A11A-0076
Biomass-burning and Anthropogenic Impacts On Arctic Tropospheric Chemistry Assessed Using Measurements At Summit, Greenland
The seasonal variation of arctic air pollution is affected by emissions from boreal wildfires and anthropogenic sources. The transport of NOy (total reactive nitrogen oxides), non-methane hydrocarbon (NMHC) emissions and PAN from boreal wildfires to the Arctic during the summertime may have a larger impact on O3 and O3 precursors than anthropogenic emissions. However, there are a limited number of field observations from boreal wildfires in the Arctic and the current understanding of the magnitude of the impact of long-range transport of reactive nitrogen oxides and NMHCs on the arctic tropospheric O3 is limited. In order to improve understanding of emission sources and their impacts on tropospheric O3 in the Arctic, automated monitors have been installed at the GEOSummit station at Summit, Greenland (3208 m altitude) for a 2-year period beginning June 2008. The instruments will provide the first continuous year- round measurements of NOx (NO and NO2), NOy, PAN and NMHC in the high-altitude Arctic. The resulting dataset, coupled with simultaneous station measurements of ozone, CO and black carbon will provide information on seasonally varying emissions and transport to the Arctic. The measurements will be analyzed to identify periods of CO enhancement and in conjunction with the FLEXPART transport model to identify specific source regions of anthropogenic and biomass-burning transport and to determine their impact on NOy and NMHC levels within the Arctic. Here, we present first data during the startup period of June to August 2008 along with FLEXPART simulations to identify pollution transport events during this period. In addition, measurements during aircraft flights over Summit in July 2008 will be used for further interpretation of the ground-based data.
A11A-0077
The air we breathed; the climatology of a 12, 000 kilometre cruise through the North Atlantic.
Aerosols have a large effect on radiation transmission in the Arctic troposphere, both directly and indirectly via clouds. The spring IPY POLARCAT project coordinated numerous projects to study transport to the Arctic of aerosols, as well as of air pollution more generally from anthropogenic sources. The NOAA International Chemistry Experiment in the Arctic Lower Troposphere (ICEALOT) cruise was conducted aboard the R/V Knorr in the North Atlantic Ocean and the Greenland, Norwegian, and Barents Seas from 41-80 degrees N during March and April of 2008. During the cruise we encountered air masses from a variety of sources including fresh continental outflow, aged plumes, pristine Arctic air pristine Arctic air, marine vessel emissions, and coastal point sources. Results from lagrangian particle dispersion modelling and synoptic meteorological analysis will be described to present a picture of the air we breathed.
A11A-0078
Measurements of Reactive Nitrogen Species From R/V Knorr During ICEALOT
The International Chemistry Experiment in the Arctic Lower Troposphere (ICEALOT) was an International Polar Year research activity to explore the sources, transport, and chemical processing of aerosol and gas phase species in the Arctic marine boundary layer. Measurements were conducted aboard the research vessel Knorr north of 60 N from March 31 to April 24, 2008. The cruise track included portions of the Norwegian, Barents, and Greenland Seas between 20 W and 30 E. The highest latitude achieved was 80 N, at the sea ice edge north of Svalbard. Measurements of individual reactive nitrogen species included NO, NO2, PAN, PPN, alkyl nitrates (C1-C3), and NOy (but not HNO3). With the exception of ports and near-shore source regions (Kola Peninsula), NOy ranged from 0.2 to 1.0 ppbv with a mean value of approximately 0.5 ppbv. The dominant individually measured NOy component was PAN which ranged from 0.05 to 0.35 ppbv with a mean value of approximately 0.24 ppbv. Mixing ratios of PPN ranged from 0.004 to 0.084 ppbv with a mean value of 0.044 ppbv. Mixing ratios of NOx were generally similar to PPN, with some periods when NOx was lower and some periods when PPN was lower. Mixing ratios of alkyl nitrates were typically quite low with 2-propyl nitrate levels higher than ethyl nitrate, which was higher than methyl nitrate. However, there were some episodes when methyl nitrate was present at levels higher than the others. Because HNO3 was not measured individually, we cannot conclude that the reactive nitrogen species budget was balanced. However, if the apparent deficit between the measured NOy and the sum of the individual NOy species is attributed to HNO3, then that compound is present in the Arctic atmosphere at levels substantially higher than previously measured.
