A33A-0808
Biomass-Burning Aerosol Particles in Mexico During the MILAGRO Campaign
Biomass burning contributes significantly to global radiative forcing through the emission of huge amounts of gaseous and particulate matter to the atmosphere. However, the uncertainty is large when modeling their effects on radiative forcing. The emissions are highly variable and depend on parameters such as vegetation, climate, and the mix of flaming and smoldering combustion. During the MILAGRO (Megacity Initiative: Local and Global Research Observations) field campaign, which took place during March 2006 in Mexico, we collected smoke samples from 63 biomass fires and adjacent haze throughout south-central Mexico using a Twin Otter aircraft (US Forest Service) and C130 aircraft (NSF/NCAR). We used transmission electron microscopy (TEM) and associated techniques such as electron tomography (ET), energy dispersive X-ray spectroscopy (EDS), and electron energy-loss spectroscopy (EELS) to analyze the morphologies, mixing states, and compositions of the emission products. Biomass-burning aerosol particles with aerodynamic diameters <0.3μm consisted mainly of soot particles, sulfates, nitrates, minerals, and organic matter (OM). Almost all soot particles collected directly from biomass-burning smoke were internally mixed with OM. In contrast, about half the soot particles collected from haze within ~10 km of the biomass fires were internally mixed with OM. Our samples that were collected from biomass plumes at different stages of aging in the ambient environment and characterized by using multiple TEM techniques will help understand the properties of biomass-burning aerosol and its contribution to climate.
A33A-0809
Resolving Organized Aerosol Structures (Rolls and Layers) with Airborne Fast Mobility Particle Sizer (FMPS) During MILAGRO/INTEX Campaign
The Hawaii Group for Environmental Aerosol Research [http://www.soest.hawaii.edu/HIGEAR] deployed a wide range of aerosol instrumentation aboard the C-130 and the NASA DC-8 as part of MILAGRO/INTEX. These were designed to provide rapid information on aerosol composition, state of mixing (internal or external), spectral optical properties (scattering and absorption), the humidity dependence of light scattering-f(RH), and the role of condensed species in changing the absorption properties of black carbon (BC) and inferred properties of organic carbon (OC). These measurements included size distributions from about 7 nm up to about 10,000 nm and their volatility at 150, 300 and 400 C; size selected response to heating (volatility) to resolve the state of mixing of the aerosol; continuous measurements of the light scattering and absorption at 3 wavelengths; measurements of the f(RH). We also flew the first airborne deployment of the new Fast Mobility Particle Sizer (FMPS, TSI Inc.) that provided information on rapid (1Hz) size variations in the Aitken mode. This revealed small scale structure of the aerosol and allowed us to examine size distributions varying over space and time associated with mixing processes previously unresolved etc. Rapid measurements during profiles also revealed variations in size over shallow layers. Other dynamic processes included rapid size distribution measurements within orographically induced aerosol layers and size distribution evolution of the nanoparticles formed by nucleation (C-130 flights 5, 6 and 9). Evidence for fluctuations induced by underlying changes in topography was also detected. These measurements also frequently revealed the aerosol variability in the presence of boundary layer rolls aligned along the wind in the Marine Boundary Layer (Gulf region) both with and without visible cloud streets (DC-8 flight 4 and C-130 flight 7). This organized convection over 1-2 km scales influences the mixing processes (entrainment, RH) and related variability of aerosol concentration and optical properties.
A33A-0810
Mexico City Aerosol Transect
A radiative impact study was conducted in Mexico City during MILAGRO/MIRAGE campaign in March of 2006. On a day when the predominant wind was from the north to the south, authors measured radiative properties of the atmosphere in six locations across the city ranging from the city center, through the city south limits and the pass leading out of the city (causing pollutants to funnel through the area). A large change in aerosol optical properties has been noticed. The aerosol optical depth has generally increased outside of the city and angstrom coefficient has changed significantly towards smaller values. Aerosol size distribution was calculated using SkyRadPack. The total optical depths allowed coincidental lidar data to calculate total extinction profiles for all the locations for 1064nm. http://piotr.physics.uiowa.edu/
A33A-0811
Plume Transport in the Mexico City Metropolitan Area Basin During the MILAGRO Field Campaign: WRF Simulations with Satellite-Derived Initialization of the Land Surface and Evaluation of FLEXPART Lagrangian Particle Trajectories with HSRL Lidar Data.
Located in a high-altitude basin with mountains on three sides, Mexico City experiences complex three- dimensional wind transport patterns strongly affected by local heating of the land surface. Analysis of chemical and aerosol measurements performed during the campaign benefits from the identification of the transport of the urban plume and other pollution sources. A mesoscale model, the Weather and Research Forecast (WRF) model, is used to simulate the winds in the basin at a 3 km resolution during the whole campaign. Improved simulations are obtained by using high resolution description of the land surface for landuse, vegetation fraction, surface albedo and ground temperature from the MODIS satellite sensor. Lagrangian trajectories of pollutant sources are performed using the FLEXPART model for the month of March 2006. The particle transport is compared with aerosol measurements from the airborne NASA Langley Research Center High Spectral Resolution Lidar (HSRL). Extensive curtain measurements obtained from flights at high altitude above Mexico City capture in detail the basin-mountain and urban circulations providing a valuable method of evaluating model transport and of analyzing local meteorological conditions.
