Exceptional Events

LADCO Exceptional Events Screening

Approach/Scope

Develop an approach for screening near real-time surface and remote sensing monitoring data for potential exceptional event contributions to air quality problems in the LADCO states. The following workflow is being used by LADCO for screening air quality data.

  • Airnow Tech is the first tool to use for this triage analysis. Tutorial below for creating (1) ozone timeseries and (2) ozone, smoke, and back trajectory maps
  • NC DNR Online GIS tool for displaying draft DVs and critical values.
  • LADCO Design Value Tracker for tabulated ozone concentrations by site in the different O3 NAAs in the region
  • EPA EE information, guidance, and additional data sources
  • LADCO will identify the days where MDA8 O3 > 70 ppb at each monitor, and highlight the top days that are contributing to the design value
  • Analysis will focus on identifying if there could be smoke enhancements on the high days and DV days at the violating monitors
  • Discussion questions:
    • How to bring in PM2.5 and CO, other pollutants?
    • What are the next steps after potential days are identified

LADCO Screening Metric

The LADCO Exceptional Event screening analysis focused on finding signals in standard surface monitoring data to identify when there is potential for smoke influences on surface air quality conditions during the ozone season (April 1 – October 31). We looked at associations between AQS observations of daily maximum 8-hour ozone (DM8h O3) and daily maximum 8-hour average CO (DM8h CO); and CASTNet daily average total PM2.5 (DA PM25).  Our hypothesis is that coincident peaks in all three of these pollutants may indicate smoke influence in a non-attainment area (NAA).

For each region of interest (e.g., 2015 O3 NAAQS NAA) we display three plots:

  • Average Standardized Log-transformed Timeseries – Plots show O3, CO, and PM2.5 concentration anomalies for the NAA during the 2018 ozone season. These plots summarize the ‘Monitor-specific Standardized Log-transformed Timeseries’ plots below and were created by averaging the standardized timeseries across all monitors within the NAA. Standardization (i.e., normalization) was done using the monthly mean and standard deviation of the log-transformed observed values at each site over the 2013-2017 period.
  • Monitor-specific Standardized Log-transformed Timeseries – Plots show O3, CO, and PM2.5 concentration anomalies at individual monitors in the NAA during the 2018 ozone season. Standardization (i.e., normalization) was done using the monthly mean and standard deviation of the log-transformed observed values at each site over the 2013-2017 period.
  • Concentration Residuals – Plots show O3, CO, and PM2.5 concentrations above the mean +1 standard deviation at individual monitors in the NAA.

All of the plots are overlaid with grey shading to indicate when the HMS smoke product qualitatively shows smoke plumes in the vicinity of the NAA. Click on a plot to expand to a full browser window.

We tested and validated this approach using monitoring and smoke data from 2016. The results for 2016 are shown below. In subsequent sections of this site, we present screening analysis for more recent years.

2016 EE Screening Results

Tools and Data

Recent State Exceptional Event Demonstrations

YearLocationDescription
2021ILChicago NAA June 2020 exceptional event demonstration submitted to U.S. EPA on February 1, 2021 | US EPA TSD to support non-concurrence
2021OHCincinnati June 2020 ozone exceptional event demonstration submitted to U.S. EPA on April 13, 2021 | US EPA TSD to support non-concurrence
2021MI2020 Western MI demonstration draft submitted to U.S. EPA on March 24, 2021
2016N/AU.S. EPA Exceptional Events Submissions Table (2016 Rule)
2017CTCT DEEP May 2016 Ozone Exceptional Event Analysis Technical Support Document
2017OHOH EPA May 2016 Canadian Wildfire Ozone and PM2.5 Exceptional Event Demonstration
2018LALA DEQ September 2017 Ozone Exceptional Event Technical Support Document  | EPA Webpage for LA EE Demo
2018N/ASTI presentation to LADCO on Baton Rouge Exceptional Event Demonstration (July 10, 2018)

First Tier Analysis

User friendly, distilled data for screening air quality data; good for first level analysis

AirNow Tech
Password protected web client available to air planning agency staff. Access to near-real time surface obs and smoke data. Key features

  • Create timeseries of O3 and PM surface data for individual monitors.
  • Overlay maps with surface pollutant concentrations and smoke plumes.
  • Create back or forward trajectories at monitors, overlaid on maps
  • Download observational data, figures, and maps of analysis products

AirNow
Public web client with access to near real time air quality index and smoke data

NASA Earthdata Atmosphere
Public web client interface to remote sensing data, such as aerosol optical depth and pollution column retrievals

NOAA Air Quality and smoke forecasts
Maps of NOAA air quality, smoke, and dust forecasts

NOAA Hazard Mapping System smoke maps
Maps of smoke plumes from NOAA’s HMS. Historical archive of KMZ and Shapefiles of HMS smoke and fire.