A11A-0079
Emissions from International Shipping in the Arctic
Studies assessing the potential impacts of international shipping on climate and air pollution demonstrate that ships contribute significantly to global climate change and health impacts through emission of GHGs and raised the potential for disproportionate impacts from shipping in the Arctic region. We present an activity- based model inventory of emissions of CO2, BC, NOx, SOx, PM, and CO for shipping in the Arctic. We estimate emissions for a particular "vessel-trip" or "voyage" based on Arctic shipping data collected by the Arctic Marine Shipping Assessment for 2004. The detailed voyage data provided for our inventory effort included some 3800 ship trips, represent some 2.6 million km of ship voyages (range 2.0 to 3.9 million km, or 1.1 to 2.1 million nautical miles), and nearly 15,000 voyage days for 2004; this is equivalent to less than 500 transoceanic voyages, compared to many tens of thousands transoceanic voyages per year to major ports around the world. In 2004, the top five vessel types, bulk carrier, general cargo, fishing, government vessels, and containerships, account for nearly 80 percent of total emissions. Preliminary results show CO2 emissions from shipping in the Arctic to be approximately 2.3 Tg CO2 per yr. Given that total CO2 emissions from international shipping globally are about 1000 Tg CO2 per yr, Arctic contributions would amount to less than 0.25 percent of total ship emissions. Relative to total CO2 emissions from all sources, the contributions of Arctic shipping are on the order of one-hundredth of one percent (0.006-0.008 percent). BC emissions from Arctic shipping, on a mass basis alone (estimated here to be ~600 tonnes /year), may have limited independent impact on global climate change compared to other sources, but could have significant regional impacts. More concerning may be micro-scale emissions (e.g., at harbor or in port) which could affect local air pollution or ecosystems, depending on regional conditions. Pollutants with more regional impact include NOx, SOx, CO, and PM. For these pollutants Arctic shipping emissions are small contributors to global inventories on a mass basis. For example, Arctic shipping accounts for about 62,400 tonnes per year of NOX pollution in the Arctic region, about 0.3 percent of 25.6 Tg of NOx (as NO2, or 7.8 Tg as N in 2007) global ship NOx emissions. Future trends toward increased international shipping in the Arctic will increase these numbers proportional to the increased traffic, although future research is needed to determine whether the increased climate-scale impacts would be proportional to Arctic shipping activity. Previous research (Granier et al, GRL 2006) indicated that shipping growth could account for an additional 0.65 to 1.3 million Tg N from Arctic shipping (2.5 Tg to 4.9 Tg NOx as NO2). Using our preliminary inventory results, this corresponds to between 40 and 70 times more Arctic shipping activity in 2050 than in 2004, representing annually compounding growth rates in the range of 8 to 10 percent. We will present our inventory and discuss data quality needs to better reduce the uncertainty in Arctic shipping inventories.
A11A-0080 [WITHDRAWN]
Investigation of the Aerosols Over the Los Angeles Basin during the ARCTAS-CARB 2008 Pilot Study
In the summer of 2008 during preparation for the second phase of the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS), detailed measurements of atmospheric composition were made on-board the NASA DC-8 over the state of California on behalf of the California Air resources Board (CARB). Four flights were conducted between 18 July and 24 July, totaling 31 hours, over southern and central California to establish upwind chemical boundary conditions and gain a better understanding of the sources, chemical characteristics and spatial distribution of smog and greenhouse gases over the state. Serendipitously, from a science perspective, this time period was marked by numerous wildfires spread throughout the state. The DC-8 sensor suite included aerosol instruments capable of measuring the number concentrations, optical properties, and size distributions of aerosols between 0.003 and 20 um in diameter. In this presentation, we will characterize aerosols sampled during sorties over the Los Angeles basin, which included several missed approaches at Los Angeles International Airport (LAX), traverses through the Long Beach and Santa Barbara ship channels, sampling in and out of the marine boundary layer, and encounters with outflow of forest fires mixed with urban smog. We will examine the evolution of the aerosols over the course of the day, as the smog accumulates within the basin and is then transported out of the basin into the surrounding atmosphere.
A11A-0081
Submicron Aerosol Composition during the ARCTAS campaign: Arctic Haze, Biomass Burning, and California Pollution
A High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS, DeCarlo et al., Anal. Chem., 2006) was deployed aboard the NASA DC-8 research aircraft as part of the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) campaign during the spring and summer of 2008. One focus of the spring phase, operated out of Fairbanks, AK, was to investigate the composition and sources of Arctic Haze (see e.g. Quinn et al., Tellus B, 2007), a persistent pollution layer that accumulates under the stable springtime Polar High anti-cyclonic weather pattern. Results are presented comparing the sulfate-dominated composition of the Arctic Haze with observed North American pollution and biomass- burning layers. A further objective of the spring phase was to investigate halogen chemistry at the sea-ice surface. High-resolution spectra clearly show bromine in the aerosol phase in the marine boundary layer during periods of ozone depletion, and relate this to concurrent gas-phase observations aboard the DC-8. During the summer phase, operated out of Palmdale, CA and Cold Lake, Alberta, the focus was investigating pollution in California and the composition and evolution of the outflow from large-scale boreal forest fires, respectively. Using recently-developed software that enabled the AMS to sample at 1 Hz, the smoke plumes could be clearly differentiated from the background aerosol, detailed vertical profiles were measured during spiral descents and aerosol volatility was characterized with a thermodenuder. Aerosol biomass-burning markers exhibit high correlation with gas-phase fire markers for both Canadian boreal and Californian forest fires. Emission ratios and composition (e.g. inorganic species, organic O/C) are characterized for the different fires. Data from smoke plumes sampled over the extensive summer fires in California provide a contrast in emission profiles to the Canadian boreal biomass-burning aerosol. Finally, aerosol pollution in Southern CA and the Central Valley is analyzed and compared to previous studies.
