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Modelling studies suggest that the climate and the hydrological cycle are sensitive to the concentrations of ice-nucleating particles (INPs). However, the concentrations, composition, and sources of INPs in the atmosphere remain uncertain. Here we report daily concentrations of INPs and tracers of mineral dust (Al, Fe, Ti, and Mn), sea spray aerosol (Na+ and Cl-), and anthropogenic aerosol (Zn, Pb, NO3-, NH4+, and non-sea-salt SO42-) at Alert, Canada during a three-week campaign in March 2016. The average INP concentrations measured in the immersion freezing mode were approximately 0.005 ± 0.002 L-1, 0.020 ± 0.004 L-1, and 0.186 ± 0.040 L-1 at -15 ºC, -20 ºC, and -25 ºC, respectively. These concentrations are within the range of concentrations measured previously in the Arctic at ground level or sea level. Mineral dust tracers all correlated with INPs at -25 ºC (correlation coefficient, R, ranged from 0.70 to 0.76), suggesting that mineral dust was a major contributor to the INP population. Particle dispersion modelling suggests that the source of the mineral dust may have been the long-range transported dust from the Gobi desert. Sea spray tracers were anti-correlated with INPs at -25 ºC (R = -0.56). In addition, INP concentrations at -25 ºC divided by mass concentrations of aluminum were anti-correlated with sea spray tracers (R = -0.51 and -0.55 for Na+ and Cl-, respectively), suggesting that the components of sea spray aerosol suppressed the ice-nucleating ability of mineral dust in the immersion freezing mode. Correlations between INPs and anthropogenic aerosol tracers were not statistically significant. These results will improve our understanding of INPs in the Arctic during spring. [ABSTRACT FROM AUTHOR]

Summertime Arctic aerosol size distributions are strongly controlled by natural regional emissions. Within this context, we use a chemical transport model with size-resolved aerosol microphysics (GEOS-Chem-TOMAS) to interpret measurements of aerosol size distributions from the Canadian Arctic Archipelago during the summer of 2016, as part of the NETwork on Climate and Aerosols: addressing key uncertainties in Remote Canadian Environments (NETCARE). Our simulations suggest that condensation of secondary organic aerosol (SOA) from precursor vapors emitted in the Arctic and near Arctic marine (open ocean and coastal) regions plays a key role in particle growth events that shape the aerosol size distributions observed at Alert (82.5° N, 62.3° W), Eureka (80.1° N, 86.4° W), and along a NETCARE ship track within the Archipelago. We refer to this SOA as Arctic marine SOA (Arctic MSOA) to reflect the Arctic marine-based and likely biogenic sources for the precursors of the condensing organic vapors. Arctic MSOA from a simulated flux (500 μg m-2 d-1, north of 50° N) of precursor vapors (assumed yield of unity) reduces the summertime particle size distribution model-observation mean fractional error by 2- to 4-fold, relative to a simulation without this Arctic MSOA. Particle growth due to the condensable organic vapor flux contributes strongly (30-50 %) to the simulated summertime-mean number of particles with diameters larger than 20 nm in the study region, and couples with ternary particle nucleation (sulfuric acid, ammonia, and water vapor) and biogenic sulfate condensation to account for more than 90 % of this simulated particle number, a strong biogenic influence. The simulated fit to summertime size-distribution observations is further improved at Eureka and for the ship track by scaling up the nucleation rate by a factor of 100 to account for other particle precursors such as gas-phase iodine and/or amines and/or fragmenting primary particles that could be missing from our simulations. Additionally, the fits to observed size distributions and total aerosol number concentrations for particles larger than 4 nm improve with the assumption that the Arctic MSOA contains semi-volatile species; reducing model-observation mean fractional error by 2- to 3-fold for the Alert and ship track size distributions. Arctic MSOA accounts for more than half of the simulated total particulate organic matter mass concentrations in the summertime Canadian Arctic Archipelago, and this Arctic MSOA has strong simulated summertime pan-Arctic-mean top-of-the-atmosphere aerosol direct (-0.04 W m-2) and cloud-albedo indirect (-0.4 W m-2) radiative effects. Future work should focus on further understanding summertime Arctic sources of Arctic MSOA. [ABSTRACT FROM AUTHOR]

