CURRENT RESEARCH

Last Updated: January 21, 2008

Our goal is to better understand the chemical composition of the atmosphere, its perturbation by human activity, and the implications for air quality, climate change, and life on Earth. Our approach involves the use of 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. NASA aircraft research missions for atmospheric composition take place every 2-3 years in different regions of the world and provide a critical link between satellite data sets and models. Jacob has been a leader of the NASA aircraft program for over 15 years and has served as mission scientist in PEM-Tropics A(1996), PEM-Tropics B (1999), TRACE-P (2001), INTEX-A (2004), INTEX-B (2006), and now ARCTAS (2008). We are present in the field throughout the missions for flight planning, forecasting, and near-real-time data analysis.

SATELLITE MISSIONS. Satellite observations are revolutionizing atmospheric chemistry research by providing global and continuous data sets of atmospheric composition. These data sets require advanced models for interpretation and we are in the thick of it. We serve on the Science Teams of the TES, MOPITT, and OCO instruments, and are also engaged in the analysis of data from MODIS, MISR, GOME, SCIAMACHY, and OMI. Our activities involve direct retrievals of satellite spectra using radiative transfer models, chemical data assimilation, inverse model analyses,and other data interpretation.
model ITCT satellite

ONGOING PROJECTS

GLOBAL TROPOSPHERIC CHEMISTRY AND BIOGEOCHEMISTRY REGIONAL AND GLOBAL AIR POLLUTION GLOBAL MAPPING OF EMISSIONS USING SATELLITES CHEMISTRY-CLIMATE INTERACTIONS NUMERICAL METHODS AND SOFTWARE ENGINEERING

[ITCT] CHEMICAL OUTFLOW FROM NORTH AMERICA: ICARTT AIRCRAFT CAMPAIGN

BACKGROUND:

North America is a major source of gases and particles to the global atmosphere. But how reliable are the current emission inventories, how good is our knowledge of continental export? What are the implications for intercontinental transport of pollution, and for the effect of North American emissions on global climate? We participated in the International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) multi-aircraft mission in summer 2004 to investigate these issues. Jacob was a co-mission scientist on that campaign.

OBJECTIVES:

  • To determine the mechanisms and fluxes for outflow of North American pollution to the global atmosphere;
  • To assess the consistency between the observed North American outflow and our a priori knowledge of North American emissions and continental boundary layer processing;
  • To quantify the implications of this North American outflow for transatlantic transport of pollution, integrating aircraft and satellite observations;
  • To determine the effect of North American emissions on radiative forcing of climate.

APPROACH:

  • Chemical hindcasting and forecasting in support of mission execution
  • Statistical analysis of pollution plumes
  • 3-D modeling of boundary layer chemistry and continental outflow
  • Inverse modeling of emissions using aircraft and satellite observations.

PEOPLE: Rynda Hudman, Lee Murray

REFERENCE:

  • 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, NOAA

[ITCT]TRANSPACIFIC TRANSPORT OF ASIAN POLLUTION: INTEX-B AIRCRAFT CAMPAIGN

BACKGROUND:

Emissions in East Asia are growing rapidly. Transpacific transport of this pollution could significantly impact air quality in North America. We participated in the spring 2006 NASA/INTEX-B aircraft campaign based in Hawaii, Anchorage, and Seattle, to observe the transpacific transport of Asian pollution and its effect on the United States. Jacob was a mission scientist on the campaign.

OBJECTIVES:

  • To quantify the impact of Asian pollution on surface ozone in the western United States;
  • To determine the value of satellite observations for observing the transpacific transport of ozone pollution
  • To determine the chemical transformation processes of Asian pollution on dust particles during transport across the Pacific

APPROACH:

  • Chemical hindcasting, forecasting, and near-real-time analyses during the campaign
  • Statistical analysis of pollution and dust plumes
  • Integration of satellite and aircraft observations
  • 3-D modeling of transport and chemistry

PEOPLE: Lin Zhang, Duncan Fairlie

COLLABORATORS:  Lyatt Jaegle (U. Washington), Steven Pawson (NASA/GMAO)

REFERENCES:

  • Recent increases in Asian emissions and consequences for transpacific ozone pollution in the United States: GEOS-Chem model interpretation of Aura and INTEX-B observations, presented by Lin Zhang at the Fall Meeting of the American Geophysical Union, San Francisco, December 14, 2007. [PPT (2.3 MB) ]

SUPPORT: NASA

[ITCT]ARCTIC POLLUTION: ARCTAS AIRCRAFT CAMPAIGN

BACKGROUND:

The Arctic is a beacon of global change. It is where climate warming has been strongest in the past decades. It is a major receptor of pollution from northern mid-latitudes. It is increasingly beset by large boreal forest fires with consequences for atmospheric chemistry and climate. Jacob is leading the NASA/ARCTAS aircraft campaign to the Arctic that will be conducted in spring/summer 2008 to address these issues.