A11A-0082
Hygroscopic Properties of Aerosol Particles in the Arctic
The hygroscopicity and volatility of aerosol particles in the Arctic were studied during the IPY-ICEALOT mission in March/April 2008 on board the R/V Knorr. A hygroscopicity tandem differential mobility analyzer (HTDMA) measured behind a thermodenuder scanning the temperature range 50-250C, thereby acquiring hygroscopic growth factors as a function of volatilization temperature. Every second scan the sample flow bypassed the thermodenuder and we measured ambient air. The sizes investigated by the HTDMA were 50, 100 and 150 nm, providing information of both Aitken and accumulation mode aerosol. On average during the cruise, the hygroscopic growth factors resembled those of ammonium sulfate. This is in line with data from a high resolution aerosol mass spectrometer (HR-AMS) which also sampled behind the thermodenuder, showing that the submicron aerosol was dominated by sulfate and oxygenated organics. The hygroscopic properties of the particles directly influence their size and therefore their radiative properties, and additionally determine the size at which a particle will activate and form a cloud droplet, contributing to the indirect cooling effect of the aerosol particles. A more detailed analysis will be performed, including case studies of continental outflow and comparisons with the HR-AMS and other chemical and physical measurements conducted on the ship.
A11A-0083
The dependence of aerosol light extinction on relative humidity during the spring 2008 ICEALOT experiment in the European Arctic
Aerosol properties were measured onboard the R/V Knorr in the European Arctic Ocean during the IPY- ICEALOT campaign (March - April 2008). This experiment was designed to give insights into the characteristics and sources of aerosols emitted within the Arctic or transported from mid-latitudes. One of the goals was the characterization of Arctic haze, a phenomenon that originates from the confinement of pollutants in the stable Arctic springtime boundary layer. The multi-wavelength cavity ring down spectrometer (CRD) provided measurement of both aerosol light extinction and its dependence on relative humidity here expressed as gamma. The CRD was coupled with the photo acoustic spectrometer to determine aerosol absorption and the single scattering albedo of the sampled aerosols. All the listed parameters are reported at 532 nm. In general, aerosol levels were rather low (< 10 Mm-1), and particles were highly hygroscopic (gamma > 0.9) and non-absorbing (albedo ~ 0.95). This study focuses on the aerosol hygroscopic properties from CRD during particular events and time periods. For instance, unusually high gamma values (up to 2.5) characterized the air masses sampled off the Kola Peninsula (71 N-19 E): such highly hygroscopic aerosols coincided generally with SO2 plumes, and at times were highly correlated with bursts of ultra-fine particles. We also present the characteristics of the aerosols under conditions of Arctic haze, i.e., slightly absorbing and less hygroscopic air masses (gamma between 0.85 and 1) compared to the emissions from the Kola Peninsula. Finally we report the emissions from fishing boats sampled in the vicinity of the Norwegian coast, and a pollution event from North Europe (as indicated by the Lagrangian model for particle diffusion and dispersion FLEXPART) during which we observed extinction up to 15 Mm-1, and slightly lower gamma and particle albedo values, indicating "fresher" air masses. These results are important for further understanding the characteristics of Arctic springtime aerosols and assessing their direct radiative effect for the overall forcing of a warming Arctic system.
A11A-0084
Single Particle Mass Spectrometry Measurements During the ASCOS 2008 Field Campaign: First results of the Aerosol Chemical Composition and CCN Activity in the Arctic
In-situ, single-particle mass spectrometric measurements of the chemical composition of the regional aerosol in the Arctic, north of 80°N, were carried out onboard the Swedish icebreaker Oden during the 2008 Arctic Summer Cloud Ocean Study ASCOS (field campaign in August through September 2008). The chemical composition was measured for single particles with diameters of ~ 300nm.
A11A-0085
CCN Measurements of Forest Fire Plumes Aboard the NASA DC-8 and P3-B Aircraft Platforms During ARCTAS
We present an overview of Cloud Condensation Nuclei (CCN) measurements for forest fire plumes sampled during the summer phase of the 2008 NASA Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) campaign. Measurements were obtained aboard the NASA DC-8 and P3-B platforms, with the primary focus of studying the characteristics and ageing of the biomass forest fire plumes present over Alberta, Canada during July, 2008. The DC-8 flew eight flights and the P3-B flew nine flights out of Cold Lake in Alberta, Canada, which included in-situ samples from fresh and aged biomass burning plumes, sampling of plumes from different stages of development, plume profiling and evolution, and interactions between smoke and cloud. We present the CCN number concentration and growth kinetics in the various biomass plumes as compared to the background conditions and will discuss the changes in growth kinetics in response to plume ageing. We will also explore the differences in CCN and growth kinetics encountered between flaming and smoldering fire plumes near the source. The comprehensive nature of the sampling and the large number of plumes encountered makes this a valuable data set for constraining uncertainties associated with prediction of CCN concentration and cloud droplet number for clouds influenced by biomass burning. These investigations related to CCN closure will have the underlying focus on improving aerosol-cloud parameterizations.