A33A-0812
Determination of the Mixing Layer Height Over two Sites, Using Pilot Balloons During the MILAGRO Campaign
Among the mechanisms that affect air quality there is a variety of meteorological processes. An important process in this context are the changes in the mixing layer height during a day and over the year. The mixing layer height is the portion of the atmosphere close to the surface layer where air pollutants get diluted, without leaving this layer. Therefore, it is important to describe the variations in the height of the mixing layer, i.e. the vertical dilution of air pollution, since this is a process mitigating naturally the impact of emissions. There exist different methods to obtain information on the mixing layer height, among them radio soundings, the application of vertical wind profilers, and launching pilot balloons. In this study, pilot balloons have been used simultaneously over two sites of the Mexico City Metropolitan Area during the MILAGRO campaign in March 2006. The objective was to determine the vertical wind profiles and derive information on the mixing layer height. Daily, four pilot balloons were launched, at 9:00, 12:00, 15:00, and 18:00 hours, over Tenango del Aire (a rural area in the Southeast of Mexico City), and over Ciudad Universitaria, in the Southern metropolitan area. At some occasions, night time measurements have been carried out at 21:00 and 24:00. A variability of the diurnal evolution of the mixing layer was observed along March, which could be related to surface temperature. The diurnal evolution showed a sudden growth of the mixing layer between 9:00 and 12:00 hours. Data intercomparisons were carried out for pilot balloons versus radio soundings during a few days at a third site, Tula, in the North of Mexico City. Both intercomparisons showed that pilot balloons are an effective method to obtain information about the development of the mixing layer.
A33A-0813
Measurements of Extensive Aerosol Optical Properties During TexAQS II: Implications for PM Compliance and Planning
In 2000, the Houston-Galveston Area (HGA) was designated as a non-attainment area for several criteria air pollutants by the US EPA. In order to meet the requirements of the federal Clean Air Act, the Second Texas Air Quality Study (TexAQS II) was designed to update the State Implementation Plan (SIP) by providing scientific air quality data over 18 months from June 2005 to October 2006. The data presented here was collected as part of the Texas Radical and Aerosol Measurement Program (TRAMP), a substudy of TexAQS II. Bulk aerosol optical properties were measured for six weeks atop the 60 m high Southwest Moody Tower on the University of Houston campus. The measurements were collected using a cavity ring-down transmissometer/nephelometer (CRDT/N) and consisted of the extensive aerosol coefficients: extinction (bext) at 532 and 1064 nm and scattering (bscat) at 530nm. In addition to daily and whole study averages and calculated mass values, positive correlations between the 1064 nm extinction and 532 nm absorption (babs = bext - bscat) values are displayed for this study period for the first time. Correlation between the particle scattering coefficient and the sum of AMS measured (UNH – PI: R. Griffin) sulfate and organic particle mass concentrations as well as covariance between optical properties and O3, CO and NOx values (ARL/NOAA – PI: W. Luke) are also examined. No correlation is expected between coarse particles (PM10), which are typically primary biogenic suspended soil minerals or windblown dust, and high ozone concentrations. Ozone levels are highest during periods of low wind when coarse particulate is likely to be at a minimum. On the other hand, secondary particles and O3 should be correlated on short time scales because both species tend to have the same precursors, NOx and VOC's, and formation of particles is favored during stagnant conditions. Fine particles (PM2.5) should also correlate with CO since both species have a common emission source. Wind roses are compared with pollution roses for each week of the study period, allowing for cluster analysis. Overall, the optical properties appear to be an effective measure of air quality when compared to other measurement techniques. Implications for aerosol effects on regional climate from long-range transport and synoptic scale recirculation are discussed.
A33A-0814
Improving our Understanding of the Relationships Between Ozone Formation and Ozone Precursors From the MILAGRO Field Study
MILAGRO (Megacity Initiative: Local and Global Research Observations) was a multi-agency field study that took place in Mexico City during the month of March, 2006. One of the components is MCMA-2006, which focused on the characterization of the emission of pollutants from the urban area, their transport and transformation. It is intended to improve the understanding of atmospheric chemistry with a vast amount of observations and incorporate into evaluation and design of air pollution related policies. The meteorological conditions were categorized into 6 episodes; O3-North, O3-South, Cold Surge, South Venting, Convection South, and Convection North. During an O3-South meteorological condition, previous study on the MCMA-2003 field campaign suggested that the urban core region during ozone peak hours is VOC-limited. This presentation will examine three major questions using O3-North meteorological condition as an initial case study for the MCMA-2006 campaign: 1) the reproduction of ozone precursors and ozone concentrations; 2) the sensitivity of ozone production to the precursor emissions during the MCMA-2006 field campaign; and 3) the comparison to the MCMA-2003 field campaign. Concentrations of air pollutants will be simulated using the Comprehensive Air Quality Model, with extensions (CAMx v4.40).
