CURRENT RESEARCH PROJECTS

Last Updated: December 8, 2011

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Our research focuses on better understanding the chemical composition of the atmosphere, its perturbation by human activity, and the implications for climate and life on Earth. We use advanced global models of atmospheric composition to interpret observations from satellites, aircraft, ground networks, and other platforms. We view our models as part of an integrated observing system bridging the information from different data sets to increase fundamental knowledge and 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. 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 enable detailed chemical characterization of atmospheric composition from the surface to the stratosphere and over the scale of the globe. We have been engaged in a large number of aircraft missions over the past 25 years in different regions of the world. We are presently involved in the NASA ARCTAS mission to the Arctic, the NSF HIPPO pole-to-pole mission, and the NASA SEAC4RS mission to Southeast Asia. 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

CURRENT PROJECTS

Link to Jennifer Logan's projects

AEROSOLS

AIR QUALITY

BIOSPHERE-ATMOSPHERE INTERACTIONS

CARBON GASES

CHEMISTRY-CLIMATE INTERACTIONS

COMPUTATIONAL METHODS AND SOFTWARE ENGINEERING

GLOBAL ATMOSPHERIC CHEMISTRY

MERCURY

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Project Descriptions

gomeNITROGEN AND OZONE DEPOSITION IN BIODIVERSITY HOTSPOTS WORLDWIDE

BACKGROUND:

Biodiversity hotspots are locations in the world that have exceptional biodiversity and are presently facing rapid loss of that diversity. Human-driven increases in nitrogen deposition and ozone exposure may be a significant factor in biodiversity loss.

OBJECTIVES:

  • Quantify the importance of different anthropogenic and natural sources to nitrogen and ozone deposition in biodiversity hotspots worldwide.
  • Understand the sensitivity of these source-receptor relationships to atmospheric chemistry and other processes.

APPROACH:

  • Apply the adjoint of the GEOS-Chem model to determine the sensitivity of nitrogen and ozone deposition in biodiversity hotspots to different emissions, chemical processes, and surface processes.
  • Complement the information from the adjoint analysis with model comparisons to observations and sensitivity simulations with the forward GEOS-Chem model.

PEOPLE: Fabien Paulot

SUPPORT: Harvard University Committee on the Environment (HUCE) Fellowship to Fabien Paulot, NASA ACMAP (PI Daniel Jacob)

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gomeNITROGEN DEPOSITION IN THE UNITED STATES

BACKGROUND:

Ammonia and nitrogen oxides emitted by human activities are eventually deposited to the Earth's surface. The resulting nitrogen enrichment in US ecosystems can cause undesired fertilization and eutrophication. The effect is of particular concern in National Parks because biodiversity loss driven by cumulative nitrogen deposition changes the original ecosystem forever. The EPA is presently considering regulating nitrogen deposition in the US through an air quality standard. We need to better understand the relative contributions of different sources to nitrogen deposition in order to develop an effective emissions control strategy.

OBJECTIVES:

  • Determine the relative contributions of anthropogenic vs. natural, domestic vs. international sources to nitrogen deposition in the US.
  • Conduct a detailed source attribution for nitrogen deposition in US National Parks.

APPROACH:

  • Conduct sensitivity simulations with the nested GEOS-Chem model at high resolution (0.5ox0.67o horizontal) over North America.
  • Evaluate nitrogen deposition and its source contributions in GEOS-Chem through extensive comparisons to US observations.

PEOPLE: Raluca Ellis, Lin Zhang

REFERENCES:

  • Zhang, L., D.J. Jacob, E.M. Knipping, N. Kumar, J.W. Munger, C.C. Carouge, A. van Donkelaar, Y. Wang, and D. Chen, Nitrogen deposition to the United States: distribution, sources, and processes, submitted to Atmos. Chem. Phys.,, 2011. [PDF]

SUPPORT: EPRI, NASA AQAST (PI Daniel Jacob)

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gomePOLICY-RELEVANT BACKGROUND OZONE IN THE UNITED STATES

BACKGROUND:

The ozone air quality standard in the US has become increasingly stringent over the past decade, and current recommendations are to further tighten it to 60-70 ppb (8-hour average). These levels approach the ozone background at northern mid-latitudes, particularly at high-elevation sites in the Intermountain West. We need to better understand background influences on ozone concentrations in the US and the sources contributing to this background.