OBJECTIVES:

  • To better understand and quantify human influence on arctic atmospheric composition;
  • To determine the implications for climate forcing, air quality, and pollutant deposition to arctic ecosystems

APPROACH:

  • Chemical hindcasting, forecasting, and near-real-time analyses in the field during the campaign
  • Evaluation of models for arctic atmospheric chemistry and for source attribution of pollution from northern mid-latitudes
  • Observation and modeling of radiative forcing from anthropogenic and forest fire aerosol layers

PEOPLE: Jenny Fisher, Chris Holmes, Justin Parrella

COLLABORATORS:Lyatt Jaegle (U. Washington), Steven Pawson (NASA/GSFC)

REFERENCES:

SUPPORT: NASA, NDSEG fellowship to Jenny Fisher

[ITCT]HEMISPHERIC TRANSPORT OF AIR POLLUTION

BACKGROUND:

Transport of pollution from North America, Europe, and Asian in prevailing westerly winds leads to a northern mid-latitudes pollution belt where we breathe each other's air. This hemispheric-scale transport of pollution needs to be better quantified in order to assist policymaking. We are active in the United Nations Task Force on Hemispheric Transport of Air Pollution (HTAP) to address this issue.

OBJECTIVES:

  • To better understand and quantify the hemispheric-scale transport of ozone and aerosol pollution, and the implications for surface air quality;
  • To develop source-receptor relationships that can guide future emission control strategies and international agreements;
  • To understand the coupling between regional and global scales in the hemispheric transport of pollution and to determine the corresponding model requirements.

APPROACH:

PEOPLE: Shiliang Wu. Rokjin Park (now at Seoul National University)

COLLABORATORS:Carey Jang (EPA/OAQPS), Bryan Duncan(NASA/GSFC)

REFERENCES:

  • Hemispheric transport of pollution: ozone, particles, and mercury, 16th Annual Harold I. Schiff Memorial Lecture presented by Daniel J. Jacob to the Faculty of Science and Engineering of York University, Toronto, Canada, December 8, 2006. [PPT (23 Mb)]

  • Intercontinental transport of air pollution with GMI and plans for the new Hemispheric Transport of Air Pollutants (HTAP) model intercomparison study, presented by Rokjin J. Park at the NASA Global Modeling Initiative (GMI) meeting, Lanham, Maryland, October 12, 2006. [PPT (1.7 Mb)]

SUPPORT: NASA, EPA

GTECANADIAN AND MEXICAN INFLUENCES ON U.S. OZONE AIR QUALITY

BACKGROUND:

The U.S. air quality standard for ozone is presently undergoing downward revision because of compelling evidence that the current standard (84 ppb) is inadequate to protect human health. As the standard gets ratcheted down, there is concern that non-domestic pollution sources outside U.S. control could play an increasing role in causing exceedances of the standard. Transboundary transport of pollution from Canada and Mexico is a particular concern.

OBJECTIVES:

  • Quantify the contributions from Canadian and Mexican sources to surface ozone concentrations in the United States;
  • Draw implications for the feasability of meeting lower U.S. air quality standards through domestic controls alone.

APPROACH:

  • Conduct high-resolution GEOS-Chem sensitivity simulations to determine the U.S. surface ozone enhancements from U.S., Canadian, Mexican, and intercontinental pollution sources;
  • Use the simulations to interpret observed occurrences of ozone pollution episodes at U.S. sites close to the borders.