A11A-0086
Airborne measurements of biomass burning aerosol distribution and composition in the springtime Arctic 2008
The springtime Arctic troposphere in 2008 was characterized by high concentrations of biomass burning aerosol. During the Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC) campaign, airborne measurements of aerosol composition by the NOAA single particle mass spectrometer instrument (PALMS) identified biomass burning particles using an established composition tracer. Fires in northern Asia produced biomass burning aerosol that were transported to the Arctic within 3-12 days. Concentrations of biomass burning aerosols were elevated not only within well defined plumes, but also regionally throughout the Arctic. Above the boundary layer, biomass burning particles dominated the total aerosol volume and were largely responsible for the Arctic Haze observed during the period of study. The composition of plume aerosols varied according to source region, transport time, and anthropogenic influence.
A11A-0087
Influence of Biomass Burning and Mid-latitude Pollution on the Arctic Atmosphere During the ARCTAS Field Campaign: A Three Dimensional Modeling Analysis
The Arctic Research on the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) field campaign took place during the spring (April 1-21) and summer (June 26-July 12) of 2008. The major objectives of this mission were to study the long range transport pathways of pollution (spring phase) to the Arctic and assess the impact of biomass burning (summer phase) on the Arctic atmosphere. Multiple observations platforms including satellites, aircrafts, and surface stations were deployed during the mission to understand the chemistry and composition of the Arctic atmosphere. The University of Iowa's Sulfur Transport and dEpostion model (STEM), a comprehensive 3-dimensional regional scale model, provided high resolution chemical weather forecasts to support the intensive aircraft measurements and to assist in interpreting the observations. In this study, we will present the results of the inter-comparison of the model trace gas and aerosol distributions with the aircraft observations. Further insights into the source receptor relationships of trace gases and aerosols using air mass trajectories and regional emission tracers will be shown to characterize the evolution of pollution and thereby improve our current understanding of the Arctic chemistry and composition.
A11A-0088
The Influence of Distant Fires on the Chemical Properties of Arctic Aerosol During the Spring of 2008
Investigating Arctic aerosol chemical properties and sources was a primary component of the spring 2008 Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC) airborne field study above Alaska and the nearby Arctic Ocean. Size-resolved, non-refractory (NR) aerosol composition was measured on a 10-second basis and with high sensitivity aboard the NOAA WP-3D aircraft using an Aerodyne Compact Time-of-Flight Aerosol Mass Spectrometer (C-ToF AMS). Other onboard measurements included aerosol black carbon, single particle aerosol mass spectra, aerosol size distributions, and aerosol extinction as well as carbon monoxide (CO), sulfur dioxide, ozone, and volatile organic compounds. The aerosol chemical composition was highly variable as a function of altitude, in some cases within a few 100s of meters, with generally higher organic mass fractions at higher altitudes. Long-range transport of biomass burning pollutants (CO, acetonitrile, and aerosols) from large fires in the Lake Baikal (Russia) and Kazakhstan regions was observed at these altitudes and contributed to the highest measured aerosol concentrations during this study. The biomass burning organic material was highly oxidized, as measured by the m/z 44 to organic mass ratio. The peak at m/z 60, considered to be an AMS marker for biomass burning, was enhanced in these plumes along with the single particle biomass burning marker of potassium. Furthermore, these markers of biomass burning particles were observed when the sulfate mass fraction was higher and with lower aerosol mass concentrations. This indicates that biomass burning was an important source of the organic mass in background Arctic aerosol during the study period.
A11A-0089
GEM-AQ Modelling of Smoke Events Observed in the High Arctic at Eureka, Canada
Fine-mode aerosol events that could be traced back to forest fires in Siberia, Russia and Northwest Territories, Canada were observed during the summer of 2007 and spring of 2008 at the Polar Environment Atmospheric Research Laboratory (PEARL) located at Eureka on Ellesmere Island. The simulation of these events was performed with the Global Environmental Multiscale Air Quality model (GEM-AQ), a global, tropospheric chemistry, general circulation model based on the three-dimensional global variable-resolution multi-scale model developed by the Meteorological Service of Canada for operational weather prediction. GEM-AQ includes a size-resolved multi-component aerosol module. The chemical mechanism used in this study is comprised of 52 gas-phase species and 137 chemical and photolysis reactions. The model output is compared with vertical profiles from the Arctic High Spectral Resolution Lidar (AHSRL) and with spectral sunphotometer data acquired at Eureka, as well as with MODIS, CALIOP and OMI products over the Arctic. In addition, modelled tropospheric columns of carbon monoxide and ethane are compared with measurements made with the PEARL Fourier transform infrared spectrometer.
