A11C-0593
TES Regional and Global Atmospheric Chemistry Data Available From the NASA Langley Atmospheric Science Data Center
TES Regional and Global Atmospheric Chemistry Data Available from the NASA Langley Atmospheric Science Data Center The Tropospheric Emission Spectrometer (TES) was launched into a sun-synchronous orbit aboard Aura, the third of NASA's Earth Observing System spacecraft, on July 15, 2004. The primary objective of TES is to make global, three-dimensional measurements of ozone and other chemical species involved in its formation and destruction. The NASA Langley Atmospheric Science Data Center (ASDC) is the archive and distribution center for data from the TES instrument. The TES instrument is a high-resolution imaging infrared Fourier-transform spectrometer that operates in both nadir and limb-sounding modes. TES standard Level 2 data products include global-scale vertical profile and total column measurements of ozone, water vapor, HDO, carbon monoxide, methane, and nitric acid for 16 orbits every other day. Additional products include atmospheric temperature profiles, surface temperatures, and land surface emissivity A recent reprocessing effort has produced a new version of the data which includes additional limb species and a new summary product. In the past year, Level 3 TES products have been released which provide daily or monthly global survey chemical species data interpolated onto a global latitude/longitude grid at selected pressure levels. Browse images for the Level 3 and associated Level 2 data are available with these new Level 3 products. Between global surveys, TES can make special observations using its ability to point at a specific location for a few minutes on any given orbit. This capability is used for targets such as gas-emitting volcanoes, for regional air quality studies, and in conjunction with field campaigns. The ASDC provides data access, services and tools for over 40 projects in the discipline areas of Earth's radiation budget, clouds, aerosols and tropospheric chemistry. Additional information is available from our web site, http://eosweb.larc.nasa.gov http://eosweb.larc.nasa.gov
A11C-0594
Changes In Atmospheric Methane And Its Stable Isotope Signatures Between 1978-2005 Deduced From Interhemispheric Differences and Trends
During the past 2 decades a slow-down in CH4 concentration has been observed. The causes for this slow- down trend are still under debate. Meanwhile, carbon and hydrogen isotopic measurements of atmospheric CH4 and its sources as well as measurements of the isotopic effect of CH4 sink processes have provided useful information on determining CH4 source and sink strengths and distributions. Here we present the synchronous relationships of CH4 mixing ratio and stable isotopes (13C/12C and D/H) between the Northern and Southern Hemispheres over the past 20 years. Our results show that the seasonally detrended interhemispheric difference (IHD) of mixing ratio has increased from about 60 to 100 ppbv over the period around 1980 to 1990, and then decreased to ca. 80 ppbv in 2005. Furthermore, the seasonally detrended IHD of carbon isotope signature has decreased from about 0.3 permil to 0.1 permil from 1990 to 2005. However, the change of the seasonally detrended IHD of hydrogen isotope signature was negligible over roughly the same period. We apply a 2-box model (N/S) to deduce the source and sink processes governing the variations of the trends with the help of the dual constraint offered by simultaneous CH4 carbon and hydrogen stable isotope data. To explain the decreasing IHD of carbon isotope signature and CH4 mixing ratio, a reduction in the NH flux of isotopically light sources (likely rice and livestock) is required. This obviates the hypothesis that a decrease in fossil fuel flux has contributed much to the leveling off of CH4 over this time period.
A11C-0595
Understanding the role of understory terpenoid emissions: The Bracken Fern story
Most biogenic emissions studies have been made based on the fact that the canopy biomass is greater than the understory biomass. Herbaceous species - like Bracken Fern- have not been taking in consideration despite the fact that other disciplines like chemical ecology have showed that those species contain a significant amount of compounds - like terpenoid compounds- that if emitted to the atmosphere, would influence the results of actual atmospheric models. This work will show the results of measurements of terpenoid fluxes from Bracken in the area of Pellston, Michigan. The case of Pteridium is a special case because it can be found in open areas as well as in the understory. This gave us the opportunity to investigate not only the contribution of an understory species to forest emissions, but it also gave us the opportunity to study landscape structure as a factor that could affect terpenoid emissions.
A11C-0596
Behavior of Tropospheric Peroxy Radicals during Several Recent Airborne Measurement Campaigns
Concentrations of HO2 and HO2+RO2 were measured during several airborne campaigns using a mass spectrometric/chemical conversion technique. MIRAGE and INTEX-B were designed to assess the behavior of urban megacity emissions at close-to-medium range, and at long range, respectively. The PASE campaign examined sulfur chemistry in the remote central Pacific Ocean basin. We will present the results of these studies using a variety of chemical and physical coordinates (e.g. altitude, time, NO concentration) and making use of photochemical model results to assess our understanding of free radical chemistry over the variety of conditions encountered during these studies.