PEOPLE:  Huiqun Wang, Philippe LeSager

REFERENCES:

  • Ozone air quality in the United States: policy-relevant background, transboundary pollution, and climate change, presented by Daniel J. Jacob at the Ozone Transport Commission Annual Meeting, Crystal City, Virginia, November 14, 2007. [PPT (3 MB) ]

SUPPORT: DOE

gome MAPPING EMISSIONS OF NITROGEN OXIDES USING SATELLITE OBSERVATIONS OF NITROGEN DIOXIDE

BACKGROUND:

Nitrogen oxide radicals (NOx), including NO and NO2, drive much of the chemistry of the troposphere. They are emitted by combustion, lightning, and soils. Satellite observations of NO2 columns provide excellent constraints on the sources of NOx. They allow to test emission inventories, identify emission hot spots, and detect emission trends. We are presently working with observations from the high-resolution OMI satellite instrument to map NOx emissions in the Middle East and interpret the particularly high tropospheric ozone concentrations observed in that region.

OBJECTIVES:

  • Use satellite observations of NO2 columns to constrain NOx emissions with high spatial and temporal resolution;
  • Determine the implications for tropospheric ozone budgets using ozone observations from aircraft, sondes, and satellites.

APPROACH:

  • Retrieve NO2 vertical columns from the OMI satellite instrument ;
  • Validate the results using in situ ground-based aircraft observations;
  • Develop high-quality top-down constraints to quantify NOx emissions in the Middle East;
  • Apply these emissions in a global 3-D model of atmospheric chemistry to determine the implications for ozone.

PEOPLE: Folkert Boersma (now at KNMI, Netherlands)

COLLABORATORS: Kelly Chance and Thomas Kurosu (Harvard/SAO), Alice Gilliland (EPA/ORD).

REFERENCES:

  • Validation of OMI tropospheric NO2 during INTEX-B and application to constrain NOx emissions in the eastern United States and Mexico, presented by Daniel J. Jacob (for K. Folkert Boersma) at the Fall Meeting of the American Geophysical Union, San Francisco, December 14, 2007. [PPT (5 MB) ]

  • Boersma, K. F., D. J. Jacob, H. J. Eskes, R. W. Pinder, J. Wang, and R. J. van der A, Intercomparison of SCIAMACHY and OMI tropospheric NO2 columns: observing the diurnal evolution of chemistry and emissions from space, submitted to J. Geophys. Res. [PDF]

  • Boersma, K. F., D. J. Jacob, E. J. Bucsela, A. E. Perring, R. Dirksen, R. J. van der A, R. M. Yantosca, R. J. Park, M. O. Wenig, T. H. Bertram, and R. C. Cohen, Validation of OMI tropospheric NO2 observations during INTEX-B and application to constrain NOx emissions over the eastern United States and Mexico, submitted to J. Geophys. Res. [PDF]

SUPPORT: NASA

gome BOREAL FIRES: EMISSIONS, INJECTION HEIGHTS, AND ATMOSPHERIC EFFECTS

BACKGROUND:

Boreal forest fires in North America and Siberia have been increasing in frequency and size over the past decades. Emissions in high fire years such as 1998, 2002, and 2003 provide a major perturbation to the atmospheric composition of the northern hemisphere. The plumes can be injected at high altitudes due to the buoyancy associated with the fires, and this has important consequence for the persistence of these plumes and their atmospheric effects. We are using satellite observations of fire locations from the MODIS instrument, carbon monoxide (CO) from the MOPITT satellite instrument, and aerosol stereoscopic data from the MISR satellite instrument to place constraints on fire emissions and injection heights. We are also investigating the effects of the fires on ozone and aerosols.

OBJECTIVES:

  • Obtain better estimates of emission rates and injection heights from boreal forest fires;
  • Assess the implications of injection above the boundary layer for trace gases
  • Assess the effects of boreal fires on air quality.

APPROACH:

  • Construct high-resolution emission inventories for forest fires using information from satellite fire counts, local fire reports, and vegetation maps;
  • Conduct model analyses of fire emissions and their injection altitudes using CO observed from space, surface sites and aircraft;
  • Use stereoscopic observations of aerosols from MISR to constrain injection heights.

PEOPLE: Maria Val Martin, Fok-Yan Leung (now at Wash. State Univ), Rose Yevich, Solene Turquety (now at Service d'Aeronomie, Paris), Jennifer Logan

REFERENCES:

  • Kahn, R. A.,  Y. Chen, D. L. Nelson, F.-Y. Leung, Q. Li, D. J. Diner, and J. A. Logan, Wildfire smoke injection heights – two perspectives from space, Geophys. Res. Lett, submitted, 2007.

