CURRENT RESEARCH

Last Updated: August 28, 2009

Our goal is to better understand the chemical composition of the atmosphere, its perturbation by human activity, and the implications for life on Earth. We use advanced global models of atmospheric composition to interpret observations from satellites, aircraft, ground networks, and other sources. We view our models as part of an integrated observing system bridging the information from different data sets to increase our understanding of atmospheric composition in a way that serves both fundamental knowledge and the need to address pressing environmental issues.

GLOBAL MODELS. A central tool in our research is the GEOS-Chem global 3-D model of atmospheric composition, developed by a large grass-roots research community at Harvard and elsewhere and applied to a very wide range of problems. See the GEOS-Chem web site for more details. We also work with the NASA/GISS general circulation model for simulations of climate change, including coupling with GEOS-Chem for study of chemistry-climate interactions and of past and future atmospheres.

AIRCRAFT MISSIONS. Aircraft provide a critical sampling platform for atmospheric chemistry. They enable detailed chemical characterization of atmospheric composition from the surface to the stratosphere and over the scale of the globle. We have been engaged in a large number of aircraft missions over the past 20 years in different regions of the world. We are presently involved in the NASA ARCTAS mission to the Arctic and the NSF HIPPO pole-to-pole mission. Our role in these missions includes overall mission design, flight planning, forecasting, and post-mission data analysis.

SATELLITE MISSIONS. Satellite observations are revolutionizing atmospheric chemistry research by providing global and continuous data sets of atmospheric composition. The data sets require advanced models for interpretation and we are at the forefront of this. Our activities include direct retrievals of satellite spectra using radiative transfer models, synthesis of data from mutiple instruments, data assimilation, inverse model analyses, and Observing System Simulation Experiments (OSSEs) for future missions.
model ITCT satellite

ONGOING PROJECTS

CHEMISTRY-CLIMATE INTERACTIONS

GLOBAL ATMOSPHERIC CHEMISTRY AND BIOGEOCHEMISTRY GLOBAL MAPPING OF EMISSIONS USING SATELLITES NUMERICAL METHODS AND SOFTWARE ENGINEERING

[ITCT] MINERAL DUST

BACKGROUND:

Mineral dust emitted from arid surfaces is the most abundant component of the atmospheric aerosol. It plays an important role in radiative forcing of climate and may also provide a site for chemical reactions in the atmosphere. Climate change could have important effects on dust generation. We are applying a global 3-D model to analysis of aircraft and ground-based dust observations to better understand the sources of dust to the atmosphere and the effect of chemical reactions on the dust.

OBJECTIVES:

  • To quantify the sources of dust to the atmosphere;
  • To understand the atmospheric chemistry of dust and its implications for ozone, sulfate, and other species.

APPROACH:

  • Analysis of Asian dust observations over the North Pacific from the INTEX-B aircraft campaign;
  • Global 3-D modeling of dust sources

PEOPLE: Duncan Fairlie

REFERENCES:

  • Fairlie, T. D., D.J. Jacob, and R.J. Park, The impact of transpacific transport of mineral dust in the United States, Atmos. Environ., 41, 1251-1266, 2007. [PDF]

SUPPORT: NASA

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[ITCT]ARCTIC POLLUTION TRANSPORT AND CHEMISTRY

BACKGROUND:

The Arctic is a receptor of pollution from northern mid-latitudes with consequences for Arctic climate, air quality, and ecosystems. Chemical evolution of this pollution in the Arctic takes place in a unique environment of intense cold and long periods of darkness and light. We are using satellite observations together with aircraft observations from the ARCTAS mission to better understand the long-range transport of pollution to the Arctic, and we are using the large ensemble of chemical observations from ARCTAS to better understand the radical chemistry in the Arctic and its implications for the evolution of ozone and other pollutants.

OBJECTIVES:

  • To better understand the pathways for long-range transport of pollution to the Arctic;
  • To better understand the radical chemistry in the Arctic atmosphere and its implications for the chemical evolution of pollutants.

APPROACH:

  • Analysis of AIRS satellite observations of carbon monoxide (CO), with validation from the ARCTAS aircraft data;
  • Interpretation of ARCTAS observations for radicals and related species;
  • Global 3-D modeling of the ARCTAS observations to test current understanding of transport and chemical pathways relevant to Arctic pollution.

