This threaded discussion forum is intended for general OTAG topics that are not covered by the discussions on other pages dealing with specific topics.

AQA Papers for AWMA - San Diago, June 14-18, 98
The AQA group has been rather productive over the past year or two and there is a wealth of high grade and useful AQA material that would be appropriate for formal publication. I would propose that we consider a two/three-phased approach:
- Submit a set of high-grade papers for the San Diego AWMA meeting. That will keep us on a schedule.
- We submit those for journal publication. That will finish the job.
- If at all possible, we expose a copy of the clean papers as shared resources on the Web

The 98 AWMA meeting has many sessions that are suitable for our material. I am not a convener any of the sessions but that should not matter. The key dates are:

Abstracts due: Sept 23, 97
Acceptance by: Dec 5, 97
Manuscript due: Feb 1, 98
Meeting: June 14-19,98

I am proposing that
- you all have a good look at your own backlog of unpublished work
- examine the AWMA program
- submit your abstracts to AWMA
- submit your abstracts to this OTAG AQA website - We will have separate page for those

Considering the completeness of much of the material, I feel that this will not prevent us from proceeding with new work between now and Feb 1, 98 whae the manuscripts are due. As always, the papers can and should be 'as short as possible but not shorter'. So, the publication effort should be an excercise in filtering, aggregating and integrating the existing material with an eye on high info density, complementarity of content minimum redundancy.

This is good place to state your respones and/or questions.

Submitted by Rudolf Husar on 9/5/97 RecID: RudolfHusar6
Re: AQA Papers for AWMA - San Diago, June 14-18, 98
The call for papers and the abstract submission form for AWMA San Diago is accessible through the Web: http:// . Hope many of you will submit!
Submitted by Rudolf Husar on 9/18/97 RecID: RudolfHusar8

Re: AQA Papers for AWMA - San Diago, June 14-18, 98
Rudy, how about an overview article on the AQAWG with you as the lead of the Group and some select papers in detail by whoever is interested?

Submitted by S.T. RAO on 9/5/97 RecID: S.T.RAO

EPA's proposed SIP call includes a paper by Rao( 10:Porter, P.S., S.T. Rao, E. Zalewsky, I Zurbenko, R.F. Henry, and J.Y. Ku, "Statistical Characteristics of Spectrally-Decomposed Ambient Ozone Time Series Data," Report to the Ozone Transport Assessment Group, 1996.) in their weight of evidence; I would like to review in detail. is it avaialble? Could not find in technical papers on AQA website. on 2/5/98

EPA's proposed SIP call includes a paper by Rao( 10:Porter, P.S., S.T. Rao, E. Zalewsky, I Zurbenko, R.F. Henry, and J.Y. Ku, "Statistical Characteristics of Spectrally-Decomposed Ambient Ozone Time Series Data," Report to the Ozone Transport Assessment Group, 1996.) in their weight of evidence; I would like to review in detail. is it avaialble? Could not find in technical papers on AQA website. on 2/5/98

Re: Re: AQA Papers for AWMA - San Diago, June 14-18, 98
As far as I am concerned, the main technical AQA summary paper is the Telling the OTAG Ozone Story with Data . It is done but needs references to the tech reports. Also, it needs to be further pruned by 30-50% for publication.
Submitted by Rudolf Husar on 9/8/97 RecID: RudolfHusar7

Little Brown Half Truths
What's wrong with the following sentence? "There are no dirty power plants, and Ohio emissions are polluting Boston." This is contradictory of course. So are a lot of statements coming out in the ozone transport war, where the Environmental Protection Agency is due to release a proposed regulation. Half truth and overstatement seems to be the name of the game.

Latest case in point are two contradictory studies from the Center for Energy and Economic Development (CEED) and the Northeast States for Coordinated Air Use Management (NESCAUM). CEED says "One common myth and misconception is that the United States allows 'dirty' power plants to operate which, in turn, has created many air quality problems".

NESCAUM concludes "The industrial Midwest is a region of significant power plant NOx emissions relative to the Northeast. Analysis (by the Ozone Transport Assessment Group) has demonstrated an impact from transported ozone out of a compact region of NOx emission sources in the industrial Midwest into the Northeast. (Therefore) NOx reductions in the Industrial Midwest will be particularly beneficial to the Northeast in attaining federal air quality standards."