Ice nucleating particles (INPs) in the Arctic can influence climate and precipitation in the region; yet our understanding of the concentrations and sources of INPs in this region remain uncertain. In the following we (1) measured concentrations of INPs in the Canadian Arctic marine boundary layer during summer 2014 on board the CCGS Amundsen, (2) determined ratios of surface areas of mineral dust aerosol to sea spray aerosol, and (3) investigated the source region of the INPs using particle dispersion modelling. Average concentrations of INPs at -15, -20 and -25 °C were 0.005, 0.044, and 0.154 L-1, respectively. These concentrations fall within the range of INP concentrations measured in other marine environments. For the samples investigated the ratio of mineral dust surface area to sea spray surface area ranged from 0.03 to 0.09. Based on these ratios and the ice active surface site densities of mineral dust and sea spray aerosol determined in previous laboratory studies, our results suggest that mineral dust is a more important contributor to the INP population than sea spray aerosol for the samples analysed. Based on particle dispersion modelling, the highest concentrations of INPs were often associated with lower latitude source regions such as the Hudson Bay area, eastern Greenland, or northwestern continental Canada. On the other hand, the lowest concentrations were often associated with regions further north of the sampling sites and over Baffin Bay. A weak correlation was observed between INP concentrations and the time the air mass spent over bare land, and a weak negative correlation was observed between INP concentrations and the time the air mass spent over ice and open water. These combined results suggest that mineral dust from local sources is an important contributor to the INP population in the Canadian Arctic marine boundary layer during summer 2014. [ABSTRACT FROM AUTHOR]

The sources, chemical transformations and removal mechanisms of aerosol transported to the Arctic are key factors that control Arctic aerosol-climate interactions. Our understanding of sources and processes is limited by a lack of vertically resolved observations in remote Arctic regions. We present vertically resolved observations of trace gases and aerosol composition in High Arctic springtime, made largely north of 80° N, during the NETCARE campaign. Trace gas gradients observed on these flights defined the polar dome as north of 66-68.5° N and below potential temperatures of 283.5-287.5 K (Bozem et al., 2018). In the polar dome, we observe evidence for vertically varying source regions and chemical processing. These vertical changes in sources and chemistry lead to systematic variation in aerosol composition as a function of potential temperature. We show evidence for sources of aerosol with higher organic aerosol (OA), ammonium (NH4) and refractory black carbon (rBC) content in the upper polar dome. Based on FLEXPART-ECMWF calculations, air masses sampled at all levels inside the polar dome (i.e., potential temperature < 280.5 K, altitude <∼ 3.5 km) subsided during transport over transport times of at least 10 days. Air masses at the lowest potential temperatures, in the lower polar dome, had spent long times (> 10 days) in the Arctic, while air masses in the upper polar dome had entered the Arctic more recently. These differences in transport history were closely related to aerosol composition. In the lower polar dome, the measured sub-micron aerosol mass was dominated by sulphate (mean 74%), with lesser contributions from rBC (1%), NH4 (4%) and OA (20%). At higher altitudes and warmer potential temperatures, OA, NH4 and rBC contributed 42%, 8% and 2% of aerosol mass, respectively. A qualitative indication for the presence of sea salt showed that sodium chloride contributed to sub-micron aerosol in the lower polar dome, but was not detectable in the upper polar dome. Our observations suggest that long-term, surface-based measurements underestimate the contribution of OA, rBC and NH4 to aerosol transported to the Arctic troposphere in spring. [ABSTRACT FROM AUTHOR]

