The 2017 Lake Michigan Ozone Study (LMOS 2017) was a collaborative, \nmulti\u2010agency field study of ozone chemistry and meteorology along the \nWisconsin\u2010Illinois Lake Michigan shoreline using a combination of \naircraft, ground\u2010based and ship\u2010based measurements. The Lake Michigan \nregion has persistently high ozone concentrations that are impacted by \ncomplex meteorology and significant transport of pollutants. The overall\n goal of the study was to better understand ozone formation and \ntransport around Lake Michigan to assist researchers and air quality \nmanagers who study, predict, and manage ozone concentrations in the \nregion. Two particularly challenging study areas are understanding the \nfactors that determine the size, location, timing, and intensity of \nozone-rich air masses, and understanding the details of the chemistry \nand meteorology that create the sharp gradients in ozone concentrations \noften observed between the lakeshore and nearby inland locations.The \ncollection of measurement assets deployed is conceptually illustrated on\n the right.<\/p>\n\n\n\n
Field activities were conducted from May 22\u2010June 22, 2017 and \nincluded two aircraft (one for remote sampling and one for in situ \nprofiling), two ground based super sites (Sheboygan, WI and Zion, IL) \noutfitted with remote sensing and in situ measurements, three mobile \nsampling platforms measuring lakeshore\u2010inland ozone concentration \ngradients or conditions on the lake surface, and additional ground\u2010based\n remote sensing instruments collocated at several other shoreline \nmonitoring locations. Air quality and meteorological forecasts provided \nflight planning guidance and in\u2010field evaluation of model prediction \nskill during the study.<\/p>\n\n\n\n
Ozone events.<\/strong> Significant ozone events occurred \nduring LMOS 2017, with exceedances of the 70 ppb 8-hr ozone threshold on\n June 2, June 11-12, and June 14-16. The LMOS 2017 aircraft observed \npolluted layers with rapid ozone formation occurring in a shallow layer \nnear the Lake Michigan surface. Modeling and observations show that this\n polluted layer over the lake is an important factor in ozone exceedance\n events, but that meteorological and photochemical model skill in \nforecasting these needs improvement.<\/p>\n\n\n\n Specifically, airborne in situ profiling during selected events \nshowed high ozone and nitrogen dioxide (NO2) concentrations within the \nmarine boundary layer over Lake Michigan, whose depth as determined by \nin situ temperature profiling ranged from ~50 to ~370 m above lake level\n depending on date, time of day, and location. Comparisons between model\n predictions and in situ airborne and surface ozone measurements showed \nthat both National Weather Service (NWS) Community Multi-scale Air \nQuality (CMAQ) and high resolution (4km) Weather Research and \nForecasting (WRF) with Chemistry (WRF-Chem) forecasts underestimated \npeak ozone concentrations and overestimated NO2 concentrations during \nthese events. Both NWS and WRF-Chem models showed persistent \nunderestimates in terrestrial boundary layer (0-3km) ozone \nconcentrations throughout the LMOS 2017 study. WRF physics sensitivity \nstudies suggest that the ability to capture the inland penetration of \nthe lake breeze circulation is dependent on accurate estimates of the \nLake Michigan water temperatures and the physics options chosen to \nrepresent boundary layer mixing and land surface exchange processes.<\/p>\n\n\n\n Sheboygan Ground Super-site.<\/strong> At Sheboygan a valuable\n dataset of continuous wind, temperature, water vapor, and \nvertically-resolved aerosol profile was recorded. Meteorological \ncharacteristics of lake breeze penetration were captured in detail, \nincluding during the June 2 ozone exceedance event. In situ chemical \nmeasurements at Sheboygan of ozone, NOx, formaldehyde, and NOx plus its \nreaction products (NOy) at 1 minute and finer time resolution captured \npeak events, as well as diurnal cycles in precursors and oxidants, and \nwind-shift related changes. Chemicals (formaldehyde and NO2) that can \nserve to indicate the chemical regime for ozone formation (i.e., NOx \nlimited and volatile organic compound (VOC) limited) were measured at \nSheboygan. Substantial variability in the indicators was recorded, \nsuggesting a complex system with some NOx limited periods, and some VOC \nlimited periods.<\/p>\n\n\n\n Zion Ground Super-site.<\/strong> At Zion, IL, a dataset of \ncontinuous wind, temperature, and water vapor vertical profile was also \nrecorded. These instruments captured thermal and wind characteristics of\n lake breeze penetration in excellent detail, including during the June 2\n ozone exceedance event. This should provide a useful dataset for future\n research and model evaluation. At Zion, a comprehensive suite of \nchemical and physical aerosol characterization was captured. This will \nbe used in ongoing source apportionment analyses and to characterize \nlocal influences on the Zion monitoring station. During LMOS 2017, low \nlevels of fine particulate matter dominated by organic matter were \nrecorded, with PM2.5 enhancements often coinciding with ozone \nenhancements. During the largest lake breeze ozone event, elemental \ncarbon concentrations were enhanced on a relative basis, consistent with\n a plume including significant combustion influence.