A11C-0597
N2O and CH4 Flux from Winter Wheat Field in the North China Plain
N2O emission and CH4 absorption in winter wheat field were measured during April to June in 2007 in North China Plain using an automatic measurement system. This study indicated that, N2O emissions peaked during 2 weeks after N application, and the N2O emission pattern is mainly driven by the timing of N fertilization. In addition, the diurnal change of N2O emission was similar to the pattern of soil temperature fluctuation especially during the following week after N fertilization and irrigation. The soil in the North China Plain was a net sink of methane, and the ambient concentration of methane was an important environmental factor that affected its uptake by soil.
A11C-0598
Simulations of Tropospheric NO2 by the Global Modeling Initiative (GMI) Model Utilizing Assimilated and Forecast Meteorological Fields: Comparison to Ozone Monitoring Instrument (OMI) measurements
We present simulations of the tropospheric composition for the years 2004 and 2005, carried out by the GMI Combined Stratosphere-Troposphere (Combo) model, at a resolution of 2°x2.5°. The model includes a new parameterization of lightning sources of NOx which is coupled to the cloud mass fluxes in the adopted meteorological fields. These simulations use two different sets of input meteorological fields: a)late-look assimilated fields from the Global Modeling and Assimilation Office (GMAO), GEOS-4 system and b) 12-hour forecast fields initialized with the assimilated data. Comparison of the forecast to the assimilated fields indicates that the forecast fields exhibit less vigorous convection, and yield tropical precipitation fields in better agreement with observations. Since these simulations include a complete representation of the stratosphere, they provide realistic stratosphere-tropospheric fluxes of O3 and NOy. Furthermore, the stratospheric contribution to total columns of different troposheric species can be subtracted in a consistent fashion, and the spatial and temporal patterns of the lightning production of NOx will depend on the adopted meteorological field. We concentrate here on the simulated tropospheric columns of NO2, and compare them to observations by the OMI instrument for the years 2004 and 2005. The comparison is used to address these questions: a) is there a significant difference in the agreement/disagreement between simulations for these two different meteorological fields, and if so, what causes these differences?; b) how do the simulations compare to OMI observations, and does this comparison indicate an improvement in simulations with the forecast fields? c) what are the implications of these simulations for our understanding of the NO2 emissions over continental polluted regions?
A11C-0599
Latitudinal variations of nitrogen and triple oxygen isotopic composition of nitrate in the marine boundary layer over the Atlantic Ocean
The analysis of the isotopic composition of nitrate (NO3-) in various environments is a fast-growing field of investigation. Atmospheric nitrate oxygen isotopes feature the appealing potential to record a footprint of the cycling between ozone (O3) and nitrogen oxides (NOx), through the transmission of an isotope anomaly (Δ17O=δ17O - 0.52 ×~δ18O) borne by the ozone molecule. This discovery has lead to the idea that the isotopic composition of nitrate preserved in firn and ice of the polar ice caps could be used as a proxy of past ozone chemistry and thus provide the long-awaited link between the climate record from ice cores and the oxidative capacity of ancient atmospheres. To better constrain the relationships between nitrate oxygen isotopes and the oxidative state of the atmosphere, we have carried out a series of ship-borne measurements in the marine boundary layer (MBL) between Cape Town, Rep. South Africa (30°S) and Bremerhaven, Germany (50°N) covering a wide range of meteorological and atmospheric chemistry conditions. Onboard the R/V Polarstern, we measured surface ozone and collected size-segregated aerosols with a latitudinal resolution of 4°. Besides major ions concentrations, nitrate contained in these samples was analyzed for all stable isotopes of its constituents (namely δ15N, δ17O and δ18O), using the denitrifier technique (based on Kaiser et al., Anal. Chem., 2007), thus providing an unprecedented latitudinal profile of nitrate isotopes in the MBL. Variations of nitrate isotopic compositions are studied as a function of particle size and changing MBL background chemistry, ranging from the remote and unpolluted Southern Atlantic Ocean (O3 20 nmol~mol-1) to the polluted English Channel area (O3 45 nmol~mol-1), through air masses influenced by North-African desert dust in the subtropical North Atlantic. Known main chemical mechanisms responsible for the formation of atmospheric nitrate are used to test our understanding of the causes for the variations of Δ17O(NO3-) in different atmospheric environments.
