Talk:Evidence for Flagging Exceptional Events

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NFrank: Initial Feedback -- NFrank 10:22, 24 April 2008 (EDT)

I have started to study the "report". There is a lot of great stuff here. (BTW, what happened to your google earth console to show the trajectories and other layers? I thought that format was really neat and added to our understandings.)

There are several aspects of your current report that can benefit from larger community input. In particular, there are a few points which are not currently clear to me. See item (1) below. I hope that you or others can clarify. I also think the conclusions need to be soften particularly for the more borderline exceedances and departures from "normal" and the outline of "affected" areas to be better delineated. Once those points are clearer, we should expose to a larger group.

(1) See the two phrases in blue below: Because of your "question mark," are your speculating or concluding that the trajectories reached Illinois and Minnesota? ... I also don't understand your connection between Ohio to Midlantic transport as basis to discount GA impact on OH. Please clarify :


On May 24, the high concentration sites stretched from Alabama northward into the Ohio River Valley. The backtrajectories for all sites show a clockwise, anti-cyclonic circulation that brings marine air from the Gulf and Atlantic into the eastern U.S. The western bundle of trajectories, which result in high concentrations at receptor sites from Georgia through Illinois/Minnesota? are all assing through the Georgia fire region. These trajectories provide evidence that the smoke has impacted eastern U.S. sites that stretch all the way up to Minnesota/Illinois. On the other hand, the backtrajectories for the air masses reaching the Ohio River Valley are passing to the mid-atlantic states, well north of the Georgia fire. Therefore, those sites in the Ohio River Valley are not likely to be influenced by the smoke.

(2) As you mentioned in earlier email, alternative moving medians or other baselines would be helpful.


In this example of this several week event, the 30-day median may itself reflect the influence of the fire. Alternative indicators of "normal" are therefore needed that look to (a) seasonal periods not affected by the event, say from the prior 3 years and (b) different baselines to more confidently distinguish exceptional from normal (e.g. 1 or 2 std deviations above seasonal normals, or even 95th/98th percentiles.)

Rudy, can the selection of normal be easily modified to permit user to consider such alternative indicators?

(3) More specificity is required to identify the boundaries of (and specific monitoring sites in ) the sub-areas for which there would not be an exceedance but for the event. The ones with high and low certainty should be id'd. This is where the alternative baselines could be helpful. It would also be helpful to extend these findings to other days claimed to be affected by the GA fires, and in particular, to isolate those exceedance days and locations with lesser amounts of evidence. The latter can include days without speciation data like May 25 with NE exceedances which is easy to examine using your


Analyst's Console. For these days, to what extend should data and conclusions reached from adjacent days be used, and therefore with more reliance placed on trajectories and perhaps with a higher baseline to represent "normal" . Other recommendations for ways to help reach conclusions are also desired. To help with the latter, we can possibly call upon STI with whom we have a work assignment to evaluate exceptional event days. For example, we can limit that task to those days and locations which have already been proposed by the States as exceptional. Let's see what we can accomplish internally first.

Re: NFrank: Initial Feedback -- Rhusar 08:20, 26 April 2008 (EDT)

Neil: The progress report on the EE analysis method and tools indeed requires clarification and further description. Below are short responses to your questions. The extended responses are incorporated in the corresponding section of the report.

  • The Data Browser Console on Google Earth Viewer GA Smoke data layers are available as GASmoke.kmz and ready for browsing. The revised report now has a section Event Data Browsing on Google Earth.
  • The section on the trajectory is substantially expanded to address the constructive comments/feedback by yourself and Brian
  • The baseline for comparing the exceptional to 'normal' is clearly vital but also exploratory. Some options are illustrated in the expanded section Normal Values.

BOrndorff: Feedback on the Analysis of Georgial Fire -- BOrndorff 06:56, 23 April 2008 (EDT)

Rudy, Here are my initial comments on your analysis of the Georgia fires. It may be beneficial for you to color code the trajectories that pass over a region of interest (i.e. - Georgia fires) differently than the other trajectories. That would make it easier for people looking at the bundles of trajectories trying to make sense of them.

Also, I didn't see anything about the height of the back trajectories. Were they all started at the same height and what was the height? The height of the trajectories as they passed over the Georgia fire region could be important too. Although at first glance your conclusions make sense, it might be premature to say that all of the air at the trajectory heights that passed over the Georgia fire region were significantly influenced by the fires. For example, if some, most or all of the trajectories going towards Illinois were well above the mixing height over Georgia and it was concluded that smoke from the fires did not penetrate much above the mixing height then the conclusions that you made that but for the fires the PM in Illinois would not be in exceedance, could be incorrect. The HYSPLIT trajectory model can be run at different starting heights and keep track of the heights along the trajectory path. It can also show the calculated mixing height along the path. Have you considered updating the tool to utilize HYSPLIT trajectories? The trajectories could also be color coded so that those above the mixing height are a different color than those below the mixing height along the trajectory path. With large fires the smoke may penetrate above the calculated mixing height and in that case if the maximum smoke plume height is estimated then the trajectories could be color coded to indicate whether they are above or below the maximum plume height. I believe there are ways to estimate the maximum smoke plume height from a fire.

From a source-receptor view, it is my understanding that back trajectories are good for determining the general region of a source and that forward trajectories are better for determining a more precise track of a plume. Again, deciding the start height of forward trajectories from a fire would require estimating the maximum smoke plume height. Brian Orndorff, Meteorologist,

Re: BOrndorff: Feedback on the Analysis of Georgial Fire -- NFrank 06:59, 24 April 2008 (EDT)

Brian... thanks for those comments. I especially like the suggestion to color code those back tractories/bundles that seem to be associated with the suspected source region. Conceivably this can be accomplished computationally with a user defined rectangle that the trajectories pass over. This would visually distinguish those trajectories from the others.

For Rudy and company -- the user console for this report does not seem to have the time window that is mentioned (and of course is part of the regular datafed. This would be very helpful to include. Modified time windows with the computed 30day normal and one showing increments above normal. would be great additions. Additional time windows with the alternative indicators of normal (i.e., based on percentiles or past years data) would be extremely useful too.

Re: BOrndorff: Feedback on the Analysis of Georgial Fire -- Rhusar 11:17, 28 April 2008 (EDT)

Brian, color coding the backtrajectories depending whether they passed though a rectangle is a terrific idea. It combines the benefits of both forward and backward trajectory analyzes. We will work on it, although it will take a few weeks to get to it.

As for the biomass fire plume height, the backtrajectory height, and the linking of the two...its the holy grail of smoke transport analysis. See the description in the expanded trajectory section.

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