A33A-0815
North American Tropospheric Ozone Profiles from IONS (INTEX Ozonesonde Network Study, 2004, 2006): Ozone Budgets, Polution Statistics, Satellite Retrievals
During INTEX-B (both Milagro and IMPEX phases in Spring 2006) and during the summer TEXAQS- 2006/GOMACCS period, the INTEX Ozonesonde Network Study (IONS-06) coordinated ozonesonde launches over North America for Aura overpasses. IONS-06 supported aircraft operations and provided profiles for ozone budgets and pollution transport, satellite validation and evaluation of models. In contrast to IONS-04, IONS-06 had a greater range (all but one 2004 IONS site plus a dozen in California, New Mexico, Mexico City, Barbados and southwestern Canada), yielding more than 700 profiles. Tropospheric pollution statistics to guide Aura satellite retrievals and contrasts in UT-LS (upper tropospheric-lower stratospheric) ozone between 2004 and 2006 are presented. With IONS-04 dominated by low-pressure conditions over northeastern North America, UT ozone originated 25% from the stratosphere [Thompson et al., 2007a,b] with significant amounts from aged or relatively fresh pollution and lightning [Cooper et al., 2006; Morris et al., 2006]. Both IONS-04 and IONS-06 summer periods displayed a persistent UT ozone maximum [Cooper et al., 2007] over the south-central US. March 2006 IONS sondes over Mexico manifested persistent UT/LS gravity wave influence and more sporadic pollution. Regional and seasonal contrasts in IONS-06 ozone distributions are described. http://croc.gsfc.nasa.gov/ intexb/ions06.html
A33A-0816
Observations of Ozone and Aerosols Over Mexico and Gulf of Mexico During INTEX- B/MILAGRO Field Experiment
The NASA Langley Research Center's Differential Absorption Lidar (LaRC/DIAL) system has been used to measure ozone and aerosol distributions in many airborne global tropospheric and stratospheric campaigns since 1980. The tropospheric configuration of this system was flown on the NASA DC-8 during the INTEX-B (Phase-I)/MILAGRO (I/M) field experiment, which was conducted from 24 February to 22 March 2006 over Mexico and the Gulf of Mexico. DIAL remote profile measurements were made from near the surface to above the tropopause along the flight track of the DC-8 with a small data void region of 750 m above and below the aircraft. Aerosol scattering ratios were determined at two wavelengths for a gross estimation of the relative size of the observed particles and measurements of aerosol depolarization were made to distinguish nonspherical aerosols, such as dust and some aerosols in aged fire plumes. In situ measurements of ozone from the FASTOZ instrument on the DC-8 were used to constrain the interpolation of the nadir and zenith ozone lidar measurements, which then provided an estimate of the entire tropospheric ozone profile along the flight track. A first order correction for aerosol attenuation was made to the aerosol profiles by using an assumed extinction-to- backscatter ratio to better characterize the attenuation by thick aerosol layers. The DIAL system was used to determine the large-scale variability and context of air masses being sampled in situ on the DC-8 and to direct the in situ sampling strategy in real time. Plumes from biomass burning in southern Mexico were often observed in the free troposphere over the Gulf of Mexico and over eastern Mexico. The Mexico City (MC) pollution plume was readily apparent with high ozone (>100 ppbv), high aerosol scattering (S>20), and enhanced aerosol depolarization (D>10%). The top of the MC pollution extended to a depth of about 2.5 km AGL. Some observations showed the MC plume spilling out over the mountains to neighboring regions, but the long-range transport of the MC plume was not readily apparent in the airborne lidar data. This presentation discusses these results and the types and characteristics of aerosol and ozone plumes that were encountered during this field experiment.
A33A-0817
An Overview of INTEX-B/MILAGRO/IMPEX Instrument and Measurement Intercomparison
During the spring of 2006, the INTEX-B/MILAGRO/IMPEX field programs carried out a series of comprehensive multi-platform measurement comparisons, including a number of species/parameters and measurement platforms, with the goal of generating a program-wide unified data set. One important component of these activities was the comparison between NSF C-130 and NASA DC-8, which was carried out through 3 separate ~ one-hour wing-tip to wing-tip formation flights. To be presented is a summary of an objective assessment of consistency between the paired measurements as well as the uncertainties of individual instruments. These results will encompass both gas phase species, ranging from radical species to long-lived species (e.g., HNO3, CFC-12) as well as particulate species including particle microphysical and optical properties and chemical composition. The level of agreement is characterized by either regression slopes and intercepts or a simple ratio between the paired measurements, primarily depending on the range of the variation relative to measurement uncertainty. In addition, the recent INTEX-B/MILAGRO/IMPEX results will also be put in context of previous measurement comparison, e.g. ICARTT/INTEX-NA.
A33A-0818
Airborne Formaldehyde Measurements Onboard the NASA DC-8 Aircraft During the 2006 INTEX-B Campaign by Tunable Diode Laser Absorption Spectroscopy
The 2006 Intercontinental Chemical Transport Experiment Phase B (INTEX-B) Campaign was designed in part to quantify the outflow and evolution of gases and aerosols from aging plumes downwind of major tropical megacities such as Mexico City. Formaldehyde (CH2O), an important reactive gas phase intermediate, is photochemically produced as such plumes age and is involved in a number of important atmospheric processes, such as: hydrocarbon oxidation, ozone production, reactive hydrogen radical formation, and generation of carbon monoxide. This talk will present CH2O results acquired by a tunable diode laser absorption spectrometer operated onboard the NASA DC-8 aircraft during this campaign. Airborne CH2O distributions and measurement- model comparisons over a wide geographic region of this study, including Mexico, the Gulf of Mexico, and vast regions over the Pacific Ocean during the second campaign phase, will be presented. Comparisons and contrasts with results from other major metropolitan areas will also be discussed.
A33A-0819
NATIVE Column Ozone Measurements Over Richland, WA During INTEX-B and Comparisons With OMI Satellite Retrievals
The Nittany Atmospheric Trailer and Integrated Validation Experiment (NATIVE, http://www.meteo.psu.edu/~btaubman/Webpage/native.html) was deployed in Richland, WA from April 21, 2006 through May 15, 2006 for INTEX-B (Intercontinental Chemical Transport Experiment, http://www.espo.nasa.gov/intex-b/). Column and vertical profile ozone measurements were made using daily ozonesonde launches, a Microtops sunphotometer, and a UV shadowband radiometer. These measurements were compared with Aura Ozone Monitoring Instrument (OMI) total column ozone (TCO) derived using the DOAS and TOMS 8 retrieval algorithms and the tropospheric ozone residual (TOR) derived by subtracting the Microwave Limb Sounder (MLS) stratospheric column ozone (SCO) from the TCO. The sonde derived TCO, TOR, and SCO data were generally greater than the satellite products when using the same dynamically defined tropopause heights. The shadowband radiometer TCO values were highly dependent on the solar irradiance values at the top of the atmosphere estimated using Langley regressions as well as the assumed ozone absorption coefficients. The DOAS derived TCO values were generally greater than those using the TOMS 8 algorithm, but the opposite was true when cloud cover exceeded 0.2. Steep horizontal ozone gradients in the upper troposphere, the result of high amplitude Rossby wave propagation over the region, also created discrepancies among the different instruments.