  • High Temporal Resolution Inverse Modeling of CO Emissions from North American Boreal Fires and Their Injection Height During the Summer of 2004, presented by Solene Turquety at the Fall Meeting of the AGU, San Francisco, December 15, 2006. [PPT (4 Mb)]

  • Leung, F.-Y., J. A. Logan, R. Park, E. Hyer, E. Kasischke, D. Streets, and L. Yuganov (2007), Impacts of biomass burning in the boreal forests on tropospheric chemistry and the sensitivity of model results to injection height , J. Geophys. Res., D10313[PDF]

  • Turquety, S., J. A. Logan, D. J. Jacob, R. C. Hudman, F. Y. Leung, C. L. Heald, R. M. Yantosca, S. Wu, L. K. Emmons, D. P. Edwards, and G. W. Sachse (2007), Inventory of boreal fire emissions for North America: importance of peat burning and pyro-convective injection, J. Geophys. Res., D12S03.[PDF]

SUPPORT: NSF, EPA, NASA

gomeADJOINT METHODS FOR HIGH-RESOLUTION INVERSE MODELING OF EMISSIONS USING SATELLITE DATA

BACKGROUND:

Satellite observations provide global continuous data on atmospheric concentrations for a number of chemicals emitted to the atmosphere. One would like to use these data to provide constraints on emissions with correspondingly high spatial and temporal resolution. Atmospheric transport complicates the matter. One must apply a chemical transport model such as GEOS-Chem to relate emissions to atmospheric concentrations, and then a Bayesian inverse analysis to retrieve emissions from the observed concentrations. Traditional approaches using analytical solution to the Bayesian inverse problem are seriously limited in the number of constraints that they can derive. A powerful alternative is to use a numerical solution based on the adjoint of the chemical transport model; this places no limit on the number of constraints other than the quality of the observational data set and of the chemical transport model.

OBJECTIVES:

  • Apply adjoint methods for high-resolution inverse modeling of emissions using satellite data.

APPROACH:

  • Develop adjoint versions of the GEOS-Chem chemical transport model;
  • Apply the adjoint to inverse modeling of MOPITT satellite data to constrain CO emissions from Asia;
  • Apply the adjoint to inverse modeling of CO2 surface fluxes using satellite observations and pseudo-observations.

PEOPLE: Monika Kopacz

COLLABORATORS: Daven Henze and John Seinfeld (Caltech), Dylan Jones (U. Toronto), Qinbin Li and Kevin Bowman (JPL), Adrian Sandu (Virginia Tech)

REFERENCES:

  • Kopacz, M., D. J. Jacob, D.K. Henze, C.L. Heald, D.G. Streets, Q. Zhang (2007), Comparison of adjoint and analytical Bayesian inversion methods for constraining Asian sources of carbon monoxide using satellite (MOPITT) measurements of CO columns, submitted to J. Geophys. Res. [PDF]

SUPPORT: NASA, NASA fellowship to Monika Kopacz

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, Rynda Hudman

COLLABORATORS:  Randall Martin (Dalhousie), Bastien Sauvage (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

[Modis]QUANTIFYING AEROSOL CONCENTRATIONS AND SOURCES USING SATELLITE OBSERVATIONS OF SOLAR BACKSCATTER

BACKGROUND:

Aerosols are of central environmental importance for issues ranging from public health to climate change. Satellite observations of aerosol optical thickness by solar backscatter from instruments such as MODIS provide an outstanding opportunity, in combination with chemical transport models such as GEOS-Chem, to map aerosol concentrations globally and constrain aerosol sources. However, a major challenge is to separate the contributions from the surface and from the aerosol to the backscattered signal observed from space. We are developing a new approach for the retrieval of aerosol information from space that will allow quantitative intepretation with a chemical transport model, including inverse analyses of emissions and inferences of surface concentrations.

OBJECTIVES:

  • Improve retrievals of aerosol optical thicknesses and aerosol reflectances from space;
  • Use satellite observations of aerosol reflectances to test global model simulations of aerosol concentrations and place constraints on aerosol sources.