The vertical distribution of black carbon (BC) particles in the Arctic atmosphere is one of the key parameters controlling its radiative forcing. Hence, this work investigates the presence and properties of BC over the high Canadian Arctic. Airborne campaigns were performed as part of the NETCARE project and provided insights into the variability of the vertical distributions of BC particles in summer 2014 and spring 2015. The observation periods covered evolutions of cyclonic disturbances to the polar dome that caused and changed transport of air pollution into the High-Arctic, as otherwise the airmass boundary largely impedes entrainment of pollution from lower latitudes. A total of 48 vertical profiles of refractory BC (rBC) mass concentration and particle size, extending from 0.1 to 5.5 km altitude, were obtained with a Single-Particle Soot Photometer (SP2). Generally, the rBC mass concentration decreased from spring to summer by a factor 10. Such depletion was associated with a decrease of the mean rBC particle diameter, from approximately 200 nm to 130 nm at low altitude. Due to the very low number fraction, rBC particles did not substantially contribute to the total aerosol population in summer. Profiles analysed with potential temperature as vertical coordinate revealed characteristic variability patterns due to different balances of supply and removal of rBC in specific levels of the stable atmosphere. Kinematic back-trajectories were used to investigate transport pathways into these levels. The lower polar dome was influenced by low-level transport from sources within the cold central and marginal Arctic. During the spring campaign, a cold air outbreak over eastern Europe additionally caused northward transport of air from a corridor over western Russia to Central Asia that was affected by emissions from gas flaring, industrial activity and wildfires. This caused rBC concentrations between about 500 to 1800 m altitude to gradually increase from 32 to 49 ng m-3. The temporal development of transport to the level above, at around 2500 m, caused the initially low concentration to increase from < 15 ng m-3 to 150 ng m-3. Despite the higher concentrations in the upper level, significantly less rBC reached the High-Arctic relative to co-emitted CO. A shift in rBC mass-mean diameter, from above 200 nm in the low-level transport dominated lower polar dome to < 190 nm at higher levels, indicates that rBC got affected by wet removal when lifting processes were involved during transport. The summer polar dome had limited exchange with the mid-latitudes. Air pollution was supplied from sources within the marginal Arctic as well as by long-range transport, but in both cases rBC was largely depleted in absolute and relative concentrations. Near the surface, rBC concentrations were < 2 ng m-3, while concentrations increased to < 10 ng m-3 towards the upper boundary of the polar dome. The mass-mean particle diameter of 132 nm was smaller than in spring. The shape of the summer mean mass-size distribution, however, resembled the spring distribution from higher levels, which was depleted of particles > 300 nm due to nucleation scavenging. Our work provides vertical, spatial and seasonal information of rBC characteristics in the High-Arctic polar dome, offering a more extensive dataset for evaluation of chemical transport models and for radiative forcing assessments than obtained before by any other aircraft campaign. [ABSTRACT FROM AUTHOR]

The occurrence of frequent aerosol nucleation and growth events in the Arctic during summertime may impact the region’s climate through increasing the number of cloud condensation nuclei in the Arctic atmosphere. Measurements of aerosol size distributions and aerosol composition were taken during the summers of 2015 and 2016 at Eureka and Alert on Ellesmere Island in Nunavut, Canada. The corresponding results provide a better understanding of the frequency and spatial extent of these nucleation and growth events as well as of the composition and sources of aerosol mass during particle growth. These events are observed beginning in June with the melting of the sea ice rather than with polar sunrise, which strongly suggests emissions from marine sources are the primary cause of the events. Frequent particle nucleation followed by growth occurs throughout the summer. Correlated particle growths events at the two sites, separated by 480 km, indicate conditions existing over such large scales play a key role in determining the timing and the characteristics of the events. In addition, aerosol mass spectrometry measurements are used to analyze the size-resolved chemical composition of aerosols during two selected growth events. It is found that particles with diameters smaller than 100 nm are predominately organic with only a small sulphate contribution. The oxidation of the organic fraction also changes with particle size with larger particles containing a greater fraction of organic acids relative to other non-acid oxygenates (e.g. alcohols or aldehydes). It is also observed that the relative amount of m / z 44 in the measured mass spectra increases during the growth events suggesting increases in organic acid concentrations in the particle phase. The nucleation and growth events at Eureka are observed most often when the temperature inversion between the sea and the measurement site (at 610 m a.s.l.) is non-existent or weak allowing presumably fresh marine emissions to be mixed upward to the observatory altitude. While the nature of the gaseous precursors responsible for the growth events are poorly understood, oxidation of dimethyl sulphide alone to produce particle phase sulphate or methanesulphonic acid is not consistent with the measured aerosol composition, suggesting the importance of condensation of other gas phase organic compounds for particle growth. [ABSTRACT FROM AUTHOR]