A33A-0820
Transport of Asian Aerosols and Trace Gases to North America During the INTEX-B Field Campaign: A Regional Chemical Transport Model Analysis.
The Intercontinental Chemical Transport Experiment-Phase B (INTEX-B) was conducted over the Pacific Ocean during the 2006 North American spring season. One of the scientific objectives of the INTEX-B field campaign was to quantify the transport and chemical evolution/aging of Asian air pollution into North America. The field campaign deployed multiple experimental platforms such as satellites, aircrafts and surface measurements stations to study the pollution outflow to North America. Three dimensional chemical transport models were used to provide chemical weather forecasts and assist in flight planning during the mission. The Sulfur Transport and dEposition Model (STEM) is a regional chemical transport model developed at the University of Iowa. The STEM model was involved in providing chemical weather forecasts and assist in flight planning during the INTEX-B intensive field campaign. In this study we will report the STEM model performance of aerosols and trace gases in its ability to capture the pollutant plume with experimental observations obtained from the field campaign. The study will then relate the emissions of trace gases and aerosols to atmospheric composition, sources and sinks using the newly developed emissions inventory for the INTEX-B field campaign.
A33A-0821
Chemical and Aerosol Characteristics of Asian Outflow as Observed during INTEX-B and TRACE-P
The NASA Intercontinental Transport and Chemistry Experiment, phase B (INTEX-B) was conducted in the spring of 2006 to investigate the transport and transformation of gases and aerosols on transcontinental/intercontinental scales and to assess the impacts of the aged pollutants on air quality and climate. To accomplish these goals, the instrumented, North Dakota DC-8 aircraft was deployed during two separate phases to study vastly different pollution and transport phenomena. During the first 3 weeks of March, the aircraft was based in Houston and flew sorties over Mexico City and the western Gulf to examine the composition, outflow pathways, and evolution of pollution from Mexico City. The second phase took place between April 17 and May 15, and involved basing the aircraft at first Hickam AFB, Hawaii, then Anchorage, AK to examine the outflow of pollution from Asia at different points along the transport pathway. In this presentation, we analyze data from the second phase of INTEX-B to characterize the composition of Asian outflow as a function of age (e.g. C2H2/CO ratio) and vertical location (0-2, 2-4, 4-6, 6-8, and >8 km). We use airmass trajectories to identify the primary Asian continental source regions that influence atmospheric composition within the Northeast Pacific region and characterize those source regions using aerosol and gas phase tracers. In addition, we compare INTEX-B vertical profiles of trace gas and aerosol species with similar measurements recorded aboard the DC-8 just off the Asian coast during the 2001 NASA Transport and Chemistry near the Equator – Pacific (TRACE-P) experiment to evaluate changes in species concentrations/characteristics during the approximately 10-day transport period between the two regions.
A33A-0822
Nonmethane Hydrocarbon (NMHC) Characterization of Asian Outflow During the INTEX-B Campaign: a Case Study from May 1
Whole air samples were collected on board of the NCAR-C130 aircraft during the Intercontinental Chemical Transport Experiment Phase B (INTEX-B). A total of 4299 samples were collected and analyzed for NMHCs, halocarbons, alkylnitrate, and selected sulfur compounds. During INTEX-B, from our measurements we identified air masses containing enhanced levels of NMHCs. On May 1 2006 during Flight 6 of the second part of the campaign two distinct plumes were encountered at high altitude (above 20,000 feet). A total of 71 samples were collected during the flight with 6 canisters filled within the first plume and 7 in the second. To understand the origin of the plumes, the enhancement of selected species was investigated. Many urban tracers (i.e. tetrachloroethene, ethyne, benzene, toluene) had elevated mixing ratios, including the tracers of Asian Outflow such as CH3Cl and Halon-1211.
A33A-0823
Observations of Processed Asian Pollution with a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) from the C-130 Aircraft During the INTEX-B Field Campaign
Measurements of submicron, non-refractory aerosol mass were made from the NCAR/NSF C-130 aircraft using a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) during the spring 2006 INTEX-B field campaign based in Seattle. We intercepted numerous Asian pollution layers, some after rapid transport across the Pacific and others after slower transport which had reduced aerosol concentrations and were depleted of short-lived tracers. The aerosol in Asian pollution layers intercepted over the Eastern Pacific Ocean was shown to have a predominance of sulfate over organic material, the latter being highly oxidized. Measurements and back trajectory calculations are consistent with the following sequence: (a) relatively more rapid conversion of organic precursors to organic aerosol compared to conversion of SO2 to sulfate just downwind of Asian urban centers and pollution sources, (b) uplift and transport of air masses resulting in washout of most aerosol material leaving relatively more SO2 available, and (c) subsequent SO2 to sulfate conversion as air masses are transported across the Pacific. This is consistent with Brock et al., JGR, 2004. Two case studies will be presented to describe this evolution of aerosol chemical composition during transport from Asia. Overall correlations of several tracers will be shown for comparing MOZART and GEOS-Chem model outputs with the measurements. Also, comparisons of AMS measurements with other aerosol instruments will be shown.
A33A-0824
Validation of AIRS v5.0.14.0 CO Retrievals From INTEX-A and B
We present observations of tropospheric carbon monoxide (CO) transport obtained by the Atmospheric InfraRed Sounder (AIRS) onboard NASA's Aqua satellite during the Intercontinental chemical Transport EXperiment-North America (INTEX-A) during the summer of 2004 and INTEX-B (Phase B) during the Spring of 2006. In situ aircraft measurements acquired during these campaigns provide crucial validation of the satellite retrievals. A previous study using INTEX-A data found version 4.0.9.0 of the AIRS CO retrieval algorithm was only validatable in the mid- troposphere, 400-500mb, due to limitations of the retrieval algorithm. Here we present results using INTEX-A and B data to validate version 5.0.14.0 of the AIRS CO retrieval algorithm. This version uses nine trapezoidal perturbation functions (v4.0.9.0 used only four), provides output at similar pressures to the MOPITT standard retrievals, and uses a first guess profile consistent with MOPITT's a priori first guess. These changes remove ad- hoc post-launch error terms and improve the vertical resolution and specificity of AIRS CO retrievals.