A11C-0600
Observational evidence for long-term trends in carbon monoxide
Changes in carbon monoxide (CO) have potentially important effects on the oxidizing capacity of the troposphere. It is commonly accepted that carbon monoxide (CO) in the Northern Hemisphere troposphere has increased significantly during the industrial era due to anthropogenic emissions. No significant trend has been determined in the Southern Hemisphere. CO is a product of fossil combustion and oxidation of CH4, both processes that have increased over the past century. The positive trend in CO is based on ice core studies, measurements of column abundances and surface time series. CO may no longer be increasing, measurements from a number of laboratories suggest CO mixing ratios have decreased over the past 20 years. This presentation will provide a re-examination of the data and evaluate the long-term trends in CO, focusing on issues that can affect trend analysis (such as short-term measurement periods and long-term calibration stability).
A11C-0601
Global Climatology of Tropospheric CO from the Atmospheric InfraRed Sounder (AIRS): Interannual Variations in Emissions from Indonesia
Five years of CO retrievals from the Atmospheric InfraRed Sounder (AIRS) onboard NASA's Aqua satellite reveal variations in tropospheric CO on timescales from twelve hours to five years. The shorter timescales are invaluable to monitor daily variations in CO emissions, for three-dimensional tracking of atmospheric motions, and for insights into atmospheric mixing. Substantial interannual variations demonstrate year-to-year changes in rainfall and drought patterns in different seasons, e.g. the Northern Hemisphere boreal forests and South America. Variations on multi-year timescales exhibit the influence of planetary scale atmospheric perturbations. In particular, we observe a quasi-biennial variation in CO emissions from Indonesia with varying magnitudes in peak emission occurring in October 2002, 2004, and 2006. Examining satellite rainfall measurements over Indonesia, we find the enhanced CO emission correlates with occurrences of low rainfall during the month of October. MOPITT CO observations also reveal Indonesian CO total columns peaked in 2002, 2004, and 2006 relative to 2000-2001. Perhaps not coincidentally, 2002, 2004, and 2006 were all El Nino years. Unfortunately, neither AIRS nor MOPITT was in orbit during the intense 1997-1998 El Nino when Indonesia experienced unprecedented burning. Continuing the satellite record of tropospheric CO with measurements from the European IASI instrument will permit construction of a long time-series useful for further investigations of climatological variations in CO emissions and their impact on the health of the atmosphere.
A11C-0602
Joint Application of Concentrations and Isotopic Signatures to Investigate the Global Atmospheric Carbon Monoxide Budget: Inverse Modeling Approach
Carbon monoxide is not only an important component for determining the atmospheric oxidizing capacity but also a key trace gas in the atmospheric chemistry of the Earth's background environment. The global CO cycle and its change are closely related to both the change of CO mixing ratio and the change of source strength. Previously, to estimate the global CO budget, most top-down estimation techniques have been applied the concentrations of CO solely. Since CO from certain sources has a unique isotopic signature, its isotopes provide additional information to constrain its sources. Thus, coupling the concentration and isotope fraction information enables to tightly constrain CO flux by its sources and allows better estimations on the global CO budget. MOZART4 (Model for Ozone And Related chemical Tracers), a 3-D global chemical transport model developed at NCAR, MPI for meteorology and NOAA/GFDL and is used to simulate the global CO concentration and its isotopic signature. Also, a tracer version of MOZART4 which tagged for C16O and C18O from each region and each source was developed to see their contributions to the atmosphere efficiently. Based on the nine-year- simulation results we analyze the influences of each source of CO to the isotopic signature and the concentration. Especially, the evaluations are focused on the oxygen isotope of CO (δ18O), which has not been extensively studied yet. To validate the model performance, CO concentrations and isotopic signatures measured from MPI, NIWA and our lab are compared to the modeled results. The MOZART4 reproduced observational data fairly well; especially in mid to high latitude northern hemisphere. Bayesian inversion techniques have been used to estimate the global CO budget with combining observed and modeled CO concentration. However, previous studies show significant differences in their estimations on CO source strengths. Because, in addition to the CO mixing ratio, isotopic signatures are independent tracers that contain the source information, jointly applying the isotope and the concentration information is expected to provide more precise optimization results in CO budget estimation. Our accumulated long-term CO isotope measurement data contribute to having more confidence of the inversions as well. Besides the benefit of adding isotope data on the inverse modeling, a trait of each isotope of CO (oxygen and carbon isotope) contains another advantageous use in the top-down estimation of the CO budget. δ18O and δ13C has a distinctive isotopic signature on a specific source; combustion sources such as a fossil fuel use show clearly different values from other natural sources in the δ18O signatures and the methane source can be easily separated by using δ13C information. Therefore, inversions of the two major sources of CO respond with different sensitivity for the different isotopes. To maximize the strengths of using isotope data in the inverse modeling analysis, various coupling schemes combining [CO], δ18O and δ13C have been investigated to enhance the credibility of the CO budget optimization.