A11A-0090
UAFSmoke Modeling in Alaska
Alaska wildfires have strong impact on air pollution on regional Arctic, Sub-Arctic and even hemispheric
scales. In response to a high number of wildfires in Alaska, emphasis has been placed on developing a
forecast system for wildfire smoke dispersion in Alaska.
We have developed a University of Alaska Fairbanks WRF/Chem smoke (UAFSmoke) dispersion system,
which has been adapted and initialized with source data suitable for Alaska. UAFSmoke system modules
include detection of wildfire location and area using Alaska Fire Service information and satellite remote
sensing data from the MODIS instrument. The fire emissions are derived from above ground biomass fuel
load data in one-kilometer resolution. WRF/Chem Version 3 with online chemistry and online plume dynamics
represents the core of the UAFSmoke system. Besides wildfire emissions and NOAA's Global Forecast
System meteorology, WRF/Chem initial and boundary conditions are updated with anthropogenic and sea
salt emission data from the Georgia Institute of Technology-Goddard Global Ozone Chemistry Aerosol
Radiation and Transport (GOCART) Model.
System runs are performed at the Arctic Region Supercomputing Center's Sun Opteron cluster "Midnight".
During the 2008 fire season once daily UAFSmoke runs were presented at a dedicated webpage at
http://smoke.arsc.edu. We present examples from these routine runs and from the extreme 2004 Alaska
wildfire season.
http://smoke.arsc.edu
A11A-0091
Study of Interannual Variability of Boreal Biomass Emission Using MODIS Aerosol Optical Depth Retrievals
During ARCTAS (Arctic Research of the Composition of the Troposphere from Aircraft and Satellites) field experiments of spring and summer phases, boreal biomass burning played an important role in the long- range transported aerosols to the Arctic. The effects are significant in aradiative forcing caused by the light- absorbing soot particles as models had indicated. To understand the transport, however, we need first to locate the source regions. Aerosol Optical Depth (AOD) retrievals from the MODerate resolution Imaging Spectroradiometer (MODIS) sensors on NASA's Terra and Aqua Satellites were used to identify source areas of significant boreal biomass burning emissions at north of 50° latitude circle. With a set of time series of daily mean AOD constructed for all source areas of 5° x 5° grids, interannual variability is analyzed from March 2000 through August 2008 The correlation of number of high smoke activity events per month with satellite/model-derived carbon emissions show a maximum value (0.8-0.9) as AOD is greater than 0.4 in both Eurasia and North America. However there appears to be no correlation between these two regions, which indicates the complexity of the causes of the biomass burning events. In studying the response to climate cycles, the time series of monthly AOD means are correlating with ENSO, PDO as well as several northern hemisphere teleconnection patterns (such as PNA, POL). In summary, it can be concluded that (1) MODIS AOD retrievals adequately characterize boreal forest biomass-burning emissions, and (2) North American seasonal fire activity is closely associated with positive ENSO phase whereas Eurasia fire activity is more related to the negative ENSO phase of the previous winter months, and (3) PDO and other teleconnection patterns appear to play a modulating role in the fire activities of boreal biomass burning.
A11A-0092
Using CALIPSO Observations to Evaluate Model Predictions of Aerosol Transport into the Arctic
It is well recognized that Arctic atmospheric chemistry and climate are impacted by the long-range transport of both natural and anthropogenic aerosol from sources at lower latitudes. Our understanding of these phenomena are largely based on model studies, aided by measurements from a very few ground sites. There are large differences in the predictions from different models, however, and transport pathways from source regions into the Arctic are not well understood. Until very recently, the utility of satellite observations for evaluating the representativeness of the predicted aerosol distributions has been rather limited. Passive satellite sensors observe the column amount of aerosols, but provide little information on the aerosol vertical distribution and have limited capabilities at high latitudes. The CALIPSO satellite, launched in April 2006, carries a two-wavelength polarization lidar which provides new opportunities for evaluating model predictions of aerosol distribution and transport. The lidar has inherently high vertical resolution and observes aerosol both day and night. Lidar retrievals provide profiles of aerosol extinction. CALIPSO observations are compared with aerosol distributions from two global models: RAQMS and the NASA GMAO GEOS-5. Significant differences are seen in the aerosol distributions predicted by the two models even though they both use the GOCART aerosol package. The zonal aerosol distribution observed by CALIPSO differs from both models in significant ways. Strengths and weakness of the models in comparison to CALIPSO observations will be discussed.