Who's right? Both and neither. CEED's point is that all power plants are controlled by the state so that federal air quality standards will be met (in that state), which is true. What CEED does not say is that these state plans do not consider the effects of transport on other states. So a plant that is clean as far as the state it is in is concerned may be dirty as far as another state is concerned.

Likewise it is true, as NESCAUM claims, that there is evidence of NOx and ozone transport from the Midwest to the Northeast. But the OTAG analysis also shows (1) that the effect on attainment is small compared to local sources in the Northeast, (2) that there is no way to tell where in particular these emissions will come from when it matters, and (3) that the number of possible sources is so large that the cost to control them all on the chance some of them might have an effect is enormous. NESCAUM's conclusion, like CEED's, is therefore overstated at best.

OTAG Cost Flash
Much otag to report from Friday. Ozone reduction cost estimates at last! How does $10 million per ppb per year sound? Or $25 billion per year overall, mostly in the Midwest, and still no attainment. This all follows from the fact that otag, like America, is very big vis a vis the nonattainment areas.

Pity the city!
Re: OTAG Cost Flash
About these facts: The old 120ppb, 1hr standard is indeed exceeded only near major metro areas like NYC, Houston, Atlanta, etc. However the exceedences of the proposed 80ppb, 8hr standard covers much of the Industrial Midwest north of the Ohio River, even if EPA allows 10+ excedance days/year. Pity the city?
Submitted by Rudolf Husar on 3/24/97 RecID: RudolfHusar4

Rift Opens Between EPA and Scientists Over Particulates
By David Wojick, from Electricity Daily, February 6, 1996:

A deep rift is opening between the scientific community and both the Environmental Protection Agency and the Ozone Transport Assessment Group regarding proposals to control ozone and fine particulates. Growing numbers of independent science advisors to these agencies are stating privately, and in some cases publicly, that there is a fundamental disconnect between EPA and OTAG policies and sound science.

For example, according to numerous statements in the recently released transcript of the latest EPA Clean Air Scientific Advisory Committee meeting on fine particles, EPA has only the shakiest of epidemiological evidence of adverse health effects, with no consistency between studies, and no known causal, biological mechanism to explain the effects. The scientists are concerned that the record does not support the grandiose health claims of EPA Administrator Carol Browner.

Comments include:

* Dan Menzel, Department of Community and Environmental Medicine, University of California, Irvine: "I have written to members of Congress regarding my concerns over the lack of basic research being carried out in support of the particulate matter standard, and my grave concern that research in this area is dreadful, and results in the uncertainties that we see in the data regarding the health effects of particulate matter."

* Petros Koutrakis, Harvard School of Public Health: "My major concern is the definition of background concentration. Particulates are a complex mixture of different compounds and we should acknowledge that when we talk about background. There is confusion between background and the minimum concentration somebody can measure in the atmosphere. It is going to create a tremendous problem to implement the new standard considering the low concentrations that EPA is using."

* Mark Utell, University of Rochester Medical Center: "I'm still waiting for the answer to come in on fine particles. The reason to go forward with a new standard is not to reduce the body counts, but to allow us to collect data and do the kinds of studies one needs, so that some years from now we actually have the data to address the question."

Several scientists advising OTAG have expressed similar concerns to Electricity Daily, charging that, while the OTAG Policy Group is sincere and hard working, it simply has not taken the time to understand the science underlying ozone transport. These scientists say that many of their colleagues share in their skepticism regarding the usefulness of the ozone control strategies OTAG is considering.
Re: Rift Opens Between EPA and Scientists Over Particulates
I concur with Michael Smith’s comment that stressing ‘rifts’ is counter-productive at this time. It is a relapse into the environmental cold war era characterized by a rigid command and control management system and great deal of adversity. To me, OTAG is evidence of a fragile environmental perestrojka, a small step toward the "The Natural Step"

"Imagine what would happen if the major decision-makers of society - in science, business and government - joined in a consensus effort to catalyze diverse groups to work toward an environmentally and economically sustainable future" (The Natural Step ).

"OTAG is a partnership between the EPA, the Environmental Council of the States (ECOS) and various industry and environmental groups. Its goal is to develop a thoughtful assessment and a consensus agreement for reducing ground-level ozone and the pollutants that cause ground-level ozone." (OTAG).

So, an altrenative to the dialog about 'rifts' is a 'toughtful assessment' of specific issues from multiple legitimate perspectives. How about the issue of the ozone exceedences raised elsewhere?