A11C-0603
Impact of Siberian forest fires on tropospheric ozone in East Asia during May 2003
Forest fire is one of the major sources of CO, VOC, NOx and aerosols in the atmosphere. During the spring of 2003, intensive forest fires occurred in Siberia, the largest seen in the last 10 years. The smoke plumes from these forest fires heavily affected East Asia as indicated by aerosol optical depth retrieved from Total Ozone Mapping Spectrometer (TOMS). Previous studies showed a significant influence of those fires on aerosol concentrations in surface air over East Asia. However, influences of them on O3 concentrations on monthly and daily time scales have not been quantified yet. We use a global 3-D chemical transport model (GEOS-Chem) driven by assimilated meteorological data to examine the impact of Siberian forest fires on O3 concentrations in East Asia. The model simulations use a global biomass burning emission inventory constrained by satellite observations in 2003. Fire influence on O3 concentrations in East Asia is determined by the difference between the baseline and sensitivity simulations without Siberian fire emission. A model evaluation is also conducted using O3 observations at Acid Deposition Monitoring Network in East Asia (EANET) sites in East Asia. Simulated increase in O? concentrations due to fire emissions in the model appears to be consistent with an observed increase in O3 concentrations in May 2003 relative to other years. Fire emissions and their long-range transport thus could be important for the year-to-year variability of seasonal O3 concentrations over East Asia. Continuing increases in forest fires as a result of climate warming may have a significant impact on future air quality in East Asia.
A11C-0604
Inter-annual Variations in CO as Seen at the Mt. Bachelor Observatory by Satellites, GEOS- Chem and Other Regional Surface Sites
Inter-annual variations in tropospheric trace gases are caused by variations in emissions (especially fires), variations in transport, OH, or other causes. Understanding this variability is essential for air quality regulation and attribution. We have made continuous measurements of O3, CO, sub-micron σsp (aerosol scattering coefficient), NOy, total airborne Hg and various meteorological parameters at the Mt Bachelor Observatory (MBO: 43.98°N, 121.69°W; 2.7 km ASL) since Feb 2004. These measurements, along with MOPITT satellite retrievals, GEOS-Chem chemical transport model output and 4 western U.S. NOAA ESRL/GMD surface sites all show the highest springtime (April) CO maximum from 2004-07 occurred in 2005. The April mean CO maximum reached 188 ppbv in 2005 at MBO. In 2006 and 2007, the April maximum was lower at ~145 ppbv (a 24% decline from 2005). This decrease, albeit on the order of 5-10 ppbv, was also observed in: MOPITT CO retrievals at 700 mb (a 5% decline from 2005 to 2006+07), GEOS-Chem output for the MBO region (a 7% decline), as well as at four ESRL/GMD sites in the western U.S (a 7% decline). We attempt to answer the following questions: 1) Why was the April CO maximum significantly higher in 2005 compared to 2006 and 2007?, and 2) Why is the decline from 2005 to 2006+07 so much greater at MBO than in the other platforms and model output? We analyze remotely sensed fire counts throughout the Northern Hemisphere to examine the role of biomass burning. We compile a climatology of backtrajectories from MBO to investigate the variability of meteorological transport conditions. We have also observed a steady decline in the late summer CO minimum at MBO from 2004-07 when all data are considered. We present several methodologies for segregating MBO data (e.g., NOx cycles, water vapor and O3 patterns, etc.) in an effort to understand the upslope / downslope flow at our mountain site on both diurnal and seasonal timescales. This has direct implications for the influence the regional BL (i.e., local wildfires) has on measurements at MBO and may provide insight into this decrease in the late summer CO minimum.
A11C-0605
The Effect of Synoptic Scale Mountain Meteorology on Nocturnal Peak Ozone Mixing Ratios for Wintertime Conditions
Nocturnal maxima in ozone mixing ratios are commonly observed in mountainous regions including those without strong emission sources of nitrogen oxides. Local photochemistry does not explain the nocturnal ozone maxima in the absence of emissions of nitrogen oxides. Simulations were performed using the on-line coupled meteorological atmospheric chemistry model (MM5-chem) with relatively course resolution to investigate the synoptic scale mechanisms that lead to nocturnal ozone peaks. These studies show that although chemistry is one factor, synoptic scale flows from mountainous terrain in the Sierra-Nevada Mountains can contribute strongly to nocturnal ozone peaks. Synoptic scale mountain waves can cause strong vertical mixing that produces complex structure in the three dimensional wind fields and ozone mixing ratios over the Sierra-Nevada Mountains and the surface ozone mixing ratios are strongly correlated with the vertical wind direction and speed. Higher ozone mixing ratios were found to be associated with stronger downward vertical winds, higher carbon monoxide and NOx mixing ratios, and with air masses of greater photochemical age. These factors often occurred at night and this suggests that synoptic scale transport of ozone was a very major factor for the high ozone mixing ratios found at many of the mountain sites.