PEOPLE: Jingqiu Mao, Jenny Fisher

COLLABORATORS: ARCTAS Science Team

REFERENCES:

  • Arctic pollution sources and transport: an integrated analysis of CO from ARCTAS, AIRS, and the GEOS-Chem model, presented by Jenny A. Fisher at the POLARCAT Workshop, University of New Hampshire, June 2, 2009. [PDF (6.7 MB)]

SUPPORT: NASA Back to projects list

gomeGLOBAL MAPPING OF CARBON FLUXES USING SATELLITE OBSERVATIONS OF CO2 AND CO

BACKGROUND:

Measurement of CO2 from space could greatly help us to quantify source and sink regions for CO2 and more generally improve our understanding of carbon budgets. But this measurement requires a very high measurement precision to be useful since CO2 concentrations in the atmosphere show little variability. Correlation with satellite observations of carbon monoxide (CO) could help in the inference of carbon budgets from the CO2 observations, as CO can be measured from space with high precision and has common source regions with CO2. We are applying this idea to the analysis of data from the current generation of CO2 satellite sensors (TES, GOSAT, IASI), also with the goal of helping design improved observing systems in the future.

OBJECTIVES:

  • Apply adjoint methods for high-resolution inverse modeling of CO emissions using multi-sensor satellite data;
  • Exploit CO2-CO correlations in inverse model analyses to improve the constraints on carbon fluxes from OCO data.

APPROACH:

  • Conduct multi-sensor global inversions of CO sources using the adjoint of the GEOS-Chem CTM;
  • Quantify CO2-CO transport error correlations in chemical transport models;
  • Apply CO2-CO error correlations in joint CO2-CO inversions to improve carbon flux constraints from current CO2 satellite sensors.

PEOPLE: Helen Wang, Monika Kopacz (now at Princeton)

COLLABORATORS: Dylan Jones (U. Toronto), Steven Pawson (NASA/GSFC)

REFERENCES:

  • Kopacz, M., D.J. Jacob, J.A. Fisher, J.A. Logan, L. Zhang, I.A. Megretskaia, R.M. Yantosca, K. Singh, D.K. Henze, J.P. Burrows, M. Buchwitz, I. Khlystova, W.W. McMillan, J.C. Gille, D.P. Edwards, A. Eldering, V. Thouret, P. Nedelec, Global estimates of CO sources with high resolution by adjoint inversion of multiple satellite datasets (MOPITT, AIRS, SCIAMACHY, TES) , Atmospheric Chemistry and Physics, submitted. [PDF text][PDF figures]

  • Wang, H., D.J. Jacob, M. Kopacz, D.B.A. Jones, P. Suntharalingam, J.A. Fisher, R. Nassar, S. Pawson, and J.E. Nielsen, Error correlation between CO2 and CO as constraint for CO2 flux inversions using satellite data, Atmos. Chem. Phys. Disc., 9, 11,783-11,810, 2009. [PDF]

SUPPORT: NASA

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lnox CONSTRAINING THE LIGHTNING SOURCE OF NITROGEN OXIDES WITH SATELLITE DATA

BACKGROUND:

Lightning emission of nitrogen oxides (NOx) largely determines the natural oxidizing power of the atmosphere and could be very sensitive to climate change. It remains poorly understood due to difficulties in measurement and uncertainties in the cloud electrification process. New lightning flash observations from satellites offer promise to effectively constrain the lightning NOx source, and from there to assess its implications for atmospheric chemistry.

OBJECTIVES:

  • Use satellite observations to constrain lightning NOx emissions;
  • Understand the implications of the lightning NOx source for global atmospheric chemistry and chemistry-climate interactions.

APPROACH:

  • Use satellite lightning flash observations from the OTD/LIS sensors to constrain the global distribution of lightning emissions
  • Apply these distributions in a chemical transport model (GEOS-Chem) to simulate the global distributions of NOx, ozone, and related species, and evaluate with satellite and in situ observations
  • Develop improved physically-based lightning parameterizations for investigating the effects of climate change and associated feedbacks.