Submitted by Rudolf Husar on 3/28/97 RecID: RudolfHusar5

Re: Rift Opens Between EPA and Scientists Over Particulates
I suggest you review the underlying concepts of The Natural Step. In this way you might put your argments in a more appropriate context

Michael Smith (I am not registered so I have arbitrarily used Jack O'Neill's name)
Submitted by Jack O'Neill on 3/26/97 RecID: JackO'Neill

OTAG Science
After speaking to a number of you separately, I feel it is important to begin a dialog on OTAG Science. Time is running out.

My concern is that the AQA scientific work, while impressive and important, has not made an commensurate impact on the OTAG policy process. Modeling is still clearly driving the strategy selection process, creating what I call episode bias, and the ISI - RUSM approach to geographic analysis seems to me trivial at best. In fact it seems that the way things are going the ISI - RUSM coalition is going to determine the recommended strategy.

Speaking of episode bias, what is the probability that one of the episodes being modeled will actually occur in the summer of 2007? Surely all that the models are telling us is that if such an event happens to occur, then here is what should happen (plus or minus 25% or so). While helpful, I don't see this as a sound basis for selecting a control strategy.

Can nothing be done to interject more science into the strategy selection process? I'd be happy to help. Suggestions?

Postdoctoral position at CAPITA
A Postdoctoral Position for Air Pollution Transport and Pattern Analysis for 1.5-2 years is open at CAPITA. Research areas include: Further development of the CAPITA Monte Carlo
Model; Improved data integration, fusion and extrapolation; Ozone, PM and visibility climatology for North
America; Air pollution transport climatology; Web-based 4D data browsing and processing tools development. See announcement.

Submitted by Rudolf Husar on 12/28/96 RecID: RudolfHusar3

RACT Requirements for Major Sources in Attainment Areas
I have heard that there are going to be RACT requirements/recommendations for major sources in attainment areas. I am specifically interested in RACT requirements for the glass manufacturing industry. I hear that these requirements/recommendations may be coming out of OTAG. Anyone have any info they would like to pass along to me?
Submitted by Lee-Ann Tracy on 11/7/96 RecID: Lee-AnnTracy

Usefulness of Midwest-only or Northeast-only sensitivity analyses
Are sensitivity analyses that examine impacts in only portions
of the modeling domain (e.g., the Northeast and Midwest as
opposed to the entire domain) useful? or is it essential that
the investigations analyze the impact on the entire OTAG region?
While sub-regional results are certainly not dispositive, it
seems that they can serve as a good indication of impacts.
Is this something those intersted in/watching the modeling
agree with or no?
Submitted by David Oppenheimer on 10/28/96 RecID: DavidOppenheimer
Re: Usefulness of Midwest-only or Northeast-only sensitivity analyses
I doubt that any of the OTAG modelers are watching this. From the air quality data analysis, it is hard to infer much about regional control effectiveness.
Submitted by Rudolf Husar on 10/29/96 RecID: RudolfHusar2
Re: Re: Usefulness of Midwest-only or Northeast-only sensitivity analyses
Among the important implications of the Rao et al. /Porter et al. statistical decomposition of long-term ozone data is the clear demonstration that a large portion of the ozone concentration at any specific site and time is completely stochastic - i.e. is not "predictable". The specific meteorological conditions associated with any specific historical episode will never occur again. There is no assurance that a set of 4 historical model episodes (which when 'ramp-up' days are discarded represent a total of about 30 days over the past 8 years), are in in any way representative of "typical" episodes or "typical" transport patterns in the past or in the future. Assuming the model is accurately reproducing the relative contributions from transport vs local formation (and indications are that it overstates the local contribution), a breakdown into smaller and smaller sub-regions increases the degree to which the model is asked to predict the unpredictable, places increased emphasis on the (questionable) accuracy of the modeled boundary conditions, and can only exagerate any tendency for the model to overstate the local vs distant contributions.
Submitted by Richard Poirot on 11/4/96 RecID: RichardPoirot2

Contribute or comment on OTAG/AQA policy issues!
The OTAG technical activities are entering the home stretch. During the August 22 meeting, a number of concerns were raised that the Air Quality Analysis workgroup has not been addressing key policy-relevant technical issues. Please note that interactive Web pages have been set up for you to submit new policy issues or to comment on existing issues. An illustrative example issue with discussion is 'What are the OTAG measures of non-attainment (NA)?'
Submitted by Rudolf Husar RecID: RudolfHusar1