APPROACH:

  • Separate surface from aerosol reflectance contributions in solar backscatter observations from the MODIS satellite instrument;
  • Simulate MODIS aerosol reflectances using the GEOS-Chem chemical transport model combined with the LIDORT radiative transfer model;
  • Apply inverse model analyses to the interpretation of MODIS reflectances in terms of the constraints on aerosol sources and surface concentrations.

PEOPLE:  Easan Drury

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

REFERENCES:

  • Drury, E.E., D.J. Jacob, J. Wang, R.J.D. Spurr and K. Chance. Improved algorithm for MODIS satellite retrievals of aerosol optical depths over land, J. Geophys. Res., submitted, 2007. [PDF]

SUPPORT:NASA fellowship to Easan Drury

[MOPITT]GLOBAL MAPPING OF CARBON SURFACE FLUXES USING CO2 SATELLITE DATA

BACKGROUND:

Only 30-50% of CO2 emitted to the atmosphere from fossil fuel combustion and deforestation actually remains in the atmosphere. The rest is taken up by oceans and by terrestrial vegetation. Quantifying these different terms and their global distributions is a critical issue for future projections of the rise of CO2 and for the design and verification of international agreements. The Orbiting Carbon Observatory (OCO)satellite instrument, scheduled for launch in 2008, will provide global measurements of CO2 mixing ratio columns to enable inverse modeling of carbon surface fluxes with high resolution. This will allow for the first time a verification of carbon budgets for individual nations and other geopolitical entities. We are part of the OCO Science Team charged with the responsibility to develop an inverse modeling capability for the instrument. We are particularly interested in the potential of using collocated satellite observations of CO and CO2 to separate anthropogenic from biospheric contributions to carbon surface fluxes.

OBJECTIVES:

  • Develop an adjoint-based inverse modeling capability for CO2 surface fluxes using OCO satellite observations;
  • Examine the effect of wildfires on the CO2 budget, and how to account for this effect in inverse studies;
  • Assess the value of atmospheric correlations of CO2 with other chemicals as constraints on surface carbon fluxes.

APPROACH:

  • Generate error covariance matrices for modeling OCO observations;
  • Conduct Observation System Simulation Experiments (OSSEs) to determine the value of concurrent CO2 and CO measurements from space for constraining CO2 surface fluxes.
  • Use aircraft observations to develop diagnostics for the influence of fires on atmospheric CO2

PEOPLE: Parvadha Suntharalingam, Monika Kopacz, Helen Wang

COLLABORATORS: Steven Pawson (NASA/GMAO)

SUPPORT: NASA

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, Shiliang Wu, Eric Leibensperger, Moeko Yoshitomi

COLLABORATORS:  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:

  • Wu, S., L.J. Mickley, E.M. Leibensperger, D.J. Jacob, D. Rind and D.G. Streets, Effects of 2000-2050 global change on ozone air quality in the United States, submitted to J. Geophys. Res. [PDF]

  • GCAP home page

SUPPORT: EPA, EPRI

EFFECTS OF CHANGING CLIMATE ON FIRES

BACKGROUND:

The occurrence and intensity of wildfires is strongly related to climate. Fires may be more common in a future warmer climate as rainfall patterns change. We are investigating the consequences of climate change on wildfires, and the impact on U.S. air quality.

OBJECTIVES:

  • To quantify the effect of present day fires on air quality in the United States;
  • To explore the relationship between climate and the frequency and magnitude of wildfires in North America, and develop scenarios for future fires;
  • To examine how different scenarios for future fires will affect air quality in a future climate;
  • To examine the trade-offs in air pollutant emissions between managed fires and catastrophic fires.

APPROACH:

  • Determine the best predictors for area burned for different ecosystems, using the Fire Weather Index system or the Fire Weather Danger Rating System
  • Conduct NASA/GISS general circulation model simulations of future climate change including tracers of wildfire pollution;
  • Perform global coupled ozone-aerosol simulations for the present day and future climates using the GEOS-Chem model driven by meteorological and area burned statistics from the GCM;
  • Perform CMAQ simulations of selected future years for more accurate prediction of the effects.

PEOPLE: Jennifer Logan, Rynda Hudman, Dominick Spracklen , Loretta Mickley, Rokjin Park .