A33A-0825
The Effect of Inlet Aspiration of Aerosol Odd-nitrogen Species on NOy Budget Determination.
During the MILAGRO/MIRAGE-MEX campaign in March 2006, the NCAR chemiluminescence NOx, NOy, O3 instrument was flown aboard the NSF C-130 in and around the Mexico City Metropolitan Area (MCMA) to sample the urban pollution plume. The NOy instrument sampled ambient air from an aft-facing inlet extended on a pylon from the bottom of the aircraft, in a continuously aspirated flow of about 1 SLM. The sample flow entrained small aerosols which is understood from a practical perspective, but until this time had not been quantified for this inlet configuration. During flights close to MCMA, relatively high values of ammonium nitrate aerosol (5.2 ppbv equivalent mixing ratio) were measured by the University of Colorado AMS instrument coincidently with high NOy readings (5.5 ppbv) from the NCAR NOy instrument. Subsequent analysis of the NOy partitioning resulted in a component NOy deficiency of 15 - 40 percent, based on independent but concomitantly measured major NOy species: NOx, PANs, HNO3, alkyl nitrates and aerosol NH4NO3. The aspiration efficiency of small aerosols from the NOy inlet was modeled using the Fluent aerodynamic model. The amount of aerosol NH4NO3 and HNO3 on fine dust were calculated based on the determined aspiration efficiencies for a range of aerosol masses, and the potential contribution of these species to the NOy budget was determined. Systematic aspiration of an unknown amount of these aerosols may at least partially explain historic examples of missing NOy.
A33A-0826
Modeling the Effects of Heterogeneous Chemistry on Aerosol Optical Properties and Atmospheric Chemistry
Heterogeneous reactions on aerosols are important for atmospheric chemistry models. But most models only consider that heterogeneous reactions remove gas phase species through adsorption and uptake and/or through reaction thereby converting one gas phase species into another. The changes of concentrations of gases and particles after heterogeneous chemistry affect atmospheric chemistry directly and indirectly. Laboratory studies have already shown that heterogeneous reactions can change the optical properties of aerosols. In order to fully understand and assess the importance of these results on photochemical processes and tropospheric chemistry, it is essential to use the data in atmospheric chemistry models. A box model is developed to study the effects of the heterogeneous uptakes of gases on aerosol optical properties and the photochemical oxidant cycle. This box model includes gas chemistry, atmospheric radiation, and an aerosol module to deal with the chemical interactions between gases and particles. Heterogeneous chemistry is included and the complex of aerosol surface is considered with it. The aerosol module also calculates the optical properties of particles. The radiative fluxes and photolysis rates are calculated using the NCAR Tropospheric Ultraviolet-Visible (TUV) radiation model, which is a one-dimensional solver for actinic flux and photolysis frequencies. It can consider the influence of aerosols and clouds on gas-phase photolysis rates and UV fluxes. The importance of heterogeneous chemistry on the photochemical oxidant cycle is shown in the box model studies. The model will also be used to explore the data from the INTEX-B field experiment.
A33A-0827
2D and 3D Eulerian Simulations of the Dynamics and Gas and Aerosol Chemistry of a Young Biomass Burning Smoke Plume from a Savannah Fire
The growth of aerosol particles and production of ozone in young smoke plumes is the result of a complex interaction between the mean flow in the smoke plume, turbulent diffusion, gas-phase oxidation, coagulation, and mass transfer between phases. Models allow us to separate the effects of these processes and predict their impact on the global environment. We present the results of two and three-dimensional Eulerian simulations of the dynamics and chemistry of the smoke plume formed by the Timbavati savannah fire studied during SAFARI 2000 (Hobbs et al., 2003, JGR, doi:10.1029/2002JD002352). The dynamical model is an extension of an Eulerian cloud-resolving model that has previously been used to study the role of deep convective clouds on tropospheric chemistry (Wang and Prinn, 2000, JGR, 105(D17) 22,269-22,297). The model includes a source of sensible heat, gases, and particles at the surface to simulate the savannah fire. The new gas and aerosol chemistry model includes heterogeneous chemistry, kinetic mass transfer, coagulation and the formation of secondary organic and inorganic aerosol. Photolysis rates are calculated based on the solution of the radiative transfer equation within the plume, including the scattering and absorption of radiation by the smoke aerosols. Our preliminary 2D Eulerian results using standard chemistry and UV fluxes show that the model can simulate the lower but not the higher levels of O3 observed. Also, the simulated 2D O3 field shows a wave-like pattern in the downwind direction, even though the emissions from the fire are held constant. This suggests that plume heterogeneity in the downwind direction may account for some of the observed variability in O3. We will present results of runs incorporating higher resolution calculation of photolysis rates, heterogeneous HONO formation, and gas phase reactions involving the uncharacterized organic compounds observed in the gas phase of the Timbavati plume in order to better simulate these higher O3 values.