A11A-0093
Investigation of tracer emission and transport in GEOS-5 during ARCTAS
The NASA aircraft experiment, Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS), was conducted during April, 2008 at Fairbanks, Alaska and June - July, 2008 at Cold Lake, Canada. During ARCTAS the NASA Global Modeling and Assimilation Office ran 0.5 x 0.666 degree global 5-day forecasts of the Goddard Earth Observing System atmospheric general circulation model and data assimilation system (GEOS-5). In addition to meteorological fields, the GEOS-5 provided atmospheric distributions of aerosols, CO, and other tracers for flight planning and for data analysis. Here we examine the comparison of GEOS5 CO and aerosol with observations from the ARCTAS mission to evaluate model's sources, sinks, chemistry, and transport. We particularly highlight the events of Asian anthropogenic long- range transport during spring phase and biomass burning emission and transport during summer phase and their impact on Arctic pollution.
A11A-0094
Daily Ozonesonde Launches at Barrow, Alaska During ARCTAS: April 1-21, 2008.
Daily ozonesondes were launched from the NOAA/ESRL Barrow Observatory (71.32N, 156.6W) from April 1- 21, 2008 during the ARCTAS spring campaign (Arctic Research of the Composition of the Troposphere from Aircraft and Satellites). Barrow was one of 13 sites in Canada and the U.S. launching daily ozonesondes (http://croc.gsfc.nasa.gov/arcions/) to look at springtime polar transport, tropospheric ozone budgets, and provide comparisons with the Tropospheric Emission Spectrometer (TES) satellite overpasses. Total column ozone from the ozonesondes were 3.9 +/- 3.5% higher than the Barrow Dobson spectrophotometer. Prelaunch surface checks showed the ozonesonde to be consistently within +/- 0.6 ppbv of the Barrow surface Thermo Environmental Instruments (TEI) ozone monitor. The daily Barrow ozonesonde launches also provided a look at the vertical extent of an Arctic springtime surface ozone depletion event. These events are believed to be due to the springtime increase of natural halogen compounds, such as bromine and chlorine that react with ozone. The ozonesondes and the surface ozone measurements at Barrow Observatory showed one event when surface ozone dropped and remained at 3-6 ppbv for 2 days from April 15 to April 17. The low ozone extended from the surface to 210-260 meters altitude where ozone increased abruptly to 40-50 ppbv. The Chukchi Sea in the Arctic Ocean surrounds Barrow Observatory to the west, north, and east, with level tundra or permafrost to the south. However, the very low ozone was measured while the wind was coming from a relatively narrow west/northwest direction.
A11A-0095
Aerosol properties derived from spectral actinic flux measurements
Measurement of aerosol properties is very important for understanding climate change. Aerosol optical properties influence solar radiation throughout the troposphere. According to the Working Group I report of the intergovernmental panel for climate change [IPCC, 2007], aerosols have a direct radiative forcing of - 0.5±0.4 W/m2 with a medium to low level of scientific understanding. This relatively large uncertainty indicates the need for more frequent and precise measurements of aerosol properties. We will show how actinic flux measurements can be used to derive important optical aerosol parameters such as aerosol optical thickness and depth, surface albedo, angstrom exponent, radiative forcing by clouds and aerosols, aerosol extinction, and others. The instrument used for this study is a combination of two spectroradiometers measuring actinic flux in the ultraviolet and visible radiation range from 280 to 690 nm with a resolution of 1 nm. Actinic flux is measured as the radiation incident on a spherical surface with sensitivity independent of direction. In contrast, irradiance is measured as the radiation incident on a plane surface, which depends on the cosine of the incident angle. Our goal is to assess the capabilities of using spectral actinic flux measurements to derive various aerosol properties. Here we will compare 1) actinic flux measurements to irradiance measurements from the spectral solar flux radiometer (SSFR), 2) derived aerosol size distributions with measurements from a white light optical particle counter (WLOPC) and ultra high sensitivity aerosol size spectrometer (UHSAS), and 3) derived aerosol optical extinction with measurements from a cavity ringdown aerosol extinction spectrometer (CRD-AES). These comparisons will utilize data from three recent field campaigns over New England and the Atlantic Ocean (ICARTT 2004), Texas and the Gulf of Mexico during (TexAQS/GoMACCS 2006), and Alaska and the Arctic Ocean (ARCPAC 2008) when the instruments were installed on board the NOAA WP-3D aircraft. IPCC (2007), Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
A11A-0096
Micro-pulse Lidar Observations of the Arctic Haze During ICEALOT 2008
The annual peak concentration of atmospheric aerosols above the Arctic occurs in March and April in an event called the Arctic haze, which has implications for climate and ecosystem health. The NOAA-funded International Chemistry Experiment in the Arctic Lower Troposphere (ICEALOT) campaign traveled to the Barents Sea aboard the R/V Knorr, beginning in Woods Hole, MA on March 19, 2008 and ending in Reykjavik, Iceland on April 24. During that time, a variety of instruments observed the Arctic haze. The University of New Hampshire's AIRMAP program contributed a micro-pulse aerosol lidar (affiliated with NASA MPLNET) to the suite of instruments. The lidar allowed detection of the planetary boundary layer, clouds, and elevated aerosols. Results show examples of Arctic haze events, especially of aerosols within the planetary boundary layer and in the lower free troposphere between 1 and 10 km altitude. Overpasses by the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) mission, which includes its own aerosol backscatter lidar, and trajectory and chemical model output to interpret atmospheric dynamics were used to support interpretation of lidar data. Particulate pollution in the Arctic can be traced to specific midlatitude emissions sources, showing evidence of long-range atmospheric transport. Interaction between Arctic aerosols and the planetary boundary layer also occurs.