COLLABORATORS:  Daewon Byun (University of Houston), David Diner, Qinbin Li, and Dominic M. Mazzoni (Jet Propulsion Laboratory)

REFERENCES:

  • Spracklen, D. V., J. A. Logan, L. J. Mickley, R. J. Park, R. Yevich, A. L. Westerling, and D. Jaffe, Wildfires drive interannual variability of organic carbon aerosol in the western U.S. in summer. , Geophys. Res. Lett., in press, 2007. [PDF]

  • Park, R. J., D. J. Jacob, and J. A. Logan (2007), Fire and biofuel contributions to annual mean aerosol mass concentrations in the United States, Atmos. Environ., in press [PDF]

SUPPORT: EPA

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, Rokjin Park .

COLLABORATORS:  Jed Kaplan (ISPRA), David Rind (NASA/GISS)

SUPPORT: NASA

CHEMISTRY, AEROSOLS, AND CLIMATE: TROPOSPHERIC UNIFIED SIMULATION (CACTUS)

BACKGROUND:

Changes in the atmospheric abundances of aerosols and tropospheric ozone are expected to make important contributions to climate change over the 21st century. In turn, climate change will affect the abundances of ozone and aerosols, resulting in complicated feedbacks. CACTUS is multi-institutional collaboration focused on understanding the mechanisms of aerosol-chemistry-climate interactions and involving groups at Caltech, NASA/GISS, CMU, Georgia Tech, and Harvard. A priority at present is improving understanding of aerosol indirect effects involving cloud modification.

OBJECTIVES:

  • To understand the roles of aerosols and tropospheric ozone on climate forcing over the next century for different scenarios;
  • To understand the underlying feedbacks.

APPROACH:

  • Simulations with a unified chemistry-aerosol-climate general circulation model and with simpler diagnostic models.

PEOPLE:  Loretta Mickley

COLLABORATORS:  David Rind (GISS), John Seinfeld (Caltech),Peter Adams (CMU), Thanos Nenes (Georgia Tech)

SUPPORT: NASA

MERCURY IN THE ENVIRONMENT

BACKGROUND:

Mercury is a toxic pollutant that bioaccumulates in the environment. It is emitted to the atmosphere in both gaseous elemental and oxidized forms; the elemental form can be transported on a global scale. The redox chemistry of atmospheric mercury is still unclear. An additional issue is the re-emission of mercury deposited to ocean and to land, and the implied legacy of anthropogenic emissions. We are using a global multi-media model analysis anchored by the GEOS-Chem chemical transport model to better understand the sources, atmospheric transport and chemistry, and biogeochemical cycling of mercury, the processing of mercury in terrestrial ecosystems, and the effects of climate change. Our global mercury simulation is being used by the U.S. EPA as boundary conditions for regional model simulations that serve as the basis for mercury regulations in the United States.

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 impacts of future changes in emissions and climate on the deposition and accumulation of mercury.

APPROACH:

  • Global 3-D modeling of mercury chemistry and transport in the atmosphere, including dynamic coupling to the surface reservoirs;
  • Development of process models for the cycling of mercury in terrestrial ecosystems;
  • Interpretation of aircraft observations from the INTEX-B, CARIBIC, and ARCTAS campaigns;
  • Interpretation of the historical accumulation of mercury with a coupled ocean-atmosphere model.

PEOPLE: Noelle Eckley Selin, Christopher Holmes, Nicole Downey, Bess Sturges, Elsie Sunderland (EPA)

COLLABORATORS: Sarah Strode and Lyatt Jaegle (U. Washington), Dan Jaffe (U. Washington), Carey Jang (U.S. EPA), Tom Braverman (U.S. EPA)

REFERENCES:

  • Chemical sources and sinks of Hg(II) in the remote atmospheric marine boundary layer, presented by Christopher D. Holmes at the Fall Meeting of the American Geophysical Union, San Francisco, December 13, 2007. [PDF (4 MB) ]

  • Selin, N.E., D.J. Jacob, R.M. Yantosca, S. Strode, L. Jaegle, and E.M. Sunderland, "Global 3-D land-ocean-atmosphere model for mercury: present-day vs. pre-industrial cycles and anthropogenic enrichment factors for deposition", submitted to Global Biogeochemical Cycles [PDF]

SUPPORT: NSF, EPA-STAR fellowships to Noelle Selin and Chris Holmes, Harvard University Committee on the Environment fellowship to Nicole Downey

soaSOURCES OF ORGANIC AEROSOLS

BACKGROUND:

Organic material is a dominant but poorly understood component of the atmospheric aerosol. Chemical production within the atmosphere from oxidation of hydrocarbons appears to be important, but fundamental questions remain as to the underlying mechanisms and the relative contributions of anthropogenic and biogenic sources. We are addressing these issues through analyses of surface, aircraft, and satellite measurements, and through global model simulations to explore possible mechanisms. We are particularly interested at present in the potential for organic aerosol formation from aqueous-phase oligomerization of dicarbonyls (glyoxal, methylglyoxal) and their oxidation products

OBJECTIVES:

  • To improve understanding of the sources of organic aerosols in the United States and in the global atmosphere;
  • To identify important mechanisms for the atmospheric formation of secondary organic aerosol (SOA).

APPROACH:

  • Statistical analyses of surface and aircraft observations of organic aerosols;
  • Implementation of mechanisms for SOA formation in the GEOS-Chem chemical transport model;
  • Global model simulation of glyoxal and methylglyoxal as SOA precursors and comparison to satellite observations of glyoxal columns.

PEOPLE:  May Fu

COLLABORATORS:Thomas Kurosu (Harvard/SAO)

REFERENCES:

  • Fu, T.-M., D. J. Jacob, F. Wittrock, J. P. Burrows, and M. Vrekoussis, Global budgets of atmospheric glyoxal and methylglyoxal, and implications for formation of secondary organic aerosols, J. Geophys. Res., submitted. [PDF]

SUPPORT: EPRI

ozoneSATELLITE OBSERVATIONS OF TROPOSPHERIC OZONE

BACKGROUND:

Tropospheric ozone is of considerable environmental importance as a major greenhouse gas, as the primary source of OH radicals, and as a toxic pollutant in surface air. Ozone is produced in the troposphere by photochemical oxidation of volatile organic compounds (VOCs) and CO in the presence of nitrogen oxides (NOx). The chemistry is highly nonlinear and coupled to transport on all scales. A quantitative understanding of tropospheric ozone requires understanding the impacts due to factors such as anthropogenic emissions, biomass burning and lightning. Recent satellite observation capabilities from TES, GOME, and OMI provide for the first time a global continuous data set for tropospheric ozone. We are analyzing these data together with correlative information to gain new insights into the mechanisms 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:

  • Compare TES tropospheric ozone with in situ observations from ozonesondes;
  • Intercompare tropospheric ozone observations from TES, OMI and GOME;
  • Evaluate global model simulations of tropospheric ozone against the satellite observations and assess the sensitivity to different sources and processes (transport, biomass burning, lightning, etc.);
  • Investigate interannual variability in tropospheric ozone including years such as 2006 which was influenced by a moderate El Nino.

PEOPLE: Ray Nassar, Lin Zhang, Jennifer Logan

COLLABORATORS: Xiong Liu (Harvard/SAO), Helen Worden (NASA/JPL)

REFERENCES:

  • Nassar, R., et al., (2008), Validation of Tropospheric Emission Spectrometer (TES) Nadir Ozone Profiles Using Ozonesonde Measurements, J. Geophys. Res., in press. [PDF]

  • Logan, J. A. et al. (2008), The effects of the 2006 El Nino on tropospheric composition as revealed by data from the Tropospheric Emission Spectrometer (TES), Geophys. Res. Lett., in press. [PDF]

SUPPORT: NASA

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 chemisytry.

APPROACH:

  • Retrieve BrO tropospheric columns from the OMI satellite instrument 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: NSF, NSF Graduate Fellowship to Justin Parrella

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

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., submitted, 2007. [PDF]

SUPPORT: NSF

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. In the past decade the growth has stopped, as a result of slower growth in emissions and trends in OH. Sources of methane and their trends are very poorly quantified. There are indications that the U.S. source is seriously underestimated in official inventories. We will participate in the HIPPO aircraft campaign in 2008 which will provide pole-to-pole observations of methane concentrations as constraints on sources.

OBJECTIVES:

  • Improve understanding of the sources of methane through top-down constraints from aircraft and satellite observations.

