FASTNET Report: 0409RegHazeEvents04

Eastern US Regional Haze Events:Automated Detection and Documentation for 2004

Contributed by the FASNET Community, Sep. 2004

Correspondence: R Husar , R Poirot

Coordination Support by

Inter-RPO WG Fast Aerosol Sensing Tools for Natural Event Tracking, FASTNET

NSF Collaboration Support for Aerosol Event Analysis

NASA REASON Coop on

EPA - OAQPS

AIRNOW PM25 - February

Eastern US PM25 Events, 2004 • A goal of the FASTNET project is to detect and document natural aerosol

events in the context of the overall PM pattern

• In the past, the definition and documentation of events has been highly subjective and dependent on the analyst, the is event type etc.

• An objective event definition is now possible through spatio-temporal statistical parameters derivable from continuous monitoring data

• The AIRNOW and ASOS monitoring systems along with the proposed detection scheme now allows the real-time detection of PM25 events

• The routine overall characterization of detected events is accomplished by the rich additional real-time data through the FASTNET Analysts Consoles

• This work illustrates the routine event detection and cursory characterization of aerosol events for the Eastern US during Jan-Sep 2004; full event assessment requires detailed customized research

2004 EUS PM25 Event Detection

• The hourly AIRNOW PM25 values are averaged over the EUS

• The hourly average values are normalized by the median to derive relative concentrations

• A regional-scale event is declared when the hourly PM25 exceeds, say 1.6x the median

• During Jan-Sep 2004, seven major Eastern US PM25 events occurred: Feb 19, Mar 25, Apr 18, Jun 7-9, Jul 21-23, Aug 18, Sep 4

Region of Event Detection: Eastern US

• The event-detection metric uses the average concentration, C, over a region

• Whenever the instantaneous regional average exceeds the spatio-temporal median by a set value (say 2x), a regional event is declared

• For the ‘2004 FASTNET Events’ below, the entire Eastern US region is used; identifying events over smaller regions follows the same procedure.

Analysts Consoles for Event Characterization

• Analysts consoles deliver the state of the aerosol, meteorology etc., automatically from real-time monitoring data

• Dozens of maps depict the spatial pattern using dozens of surface and satellite-detected parameters

• The temporal pattern are presented on time series for the regional average and for individual stations

• The following pages illustrate the 2004 EUS events, through a subset of the monitored parameters.

• The event-presentation includes limited interpretative comments; the full interpretation of this rich context is left to subsequent communal analysis

Spatial Console

Temporal Console

Feb 19 2004: • Isolated high PM25 occurs over the Midwest, Northeast and Texas• The aerosol patches are evident in AIRNOWPM25, ASOS and Fbext maps• The absence of TOMS signal indicates the lack of smoke or dust at high elevation• The high surface wind speed over Texas, hints on possible dust storm activity

• The NAAPS model shows high sulfate over the Great Lakes, but no biomass smoke

• Possible event causes: nitrate in the Upper Midwest and Northeast, sulfate around the Great Lakes and dust over Texas

Mar 25• Broad, contiguous AIRNOW PM25 belt covers the upper Midwest and the Northeast• The ASOS is moderate throughout, while the surface FBExt is high over the U. Midwest• The absence of TOMS signal indicates the lack of smoke or dust at high elevation• The surface winds indicates war air transport from the Gulf to the U Midwest

• NAAPS shows high sulfate over the Great Lakes, but no biomass smoke or dust

• Possible causes: nitrate in the Upper Midwest and sulfate around the Great Lakes

Apr 18• This modest episode stretches from Wisconsin over Pennsylvania to the Mid-Atlantic States• The ASOS is high over the Great Lakes and the surface FBExt is high over the U. Midwest• TOMS shows smoke(?) over Mexico; MODIS AOT is moderate over the Mid-Atlantic• The surface winds indicate air transport from the Gulf to the Upper Midwest

• NAAPS model indicates high sulfate over Pennsylvania and smoke over the Midwest

• Possible causes: nitrate and smoke over the Midwest, in the and sulfate around the Great Lakes

Jun 6-8• This intensive 3-day episode covers much of the Eastern US• The AIRNOW, ASOS and Visibility FBext are all elevated• TOMS shows smoke(?) over the Gulf and Mexico; MODIS AOT over the Northeast• The surface winds indicate stagnation over the EUS

• NAAPS model shows intense sulfate accumulation over the industrial Illinois-New York .

• Possible causes: sulfate episode

Jul 21-23• This intensive 3-day episode covers much of the Eastern US• The AIRNOW, ASOS and Visibility FBext are all elevated• Extremely high MODIS AOT and GASP AOT values cover the East Coast and Gulf Coast• The surface winds indicate stagnation over much of the East Coast

• NAAPS model predicts elevated sulfate throughout the Eastern US.

• Possible causes: sulfate episode

Aug 18• This episode has an intensive region in the Northeast and another in the Southeastern US• The AIRNOW, ASOS and Visibility all show similar location of elevated aerosol • Highest MODIS AOT and GASP AOT values occur over the Northeast• The surface winds indicate stagnation over the southeastern EUS

• NAAPS model predicts high sulfate in the Northeast and biomass smoke over the Southeast

• Possible causes: sulfate episode in the Northeast, smoke and sulfate in the Southeast(?)

Sep 4• A single strong aerosol ‘blob’ cover the Midwest

• The AIRNOW PM25, ASOS and Fbext maps all show a consistent spatial pattern

• The MODIS AOT confirms the Midwestern haze; the GASP AOT peaks further south

• The surface winds are low over much of the EUS

• NAAPS model also predicts a sulfate ‘blob’ over the Midwest without significant smoke or dust

• Possible causes: sulfate episode from stagnation over the source region

Discussion: The Role of Averaging Region

• The size and location of the region strongly influences the event-detection; e.g. events in the Northeast occur at different times than Southwestern events.

• ‘EUS events’ can occur either from a single contiguous ‘haze blob’ or from multiple smaller aerosol patches at different parts of the Eastern US

• It would be desirable to develop a detection scheme that can identify events regardless of geographic size, location or duration

• One possible time metric would be the integral of ‘bulges’ over space and time

Application of Automatic Event Detection:A Trigger and Screening Tool

• The algorithmic aerosol detection and characterization provides only limited information about events

• However, it can be used to trigger further action during real-time monitoring of events

• Also, automatic event quantification can be used as a screening tool for the further analysis of qualified events, e.g. the selection of ‘natural events’ from the total event pool