NASA Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) 
Satellite derived vertical profiles of clouds and aerosols in the atmosphere. Historical archive of KMZ profiles.

NOAA High Resolution Rapid Refresh (HRRR) smoke model
Static and interactive maps of modeled hourly smoke forecasts, including surface smoke product

Environment Canada smoke and air quality forecasts
Maps of Canadian air quality and smoke modeling forecasts

Ventusky
Modeled and observational data of meteorology and chemistry parameters.

Second Tier Analysis

Low level and raw observational and remote sensing data; good for deep dive into remote sensing data

Remote Sensing Information Gateway
Desktop client for accessing EPA modeling data, remote sensing data, and surface obs

NASA GIOVANNI
Web client for accessing raw remote data from many of NASA’s atmospheric science remote sensing assets.

2023 Analysis and Call Notes

Objectives of the 2023 EE workgroup:

  1. Updated the LADCO O3-PM2.5-CO anomaly metric to use a 5-year rolling average rather than a fixed period average. Specifically, 2023 EE data was normalized by monthly mean and standard deviation recorded in 2018-2022 period (completed in Apr 2023).
  2. Automated the process of integrating HMS smoke information and AirNow Tech data into the EE screening (completed in Sep 2023)
  3. Prototype (and possibly deploy) an integration of meteorological variables and air mass transform direction into the EE screening
  4. Prototype (and possibly deploy) an identification algorithm for similar meteorological days as to the smoke-influenced screened days using a Classification & Regression Analysis Tree (CART) analysis
  5. Conduct exploratory analysis for PM2.5 EE screening metric development: tracking daily total PM2.5 against the PM2.5 annual and 24-hour standards; determining indicator variables and anomaly values for identifying the potential smoke influence on PM2.5 concentration

2023 EE Screening Results (data retrieval on Sep 2, 2023)

2022 Analysis and Call Notes

Objectives of the 2022 EE workgroup:

  • Update the LADCO O3-PM2.5-CO anomaly metric to use a 5-year rolling average rather than a fixed period average. For example, 2021 EE data was normalized by monthly mean and standard deviation recorded in 2017-2021 period.
  • Prototype (and possibly deploy) a machine learning algorithm for smoke impact screening

2022 EE Screening Results (as of Sep 29, 2022)

2021 Analysis and Call Notes

Objectives of the 2021 EE workgroup:

  • Integrate metrics developed during the 2020 Chicago/W Michigan/Cincinnati EE project for identifying smoke impacts into our suite of EE screening products
  • Update the LADCO O3-PM2.5-CO anomaly metric to use a 5-year rolling average rather than a fixed period average. For example, 2021 EE data was normalized by monthly mean and standard deviation recorded in 2016-2020 period.
  • Prototype (and possibly deploy) a machine learning algorithm for smoke impact screening
  • Catalog all data that we’re using for EE screening and that are useful in an EE demonstration and come up with a plan to download and archive ephemeral data during potential smoke events before they’re deleted
  • Connect state air quality forecasters in the region with the EE workgroup such that we get notifications when there are smoke events impacting the region

2021 EE Screening Results (as of Oct 27, 2021)

2021 Call Notes

2020 Analysis and Call Notes

Objectives of the 2020 EE workgroup:

  • Identify potential EEs for ozone and PM2.5 in 2020
  • Review the 2018-19 records and find potential for regulatory significant EE events
  • Learn how to integrate other data, including satellite data into EE screening
  • Build a conceptual model for a regional EE demo

2020 EE Screening Results (as of Nov 20, 2020)

These plots will be updated through the season in advance of the monthly calls.  Note that ozone doesn’t appear on these plots until one of the monitors in the screening area violates the 2015 NAAQS (>70 ppb).

2020 Call Notes

Click to expand/collapse the call notes below

2019 Analysis and Call Notes

Objectives of the 2019 EE workgroup:

  • Identify potential EEs for ozone and PM2.5
  • Refine the screening metric
  • Learn how to integrate other data, including satellite data into EE screening
  • Learn from other areas/states that have conducted EE demonstrations

2019 EE Screening Results (as of October 3, 2019)

These plots will be updated through the season in advance of the monthly calls.  Note that ozone doesn’t appear on these plots until one of the monitors in the screening area violates the 2015 NAAQS (>70 ppb).

2019 Call Notes

Click to expand/collapse the call notes below

2018 Analysis and Call Notes

Summary: LADCO, the LADCO member states, and EPA R5 held monthly calls starting in August 2018 to review air quality data in the context of identifying potential exceptional events for ozone in the region.  Over the course of the ozone season, LADCO, in consultation with the regional EE workgroup, developed a screening metric using readily available monitoring data to identify EE potential in the region.  The final 2018 screening results, call notes, and presentations are included below.

2018 EE Screening Results

2018 Call Notes

Click to expand/collapse the call notes below