Re: Integrating Models and Observations for Sound Air Quality Management
Time to rock the boat a little -- I am somewhat concerned by the continued emphasis on trajectory presentations and the lack of "big picture" air quality analyses in the AQA group and its presentations to the policy group. Trajectories provide useful information about atmospheric flow patterns but do not provide information regarding precursor transport and subsequent chemistry. Even in the unlikely event that a source region were unequivocably identified (exceedances only and always occurred when the air came from there to a certain location), the question of level of control is not at all addressed. I hope that the AQA group can avoid limiting its thinking to the 4 selected episodes which is a constraint of the photochemical modelers. Instead, the AQA should focus on trends in air quality, including but not limited to ST Rao-type efforts. After all, we all know that there is a high level of uncertainty in the modeling. We should be looking at whether post-'88 ozone progress looks real and is likely to continue with the programs in place. RecID: 6

Integrating Models and Observations for Sound Air Quality Management
Much emphasis has been placed on the complementary and integrated use of models and ambient data in air quality management practice. Several facets are associated with this topic, ranging from the need to evaluate models with sound data bases to conducting fully integrated analysis optimized through the separate, strong attributes of data and models. As the technical debate on the use of models and data continues to mature, perceptions such as "model" or "data" are replaced by the intelligent and integrated use of "models and data." Clearly, the demand for measurements as ground- truthing and feedback information loops initiated by the National Academy of Sciences Ozone Report (NRC, 1991) has been adopted by large segments of the air quality community.

An appreciation of the strengths of both models and observations can assist the understanding of current analyses and lead to improved techniques. A model's strength is its ability to (1) integrate an enormous spectrum of data (e.g., emissions and meterological variables) and process understandings (e.g., chemical mechanisms and flow phenomena), and (2) serve as an exceptional space and time mapping tool. This latter attribute reflects the model's unique ability to predict into the future and to supplemant (or fill in) present gaps in observed data. The process formulations imbedded in models enable the addressing of so many "what if" questions related to emissions control. However, models are engineering tools that invoke substantial approximations of scientific understandings of natural phenomena, and both their formulations and application methods reflect engineering principles more than fundamental science. Observations, on the other hand, provide a basis for testing and diagnosing models, but in some instances can capture process-type relationships all by themselves (e.g., the emergence of observational-based models for defining NOx and VOC control preferences). Applied in isolation, the use of models or observations is not acceptable. Space and time constraints often bias the interpretation of observational analyses (i.e., analysis results reflect time and space of monitors which may or may not be reflecting the scales of concern). Models suffer from a very large spectrum of weaknesses, because they attempt to portray so many phenomena. Most critical though is the risk of using a potentially-biased model that is assumed to be bias-free. The integrated use of observations and models mitigates the individual weaknesses of both approaches and produces a powerful air quality management tool.

National Research Council, "Rethinking the Ozone Problem in Urban and Regional Air Pollution," National Academy Press, 1991.

Submitted by David Guinnup RecID: DavidGuinnup

Suggested presentation to Policy group at the July 24 OTAG meeting
After listening to the presentations and questions from the Policy Committee at the OTAG meeting in Washington, D.C. June 6th, it occurred to me that perhaps we should use our visualization software on one of the four OTAG episodes at the next Policy Committee meeting. Personally, I think that the work being done by the AQA Work Group is very significant and is (and will) provide scientific insight into ozone transport. However, I am concerned that we are not conveying our message well to the policy group. Please consider the following as a suggestion designed to help remedy our apparent communication problem and not as a change in the direction of our research. My suggestion is to limit our discussion before the Policy Committee to a single presentation (and presenter) and to focus on a single OTAG episode, whichever one for which we can get the data we need. That presentation would be a set of panels to help the policy committee understand the episode. These panels might include some of the same panels you have already developed, such as 2 p.m. - 2 p.m. interpolated ozone and temperature. In addition, they might include NOx (or NOy) and VOC emissions. We might want to create a panel showing ppm-hour population exposure (i.e., the number of hours * number of people exposed to ozone > 0.12 ppm. Personally, I would like to see this augmented with an equivalent for 8-hour average > 0.08.) I also think that the daily plots that interpolate will be easier for the Policy Committee to understand in a short presentation. Is there a way to show transport (wind fields) that way? (Currently we seem to rely on the uniform emission of particles.) Also, is there any way to animate residence time? Finally, if we can get any model runs (all the rest of these panels rely only on base case input data), can we do difference plots. One difference plot could show base case model results vs. actuals (ozone, and possibly NOx and VOC). Two other difference plots could show modeled emissions differences (base year - future year) and ozone differences (base year - future year). I realize that this suggestion represents a lot of work and perhaps can't be done in time for the next Policy Committee meeting. However, I am concerned that unless we link up our presentations more directly and concretely with those of the modeling group, we will loose our voice in the OTAG process.
Submitted by Mark Wolcott RecID: MarkWolcott
Re: Suggested presentation to Policy group at the July 24 OTAG meeting
I agree with most of your ideas concerning the types of presentations but we have to be careful that the presentations are properly interpreted. Gary Moore (Earth Tech) has a great video of the emissions for the 1995 episode. It really presents a nice picture of the diurnal patterns and urban/rural differences.
Submitted by Jeffrey West RecID: JeffreyWest
Re: Re: Suggested presentation to Policy group at the July 24 OTAG meeting
Would it be possible to show the video to the Policy Committee? Can we get a big enough screen and video projector?
Submitted by Saravanan Arunachalam RecID: SaravananArunachalam