PEOPLE:  Lee Murray

COLLABORATORS:  Randall Martin (Dalhousie)

REFERENCES:

  • Hudman, R. C., D. J. Jacob, S. Turquety, E. M. Leibensperger, L. T. Murray, S. Wu, A. B. Gilliland, M. Avery, T. H. Bertram, W. Brune, R. C. Cohen, J. E. Dibb, F. M. Flocke, A. Fried, J. Holloway, J. A. Neuman, R. Orville, A. Perring, X. Ren, G. W. Sachse, H. B. Singh, A. Swanson, P. J. Wooldridge, Surface and lightning sources of nitrogen oxides over the United States: magnitudes, chemical evolution, and outflow, J. Geophys. Res., 112, D12S05, doi:10.1029/2006JD007912. [PDF]

SUPPORT: NASA, NASA Graduate Fellowship to Lee Murray

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NASA satellites SATELLITE OBSERVATIONS FROM GEOSTATIONARY ORBIT

BACKGROUND:

All satellite observations of atmospheric composition so far have been from low-elevation orbit (500-100 km). This enables global mapping but the data are sparse. There is rising interest in using satellites in geostationary orbit (36,000 km) to provide continuous observations over large continental regions. A system of geostationary satellites over North America, Europe, and East Asia would enable detailed mapping of air quality, of pollution sources, and of long-range transport. We are working to help design the North American component, called GEO-CAPE. This involves conducting Observing System Simulation Experiments (OSSEs) in which we fly the satellite over a pseudo-atmosphere produced by our models and determine what instrument specifications are needed in order to produce valuable information.

OBJECTIVES:

  • Determine the ability of geostationary observations to improve ozone air quality forecasts;
  • Determine how a multi-species measurement strategy from geostationary orbit can help to better understand the transport and chemical evolution of ozone pollution;
  • Exploit geostationary observations to better constrain the radiative forcing from tropospheric ozone and its relation to ozone precursor emissions.

APPROACH:

  • Conduct high-resolution 3-D model simulations, and sample this pseudo-atmosphere along the satellite orbit tracks and with the satellite observing error statistics;
  • Use thse pseudo-observations to assess the capability of the satellite observing system towards delivery of its scienitific objectives.

PEOPLE:  Peter Zoogman

REFERENCES:

SUPPORT: NASA

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[Modis] IMPROVING AEROSOL OBSERVATIONS FROM SPACE

BACKGROUND:

Aerosols are of central environmental importance for issues ranging from public health to climate change. Satellite observations of solar backscatter offer an outstanding potential resource for global mapping of aerosol concentrations and inference of aerosol sources. Quantitative retrieval of aerosol information is difficult, however, because of the lack of strong spectral signatures and the need to resolve reflection from the Earth's surface. Our work focuses on developing improved aerosol retrieval schemes by using ancillary information from the GEOS-Chem global model and from vertical profiles observed by aircraft.

OBJECTIVES:

  • Develop improved retrievals of aerosol optical depths from satellite observations;
  • Use the resulting satellite observations to test global model simulations of aerosol concentrations and place constraints on aerosol sources.

APPROACH:

  • Use improved constraints on surface reflectance and aerosol optical properties in the MODIS satellite aerosol retrieval;
  • Integrate the resulting aerosol product over North America with in situ measurements from aircraft and from surface sites;
  • Compare to GEOS-Chem model aerosol simulations to infer model biases.

PEOPLE:  Easan Drury (now at NREL)

COLLABORATORS:  Kelly Chance (Harvard/SAO), Yang Liu (Harvard School of Public Health), Jun Wang (U. Nebraska)

REFERENCES:

  • Drury, E., D.J. Jacob, R.J.D. Spurr, J. Wang, Y. Shinozuka, B.E. Anderson, A.D. Clarke, J. Dibb, C. McNaughton, and R. Weber, Synthesis of satellite (MODIS), aircraft (ICARTT), and surface (IMPROVE, EPA-AQS, AERONET) aerosol observations over North America to improve MODIS aerosol retrievals and constrain surface aerosol concentrations and sources , J. Geophys. Res., submitted. [PDF]

SUPPORT:NASA

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EFFECT OF CLIMATE CHANGE ON AIR QUALITY

BACKGROUND:

Weather is a major factor affecting air pollution, and it follows that climate change could have significant implications for air pollution control strategies. We lead a multi-institutional project (GCAP) to explore the effects of future changes in climate and global emissions on air quality in the United States and elsewhere. The work involves analysis of air pollution meteorology in the NASA/GISS general circulation model for present and future climate, interface with the GEOS-Chem chemical transport model for global simulations of future atmospheric composition, and downscaling to the regional scale with the EPA/CMAQ air pollution model. We also use correlation statistics of air pollution variables with meteorological variables for present-day climate to draw inferences on the effects of climate change. Our focus is on ozone and particulate matter air pollution as well as on mercury deposition and accumulation in ecosystems.