From November 2015 to December 2016, the ARM West Antarctic Radiation Experiment (AWARE) measured submicron aerosol properties near McMurdo Station at the southern tip of the Ross Island. Submicron organic mass (OM), particle number, and cloud condensation nuclei concentrations were higher in summer than other seasons. The measurements included a range of compositions and concentrations that likely reflected both local anthropogenic emissions and natural background sources. We isolated the natural organic components by separating a natural factor and a local combustion factor. The natural OM was 150 times higher in summer than in winter. The local anthropogenic emissions were not hygroscopic and had little contribution to the CCN concentrations. Natural sources that included marine sea spray and seabird emissions contributed 56 % of OM in the austral summer but only 3 % in the austral winter. The natural OM had high hydroxyl group fraction (55 %), 6 % alkane, and 6 % amine group mass, consistent with marine organic composition. In addition, the Fourier transform infrared (FTIR) spectra showed the natural sources of organic aerosol were characterized by amide group absorption, which may be from seabird populations. Carboxylic acid group contributions from natural sources were correlated to incoming solar radiation, indicating that some OM formed by secondary pathways. [ABSTRACT FROM AUTHOR]

Black carbon (BC) contributes to Arctic warming, yet sources of Arctic BC and their geographic contributions remain uncertain. We interpret a series of recent airborne (NETCARE 2015; PAMARCMiP 2009 and 2011 campaigns) and ground-based measurements (at Alert, Barrow and Ny-Âlesund) from multiple methods (thermal, laser incandescence and light absorption) with the GEOS-Chem global chemical transport model and its adjoint to attribute the sources of Arctic BC. This is the first comparison with a chemical transport model of refractory BC (rBC) measurements at Alert. The springtime airborne measurements performed by the NETCARE campaign in 2015 and the PAMARCMiP campaigns in 2009 and 2011 offer BC vertical profiles extending to above 6 km across the Arctic and include profiles above Arctic ground monitoring stations. Our simulations with the addition of seasonally varying domestic heating and of gas flaring emissions are consistent with ground-based measurements of BC concentrations at Alert and Barrow in winter and spring (rRMSE< 13 %) and with airborne measurements of the BC vertical profile across the Arctic (rRMSED 17 %) except for an underestimation in the middle troposphere (500-700 hPa). Sensitivity simulations suggest that anthropogenic emissions in eastern and southern Asia have the largest effect on the Arctic BC column burden both in spring (56 %) and annually (37 %), with the largest contribution in the middle troposphere (400-700 hPa). Anthropogenic emissions from northern Asia contribute considerable BC (27% in spring and 43% annually) to the lower troposphere (below 900 hPa). Biomass burning contributes 20% to the Arctic BC column annually. At the Arctic surface, anthropogenic emissions from northern Asia (40-45 %) and eastern and southern Asia (20-40 %) are the largest BC contributors in winter and spring, followed by Europe (16-36 %). Biomass burning from North America is the most important contributor to all stations in summer, especially at Barrow. Our adjoint simulations indicate pronounced spatial heterogeneity in the contribution of emissions to the Arctic BC column concentrations, with noteworthy contributions from emissions in eastern China (15 %) and western Siberia (6.5 %). Although uncertain, gas flaring emissions from oilfields in western Siberia could have a striking impact (13 %) on Arctic BC loadings in January, comparable to the total influence of continental Europe and North America (6.5% each in January). Emissions from as far as the Indo-Gangetic Plain could have a substantial influence (6.3% annually) on Arctic BC as well. [ABSTRACT FROM AUTHOR]