A11C-0606
Singular value decomposition analyses of tropical tropospheric ozone determined from satellites
A controversial dispute in space-based tropospheric ozone remote sensing is the puzzling discrepancy in the spatiotemporal distribution between residual-based satellite ozone observations and biomass-burning activity in the tropics during boreal winter. This study focuses on evaluation and analyses of two tropospheric ozone products determined from Earth Probe TOMS, AURA/OMI, and AURA/TES measurements. Rather than using the typical station-to-station inter-comparison with ozonesounding measurements, the evaluation was performed at the global scale using temporal and spatial patterns derived from Singular Value Decomposition (SVD) analyses. The satellite observations of ozone precursors from MOPITT CO and GOME and OMI NO2 serve as markers identifying airmasses influenced by biomass burning. The SVD analyses reveal that the SAM tropospheric ozone product is remarkably consistent (99% significance level) with the two measured ozone precursors, CO and NO2, in distribution as well as in seasonality. The analyses provide compelling evidence that there is no discrepancy between tropospheric ozone and its precursors during boreal winter.
A11C-0607
Comparative Analysis of the Long-term Trends of the Surface Ozone Concentration at Elevated Sites in the Alps and in Caucasus Region
Analysis of the long-term surface ozone records of two mountain sites, namely Kislovodsk High Mountain Station (KHMS) in Caucasus, Russia (43.7°N, 42.7°E, 2070 asl.) and Jungfraujoch (JFJ) in Switzerland (46.5°N, 7.9°E, 3580m asl) will be presented. A strong increase in ozone concentration (up +0.46±0.11ppb/year) was found at JFJ while ozone significantly deceased at KHMS (-0.65 ±0.09 ppb/year) during 1990-2005. We will compare trends values for earlier years (1990-2001) and for the latter ones (1993-2005). Among the possible reasons of the trends difference the impact of atmospheric transport is studied. Both vertical and horizontal components are considered in connection with ozone concentration trends. Transport analysis is based on 3D trajectories using LAGRANTO. There was no substantial difference in trends detected for different PV-levels or PBL filtered cases, while the main difference has been found in the source areas of the air masses at the two locations and inside different advection sectors at the each particular site. Trends will be compared (for the two receptor sites and two periods) for filtered subsets of upper tropospheric/stratospheric cases (based on PV and trajectory altitude), cases impacted by Planetary Boundary Layer (based on PBL height) and in different horizontal advection clusters. The work is financially supported by the Swiss National Science Foundation (JRP IB7320-110831), European Commission (Marie-Curie IIF project N 039905 - FP6-2005-Mobility-7) and Russian Foundation for Basic Research (projects 06-05-64427 and 06-05-65308) and contributes to ACCENT T&TP project.
A11C-0608
Using CFC-12 and HCl to quantify the annual cycle of the stratospheric contribution to ozone in the Arctic troposphere
In this study, we use CFC-12 and hydrochloric acid (HCl) to quantify the annual cycle of stratosphere-to- troposphere transport of O3 to the Arctic troposphere. To do so, we analyze results from a 5-year stratosphere and troposphere simulation from the Global Modeling Initiative (GMI) Chemical Transport Model (CTM) for 1994- 1998 and a 10-year simulation using the GEOS Chemistry Climate Model (GEOS CCM) for 1995-2004. The later includes a tagged CFC-12 tracer to track the transport of aged stratospheric air into the troposphere. We compare the simulated CFC-12 with 10 years surface CFC-12 measurements at two NOAA-GMD sites, Alert and Barrow. We compare O3 with 10 years of ozonesondes at Alert, Eureka, and Resolute. CFC-12, HCl and O3 are all compared with satellite observations from the Advanced Composition Explorer (ACE) and several MkIV balloon measurements in the Arctic. The GEOS CCM and GMI CTM simulations capture well the observed magnitude and annual cycle of CFC-12, HCl, and O3 in the stratosphere and troposphere. Since CFC-12 is emitted at the surface and destroyed in the stratosphere while HCl and O3 are produced in the stratosphere, the stratospheric air shows strong correlation between HCl and O3 and anti-correlation between CFC-12 and O3. We use the CFC-12 tagged tracer to track the transport from the stratosphere to the troposphere and the subsequent transport into the lower troposphere in the Arctic. HCl is paired with O3 to quantify the stratospheric contribution to O3 in the troposphere by applying a scaling factor to the simulated HCl using the HCl-O3 regression ratio. O3 and its annual cycle in the upper troposphere are dominated by stratospheric influence, which peaks in spring. The stratospheric contribution decreases as altitude decreases, accompanied by a delay in the phase of maximum. In the middle troposphere (2-6km), the stratospheric contribution peaks during the summer and is comparable to that of net photochemistry. Due to inefficient transport into the lower Arctic surface, the stratospheric contribution of O3 at the surface accounts for only a few (<5) ppbv.