OBJECTIVES:

  • Quantify the ozone background over the US contributed by natural and external sources, with particular focus on the Intermountain West;
  • Determine to what extent this background is affected by international anthropogenic emissions;
  • Conclude as to the achievability of different ozone air quality standards through domestic emission controls and international agreements.

APPROACH:

  • Evaluate the nested GEOS-Chem model over North America (0.5ox0.67o horizontal resolution) with surface and ozonesonde observations;
  • Conduct model sensitivity simulations to quantify background ozone and the influences of various sources on this background.

PEOPLE: Lin Zhang, Katherine Travis

REFERENCES:

  • Zhang, L., D.J. Jacob, N.V. Smith-Downey, D.A. Wood, D. Blewitt, C.C. Carouge, A. van Donkelaar, D.B.A. Jones, L.T. Murray, and Y. Wang, Improved estimate of the policy-relevant background ozone in the United States using the GEOS-Chem global model with 1/2ox2/3o horizontal resolution over North America, Atmos. Environ., 45, 6769-6776, 2011. [PDF]

SUPPORT: BP, NASA AQAST (PI Daniel Jacob)

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

BACKGROUND:

Observation of CO2 from space could provide a unique resource for mapping surface fluxes of CO2. Very high measurement precision is necessary because atmospheric CO2 has little variability. Correlation with satellite observations of carbon monoxide (CO) could provide precious additional information, 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) and for planning the next generation of sensors (OCO-2, ASCENDS).

OBJECTIVE:

  • Exploit CO2-CO error correlations in inverse model analyses to improve the constraints on carbon fluxes from satellite data.

APPROACH:

  • Characterize CO2-CO model error correlations for surface air observations from the NOAA flask network, ground-based column measurements from the TCCON network, and the TES and GOSAT satellite instruments,
  • Apply these error correlations as constraints in joint CO2-CO inversions of CO2 surface fluxes using TES and GOSAT data.

PEOPLE: Helen Wang

COLLABORATORS: Dylan Jones (U. Toronto), Susan Kulawik (JPL).

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) , Atmos. Chem. Phys., 10, 855-876, 2010. [PDF]

  • 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 ACOS (Helen Wang and Daniel Jacob subcontracts to JPL)

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lnox SENSITIVITY OF ATMOSPHERIC OXIDANTS TO LIGHTNING

BACKGROUND:

Lightning emission of nitrogen oxides (NOx) increases the global concentrations of atmospheric oxidants (tropospheric ozone and OH) but is very poorly represented in chemical transport models. It is very sensitive to climate change and could thus drive important climate feedbacks. Long-term records of lightning flash observations from satellites offer a resource to effectively constrain the global distribution of the lightning NOx source and from there to assess its implications for atmospheric chemistry.

OBJECTIVES:

  • Use satellite observations to constrain lightning NOx emissions globally;
  • Better understand the sensitivity of tropospheric ozone and OH to changes in lightning including interannual variability;
  • Develop new physically-based parameterizations of lightning in global climate models to study climate-lightning-chemistry feedbacks.

APPROACH:

  • Use satellite lightning flash observations from the OTD/LIS sensors to constrain the global distribution and interannual variability of lightning emissions in the GEOS-Chem model
  • Apply this lightning distribution in GEOS-Chem to simulate the global distributions of NOx, ozone, OH, and related species, and assess the sensitivity to lightning;
  • Use the satellite lightning data as constraints to test new physically-based lightning parameterizations for global models.

PEOPLE:  Lee Murray

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 ACMAP (PI Daniel Jacob)

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NASA satellites GEOSTATIONARY SATELLITE OBSERVATIONS OF AIR QUALITY AND CLIMATE FORCING

BACKGROUND:

All satellite observations of atmospheric composition so far have been from low-elevation orbit (500-100 km). This allows global mapping but the data are sparse. A satellite in geostationary orbit (36,000 km) would provide continuous observations over a source continent to monitor air quality, long-range transport of pollution, sources of gases and particles, and radiative forcing. Daniel Jacob leads the Science Working Group for GEO-CAPE, a NASA geostationary mission for air quality and climate forcing scheduled for launch in the 2020 time frame. We need at this stage to define the mission capabilities and requirements. This involves conducting Observing System Simulation Experiments (OSSEs) in which we fly the satellite over a synthetic atmosphere produced by our models and determine what instrument specifications and observing modes generate the most valuable information.