The first multi-year contributions from organic functional groups to the Arctic submicron aerosol are documented using 126 weekly-integrated samples collected from April, 2012 to October, 2014 at the Alert Observatory (82.45° N, 62.51° W). Results from the particle transport model FLEXPART, linear regressions among the organic and inorganic components and Positive Matrix Factorization (PMF) enable associations of organic aerosol components with source types and regions. Lower organic mass concentrations (OM) but higher ratios of OM to non-sea-salt sulphate mass concentrations (nss-SO4=) accompany smaller particles during the summer (JJA). Conversely, higher OM but lower OM/nss-SO4= accompany larger particles during winter-spring. OM ranges from 7-463 ng m-3, and the study average is 129 ng m-3. The monthly maximum in OM occurs during May, one month after the peak in nss-SO4= and two months after that of elemental carbon (EC). Winter (DJF), spring (MAM), summer and fall (SON) values of OM/nss-SO4= are 26 %, 28 %, 107 % and 39 %, respectively, and overall about 40 % of the weekly variability in the OM is associated with nss-SO4=. Respective study-averaged concentrations of alkane, alcohol, acid, amine and carbonyl groups are 57 ng m-3, 24 ng m-3, 23 ng m-3, 16 ng m-3 and 11 ng m-3, representing 42 %, 22 %, 18 %, 14 % and 5 % of the OM, respectively. Carbonyl groups, detected mostly during spring, may have a connection with snow chemistry. The seasonally highest O/C occurs during winter (0.85) and the lowest O/C is during spring (0.51); increases in O/C are largely due to increases in alcohol groups. During winter, more than 50 % of the alcohol groups are associated with primary marine emissions, consistent with Shaw et al. (2010) and Frossard et al. (2011). A secondary marine connection, rather than a primary source, is suggested for the highest and most persistence O/C observed during the coolest and cleanest summer (2013), when alcohol and acid groups made up 63% of the OM. A secondary marine source may be a general feature of the summer OM, but higher contributions from alkane groups to OM during the warmer summers of 2012 (53 %) and 2014 (50 %) were likely due to increased contributions from combustion sources. Evidence for significant contributions from biomass burning (BB) was present in 4 % of the weeks. During the dark months (NDJF), 29 %, 28 % and 14 % of the nss-SO4=, EC and OM were associated with transport times over the gas flaring region of Northern Russia and other parts of Eurasia. During spring, those percentages drop to 11 % and 8 % for nss-SO4= and EC, respectively, and there is no association of OM. Large percentages of the Arctic Haze characterized at Alert likely have origins farther than 10 days transport time and may be from outside of the Eurasian region. Possible sources of unusually high nss-SO4= and OM during September-October, 2014 are volcanic emissions or the Smoking Hills' area of the Northwest Territories, Canada. [ABSTRACT FROM AUTHOR]