Re: Suggested presentation to Policy group at the July 24 OTAG meeting
I agree that if the policy making group is overwhelmed by the complexity of technical presentations, it is certainly likely that any pertinent results of our work will be lost in the process. I generally agree with the suggestions made, however it is important for those of us working on analysis of data using a variety of techniques continue to develop those techniques through the type of cooperative efforts that have resulted from the process so far. With respect to your specific question about whether residence time plots can be animated, I offer the following:

A single residence time plot is the aggregation of a set of individual back trajectories to allow a statistical representation of air mass histories for a particular time period (usually covering months or years). The residence time type plots do not say much if anything about a specific episode within that time period. Individual trajectories do pertain to the particular episode more directly, however each has its own uncertainties. The uncertainties of an individual trajectory are less important within the context of a long period residence time representation of the air mass history.

The fact that a single residence time plot represents such a long time period makes it less intuitive to utilize a animation ( which generally represents a series of snapshots in time). However , your question has caused us to think about this possibility more carefully, and there are a few ways in which animated sequences showing a variety of residence time results might prove useful to understanding the implications (if any) of a particular residence time plot. We are experimenting with using the seven year (june-august periods) ozone record for a site to generate residence time plots for 2 or 3 year periods, repeatedly moving the whole time period forward 7 days for example. This would generate approximately 60 or so separate residence time plots which sequentially are using slightly different sets of trajectories (drop earliest 7 dates & add next 7 new ones).
This has proved interesting in that it allows us to see how the residence time result would have slowly changed (or remained relatively constant) over the entire 7 year period. There may be indications in the results of such an animation which further elucidate potential source/receptor relationships. Another possibility would be to run residence time plots for the exact same time periods but with each run extend the trajectory set back one more 3 hour time step. An "animation" of this nature might be 30 to 36 frames showing how the length of the back-trajectory chosen might affect the residence time results. These methods for displaying the residence time results might prove illustrative of the stability of the results obtained so far, therefore we are exploring them further.
Submitted by Paul Wishinski RecID: PaulWishinski2

Comparative Study: CAPITA MonteCarlo Model & HY-SPLIT Model
NOTE to Webmaster: This is not Rich Poirot offering this comment, but Paul Wishinski. Since my name starts with W it is at the bottom of the "drop-down" list for submittal of comments, and there are now so many people registered at this site that my name does not appear in the box , not enough space for the full list. This needs to be corrected!