A11C-0609
The temporal and spatial variability of halogenated trace gases in the upper troposphere.
Halogenated trace gases play an important role in stratospheric and tropospheric chemistry, particularly affecting ozone concentrations. In addition they have direct and indirect effects on radiative forcing, and impact on tropospheric reactivity. Data from the CARIBIC project (Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrumented Container) have been used in conjunction with back-trajectory analysis to further our understanding of the chemical composition, inter-hemispheric distribution and source regions of halogenated compounds in the upper troposphere and lower stratosphere. Whole air samples collected within CARIBIC, have been analyzed using gas chromatography mass spectrometry for around 35 halocarbons and related trace gases, among them many potent greenhouse gases and species important for ozone depletion. The large spatial and temporal coverage of the CARIBIC project has enabled new work to be done investigating recent inter-annual trends in the CFCs, halons, and other anthropogenic halocarbons, as well as identifying clear inter-hemispheric and seasonal variability for a number of species, such as methylene chloride, HCFCs, methyl chloride, methyl bromide, methyl iodide and several reactive short lived bromo and chloro carbons. In this paper results from the CARIBIC flights to China and the Philippines will be highlighted, to discuss anthropogenic emissions of ozone depleting and greenhouse gases, from Asia and Africa. Data from flights to South America will also be presented. As production and consumption of many of these substances are being phased out in Europe and North America, emissions from Asia, Africa and also South America are becoming increasingly more important. Emissions from these regions are also of interest, as the most significant sources are often collocated with regions of convection in the tropics and sub-tropics. Thus enabling a greater proportion of the substances emitted to reach the stratosphere, where they have the largest impact on ozone.
A11C-0610
Seasonal and Diurnal Variations of Hg(0) Over New England
Diurnal to interannual variability of Hg° over New England was investigated using multiple years of Hg° measurements at two inland sites, Thompson Farm (TF, 43.11° N, 70.95° W, 24 m, 25 km inland) and Pac Monadnock (PM, 42.86° N, 71.88° W, 700 m, 180 km inland), and one summer of measurements from a marine site, Appledore Island (AI, 42.97° N, 70.62° W, sea level), from the University of New Hampshire AIRMAP observing network. Possible sources were identified via a thorough examination of relationships between Hg° and a number of trace gases, e.g., CO, CO2, CH4, NOy, NO, SO2, and VOCs. The measurements of Hg„a at TF showed distinct seasonality with an annual maxima in late winter - early spring and a minima in early fall, with large day-to-day variation. A decreasing trend in the mixing ratio of Hg„a over the time period of March - September occurred at a rate of 0.5 - 0.6 ppqv d-1 for all years except 2004 (0.3 ppqv d-1). Measurements of Hg° at the elevated site PM exhibited much smaller daily and annual variation, particularly reflected in the slower warm season decline (relative to TF) of 0.2 and 0.3 ppqv d-1 in 2005 and 2006 respectively. The AI data appeared to track the variation observed at TF albeit with much higher minima. Hg° was correlated most strongly with CO and NOy in winter suggesting that anthropogenic emissions were the primary source of Hg° . Applying the Hg° - CO relationship, we found that the seasonally averaged Hg° mixing ratio of ~160 ppqv at PM can be considered the regional background level. The positive Hg° -NOy correlation along the lower boundary of all data points indicated dry deposition as a stronger sink for Hg° than suggested by previous studies. We estimated a dry deposition velocity for Hg° of 0.17 - 0.20 cm s-1, and a lifetime of ~11 days in the local PBL at TF. Correlation between Hg° and CHBr3 at both TF and AI suggested a role of the oceanic source influencing the ambient levels of Hg° in the marine and coastal environments. It was also hypothesized that the overall significantly lower Hg° levels and steeper decreasing trend during the warm season at TF compared to those at PM may reflect the impact of marine halogen chemistry. The stronger decline in warm season Hg° during 2005 compared to 2004 may indicate that changes in precipitation played a role in mitigating evasion from the surface. Colder winter climate was found to be accompanied by higher levels of all anthropogenic tracers except Hg° , possibly a result of the predominant meridional flow that entrained fresh emissions during transport of the polluted Arctic air mass as it circulated over the eastern U.S. In contrast, little variation in Hg° indicates a homogeneous distribution of surface Hg° mixing ratios in winter and/or quick removal of mercury released from anthropogenic sources. During warmer winters the Hg° -CO slope value possibly reflects the ratio of Hg° loss relative to changes in CO more than their emission ratios.