Absorption of sunlight by black carbon (BC) warms the atmosphere, which may be important for Arctic climate. The measurement of BC is complicated by the lack of a simple definition of BC and the absence of techniques that are uniquely sensitive to BC (e.g. Petzold et al., 2013). At the Global Atmosphere Watch baseline observatory at Alert, Nunavut (82.5°N), BC mass is estimated in three ways, none of which fully represent BC: conversion of light absorption measured with an Aethalometer to give equivalent black carbon (EBC), thermal desorption of elemental carbon from weekly-integrated filter samples to give elemental carbon (EC), and measurement of incandescence from the refractory black carbon (rBC) component of individual particles using a Single Particle Soot Photometer (SP2). Based on measurements between March 2011 and December 2013, EBC and EC are 2.7 and 3.1 times higher than rBC respectively. The EBC and EC measurements are influenced by factors other than just BC, and higher estimates of BC are expected from these techniques. Some bias in the rBC measurement may result from calibration uncertainties that is difficult to estimate here. Considering a number of factors, our best estimate of BC mass at Alert, which may be useful for evaluation of chemical transport models, is an average of the rBC and EC measurements with a range bounded by the rBC and EC combined with the respective measurement uncertainties. Winter, spring, summer, and fall averaged (±atmospheric variability) estimates of BC mass at Alert for this study period are 49±28ngm-3, 30±26ngm-3, 22±13ngm-3, and 29±9ngm-3, respectively. Average coating thicknesses estimated from the SP2 are 25% to 40% of the 160-180nm diameter rBC core sizes. For particles of approximately 200-400nm optical diameter, the fraction containing rBC cores is estimated to be between 10% and 16%, but the possibility of smaller undetectable rBC cores in some of the particles cannot be excluded. Mass absorption coefficients (MAC)±uncertainty at 550nm wavelength, calculated from light absorption measurements divided by the best estimates of BC mass concentrations, are 8±4, 8±4, 5±2.5 and 9±4.5m2g-1, for winter, spring, summer and fall respectively. Adjusted to better estimate absorption by BC only, the winter and spring values of MAC are 7.6±3.8 and 7.7±3.8m2g-1. There is evidence that the MAC values increase with coating thickness. [ABSTRACT FROM AUTHOR]

Observations addressing effects of aerosol particles on summertime Arctic clouds are limited. An airborne study, carried out during July 2014 from Resolute Bay, Nunavut, Canada, as part of the Canadian NETCARE project, provides a comprehensive in situ look into some effects of aerosol particles on liquid clouds in the clean environment of the Arctic summer. Median cloud droplet number concentrations (CDNC) from 62 cloud samples are 10 cm-3 for low-altitude cloud (clouds topped below 200 m) and 101 cm-3 for higher-altitude cloud (clouds based above 200 m). The lower activation size of aerosol particles is ≤50 nm diameter in about 40% of the cases. Particles as small as 20 nm activated in the higher-altitude clouds consistent with higher supersaturations (S) for those clouds inferred from comparison of the CDNC with cloud condensation nucleus (CCN) measurements. Over 60% of the low-altitude cloud samples fall into the CCN-limited regime of Mauritsen et al. (2011), within which increases in CDNC may increase liquid water and warm the surface. These first observations of that CCN-limited regime indicate a positive association of the liquid water content (LWC) and CDNC, but no association of either the CDNC or LWC with aerosol variations. Above the Mauritsen limit, where aerosol indirect cooling may result, changes in particles with diameters from 20 to 100 nm exert a relatively strong influence on the CDNC. Within this exceedingly clean environment, as defined by low carbon monoxide and low concentrations of larger particles, the background CDNC are estimated to range between 16 and 160 cm-3, where higher values are due to activation of particles ≤50 nm that likely derive from natural sources. These observations offer the first wide-ranging reference for the aerosol cloud albedo effect in the summertime Arctic. [ABSTRACT FROM AUTHOR]