Following up on an item briefly mentioned during the April 25, 1996 AHAT conference call; CAPITA and VT DEC are currently conducting a limited comparison between sets of back-trajectories produced by the CAPITA MonteCarlo Trajectory Model and the NOAA HY-SPLIT Trajectory Model. We are set to begin a comparison of the JUNE thru AUGUST 1995 time period. We intend to use NGM archive data for this period (2 hr time resolution, 180 km spatial resolution) to drive both trajectory models. Focus will be primarily to compare the "residence time" type of statistical climatology for this set of trajectories (@ 4/date, roughly 360 will be calculated). We will be selecting 2 sites at least, but could do up to 4 sites. We would like suggestions for ozone monitoring sites of particular interest in the OTAG domain. Preferentially, sites should be from the OTAG Modeling Workgroup, model evaluation site list. Submit suggested site NAME, LATITUDE, LONGITUDE, and HT above sea level in METERS through a response to this comment before May 4, 1996 to be considered for addition to this study. The site must have a valid set of ozone hourly measurements for the entire June thru August 1995 time period and these measurements must be available on the AIRS system..
Submitted by Paul Wishinski RecID: PaulWishinski1
Possible Sites for the Comparitive Study
Several criteria that one might consider when selecting the sites for the back trajectory comparison are: 1) Each site should be in a region of the Eastern US where the transport is dominated by different types of airmasses. 2) The sites should be located in rural areas dominated by regional scale ozone concentrations 3) The results should have applicability beyond the model comparison. Based upon the criteria above, three possible sites would be located in:
Location NameLatitudeLongitudeElev. (m)
New England; Whiteface Mt, NY:44.36573.9021480
Southeast; Great Smokey Mt, TN:35.63183.944793
Midwest; Boston Mt, AK:35.893.2
Each of these sites are located in rural areas, and exhibit ozone time trends of high elevation sites. Whiteface Mt. is often influenced by the dry and cool continental polar airmass coming from Canada, while the Great Smokey Mt are more likely to be influenced by the warm and wet maritime tropical airmasses of the Gulf of Mexico. The residence time analysis used for the model comparison from these sites would compliment the long term residence time analysis of Wishinski and Poirot (1996) conducted at Whiteface Mt. and Great Smoky Mt. For example, this analysis would allow for the determination of how "typical" the transport to these sites during 1995 were compared to the years 1988 to 1995.
Submitted by Bret Schichtel RecID: BretSchichtel
Re: Comparative Study: CAPITA MonteCarlo Model & HY-SPLIT Model
It occurs to me that among your site selection criteria, the desirability of sites which are periodically subject to influences from airmasses of different origin (ie. different potential transport pathways), is also conducive to 2 other kinds of analysis. Neither of these relates directly to your original (model comparison) objectives, but both might be viewed as suplementary efforts to take advantage of the effort you will need to make to calculate the trajectories and get them in common, comparable formats, etc.

1. Trajectory cluster analysis (as developed by Barbara Stunder at NOAA-ARL, Jeannie Moody and others), might be applied to the same sites & time periods. This clustering - which groups trajectories according to common spatial characteristics, could help provide an objectively-derived answer to the question: "what are the predominant pathways of airmass movement to the site?". Summary statistics on the ozone concentrations associated with the arrival times of the trajectories in each cluster could then be calculated and compared. In this way, your initial objective of comparing residence time results from 2 different trajectory models could be expanded to a comparison of residence time vs. cluster analysis results...

2. ST Rao's statistical disaggregation of the hourly ozone concentration might be used as a basis for sorting trajectories (via residence time analysis) or used to calculate new summary statistics for trajectory clusters. For example, the "short-term noise" component of ST's statistical disaggregation has been shown to be "random" in time from the perspective of an individual site, but also exhibits strong spatial correlations with other sites over broad regions. ST's short-term (or baseline, or met-adjusted, or long-term) values for your selected receptor sites might be used as a basis for trajectory sorting via residence time approaches, or applied to calculate summary statistics for predominant trajectory clusters.
Submitted by Richard Poirot RecID: RichardPoirot