OBJECTIVES:

  • Determine the ability of geostationary observations to improve monitoring of ozone air quality and to detect high-ozone events driven by background sources;
  • Determine the ability of geostationary observations to better quantify methane sources;
  • Study how a multi-species measurement strategy from geostationary orbit can help to better understand the transport and chemical evolution of ozone pollution.

APPROACH:

  • Develop and OSSE framework using two independent chemical transport models (CTMs), one describing the "true" atmosphere to be sampled by the satellite and the other serving as forward model for data assimilation;
  • Apply this OSSE framework to determine the GEO-CAPE measurement requirements for ozone;
  • Determine the added value of concurrent measurements of CO, NO2, and formaldehyde from GEO-CAPE to constrain the distribution of surface ozone;
  • Demonstrate the capability of GEO-CAPE for inversion of methane sources with high spatial and temporal resolution.

PEOPLE:  Peter Zoogman, Kevin Wecht, Daniel Jacob

REFERENCES:

  • GEO-CAPE Science Goals and Requirements - Atmosphere, presentation by Daniel J. Jacob at the NASA GEO-CAPE Community Workshop, Boulder, Colorado, May 11, 2011. [pdf]

  • Zoogman, P., D.J. Jacob, K. Chance, L. Zhang, P. Le Sager, A.M. Fiore, A. Eldering, X. Liu, V. Natraj, S.S. Kulawik, Ozone Air Quality Measurement Requirements for a Geostationary Satellite Mission. Atmos. Environ., 45, 7,143-7,150, 2011.[PDF]

SUPPORT: NASA Graduate Fellowships to Peter Zoogman and Kevin Wecht

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[Modis]GLOBAL TRANSPORT AND SCAVENGING OF AEROSOLS

BACKGROUND:

Aerosols are crucially important for a wide range of environmental issues ranging from public health to climate change. Satellite observations offer a unique resource for mapping the global transport of aerosols and studying the environmental implications of this transport. However, the interpretation of satellite data is challenging because of the complexity of aerosol types and interferences from surface and cloud reflectivity.

OBJECTIVES:

  • Interpret the CALIOP space-based lidar observations of aerosols in terms of continental outflow and global-scale transport of aerosols;
  • Combine CALIOP with information from other space-based aerosol sensors (in particular MODIS) to improve understanding of the sources, transport, and removal of aerosols.

APPROACH:

  • Use MOPITT CO observations with two pieces of information in the vertical to constrain the ventilation of aerosol source regions;
  • Correlate space-based aerosol and CO observations in continental outflow to deduce the aerosol scavenging efficiency;
  • Use CALIOP observations to better constrain the aerosol outflow at different altitudes.

PEOPLE:  Sungshik Kim

COLLABORATORS:  David Winker, Duncan Fairlie (NASA LaRC).

SUPPORT: DOE Graduate Fellowship to Sungshik Kim, NASA ACMAP (PI Daniel Jacob)

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[BC] GLOBAL SOURCES AND SINKS OF BLACK CARBON

BACKGROUND:

Black carbon (BC) particles are emitted to the atmosphere by incomplete combustion. They efficiently absorb solar radiation, with important and complicated impacts on climate. Current chemical transport models fail abysmally at reproducing observed BC concentrations in the remote atmosphere, with discrepancies often exceeding an order of magnitude. We need to better understand the sources of BC on a global scale and the mechanisms by which BC is scavenged from the atmosphere. A unique resource for this purpose is the NSF HIPPO aircraft campaign, which provided curtains of BC concentrations over the Pacific from pole to pole during five deployments in 2009-2011.

OBJECTIVES

  • Use the HIPPO data together with surface observations to improve our understanding of the sources and sinks of atmospheric BC on a global scale.

APPROACH:

  • Provide chemical forecasting support during HIPPO execution to ensure the collection of an optimal data set;
  • Apply the GEOS-Chem model to simulate BC during HIPPO and use the comparison to observations as constraint for improving the model representation of BC sources and sinks;
  • Examine the consistency between the HIPPO data and the ensemble of data from surface measurement networks.

PEOPLE: Qiaoqiao Wang

COLLABORATORS:  Ryan Spackman, Shuka Schwarz (NOAA/ESRL).