The Arctic is extremely sensitive to climate change. Shrinking sea ice extent increases the area covered by open ocean during Arctic summer, which impacts the surface albedo and aerosol and cloud properties among many things. In this context extensive aerosol measurements (aerosol composition, particle number and size, cloud condensation nuclei, and trace gases) were made during 11 flights of the NETCARE July, 2014 airborne campaign conducted from Resolute Bay, Nunavut (74N, 94W). Flights routinely included vertical profiles from about 60 to 3000 m a.g.l. as well as several low-level horizontal transects over open ocean, fast ice, melt ponds, and polynyas. Here we discuss the vertical distribution of ultrafine particles (UFP, particle diameter, dp: 5-20 nm), size distributions of larger particles (dp: 20 nm to 1 μm), and cloud condensation nuclei (CCN, supersaturation = 0.6%) in relation to meteorological conditions and underlying surfaces. UFPs were observed predominantly within the boundary layer, where concentrations were often several hundreds to a few thousand particles per cubic centimeter. Occasionally, particle concentrations below 10 cm-3 were found. The highest UFP concentrations were observed above open ocean and at the top of low-level clouds, whereas numbers over ice-covered regions were substantially lower. Overall, UFP formation events were frequent in a clean boundary layer with a low condensation sink. In a few cases this ultrafine mode extended to sizes larger than 40 nm, suggesting that these UFP can grow into a size range where they can impact clouds and therefore climate. [ABSTRACT FROM AUTHOR]

Biomass burning emissions emit a significant amount of trace gases and aerosols and can affect atmospheric chemistry and radiative forcing for hundreds or thousands of kilometers downwind. They can also contribute to exceedances of air quality standards and have negative impacts on human health. We present a case study of an intense wildfire plume from Siberia that affected the air quality across the Pacific Northwest on July 6-10, 2012. Using satellite measurements (MODIS True Colour RGB imagery and MODIS AOD), trajectories, and dispersion modelling, we track the wildfire smoke plume from its origin in Siberia to the Pacific Northwest where subsidence ahead of a subtropical Pacific High made the plume settle over the region. The normalized enhancement ratio of O3 and PM1 relative to CO of 0.26 and 0.09 are consistent with a plume aged 6-10 days. The aerosol mass in the plume was mainly submicron in diameter (PM1/PM2.5 = 0.97) and the part of the plume sampled at the peak of Whistler Mountain was 87% organic material. Stable atmospheric conditions along the coast limited the initial entrainment of the plume and caused local anthropogenic emissions to buildup. A synthesis of air quality from the regional surface monitoring networks describes changes in ambient O3 and PM2.5 during the event and contrasts them to baseline air quality estimates from the AURAMS chemical transport model without wildfire emissions. Overall, the smoke plume contributed significantly to the exceedances in O3 and PMM2.5 air quality standards and objectives that occurred at several communities in the region during the event. Peak enhancements in 8-hr O3 of 34-44 ppbv and 24-hr PM2.5 of 14-32 μg/m³ were attributed to the effects of the smoke plume across the Interior of British Columbia and at the Whistler Peak high elevation site (2182 m ASL). Lesser enhancements of 10-12 ppbv for 8-hr O3 and of 4-9 μg/m³ for 24-hr PM2.5 occurred at Whistler Peak and across coastal British Columbia and Washington State. The findings suggest that the large air quality impacts seen during this event were a combination of the efficient transport of the plume across the Pacific, favorable entrainment conditions across the BC interior and the large scale of the Siberian wildfire emissions. A warming climate increases the risk of increased wildfire activity and events of this scale re-occurring under appropriate meteorological conditions. [ABSTRACT FROM AUTHOR]

A ground-based lidar system that has been deployed in Whistler, British Columbia, Canada, since the spring of 2010 provides a means of evaluating vertical aerosol structure in a mountainous environment. This information is used to help to determine when an air chemistry observatory atop Whistler Mountain (2182 m MSL) is within the free troposphere or is influenced by the valley-based planetary boundary layer (PBL). Three case studies are presented in which 1-day time series images of backscatter data from the lidar are analyzed along with concurrent meteorological and air-chemistry datasets from the mountaintop site. The cases were selected to illustrate different scenarios of diurnal PBL evolution that are expected to be common during their respective seasons. The lidar images corroborate assumptions about PBL influence as derived from analysis of diurnal trends in water vapor, condensation nuclei, and ozone. Use of all of these datasets together bolsters efforts to determine which atmospheric layer the site best represents, which is important when evaluating the provenance of air samples. [ABSTRACT FROM AUTHOR]