Impacts of the Denver Cyclone on Regional Air Quality and Aerosol Formation in the Colorado Front Range during the Front Range Air Pollution and Photochemistry Éxperiment (FRAPPÉ) 2014

Monday, 14 December 2015: 11:20
3010 (Moscone West)
Kennedy-kiet T Vu1, Justin Hernandez Dingle1, Roya Bahreini1, Eric C Apel2, Teresa Lynn Campos3, Christopher A Cantrell4, Frank M Flocke3, Alan Fried4, Scott C. Herndon5, Alan J Hills6, Rebecca S Hornbrook3, L Gregory Huey7, Lisa Kaser3, Lee Mauldin8, Denise D Montzka3, John B Nowak5, Dirk Richter9, Joseph R Roscioli5, Stephen Shertz3, Meghan H Stell3, David Tanner10, Geoffrey S Tyndall11, James Walega9, Petter Weibring9 and Andrew John Weinheimer3, (1)University of California Riverside, Riverside, CA, United States, (2)University Corporation for Atmospheric Research, Boulder, CO, United States, (3)National Center for Atmospheric Research, Boulder, CO, United States, (4)Univ of Colorado, Boulder, CO, United States, (5)Aerodyne Research Inc., Billerica, MA, United States, (6)NCAR, Boulder, CO, United States, (7)Georgia Institute of Technology Main Campus, Atlanta, GA, United States, (8)Pacific Northwest National Laboratory, Richland, WA, United States, (9)University of Colorado at Boulder, INSTAAR, Boulder, CO, United States, (10)Georgia Tech, Atlanta, GA, United States, (11)Natl Ctr Atmospheric Research, Boulder, CO, United States
The northern Colorado Front Range continues to face challenges related to air quality, specifically ozone, and has been classified as a marginal non-attainment area by the U.S EPA. The highly complex topography and meteorology in the Colorado Front Range provide flow patterns that are driven by mountain-valley circulation, resulting in formation of the Denver Cyclone, strongly influencing concentrations of ozone and aerosol particles. However, the impact of the Denver Cyclone on aerosol formation has not been previously explored.

In this study, airborne measurements were made during July 16 - August 18, 2014 aboard the NSF C-130 aircraft during the 2014 Front Range Air Pollution and Photochemistry Éxperiment (FRAPPÉ) project. We carried out fast time resolved measurements of ambient aerosol chemical constituents (organics, sulfate, nitrate, ammonium, and chloride) of non-refractory sub-micrometer particles using an Aerodyne compact time-of-flight aerosol mass spectrometer (mAMS).

Pronounced increased mass concentrations of organics, nitrate, and sulfate in two distinct regions in the Front Range were observed during the cyclone episodes, in contrast to the non-cyclonic days. Organics dominated the mass concentrations on all days evaluated. The average mass concentration of organics during a cyclone event was 5.79 ± 1.48 μg·m-3 and were lower during the two non-cyclonic measurement days, 3.09 ± 1.18 μg·m-3. Average sulfate mass concentrations were 1.25 ± 0.41 μg·m-3 vs. 0.58 ± 0.20 μg·m-3 followed by nitrate with an average of 1.66 ± 0.92 μg·m-3 vs. 0.32 ± 0.41 μg·m-3 on cyclone vs. non-cyclonic days, respectively. Correlations between trace gas markers (carbon monoxide, nitrogen oxides, ozone, ammonia, and ethane), meteorological variables (relative humidity, temperature), and the extent of aerosol aging are evaluated and used to assess the Front Range aerosol formation and air quality impacts in the region during these events.