OBJECTIVES:

  • Examine long-term trends in air pollution meteorology driven by climate change;
  • Determine the effects of expected 2000-2050 climate change on surface air quality and mercury deposition in the United States and worldwide, independent of changes in anthropogenic emissions;
  • Determine the combined effects of 2000-2050 changes in climate and global anthropogenic emissions on air quality;
  • Examine how climate change will affect the intercontinental transport of pollution.

APPROACH:

  • Conduct transient 1950-2050 climate change simulations with the GISS GCM, diagnose trends in air pollution meteorology including in particular mid-latitude cyclone frequency, compare to available climatology;
  • Use the GEOS-Chem chemical transport model coupled to the GISS GCM to examine trends in ozone, particulate matter, and mercury;
  • Interface the GISSr/GEOS-Chem global modeling system with the CMAQ regional model for local diagnostic of future air pollution levels;
  • Examine correlations of air pollution levels with meteorological variables for present-day climate.

PEOPLE: Loretta Mickley, Eric Leibensperger, Moeko Yoshitomi, Amos Tai

COLLABORATORS:  Shiliang Wu (Michigan Tech), Daewon Byun (U. Houston), Joshua Fu (U. Tenn), David Rind (GISS), John Seinfeld (Caltech), Havala Pye (Caltech), David Streets (Argonne), Ruby Leung (PNL), Alice Gilliland (EPA/ORD)

REFERENCES:

  • Tai, A. P. K., L. J. Mickley, and D. J. Jacob, Correlations between fine particulate matter (PM2.5) and meteorological variables in the United States: implications for the sensitivity of PM2.5 to climate change, Atmos. Chem. Phys., submitted. [PDF]

  • Leibensperger, E. M., L. J. Mickley, D. J. Jacob, Sensitivity of U.S. air quality to mid-latitude cyclone frequency and implications of 1980-2006 climate change, Atmos. Chem. Phys., 8, 7075-7086, 2008.[PDF]

  • Jacob, D.J., and D.A. Winner, Effect of climate change on air quality , Atmos. Environ., 43, 51-63, 2008. [PDF]

  • GCAP home page

SUPPORT: EPA, EPRI

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EFFECTS OF LAND COVER CHANGE ON CHEMISTRY-CLIMATE INTERACTIONS

BACKGROUND:

Land cover change can have large impacts on the concentrations of aerosols and tropospheric ozone, with consequences for air quality and climate change. For example, biogenic emissions are important sources of ozone and aerosol precursors. Dust is more easily mobilized from dry regions with little vegetation. Deforestation may lead to regional meteorological changes (e.g., decreased humidity and increased surface winds), enhancing the frequency of forest fires, which in turn emit ozone precursors, carbonaceous aerosol, and ammonia. We are presently investigating these effects of land cover changes on atmospheric composition, the implications for climate change, and the feedbacks on land cover.

OBJECTIVES:

  • To predict the impact of future land cover change on atmospheric composition;
  • To investigate the climate response.

APPROACH:

  • Perform 2000-2100 GCM climate simulations, with present-day vegetation maps and with vegetation maps calculated by the LPJ and Hyland models for future conditions;
  • Perform 5-year GEOS-CHEM simulations at 25-year intervals, from 2000 to 2100, with present-day vegetation and GCM control meteorology and with changing vegetation and the corresponding GCM meteorology;
  • Validate model vegetation maps for the present-day with data from the MODIS satellite instrument.

PEOPLE:  Loretta Mickley, Amos Tai

COLLABORATORS:  Jed Kaplan (ISPRA), David Rind (NASA/GISS), Shiliang Wu (Michigan Tech)

SUPPORT: NASA

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EFFECTS OF U.S. AEROSOLS ON CLIMATE

BACKGROUND:

Aerosols have a cooling effect on climate by scattering solar radiation to space and increasing the reflectivity of clouds. At the same time, they represent a major component of air pollution, clearly linked to human mortality and acid rain. Aerosol sources in the U.S. are increasingly controlled to address these pollution concerns, but what will be the consequence for climate change? We need to understand whether removal of this cooling umbrella could expose us to the full brunt of greenhouse warming.