A33A-0828
Behavior of Atmospheric Phosphorus in Aerosol over the Central North Pacific
Phosphorus is an essential element of ocean primary production as well as nitrogen and iron. However, it usually depletes in the surface layer of the central area of an open ocean since most phosphorus in the ocean is supplied by a riverine input. Thus, the input of phosphorus from air to sea plays important role on the surface layer of the ocean remote from the land. To clarify a distribution and a behavior of phosphorus over the central North Pacific, the observation was carried out on the KH-05-2 cruise of the R/V Hakuho-maru (8 August to 21 September, 2005). The mean concentrations of atmospheric phosphorus over the central North Pacific in the fine mode (D<2.5 μm), the coarse mode (D>2.5 μm) and total mode were 1.3±1.1, 1.7±2.3 and 3.0±2.8 ng m-3, respectively. It was estimated that phosphorus derived from sea salt, crustal substance and the other were 1%, 10% and 89%, respectively. The unknown phosphorus could be land-origin since it had similar trends of Al and NH4+ and was transported from the Asian continent by a backward trajectory analysis. The central Pacific Ocean was classified into four areas (Southwest, central south, central north and Northwest) on the basis of airmass type. The mean phosphorus concentration in the coarse mode varied from 1.1 to 2.6 ng m-3 in the four areas, while mean phosphorus concentration in fine mode was almost constant. And the influxes of phosphorus from air to the ocean were estimated to be 1.8-4.6 μg m-2 d-1 in the coarse mode and 0.11 μg m-2 d-1 in the fine mode.
A33A-0829
CCN Properties of Water-Soluble Organics Collected From PILS During GoMACCS 2006
By behaving as cloud condensation nuclei (CCN) that may enhance cloud reflectivity and lifetime, aerosols can have significant impacts on global and regional cloud formation. Little is understood about the composition and characteristics of these aerosols necessary to model droplet growth. In this study we investigate the CCN activity of aerosols obtained from a particle-in-liquid sampler (PILS) during the Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCs) in 2006. A sampling and experimental strategy is employed to characterize and understand differences in aerosols that have been activated within cloud regions (top, middle, and bottom) and below cloud regions influenced by urban and industrial plumes. Aerosols are collected through a PILS either after a counter-flow virtual impactor (CVI) when in-cloud or directly from the sample when out-of-cloud. Particular emphasis will be placed on the impact of organics on growth kinetics and the ability to achieve CCN activity closure based on resolved speciation.
A33A-0830
Insights into the Sources and Chemical Processes of Submicron Aerosol at the Whistler Summit, BC based on Aerodyne High-Resolution Time-of-Flight Aerosol Mass Spectrometry
A new Time-of-Flight Aerosol Mass Spectrometer with a high mass resolution of ~ 5000 (HR-ToF-AMS; DeCarlo et al., Anal. Chem., 2006) was deployed at the summit of the Whistler Mountain (elev. ~ 2200 m), British Columbia, in spring 2006, as part of the NASA INTEX-B mission. With this instrument, we determined the concentration, composition, and chemically speciated size distributions of non-refractory (NR) submicron particles (approximately PM1) every 5 minutes. We also obtained the highly m/z-resolved mass spectra, based on which the elemental composition of most small ion fragments (m/z <100 amu) was quantitatively determined. Organic aerosol (OA) prevailed at the Whistler summit accounting for ~ 50 per cent of the total NR-PM1 mass. Sulfate was usually less abundant than organics in NR-PM1 but episodes of strongly enhanced sulfate aerosol were observed. A major sulfate episode occurred on May 15, 2006, during which sulfate and ammonium contributed > 90 per cent of the NR-PM1 mass. This episode lasted for ~ 0.5 day and was followed by a high OA episode. The OA detected during the sulfate period are highly oxidized, with mass spectral similar to fulvic acid and estimated O to C ratio > 1. The high resolution mass spectra indicate significant structural differences in organic species between these two episodes. Simulations from a global model of oxidant-aerosol chemistry (GEOS-Chem), backtrajectory analysis, evolution of the size distributions of aerosol species, mass spectra analysis, and correlations with tracer pollutants (e.g., O3, CO, and mercury) support Asian influence during the high sulfate period, in contrast with regional biogenic and anthropogenic influences during the high organic period.
A33A-0831
A Lagrangian model investigation of chemico-microphysical evolution of northeast Asian pollution plumes within the MBL during TRACE-P
In this work, we determine the major channels through which air pollutants, mainly originating in Northeast Asian mega-cities, flow out into the Northwestern Pacific atmosphere. For this purpose, comprehensive backward/forward trajectory analyses are conducted. Two important channels along which pollutants from the Northeast Asian mega-cities flow out are defined, and are labeled as ˘®ˇĆDC8 transport path˘®ˇľ and ˘®ˇĆP3B transport path˘®ˇľ. We then comprehensively examine the chemico-microphysical transformations of the anthropogenic pollutants from the Northeast Asian mega-cities along the two major transport paths, using a new Lagrangian forward-trajectory photochemical model. In the newly developed model, state-of-the-science parameterizations for considering chemico-microphysical aging processes and atmospheric aerosol processes are incorporated. As air masses travel toward low latitudes through the marine boundary layer (MBL), the temperature increases along the trajectories and large amounts of PAN experience thermal decomposition. By this process, PAN can be an important supplier of NO2 in the remote MBL. The O3 productions in the remote Northwestern Pacific MBL are fueled and maintained by NOx provided from the PAN decomposition. High O3 levels (> 50 ppb) are observed within the remote MBL of the Northwestern Pacific Oceans from several TRACE- P DC8 and P3B measurements under the continental outflow situations. Gas-phase SO2 is continuously converted into nss-sulfate via heterogeneous oxidation reaction with H2O2 at a particle pH of 2~5. The Lagrangian-trajectory modeling studies also indicate that in the remote MBL of Northwestern Pacific Ocean under continental outflow situations, conditions are unfavorable for nucleation events, because of the depletion of SO2, the large aerosol surface areas available for H2SO4 sink, and high temperatures.