HY-SPLIT back trajectory calculations: Interpolated Surface Layers
If anyone is familiar with the option for specifying additional levels below the lowest meteorological level available in the NGM archived data files through an Ekman/similarity interpolation approach, I would like suggestions on 1) how to select additional levels, and 2) criteria as to when such an interpolation might be completely unwarrented or "off the wall".
In calculating back-trajectories from a near sea-level surface ozone monitoring site for example, when HY-SPLIT is run without interpolation below the lowest met level, the assumed wind-field is based on the first met level which for NGM tends to be several hundred meters above sea level.
Submitted by Paul Wishinski RecID PaulWishinski
Re: HY-SPLIT back trajectory calculations: Interpolated Surface Layers
Following (with the author's permission) is an E-mail note from Barbara Stunder of NOAA's Air Resources Lab, which responds to Paul's question on the use of "sub-layer" options in HY-SPLIT, and also reports on ARL plans for future HY-SPLIT model revisions:
I asked Roland Draxler about the HYSPLIT sub-layers. This is what he said:
"The only time one might want to use sublayers is when there is a lot of stability and shear between the ground and the first meteo layer (180 m for NGM). That might be in winter. Its just an Ekman interpolation to the ground. Over complex terrain (Vermont) the whole procedure is suspect. When there are great differences between trajectories when using interpolated layers, then the results are very sensitive to level (lot of shear) and therefore individual trajectories have a lot of uncertainty associated with them (rather than deriving any conclusions from their direction)."
Roland is also working on a new version of HYSPLIT. The new trajectory code is written up in Weather and Forecasting, March 1996, pp. 111-114, "Trajectory optimization for balloon flight planning, R.R. Draxler). He's planning on making HYSPLIT4-trajectories available by anonymous ftp after he returns from Australia this summer. He says he has a comparable, but different procedure for the sublayers in HYSPLIT4. Our newer datasets we get from NCEP, Eta and AVN, have 10 m winds, which HYSPLIT4 uses. That would help you a lot. We have some Eta data archived, but sometime this summer we will stop archiving NGM and replace it with Eta (91 km horiz). [Our current global archive (381 km) will be upgraded to the 180 km AVN (NCEP Final Analysis) also.] The HYSPLIT4 concentration code is still in the developmental stage.
I haven't yet tried to access the CAPITA trajectories, but I plan to soon. We have an email system set up such that you email the trajectory info to our computer (, send HELP in message if you'd like to try it). The meteorology defaults to the current *forecast* but can access the latest semimonthly archived data. So this is designed primarily for the forecast mode, whereas CAPITA's seems to be for archived data.
I won't be available for the next AHAT conference call on April 25th, but I can see if someone else here can participate.
Let me know if you need anything else from me.
Barbara Stunder
NOAA Air Resources Laboratory
SSMC3, Rm. 3151 (R/E/AR) Voice: 301-713-0295 Ext. 114
1315 East-West Highway Fax: 301-713-0119
Silver Spring, MD 20910 Email:
Submitted by Richard Poirot RecID: RichardPoirot1

Is Rich the only one who writes here?
So the next meeting is two days ago. No wonder folks are worried about OTAG
being on time! Just testing the system and hungry for some data anlayses.
Submitted by John Bachmann RecID JohnBachmann
Re: Is Rich the only one who writes here?
John Bauchman could not be any more correct in his praise for Rich Poirot, although he could have expressed himself a bit more elequently. Fortunately, for the rest of us poor souls juggling 50 balls in the air, the State of Vermont had realized what gains can be made by actually looking at the data collected. Obviously, the work by Rudy Husar and James Hemby should not be overlooked either. Hey John, how about contributing yourself?
Submitted by Cliff Michaelsen RecID CliffMichaelsen
Re: Re: Is Rich the only one who writes here?
I just have to respond this way: those who can do, those who can't make policy. In any event, I'll note an interesting presentation by the Radian folks. They have been adapting a neural network model for the Texas NRCC folks to examine PAMS type chemistry and met data. The initial work produces a model with an R2 of 0.91. The base approach considered weather. Adding NOx data improved the predictions. Adding VOC data categorized into CBIV classes improved still further. So far it is one site. It would be interesting to get Chameides looking at this one. For further info, Dave Guinnup was also present.
Submitted by John Bachmann RecID JohnBachmann

Modeling Subgroup
It should be useful to OTAG that Rich Poirot has responded promptly to the request from the Modeling subgroup for a list of ozone monitoring sites suitable for model comparison. However, feel that the criteria for tsite selection and the selection itself, could be refined substantially if some (test) model runs were available for comparison; preferably from the major candidate models. Understanding the space-time characteristics of the model outputs would certainly aid a meaningful the site selection process. My general point is that ideally, site selection for model 'validation' should be an iterative full two-way interactions between the Air Quality Analysis and the Modeling subgroups.

Does anyone know, if test model outputs are available for such comparison? Hourly data are available for any time period and for the entire country. We could compile the model outputs into Voyager files for easy comparison with the data.

Such 'pilot' comparisons at an early OTAG phase with both workgroups participating, would help building confidence and consensus. Also, such interaction would help creating the necessary mechanical and personal interfaces between the Modeling and Air Quality Analysis OTAG subgroups fo rthe actual model-data comparison that follows.
Submitted by Rudolf Husar RecID RudolfHusar

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