OBJECTIVES:

  • To understand the roles of anthropogenic U.S. sources of aerosols on climate change in the U.S. and globally, over the past several decades and projecting into the future.

APPROACH:

  • Historical reconstructions and future projections of aerosol concentrations over the U.S. and downwind using the GEOS-Chem model.
  • Climate simulations with the GISS GCM driven by historical and future aerosol concentrations.

PEOPLE:  Eric Leibensperger, Loretta Mickley

COLLABORATORS:  David Rind (GISS), John Seinfeld (Caltech)

>REFERENCES:

  • Regional Climate Response to U.S. Aerosol Sources, presented by Eric Leibensperger at the AGU 2008 Fall Meeting, San Francisco, CA, December 19, 2008. [PDF (1.4 MB)]

SUPPORT: EPRI

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MERCURY IN THE ENVIRONMENT

BACKGROUND:

Mercury as an element cycles naturally between the different reservoirs of the Earth system. This natural cycle has been perturbed dramatically in the past century by human emissions to the atmosphere from combustion, mining, and waste disposal. Once in the atmosphere, mercury has a long lifetime as it cycles between elemental and oxidized forms, allowing transport on the global scale. It eventually deposits to the oceans and land, resulting in toxic accumulation in biota. Subsequent re-emission of mercury to the atmosphere leads to complex atmosphere-ocean-land cycling. Development of policies to reduce mercury in the environment has been thwarted by lack of knowledge of the biogeochemical cycling of mercury and of the link between anthropogenic emission of mercury to the atmosphere and ecosystem build-up of methylmercury, the main toxic form. We are working to build this knowledge.

OBJECTIVES:

  • Understand the sources, chemical cycling, and transport and deposition pathways of atmospheric mercury;
  • Understand the cycling of mercury through its different biogeochemical reservoirs;
  • Understand the link between mercury deposition to the ocean and formation of methylmercury;
  • Understand the impacts of future changes in emissions and climate on the deposition and accumulation of mercury.

APPROACH:

  • Global 3-D modeling of mercury in the atmosphere-land-ocean system;
  • Development of process models for the cycling of mercury in the atmosphere, land, and ocean;
  • Interpretation of mercury observations in the atmosphere and oceans;
  • Projection of the effects of future changes in global anthropogenic emissions and climate.

PEOPLE: Elsie Sunderland, Christopher Holmes,Bess Corbitt

COLLABORATORS: Lyatt Jaegle (U. Washington), Dan Jaffe (U. Washington), Carey Jang (U.S. EPA), Tom Braverman (U.S. EPA), Rob Mason (U. Connnecticut), Noelle Selin (MIT), Anne Sorensen (U. Aarhus)

REFERENCES:

  • Smith-Downey, N.V., Sunderland, E.M., and Jacob, D.J., Anthropogenic impacts on global storage and emissions of mercury from terrestrial soils: insights from a new global model , J. Geophys. Res., submitted. [PDF]

  • Holmes, C.D., D.J. Jacob, R.P. Mason, D.A. Jaffe, Sources and deposition of reactive gaseous mercury in the marine atmosphere,Atmospheric Environment,43, 2278-2285, 2009. [PDF]

SUPPORT: NSF, EPA-STAR fellowship to Chris Holmes Back to projects list

soa ARCTIC AEROSOLS

BACKGROUND:

Current climate models are unable to explain the rapid warming observed in the Arctic over the past decades. This is a grave concern as an ice-free Arctic would lead to dramatic global climate change. Radiative forcing by aerosol particles may play a critical role in Arctic warming but this role is poorly represented in models. Major uncertainties relate to the sources and fate of aerosols in the Arctic, the aerosol optical properties, and the effect of black carbon (BC) aerosol deposited to snow. We are addressing these uncertainties through analysis of observations from the ARCTAS aircraft mission and concurrent satellite data.

OBJECTIVES:

  • Improve understanding of the sources of sulfate, black carbon (BC), and organic carbon (OC) aerosols to the Arctic atmosphere;
  • Assess the fate of these aerosols, including in particular the deposition of BC to snow;
  • Assess the climatic effect of Arctic aerosols.

APPROACH:

  • Global 3-D modeling and analysis of observations from the ARCTAS aircraft mission;
  • Interpretation of CALIPSO satellite observations of vertically-resolved aerosol extinction;
  • Simulations of Arctic climate using the GISS general circulation model constrained with aerosol information from ARCTAS.