A33A-0832
Scavenging processes of marine aerosols by sea fog over the northern North Pacific
Sea fog appears frequently over the subarctic North Pacific in summertime. Typical advection fog over this region may affect the distribution of natural and anthropogenic substances from lands as well as marine biogenic substances. To clarify the variation of chemical composition in fog water, size distribution of fog droplets and fog scavenging processes, investigation was conducted over the northern North Pacific, where sea fog appears frequently in summer, during the KH-04-3 cruise of R/V Hakuho-maru in 2004. The sea salt composition is governed 65% of total concentration of inorganic ions and the non-sea-salt (nss-) sulfate occupied 10 % in the 90 sea fog water samples. The average size distribution of liquid water content (LWC) of sea fog showed a bimodal pattern with peaks of 7.0 and 27.5 μm in diameter, while its distribution on land fog commonly showed a monomodal pattern. LWC, number concentrations of fog droplets and concentrations of sea salt composition were high at the edge of the fog area, and decreased toward the center of the fog area. The peak of LWC size distribution was shifted from 17.0 μm at the edge to 36.5 μm in the center area. Based on the relationship of chemical compositions between aerosols and fog droplets, nss-SO42- and NH 4 + in sea fog water consisted of 85 % of the coarse mode aerosol and 15 % of the fine mode by ion basis. The fog droplets are expected to deposit with growing of its droplet size with coagulation and adsorbing reactive gases as a function of the distance from the edge of the sea fog area. These results suggest that sea fog over the subarctic North Pacific is an important as a scavenger of natural and anthropogenic substances transported from the Asian continent and its nitrogen flux to the marine environment may stimulate phytoplankton growth.
A33A-0833
Ground-based Measurement Of Saharan Dust In Marine Environment
An extensive field experiment, named NASA African Monsoon Multidisciplinary Analyses (NAMMA) was conducted during August-September of 2006 to investigate the genesis and development of hurricanes. Two ground-based mobile laboratories, Surface-sensing Measurements for Atmospheric Radiative Transfer (SMART) and Chemical, Optical, Microphysical Measurements of In-situ Troposphere (COMMIT), were deployed at Sal Island, Cape Verde to continuously monitor the structure and composition of the atmosphere in the major path of the Saharan Air Layer and the African Easterly Waves. A Micro-Pulse Lidar in SMART, which measures the vertical profiles of backscatter from the atmospheric particulates continuously, caught several episodes of Saharan dust layers reached the surface site. Simultaneously, physical and optical properties of aerosols (e.g., mixture of the Saharan dust and maritime aerosols) were captured by several instruments in COMMIT. In this study, we propose a novel method to separate dust properties from those of marine background aerosols by utilizing the synergy of a suite of in-situ measurements. Derived parameters are mass scattering coefficients and single scattering albedo (SSA) for dust near the surface (~10m). As a crosscheck, the SSA based on the surface measurements is compared with the result of Deep Blue satellite-based aerosol retrievals, which is now incorporated in the operational MODIS aerosol product. The presented preliminary results will be useful in studying the properties of Saharan dust originated from various source regions, which, in turns, can be used as inputs to aerosol transport models to help better understand the interactions between aerosol and cloud water cycle.
A33A-0834
Aerosol dry deposition on canopies of plane obstacles
A new model to describe aerosol transport and dry deposition on vegetative canopies has been proposed recently by Petroff et al. and applied to canopies of cylindrical obstacles such as coniferous forest (Petroff et al., 2007, Aerosol dry deposition on vegetative canopies. Part II: A new modeling approach and applications, submitted to Atmospheric Environment). In the present study, the approach is extended to canopies of plane obstacles such as grass, crop or broadleaf forest. The model takes into account the characteristics of the canopy, the aerosol and the aerodynamics. Deposition terms are modeled following an up-scaling procedure, which is based on the knowledge of collection dynamics on each individual obstacle and on the statistical distribution of these collecting elements. The statistical description applies to geometrical properties such as leaf characteristic length and orientation. Deposition mechanisms considered in this model include Brownian diffusion, interception, inertial impaction, turbulent impaction and gravitational settling. For interception, no adequate parameterisation is available in the literature to describe the collection on individual obstacle. Thus, an original parameterisation is derived for plane obstacle and is based on potential flow theory. Aerosol transport is described in a mono-dimensional configuration and neutral stratification of the atmosphere is assumed. Preliminary results indicate that the present model agrees with existing measurements data obtained both in wind-tunnel and on site.
A33A-0835
Three-Year Observation of Levoglucosan Over Chichi-jima Island in the Northwestern Pacific
Levoglucosan (1,6-anhydro-β-D-glucopyranose) is a major constituent of biomass burning aerosol particles, and has been suggested to be useful as a tracer of biomass burning aerosols in the atmosphere. In this study, we analyzed levoglucosan in aerosol samples collected in Chichi-jima Island, the northwestern Pacific from January 2001 to January 2004. Aerosol samples (n = 149) were collected on quartz fiber filters using a high volume air sampler. Levoglucosan and other organics on a filter cut were extracted with methanol/dichloromethane and derivatized with BSTFA. The derivatives were injected to GC-MS for quantification. A clear seasonal variation of the concentration of levoglucosan was observed with a maximum in autumn to spring. The highest concentration was above 10 ng m-3. The mean concentration of levoglucosan in the period from January to March (2 ng m-3) was one order of magnitude higher than that in the period from July to September (0.2 ng m-3). The ratios of levoglucosan carbon (levoglucosan-C) to organic carbon (OC) were in most cases above 1 × 10-3 in winter season (October - March), whereas the ratios were in many cases below 1 × 10-4 in summer season (April - September). The higher ratio in winter suggests a relatively larger contribution of biomass burning to OC during the period, nevertheless the ratio is two orders of magnitude lower than that of freshly emitted biomass burning particles. Given that the transport of biomass burning aerosols from Asia to the Pacific is expected to be substantial, the low [levoglucosan-C]/OC ratio may be explained by the decomposition of levoglucosan and/or the secondary production of OC during the long-range transport. While the variation of the concentration of levoglucosan probably represents the change in the contribution of biomass burning aerosols over Chichi-jima, more analyses are required to quantitatively understand the observed low levoglucosan abundance.