A11A-0097
Tropospheric ozone surface depletion (spring) and pollution (summer) in 2008 from the ARCTAS Intensive Ozonesonde Network Study (ARC-IONS) soundings
During NASA's ARCTAS (Arctic Research of the Composition of the Troposphere with Aircraft and Satellites; http://espo.nasa.gov/arctas) spring and summer 2008 campaigns, an ozonesonde network, ARC- IONS (ARCTAS Intensive Ozonesonde Network Study), launched ozonesonde-radiosonde packages each day (1-20 April, 26 June-12 July) during the A-Train satellite constellation overpass, ~1300 local. Seventeen ARC-IONS stations were located across the northern tier of North America, over both Alaska and Canada, with one site in Greenland and two in the western US; map at (http://croc.gsfc.nasa.gov/arcions). In addition to satellite validation, the soundings provided a coherent, well-distributed set of ozone profiles for: (1) comparison with and interpretation of airborne measurements; (2) complementarity to ARCTAS and IPY (International Polar Year) ground bases at Greenland, Barrow, Eureka, Yellowknife; (3) model evaluation; (4) investigations of processes affecting day-to-day ozone variability. Two aspects of tropospheric ozone variability are described here. First, ozone depletion likely associated with rapid halogen reactions, is prominent in spring at Barrow (71N, 157W) and Resolute (75N, 95W). Second, during summer, relationships among long-range transport of Asian pollution (industrial and fires), California and Canadian fires and daily ozone budgets are established with trajectories, satellite smoke/fire data and laminar identification, the latter method developed in Thompson et al. (2007) and Yorks et al. (2008). Canadian maritime stations display eastern seaboard pollution and stratospheric influences as in IONS-04 (INTEX Ozonesonde Network Study).
A11A-0098
Greenland Environmental Observatory at Summit (GEOSummit): Year-Round Measurements and Results
Long-term year-round sampling of the Arctic atmosphere and surface snow provide insight to the relationship
between aerosol and snow chemical compositions. Current research at the Greenland Environmental
Observatory, Summit Station (GEOSummit) includes high temporal resolution year-round measurements of
snow accumulation and spatial variability, IC and ICP-MS trace-element measurements of surface-snow and
snow-pit samples, DRUM aerosol size and S-XRF elemental composition, and other meteorological and snow
properties. These measurements allow for a better understanding of the magnitude and timing of the
seasonal cycles in aerosol elemental concentrations that are deposited and preserved in the snow pack,
some of which have not been previously reported. For example, specific events that transport pollution or
dust from North America and/or Asia can be identified. The source regions of these specific events are
identified using the Lagrangian Particle Dispersion Model (LPDM) FLEXPART. In addition, several elements
exhibit distinct seasonal cycles in concentrations preserved in the surface snow samples. Concurrent snow
accumulation rates were measured, thereby aiding the evaluation of wet and dry deposition as well as
quantifying the inter-annual variability in snow accumulation. Continuous longer-term records are necessary
for evaluating links between aerosol and snow chemistry to geophysical processes with multi-year
periodicities (e.g. NAO, AMO, etc). Future plans include continuing research measurements at GEOSummit
(5-yr continuation proposal submitted) to better characterize elemental concentrations in aerosols and snow,
annual to decadal variability in snowfall, and connections with atmospheric circulation and transport.
http://www.geosummit.org
A11A-0099
Aerosols in Alaska
We are measuring the latitudinal gradient and time variation of aerosol chemical composition across Alaska looking for drifts that might be attributable to alteration in sources and chemical signatures that might allow the identification of sources. Alaska is a very clean region in the sense that the state has a low population density with little polluting emission sources. However it "receives" anthropogenic chemical signals from areas upstream in the westerly's, such as from China, and impacts of Arctic Haze. The region also generates sometime copious amounts of aerosol from wildfire in its boreal forests and condensed compounds from gases emitted by its surrounding oceans. The time series of aerosol composition from this small network goes back about a decade and shows clearly the spring peaking of anthropogenic signal known as Arctic Haze. This signal peaks year after year in spring months at all stations, but is most concentrated at north most stations. On the other hand, a signal indicative of products from the ocean, mainly sulfate with large fractional amounts of MSA peaks, year after year, in the summer and is strongest at the lower latitudes. We have identified not only chemical signatures associated with wildfire smoke from wildfires in Alaska, but the changed signatures from wildfires in far away regions, from Mongolia for example.