PEOPLE:  Jenny Fisher, Qiaoqiao Wang

COLLABORATORS: David Winker (NASA/LaRC)

SUPPORT: NASA

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ozoneSATELLITE OBSERVATIONS OF TROPOSPHERIC OZONE

BACKGROUND:

Tropospheric ozone is of importance as a major greenhouse gas, as the primary source of the OH radical (the main atmospheric oxidant), and as a toxic pollutant in surface air. Satellite observations are beginning to provide a global perspective on the distribution of tropospheric ozone but the measurement is difficult. We work to validate the satellite observations and exploit them to improve our understanding of the factors controlling Ozone.

OBJECTIVES:

  • Use satellite observations of tropospheric ozone and its correlations with other gases to improve understanding of the factors controlling ozone concentrations;
  • Assess the implications for the influence of human activity and climate change.

APPROACH:

  • Intercompare tropospheric ozone observations from TES, OMI and GOME;
  • Evaluate global model simulations of tropospheric ozone against the satellite observations.

PEOPLE: Lin Zhang

COLLABORATORS: Xiong Liu (NASA/GSFC), Anne Marie Eldering (JPL)

REFERENCES:

  • Intercomparison of tropospheric ozone measurements from TES and OMI - a new method using a chemical transport model as comparison platform, presented by Lin Zhang at the Aura Science Team Meeting, Columbia, Maryland, October 28, 2008. [PPT (4.8 MB)]

SUPPORT: NASA

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broBROMINE TROPOSPHERIC CHEMISTRY

BACKGROUND:

Bromine radicals are known to be very important for stratospheric chemistry, but could they be important in the troposphere as well? It has been known for over a decade that high concentrations of BrO in surface air in arctic spring cause regional ozone and mercury depletion events. The source of this BrO is still not clear. More recently, there has been evidence from satellite and in situ observations for ubiquitous presence of BrO concentrations in the troposphere at levels that would have profound effects on oxidant and mercury chemistry. We are working to improve the retrieval of satellite data for tropospheric BrO with the goal of using these data as constraints in a global model for tropospheric bromine chemistry.

OBJECTIVES:

  • Improve satellite retrievals of tropospheric BrO;
  • Use these and other observations as constraints for our understanding of tropospheric bromine chemistry;
  • Assess the implications for the effects of bromine radicals on global tropospheric chemistry.

APPROACH:

  • Retrieve BrO tropospheric columns from the OMI and SCIAMACHY satellite instruments through spectral fitting and application of air mass factors;
  • Develop a global model of tropospheric bromine chemistry for interpretation of the satellite observations.

PEOPLE: Justin Parrella

COLLABORATORS: Kelly Chance (Harvard/SAO)

SUPPORT: NASA

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panGLOBAL ATMOSPHERIC BUDGET OF CARBONYL SULFIDE (COS)

BACKGROUND:

Carbonyl sulfide (COS) is the longest-lived form of sulfur in the atmosphere. It is emitted by the oceans and by combustion processes, and is removed by atmospheric oxidation and uptake by vegetation. The magnitudes of these different terms are poorly known. Better understanding is needed because COS provides a major source of sulfate aerosol to the stratosphere, and because uptake of COS by vegetation provides an important constraint on global photosynthesis rates (global primary productivity or GPP). A large network of surface observations of COS is available that can support inverse model analyses of the COS budget, and there are also attempts to observe COS from space.

OBJECTIVES:

  • Better constrain the global budget of COS through global atmospheric model simulations and evaluation with observations;
  • Infer constraints on global primary productivity (GPP).

APPROACH:

  • Develop a COS simulation capability in the GEOS-Chem chemical transport model;
  • Conduct inverse analyses to exploit the information from surface and satellite observations of COS.

PEOPLE:Parvadha Suntharalingam (now at U. East Anglia)

COLLABORATORS: A.J. Kettle (U. East Anglia)

REFERENCES:

  • Suntharalingam, P., A.J. Kettle, S.M. Montzka, and D.J. Jacob, Global 3-D model analysis of the seasonal cycle of atmospheric carbonyl sulfide: implications for vegetation uptake, Geophys. Res. Lett.,, 35, L19801, doi:10.1029/2008GL034332, 2008. [PDF]

SUPPORT: NSF

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GTEGLOBAL BUDGET OF METHANE

BACKGROUND:

Methane is the second most important anthropogenic greenhouse gas. It was rising for most of the 20th century at the rate of 1-2 %/yr. The growth has stopped in the past decade and we don't understand why. Sources of methane and their trends are very poorly quantified. We are analyzing methane observations from aircraft and satellite to better understand and quantify methane sources.