A33A-0836
A-Train Observations of Pyrocumulonimbus Events
Until relatively recently, it was believed that only volcanic eruptions released enough energy to directly inject aerosols from the troposphere to the stratosphere. Now, numerous satellite and ground-based observations reveal troposphere to stratosphere exchange by convection due to large fires, pyrocumulonimbus (pyroCb). NASA's A-Train satellite suite is uniquely equipped to study pyroCb with instruments including the Atmospheric InfraRed Sounder (AIRS) and Moderate Resolution Imaging Spectroradiaometer (MODIS) on Agua, the CALIPSO lidar, and the Microwave Limb Sounder (MLS) and Ozone Monitoring Instrument on Aura. We present integrated analyses of several recent pyroCb events to illustrate the A-Train's capabilities to monitor the occurrence of pyroCb's, track their downwind motions in three dimensions, and measure their chemical and particulate impacts.
A33A-0837
Documenting PyroCb Development on High-Intensity Boreal Fires: Implications for the Arctic Atmosphere
The recent confirmation that smoke from high-intensity boreal forest fires can reach the Upper Troposphere/Lower Stratosphere (UTLS) through pyroconvection and be transported long distances has raised concern over the wider-scale environmental impact of boreal fire smoke. This concern is further elevated as climate change projections indicate a significant increase in the frequency and severity of boreal forest fires over the next century. Smoke in the UTLS is frequently transported to the Arctic and may have important implications for the radiative energy budget in the polar region. Soot deposition from fires may lead to enhanced melting of sea ice and glaciers, and the chemical impact of fire emissions at high altitudes is largely unknown. This knowledge gap will be addressed during the International Polar Year (IPY), as boreal fire emissions will be tracked and documented in detail through aerial, satellite and ground-based measurements, as a key component of the POLARCAT (Polar Study using Aircraft, Remote Sensing, Surface Measurements and Models, of Climate, Chemistry, Aerosols, and Transport) and ARCTAS (Arctic Research of the Composition of the Troposphere from Aircraft and Satellites) projects to be conducted in 2008. A large fire in the Canadian Northwest Territories burned throughout the month of June 2007, in a remote region where forest fires are not actively suppressed, eventually reaching 90,000 hectares in size. This fire was monitored for blowup one week in advance; it erupted into pyroconvection on June 25, 2007. We present an analysis of this event combining satellite data with ground-based measurements to document the development and impact of this classic pyroCb event. Under extreme fire danger conditions, the fire burned close to 20,000 hectares on that day. Fire behavior was consistent with predictions using the Canadian Fire Behavior Prediction System, with the fire spreading at 2.7 km/hr, consuming 33,000 kg of fuel hourly, generating an energy release rate of ~45,000 kW/m. This constitutes a typical high-intensity boreal crown fire, common across northern Canada every summer, and often capable of producing independent pyroconvection. The June 25 blowup was monitored using OMI AI, CALIPSO, Aqua MODIS, AVHRR and GOES satellite imagery, and these measurements validated the predicted fire behavior, including the development of a convection column that rose 10-11 km and injected smoke within the UTLS. Over subsequent days this smoke spread to Arctic latitudes (70-80 degrees N).
A33A-0838
In-Situ Observations and Modeling of Black Carbon Aerosols in Arctic Snow
Black Carbon (BC) particles emitted by fossil fuel and biomass combustion are transported to the Arctic and deposited in snow and ice, leading to reduced surface albedo and thus a warming of the climate. BC aerosols in the air have the direct effect of absorbing solar radiation, as well as semi direct and indirect effects on clouds. These mechanisms generally have a warming effect, but the activities that lead to emissions of BC also have associated emissions of other compounds, including some that have a cooling effect. The presentation is fourfold and details (i) BC concentrations on a regional scale and (ii) a local scale from snow samples, (iii) BC levels from modelling, and (iv) the relationship between BC and snow optical properties. The concentration of BC from snow in Norway (mainland), the Svalbard archipelago and the Arctic Ocean is determined from snow samples collected in the field, melted and filtered in the lab, and analysed for elemental carbon with a thermo- optical method. Chemical Transport Model calculations of the BC deposition at the observational sites during the relevant period leading up the observational period are performed to compare and validate the BC deposition in the model. Small scale studies concern BC concentrations as a function of altitude along a Svalbard glacier and of depth through the seasonal snow-pack. The optical properties of snow is affected by, most importantly, snow grain size, light conditions (clouds and solar height), snow thickness and impurities like BC, so it is not straightforward to derive the alteration from BC alone. To complicate the picture even more, BC particles can be embedded within the snow grains or the mixing can be external. This contribution tries to answer some of the uncertainties associated with BC in snow.
A33A-0839
Composition of Individual Aerosol Particles Measured in the Arctic
Aerosol particles in a given environment are largely influenced by surrounding regions which can act as either direct sources or via the production of species which become incorporated into pre-existing particles. Presented here are the major characteristics, including chemical composition, of ambient aerosols measured by an Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) and other instruments 200 km above the Arctic Circle. Abisko Scientific Research Station, operated by the Royal Swedish Academy of Sciences, is subject to airmasses with several different origins. By comparison of wind trajectories, the influence of the sea, boreal forest, and industrial regions surrounding Abisko are evident in the measured spectra. These aerosol particles are of further interest due to the climate changes occurring in the polar region. Also important to this study is the simultaneous occurrence of an International Polar Year, an intensive research period focusing on the environments of both polar areas.