A11A-0100
Distribution of Sulfate Aerosol over Northern North America and the Arctic Ocean during April, 2008
The NASA DC-8 conducted seven science and two transit flights during phase one of the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) campaign. Of these flights, three were local science flights from Fairbanks, Alaska, targeting the atmosphere over Alaska, the Bering Sea, and the Arctic Ocean north of Alaska. The other four science flights were overnight pairs from Fairbanks to Thule, Greenland and to Iqaluit, Nunavut. The overnight flights extended to the eastern Arctic near and north of Greenland. During all flights, fine (submicron) SO4= was measured at 90 second resolution using the paired mist chamber/ion chromatograph technique. Plumes of greatly enhanced SO4= were observed throughout the ARCTAS study region, but there was a significant difference in the background levels between the western and eastern regions sampled. Geometric mean mixing ratios in 1 km altitude bins below 6 km ranged from 245 to315 pptv west of 100° longitude compared to 170- 235 pptv to the east. In both regions observed mixing ratios were generally lower at higher altitudes. Bulk filter samples (5 - 10 minute resolution) indicate that the sulfate aerosol in the eastern region (and high Arctic) is dominantly a mixture of H2SO4 and NH4HSO4, compared to a mix of NH4HSO4 and (NH4)2SO4 over Alaska. These differences appear to reflect strong impact of Asian outflow on the airmasses sampled over the Bering Sea and Alaska compared to a mix of North American and European sources influencing the eastern Canadian Arctic and the Arctic Ocean north of Greenland. Surprisingly, the vertical profile of SO4= below 6 km in the eastern ARCTAS region was very similar to those observed during two April missions in the same broad region sampled as part of TOPSE in 2000.
A11A-0101
Observations and Comparison of SO2 Measurements Aboard the NOAA P-3 during ARCPAC
Instrument inter-comparisons play a crucial role in the successful execution of atmospheric measurement campaigns. The ability to quantify agreement among instruments that measure atmospheric compounds lends credence to the individual measurements and extends the scope of the overall study. One such measurement is that of sulfur dioxide (SO2). SO2 is the predominant anthropogenic sulfur- containing air pollutant. It plays an important role in the atmospheric sulfur cycle through its contribution to acidic aerosol formation, aerosol and cloud droplet modification, and acidic precipitation. Due to its large indirect impact on climate it is important to precisely know its sources, sinks and its atmospheric distribution. A modified TECO 43C-TL pulsed fluorescence instrument and a Chemical Ionization Mass Spectrometer (CIMS), were both deployed aboard the NOAA P-3 aircraft to measure SO2 during the Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC) field program. The detection technique, sampling configuration, and calibration methods of the instruments are described. The performance of each instrument is assessed using ambient data to examine detection sensitivity, background signal, and time response. Lastly, an evaluation of the comparative performance of the two measurements is presented, as are preliminary results examining both the Arctic SO2 distribution observed from the NOAA P-3 and SO2 emissions from the Fairbanks urban area.
A11A-0102
Behavior of OH, H2SO4, and MSA during ARCTAS
The NASA ARCTAS study presented a very unique opportunity to investigate the tropospheric chemistry of the Arctic environment, both rural and urban areas of California, and plumes and outflows from boreal fires in northern Canada. Here OH, H2SO4, and MSA data obtained from the NASA DC-8 will be presented. OH showed a large variation depending upon the type of environment sampled with values as low as 2-3 x 105 molecule cm-3 in the clean Arctic to well over 107 molecule cm-3 in urban areas or fire plumes. Values from H2SO4 reveal broad sources of sulfur outflow from both the L.A. and San Francisco regions with concentrations as high as 1x108 molecule cm-3. H2SO4 concentrations from the Arctic were highly varied with values ranging from 3-5x105 to 1x108 molecule cm-3. Observations of MSA, a product of DMS oxidation and presumably of marine origin, help to distinguish air masses with a marine contribution, however measurements from this study may indicate that there are also industrial sources of this species.
A11A-0103
Carbonyl sulfide uptake and chloroform emissions from an Arctic site
The Arctic Region is most sensitive to future climate change. Quantifying emissions and sinks of many important biogenic trace gases there may become important indicators of potential climate feedback. Once snowmelt at Pt. Barrow, Alaska (77o N) occurs, ground cover is exposed by sunlight and higher temperatures, then photosynthesis starts up. Peaks of chloroform (CHCl3) appear throughout the summer from southerly-based air masses based over northern Alaska and northwest Canada. Carbonyl sulfide (COS) undergoes uptake throughout the summer season through the same enzymes that uptake carbon dioxide (CO2). We will calculate the footprint of emissions of CHCl3 and uptake of COS using high frequency in situ observations, and the NAME and FLEXPART models. Previous studies show a large source of CHCl3 (8% of the total budget) may be coming from soils in high latitude pine forests. We will examine emissions of CHCl3 to see whether or not they are coming from the tundra just south of Pt. Barrow. We will identify the regions for uptake of COS and CO2 from the footprint generated from the models.