1. FASTNET Report: 0409FebMystHaze Mystery Winter Haze: Natural? Nitrate/Sulfate? Stagnation? Contributed by the FASNET Community, Sep. 2004 Correspondence to R Husar, R PoirotR 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 EPA -OAQPS AIRNOW PM25 - February

2. Secondary MP25 Peak in February-March The AIRNOW PM25 data are available real-time for 300+ stations since July 2002. The 30-day smoothing of the average hourly data shows the Eastern US PM25 seasonality The seasonal pattern shows the summertime sulfate peak and a second Feb/Mar peak The the existence, characteristics and origin of this regional peak is not known The objective of effort is to characterize this ‘mysterious’ phenomenon over the EUS The approach is to seek out the community as a resource for collaborative analysis Sulfate-driven Jul-Aug peak Feb-Mar peak, of unknown origin

3. Seasonal PM25 by Region The 30-day smoothing average shows the seasonality by region The Feb/Mar PM25 peak is evident for the Northeast, Great Lakes and Great Plains This secondary peak is absent in the South and West

4. PM25 Monthly Concentration Monthly average PM25 are shown as circle and contour (Blue: 0; Red: 25  g/m 3 ) The Feb/Mar peak is clearly evident in the Upper Midwest region JANFEB MARAPR MAYJUNJULAUG SEPOCTNOVDEC Blue: 0 Red: 25 AIRNOW Jul 02-Sep 04

5. FRM PM25 Monthly Concentration Monthly average FRM PM25 are shown as circle and contour (Blue: 0; Red: 25  g/m 3 ) The Feb/Mar peak is clearly evident in the Midwest region; also in January Hence, there is some deviation in peak location and time among the networks JANFEB MARAPR MAYJUNJULAUG SEPOCTNOVDEC EPA AIRS 1999-2002

6. February 2005 ‘Nitrate’ Event AIRNow shows the high surface PM2.5 concnetration during the January 2005 event. This PM2.5 episode in Minneapolis made it to the CNN nightly news) 050126050128050129 050130050131050201050202 050127

7. Satellite Data: POLDER Aerosol Polarization Index The (short-lived, Nov 96-Jun97) POLDER satellite sensor measured the of aerosol polarization, which is sensitive to fine particles, < 1  m For Jan-Mar the data show a strong aerosol signal over the Upper Midwest and adjacent Canada Skeptics have attributed the ‘anomalous’ aerosol zone to interferences such as snowy ground reflectance In light of the recent ground-based PM25 monitoring data, the early (1997) POLDER results deserve full attention Dauze et. al, 2001

8. Satellite Data: MISR Aerosol Optical Thickness The MISR sensor on Terra satellite performs multi-angle (60-150 deg?) scans for aerosol retrieval Four years of AOT data over land (2001-04) provide further evidence of the Jan-Mar aerosol peak Interestingly, both POLDER and MISR show the aerosol patch extending deep into Central Canada

9. Where do we go from here? Is it real ??? Natural? Nitrate/Sulfate? Stagnation?