://mesowest.utah.edu/index.html) and one-hour average ozone in ppb (square labels) at hour ending at 12:00 MST across Colorado.

Contours of surface wind gusts in mph between 10:45 and 11:00 MST on May 24, 2010,from the University of Utah’s MesoWest web products (http://mesowest.utah.edu/index.html).

An Intrusion event on April 6, 2012, was accompanied by high winds and a dust storm insouth-central Colorado (MODIS Aqua image on right is for the area circled in red on the left).Strong winds were ahead of and behind the front. Dry subsident air (orange) in the water vaporImage on the left can be diagnostic of a tropopause fold.

May 24, 2010, HYSPLITback trajectories for 21Z and20Z originate at roughly 9 kmabove ground level in theneighborhood of the troughon the previous day.

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Left: Time series of hourly average ozone concentrations in ppb for May 23-24, 2010, at FortCollins West (FTCW), Great Basin National Park (GBNP), Dinosaur National Monument (DNM),and Kenosha Pass (KEN).

Right: Time series of hourly average ozone concentrations in ppb for May 24 at Aurora (AURE)Chatfield (CHAT), Manitou (MAN), Aspen Park (ASP), Fort Collins West (FTCW), Gothic(GOTH), and Kenosha Pass (KEN). Fifteen-minute average ozone data for Kenosha Passshowed an increase from 61 ppb to 115 ppb in just 75 minutes.

Time in MST and concentrations for the hour ending at the indicated time.

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Niwot Ridge Delta CFC11 in ppt

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Difference between daily CFC11 concentration and 15-day moving average – Top - Chloroflurocarbon-11data from the NOAA/ESRL halocarbons in situ program. DMAX 8-hour O3 in ppm RMNP and MAN – Bottom.

Data for May 2008Significant ColoradoIntrusion EventMay 24 & 25

Short Summary List of Important “Operational” Forecasting and Diagnostic Resources:

Unidata’s Integrated Data Viewer for plotting IPV, cross-sections, and other data (http://www.unidata.ucar.edu/software/idv/)

CIMSS Realtime GOES Derived Products – Total Ozone (http://cimss.ssec.wisc.edu/goes/rt/viewdata.php?product=o3_us)

NCEP 0.5 by 0.5 degree GFS forecast model total column ozone.

NOAA NESDIS GOME total ozone (http://cimss.ssec.wisc.edu/goes/rt/viewdata.php?product=o3_us)

NCEP NAM12 and other forecast models.

What are needed but not readily available from these resources are modeled stratospheric contributions to surface O3, modeled vertical profiles of O3, and measured vertical profiles of ozone – preferably with good temporal and spatial resolution.

“Research-oriented” models could meet many of these needs:

GFDL’s AM3.

MOZART

NOAA/NASA RAQMS

We will take a look at output for recent intrusion events in Wyoming and Colorado from RAQMS, the Realtime Air Quality Modeling System.

RAQMS runs for the NSF Deep Convective Clouds and Chemistry Experiment (DC3) have been very useful for Colorado air quality forecasts and documenting potential intrusion events.

Realtime AirQuality ModelingSystem (RAQMS)forecast surface O3for 6 PM MDT May 24, 2012, showinghourly O3 above 75 ppb in intrusionover Colorado.

One-hour O3 peakedat 79 and 83 ppb attwo sites nearColorado Springs.

12Z 05/23/2012 RAQMS forecast cross section for 0Z May 25 along 40 Norththrough Colorado showing pronounced tropopause fold forming a “doubletropopause” with high O3 and some vertical mixing of this O3 to ground level overthe higher terrain of Colorado.

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RAQMS captures the high O3 intrusionevent of June 6 and 7 at South Pass,a high-elevation site in western Wyo.

Measured 6-hour O3 in black asterisks, modeled in red dots.

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RAQM misses the local event with a99 ppb 1-hour O3 associated with theintrusion on June 6 at Thunder Basin,a plains site in far northeastern Wyo.

Coarser-scale models may notreproduce the lee-wave phenomenathat enhance downward transport eastof the mountains.

Higher resolution models such as the RUC (20 km) can resolve some of the lee waveeffects that affect mesoscale tropopause folding east of high terrain. Tropopause pressurelevels in HA for May 24, 2010.

A Colorado Wish List for AQAST Initiated Data or Products to Support Its Air Quality Management Mission

Characterization of ozone transport from Asia, states upwind, Mexico, and Canada.

Stratospheric O3 impacts both for forecasting, exceptional event analyses, and policy analysis.

How much of the state’s O3 is controllable by means of a State Implementation Plan (SIP)? Policy Relevant Background aside, what portion of the modeled event O3 can Colorado address? Where and when are we NOx-limited or VOC-limited for O3? Indicator ratios of high spatial and temporal resolution?

Emissions inventory verification or enhancement, e.g., are we missing oil and gas field emissions? What are the trends in emissions? What are the true emissions from biogenics? How does beatle-kill pine affect biogenic emissions? Do we need a review paper on biogenics?

Are we monitoring ground-level O3, PM10, PM25, and NOx in the right locations?

Are there additional basins that experience high winter O3 similar to the Upper Green River Basin in Wyoming and the Uintah Basin in Utah and Colorado?

Products for improved air quality forecasting in general and improved forecasting and analysis of O3 and particulate (blowing dust) exceptional events. Vertical profiles of ozone.

Gail Tonnesen of EPA Region 8 has convened a multi-agency WorkgroupOn Stratospheric Ozone Intrusions that includes several western states andEPA regional offices. Three contacts for this workgroup are listed below:

Gail TonnesenEPA Region 8Tonnesen.Gail@epamail.epa.gov

Ryan McCammon, Upper Green Data Analyst/MeteorologistState of Wyoming DEQ - Air Quality Division - Monitoring Section ryan.mccammon@wyo.gov

Pat ReddySenior Air Quality MeteorologistColorado Department of Public Health & Environmentpatrick.reddy@state.co.us