OBJECTIVES:

  • Improve understanding of the sources of methane through analyses of aircraft and satellite observations.

APPROACH:

  • Compare aircraft (INTEX, ARCTAS, HIPPO) and satellite (SCIAMACHY, AIRS) observations of methane to a GEOS-Chem global simulation including our best understanding of methane sources;
  • Apply an inverse model to these and other methane data sets to better quantify the sources of methane;
  • Exploit correlations of methane with other chemical tracers, in particular ethane (natural gas), as additional constraints on methane sources.

PEOPLE:  Christopher Pickett-Heaps, Kevin Wecht

REFERENCES:

SUPPORT: NSF

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GTENUMERICAL METHODS FOR GLOBAL CHEMICAL TRANSPORT MODELS

BACKGROUND:

Chemical transport models for the atmosphere represent a grand computational challenge. One has to describe the 4-D evolution of a stiff system of nonlinearly interacting species in a highly turbulent flow field. This requires computational compromises between spatial resolution, complexity of the physics and chemistry, fidelity of the parameterizations, and accuracy of the numerical solution. Development of efficient numerical methods is a critical component of progress.

OBJECTIVES:

  • To develop efficient numerical methods for global 3-D chemical transport models.

APPROACH:

  • Increase efficacy of chemical solvers through a spatial reduction algorithm;
  • Improve the model representation of transport for pollution plumes transported on global scales.

PEOPLE: Mauricio Santillana, Philippe LeSager, Claire Carouge

COLLABORATORS: Michael Brenner (Harvard)

REFERENCES:

  • Rastigeyev, Y., R. Park, M.P. Brenner, and D.J. Jacob, Resolving intercontinental pollution plumes in global models of atmospheric transport , J. Geophys. Res., submitted. [PDF]

SUPPORT:HUCE postdoctoral fellowship to Mauricio Santillana

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GTECHEMICAL DATA ASSIMILATION AND EARTH SYSTEM MODEL FRAMEWORK

BACKGROUND:

Developing efficient interfaces between atmospheric chemistry models and other Earth Science models is increasingly needed for a wide range of applications. For example, chemical data assimilation requires efficient interface with atmospheric dynamics models. Modeling the fate of elements as they cycle between the atmosphere and surface reservoirs requires coupling with ocean and terrestrial models. We are working in collaboration with the NASA Global Modeling and Assimilation Office (GMAO) to interface the GEOS-Chem model with atmospheric dynamics and other Earth Science model. Part of this work involves development of an Earth System Modeling Framework (ESMF) structure for GEOS-Chem to enable plug-and-play exchange with other models and model components.

OBJECTIVES:

  • Develop the capability for plug-and-play exchange of modules between GEOS-Chem and other models of atmospheric composition;
  • Develop the capability to interface GEOS-Chem with other Earth system model components;
  • Contribute to the chemical data assimilation capability of the NASA Global Modeling and Analysis Office (GMAO).

APPROACH:

  • Fully modularize GEOS-Chem;
  • Develop an ESMF capability for GEOS-Chem;
  • Contribute to the chemical data assimilation capability at GMAO.

PEOPLE:  Bob Yantosca, Philippe LeSager

, Claire Carouge

COLLABORATORS:Tom Clune, Steven Pawson (NASA/GSFC)

SUPPORT: NASA

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GTEBIOGENIC EMISSIONS FROM AFRICA

BACKGROUND:

Africa is host to diverse and active ecosystems, with large biogenic emissions that may contribute to regional and global climate forcing. Very little information is available on the ground. Satellites provide a unique opportunity to observe and quantify these emissions, understand the factors controlling them, and make future projections for the effect of changing climate and land use.

OBJECTIVES:

  • Use satellite observations to quantify the biogenic sources of isoprene, methane, and aerosols from Africa;
  • Better understand the role of human pressures and climate change in affecting these emissions.

APPROACH:

  • Use satellite observations of formaldehyde from OMI as constraint on isoprene emissions.

PEOPLE:  Eloise Marais

COLLABORATORS:Thomas Kurosu, Kelly Chance (Harvard/SAO)

SUPPORT: NASA

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