A11C-0611
Seasonal and Diurnal Variation in Reactive Gaseous Mercury (RGM) in New England
Elemental (Hg°) and reactive gaseous mercury (RGM) were measured continuously at two sites in New Hampshire throughout 2007. Additionally, these species were monitored at an oceanic site (Appledore Island, Gulf of Maine) during the summer of 2007. At Thompson Farm, a rural site located 25 km inland, RGM mixing ratios ranged from 0-22 ppq with a mean of 0.5 ppq. Distinct diurnal variation in RGM was observed, with highest concentrations in the mid-afternoon, several hours after the daily peak in Hg°, and diminishing to near zero at night, suggesting photochemical production of RGM during the daytime and depletion at night. Strong summertime correlation of RGM with Hg° and ozone (O3), especially at night, suggests fast deposition or RGM. Seasonal variation in RGM was also observed, with highest concentrations in spring and lowest in summer. RGM was well-correlated with sulfur dioxide (SO2), suggesting influence from combustion sources at local to regional scales. At Pac Monadnock, a high-elevation site located l85 km inland, RGM was significantly lower than at TF throughout the year (Hg° was lower in all seasons except for summer), with a mean mixing ratio of ~0.16 ppqv. Mean RGM mixing ratios were close to or below the detection limit in spring and summer, and little diurnal variation was observed. This site is situated far from combustion sources and therefore shows a more regional signal that is largely devoid of RGM. During summer of 2007, RGM at Appledore Island was significantly higher than at the other two sites, ranging from 0-50 ppqv with a mean of ~10 ppqv, and representing approximately 6% of TGM. This and the elevated Hg° concentrations at the site (156 ppqv in summer, compared to 143 and 146 ppqv at Thompson Farm and Pac Monadnock, respectively) may suggest a strong oceanic source of Hg°, and significant production of RGM in the presence of halogen species. Additionally, enhanced RGM was observed at TF during summertime under easterly and southeasterly flow, possibly suggesting oceanic impact on Hg chemistry at TF.
A11C-0612
Continuous measurements of perfluorocarbons at remote monitoring stations in Japan
In order to determine the trends and regional sources in East Asia, continuous measurements of halocarbons including perfluorocarbons (PFCs), powerful greenhouse gases, has been performed by fully-automated preconcentration/gas chromatograph/mass spectrometer at remote monitoring stations at Hateruma island (24.1 ° N, 123.8 ° E) since 2004 and Cape Ochiishi (43.1 ° N, 145.3 ° E) since 2006 in Japan. The measurements show that the background concentrations of PFCs in 2007 were 3.7 ppt for PFC-116, 0.5 ppt for PFC-218, and 1.3 ppt for PFC-318. As for PFC-116, slight increasing trend was observed at Hateruma. Enhanced concentration above the baseline were occasionally observed in air masses which had passed over urban areas such as Shanghai, Taipei, and Tokyo, suggesting great anthropogenic emission there, while the frequency of the enhancements were relatively low compared to those of hydrofluorocarbons.
A11C-0613
Optimal Estimation of the Surface Fluxes of Chloromethanes Using a 3-D Global Atmospheric Chemical Transport Model
The four chloromethanes - methyl chloride (CH3Cl), dichloromethane (CH2Cl2), chloroform (CHCl3), and carbon tetrachloride (CCl4) are chlorine-containing gases contributing significantly to stratospheric ozone depletion and/or having adverse health effects. Large uncertainties in estimates of their source and sink magnitudes and temporal and spatial variations currently exist. GEIA inventories and other bottom-up emission results are used to construct a priori maps of surface fluxes of these species. The Model of Atmospheric Transport and CHemistry (MATCH), driven by NCEP interannually varying meteorological fields, is then used to simulate the trace gas mole fractions using the a priori emissions and to quantify the time series for sensitivities of tracer concentrations to different aseasonal, seasonal, and regional sources and sinks. We then implement the Kalman filter (with the unit pulse response method) to estimate time-varying surface fluxes at a monthly resolution for the three short-lived species between 2000-2004, and at a 3-month resolution for CCl4 between 1996-2004. The high frequency observations from AGAGE, SOGE, NIES and NOAA/GMD/ESRL HATS CATS and other low frequency flask observations from NOAA/GMD/ESRL HATS are used to constrain the source and sink magnitudes estimated as multiplying factors for the a priori emissions and contained in the state vector in the Kalman filter. The CH3Cl inversion results indicate large CH3Cl emissions of ~ 2278 Gg/yr from the tropical plants. Relative to their a priori magnitudes, the inversion nearly doubles global fungal emissions, slightly increases emissions from biomass burning and salt marshes, and reduces the global ocean source and soil sink. The inversion also implies greater seasonal oscillations of the natural sources and sink of CH3Cl compared to the a priori. These results and those for the CH2Cl2, CHCl3 and CCl4 inversions will be presented and discussed.