<\/p>\n\n\n\n Continuous or semi-continuous measurements of ozone, NOx, nitric \nacid, hydrogen peroxide, and many volatile organic compounds (VOC) and \noxygenated volatile organic compounds (OVOC) were conducted. Some \nprominent VOC and OVOC compounds measured included benzene, toluene, \nisoprene, monoterpenes, methyl vinyl ketone, and methacrolein. \nPreliminary analysis of these indicates that the field observation \nperiod can be divided into two periods \u2013 an initial period of low \nbiogenic influence and higher anthropogenic influence (higher \nanthropogenic VOCs, low isoprene) up until about June 5. After June 5, \nconditions shift to a higher biogenic influence with lower \nconcentrations of anthropogenic VOCs.<\/p>\n\n\n\n Chemicals (nitric acid and hydrogen peroxide) that can serve to \nindicate the chemical regime for ozone formation (i.e., NOx limited and \nVOC limited) were measured at Zion. Background conditions with westerly \nwinds were mainly NOx limited as expected given regional sources of VOCs\n exceeding regional NOx sources. Lake breeze ozone events exhibited \nhigher VOC sensitivity than other periods, and analyses of these is \nongoing. As was the case for Sheboygan, the chemical regime for ozone \nformation at Zion had a complex time history; however, within this \ncomplexity, the lake breeze influence is clearly evident and this is \nexpected to be useful in ongoing investigations.<\/p>\n\n\n\n Ground-based remote sensing. USEPA deployed remote sensing \ninstruments for mixed layer height, cloud layer height, column NO2, and \ncolumn ozone (Vaisala CL51 ceilometers, and UV\/visible Pandora \nspectrometers). The ceilometers were installed at Grafton, WI and \nMilwaukee, WI, and Zion, IL. The Pandora spectrometers were installed at\n Sheboygan, Grafton, Milwaukee, Zion, and Schiller Park (Chicago). Data \non mixed layer height, ozone column amounts, and NO2 column amounts are \nbeing included in ongoing analyses such as comparison to models, \ncomparison to aircraft insitu profiles, and comparison to other remote \nsensing instruments such a GeoTASO and satellites.<\/p>\n\n\n\n Aircraft measurements. Airborne sampling captured critical air \npollution and meteorological features during LMOS 2017. The \nGeostationary Trace gas and Aerosol Sensor Optimization (GeoTASO) flew \n21 research flights on board the NASA LarC UC-12 aircraft. A light \naircraft (Scientific Aviation) flew 22 research flights, measuring NO2, \nozone, carbon dioxide, methane, and meteorological parameters. \nPreliminary analysis of these datasets indicates that they captured \ntheir research objectives well, including strong spatial gradients \nassociated with point and area sources, spatial gradients associated \nwith oxidative aging of plumes, chemical and thermal stratification over\n Lake Michigan, and weekday-weekend differences in NOx emissions. A \npreliminary comparison between Pandora, aircraft, and GeoTASO NO2 \nprofiles has been completed and indicates satisfactory agreement.<\/p>\n\n\n\n Other mobile platforms. Three additional mobile platforms operated \nduring LMOS 2017 at the surface: (i) the Geospatial Monitoring of Air \nPollution (GMAP) mobile vehicle sampled ozone in transects parallel and \nperpendicular to the shore, (ii) mobile meteorological and ozone \nsampling was performed, and (iii) and an instrumented research ship \noperated out of Sheboygan with daily measurements of a number of \nrelevant chemical and meteorological parameters.<\/p>\n","protected":false},"excerpt":{"rendered":" Executive Summary The 2017 Lake Michigan Ozone Study (LMOS 2017) was a collaborative, multi\u2010agency field study of ozone chemistry and meteorology along the Wisconsin\u2010Illinois Lake Michigan shoreline using a combination of aircraft, ground\u2010based and ship\u2010based measurements. The Lake Michigan region has persistently high ozone concentrations that are impacted by complex meteorology and significant transport of […]<\/p>\n","protected":false},"author":58,"featured_media":0,"parent":22,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"footnotes":"","_members_access_role":[],"_members_access_error":""},"class_list":["post-19","page","type-page","status-publish","hentry"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.ssec.wisc.edu\/staff\/wp-json\/wp\/v2\/pages\/19","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.ssec.wisc.edu\/staff\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.ssec.wisc.edu\/staff\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.ssec.wisc.edu\/staff\/wp-json\/wp\/v2\/users\/58"}],"replies":[{"embeddable":true,"href":"https:\/\/www.ssec.wisc.edu\/staff\/wp-json\/wp\/v2\/comments?post=19"}],"version-history":[{"count":4,"href":"https:\/\/www.ssec.wisc.edu\/staff\/wp-json\/wp\/v2\/pages\/19\/revisions"}],"predecessor-version":[{"id":29,"href":"https:\/\/www.ssec.wisc.edu\/staff\/wp-json\/wp\/v2\/pages\/19\/revisions\/29"}],"up":[{"embeddable":true,"href":"https:\/\/www.ssec.wisc.edu\/staff\/wp-json\/wp\/v2\/pages\/22"}],"wp:attachment":[{"href":"https:\/\/www.ssec.wisc.edu\/staff\/wp-json\/wp\/v2\/media?parent=19"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}