APPROACH:

  • Compare aircraft (INTEX, HIPPO) and satellite (SCIAMACHY, AIRS) observations of methane to a GEOS-Chem global simulation using our best understanding of methane sources;
  • Exploit correlations of methane with other chemical tracers, in particular ethane (natural gas), as additional constraints on methane sources.

PEOPLE:  Kevin Wecht

REFERENCES:

SUPPORT: NSF

duoleaf2.gifASIAN AIR QUALITY AND ITS EFFECTS ON THE GLOBAL ENVIRONMENT

BACKGROUND:

Rapid industrial development over the past 20 years in East Asia and specifically in China has resulted in unprecedented growth in emission of important trace gases with implications for both the global and regional environment. An important objective of this study is to define the nature and extent of these emissions. An important objective of this study is to define the nature and extent of these emissions through integrated model analysis of atmospheric measurements on different platforms (aircraft, surface, and satellite).

OBJECTIVES:

  • To improve emission estimates of CO and NOx from Asia given the constrains provided by an integration of aircraft and surface station data
  • To develop 'top-down' constraints on NOx budget in China using observations from space
  • To better understand tropospheric ozone chemistry in China, with a focus on high ozone episodes in north China in summer
  • To improve understanding of emissions of CO2 associated with Chinese fossil fuel consumption and the role of the biosphere for the regional budget of CO2 over China

APPROACH:

  • Forward and inverse modeling with the nested grid GEOS-Chem model
  • Model analysis of space-based observations of NO2 columns
  • Model analysis of near-source observations of trace gases and their correlations

PEOPLE: Yuxuan Wang, Michael B. McElroy, Jennifer Logan

COLLABORATORS: China Project of the Harvard University Center for the Environment

REFERENCES:

  • Wang, Y.X., M.B. McElroy, D.J. Jacob, R.M. Yantosca (2004), A nested grid formation for chemical transport over Asia: applications to CO, J. Geophys. Res. , D22307, doi:10.1029/2004jd005237. [PDF]

  • Wang, Y.X., M.B. McElroy, T. Wang, and P.I.Palmer (2004). Asian emissions of CO and NOx: constraints from aircraft and Chinese station data. J. Geophys. Res. , D24304. [PDF]

  • McElroy, M.B., and Wang, Y.X. (2005), "Human and Animal Wastes: Implications for Atmospheric N2O and NOx", Global Biogeochem. Cycles , 19, GB2008, doi:10.1029/2004GB002429. [PDF]

  • Wang, Y.X., M. B. McElroy, R. V. Martin, D. G. Streets, Q. Zhang, and T.-M. Fu (2007), "Seasonal variability of NOx emissions over east China constrained by satellite observations: Implications for combustion and microbial sources", J. Geophys. Res., in press. [PDF]

SUPPORT: NSF

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;
  • Examine the numerical diffusion associated with Eulerian transport in a variable flow field, and infer model resolution requirements.

PEOPLE: Philippe LeSager

COLLABORATORS: Michael Brenner (Harvard)

REFERENCES:

  • Rastigeyev, Y., M.P. Brenner, and D.J. Jacob, Spatial reduction algorithm for atmospheric chemical transport models, PNAS, 104, 13875-13880, 2007. [PDF]

SUPPORT:NSF

GTECHEMICAL DATA ASSIMILATION AND EARTH SYSTEM MODEL FRAMEWORK

BACKGROUND:

Developing efficient interfaces between different atmospheric modeling components and different Earth science models is increasingly needed for a wide range of applications. For example, chemical data assimilation requires efficient interface with atmospheric dynamics models. Sharing of codes is important for error characterization and to promote progress in models. Some atmospheric composition problems (such as carbon and mercury) require dynamic coupling with ocean and terrestrial models. We are members of the NASA Global Modeling Initiative (GMI) to develop a next-generation capability for modeling of atmospheric composition by drawing on expertise and code from many modeling groups. Part of this work involves development of an Earth System Modeling Framework (ESMF) capability to enable plug-and-play exchange between models and model components.

OBJECTIVES:

  • Develop the capability for plug-and-play exchange of modules between GEOS-Chem and other models of atmospheric composition as part of the NASA Global Modeling Initiative;
  • 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;
  • Exchange modules with other GMI components;
  • Contribute to the chemical data assimilation capability at GMAO.

PEOPLE:  Bob Yantosca, Philippe LeSager

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

SUPPORT: NASA