A11C-0614
Constraining Modern and Historic Mercury Emissions From Gold Mining
Mercury emissions from both historic gold and silver mining and modern small-scale gold mining are highly uncertain. Historic mercury emissions can affect the modern atmosphere through reemission from land and ocean, and quantifying mercury emissions from historic gold and silver mining can help constrain modern mining sources. While estimates of mercury emissions during historic gold rushes exceed modern anthropogenic mercury emissions in North America, sediment records in many regions do not show a strong gold rush signal. We use the GEOS-Chem chemical transport model to determine the spatial footprint of mercury emissions from mining and compare model runs from gold rush periods to sediment and ice core records of historic mercury deposition. Based on records of gold and silver production, we include mercury emissions from North and South American mining of 1900 Mg/year in 1880, compared to modern global anthropogenic emissions of 3400 Mg/year. Including this large mining source in GEOS-Chem leads to an overestimate of the modeled 1880 to preindustrial enhancement ratio compared to the sediment core record. We conduct sensitivity studies to constrain the level of mercury emissions from modern and historic mining that is consistent with the deposition records for different regions.
A11C-0615
Distributions of Tropospheric SO2 from the INTEX field campaign
SO2 was measured in the troposphere by chemical ionization mass spectrometry from the NASA DC-8 research aircraft during the Intercontinental Chemical Transport Experiment (INTEX). During the three phases of the INTEX field campaign, we sampled outflow from the eastern U.S., Mexico City, and Asia. In the eastern U.S. and its outflow region, significantly enhanced free tropospheric SO2 (tens - hundreds pptv) was observed from active deep convection and frontal uplift processes in the summer of 2004. Over the Gulf of Mexico in March, 2006, the median SO2 profile demonstrates very high SO2 (few ppbv) in the lower troposphere (0 – 4 km) and very low SO2 (mostly < 5 pptv) in the mid and upper troposphere (4 - 12km). Back trajectory analysis indicated that the high SO2 episodes in the lower troposphere have distinct origins such as Veracruz and the Yucatan Peninsula for the MBL and inland Mexico for altitudes above 1 km. In the eastern Pacific during spring 2006, enhanced SO2 layers (up to ~1 ppbv), transported from Asia were frequently found throughout the free troposphere especially in the latitude range 40-60 oN. A correlation analysis with aerosol parameters illustrates that upper tropospheric SO2, transported by deep convection shows a strong correlation with ultrafine aerosols. However, non volatile aerosols show a strong correlation with upper tropospheric SO2, transported by the frontal uplift process. This characteristic indicates that most high SO2 episodes, sampled over the eastern Pacific were transported by frontal uplift processes in Asia. However, those sampled over the eastern U.S. were transported by both deep convections and frontal uplift processes from the south eastern U.S. and the Ohio Valley.
A11C-0616
Decrease events of atmospheric carbonyl sulfide and methyl chloride observed at Hateruma Island in spring
Carbonyl sulfide (COS) and methyl chloride (CH3Cl) are the most abundant sulfur-containing organic gas, and the most abundant chlorine-containing organic gas, respectively, and their sources and sinks are not fully understood. We have conducted high frequency measurements of these two compounds along with twenty more VOCs using an automated preconcentration/GC-MS at Hateruma Island(lat. 24.1°N, long. 123.8°E). The observation showed occasional decrease of their baseline concentrations (up to -200 ppt for COS and -60 ppt for CH3Cl) in spring, as well as occasional short-term enhancements over hours to days. The latter enhancements were also observed for other anthropogenic gases such as HFCs and HCFCs, and are considered to be caused by surrounding East Asian sources. On the other hand, the baseline drops were obvious only for COS and CH3Cl, being related to the airmass trajectory from high altitude inland China. Considering that spring is the "kosa" (yellow dust originating mainly from Gobi Desert and Takla Makan Desert) season, a possible cause for the decrease might be adsorptive loss of COS and CH3Cl to the dust during the long range transport.