REFERENCES:

  • Altitude-dependent Sources and Export Efficiency of BC ove the Pacific, presented by Qiaoqiao Wang at the HIPPO Science Team Meeting, Boulder, Colorado, March 17, 2011. [pdf]

SUPPORT: NSF HIPPO (Daniel Jacob subcontract to Steve Wofsy)

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EFFECT OF CLIMATE CHANGE ON PARTICULATE MATTER AIR QUALITY

BACKGROUND:

Climate change could have important implications for air pollution by changing the meteorological and chemical environment for generation and removal of pollutants. There is general consensus that 21st warming will cause higher surface ozone concentrations in polluted regions. By contrast, there is no consensus as to the effect of climate change on fine particulate matter (PM2.5) concentrations. This is a difficult problem because of the diversity of PM2.5 components and the complexity of meteorological influences including coupling of PM2.5 to the hydrological cycle.

OBJECTIVES:

  • Determine the dominant meteorological modes of variability for PM2.5 in the US;
  • Determine the effect of climate change on these meteorological modes and the implications for PM2.5 air quality.

APPROACH:

  • Correlate long-term records of PM2.5 concentrations in the US with meteorological variables;
  • Conduct principal component analysis to isolate the dominants modes of meteorological variability affecting PM2.5;
  • Examine the 21st-century trends in these meteorological modes using output from an ensemble of IPCC climate models;
  • Assess the implications for PM2.5 air quality.

PEOPLE: Amos Tai

REFERENCES:

  • Tai, A.P.K., L.J. Mickley, D.J. Jacob, E.M. Leibensperger, L. Zhang, J.A. Fisher, and H.O.T. Pye, Meteorological modes of variability for fine particulate matter (PM2.5) air quality the United States: implications for PM2.5 sensitivity to climage change, submitted to Atmos. Chem. Phys., 2011. [PDF]

  • 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 climage change, Atmos. Environ., 44, 3976-3984, 2010. [PDF]

SUPPORT: Harvey Fellowship to Amos Tai, NASA AQAST (PIs Loretta Mickley and Daniel Jacob)

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EFFECT OF THE SOUTHEAST ASIAN MONSOON ON GLOBAL ATMOSPHERIC COMPOSITION

BACKGROUND:

The Southeast Asian Monsoon triggers some of the deepest convective activity in the world, providing a conduit for fast transport of surface air to the upper troposphere and lower stratosphere. This convective ouflow feeds tropospheric circulation cells that subside over vast areas of the tropics and subtropics. In this manner, anthropogenic and natural emissions in Southeast Asia can have extensive effects on the composition of the global troposphere. These emissions are rapidly changing through development and agricultural practices. The NASA SEAC4RS aircraft mission, to be conducted in August-September 2012 from a primary base in Thailand, will focus on better understanding deep convective transport of gases and particles in the Southeast Asian Monsoon and its implications for atmospheric composition, clouds, and climate. It will use three aircraft (NASA DC-8 and ER-2, NSF/NCAR GV (HIAPER)) for observations through the depth of the convective column and reaching into the lower stratosphere. Jacob is Mission co-Lead for SEAC4RS with responsibility for the tropospheric chemistry component.

OBJECTIVES:

  • Quantify natural and anthropogenic emissions in Southeast Asia;
  • Understand the chemical evolution and scavenging taking place in the deep convection of the Southeast Asian Monsoon;
  • Determine the chemical and aerosol evolution of the convective outflow in the upper troposphere;
  • Infer the implications for tropical tropospheric composition and the associated climate forcing.

APPROACH:

  • Use GEOS-Chem hindcast simulations for 2005-2009 to help plan the mission;
  • Contribute to the execution of the mission through near-real-time GEOS-Chem simulations and data analysis in the field;
  • Interpret the aircraft observations together with ancillary satellite data using a high-resolution nested version of the GEOS-Chem model.

PEOPLE: Daniel Jacob, Jenny Fisher, Sungshik Kim, Lin Zhang

SUPPORT: NASA SEAC4RS (PI Daniel Jacob)

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GLOBAL BIOGEOCHEMICAL CYCLING OF MERCURY

BACKGROUND:

Mercury as an element cycles naturally between the different reservoirs of the Earth system. This natural cycle has been perturbed dramatically since the 19th 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 modulated by redox chemistry in the different reservoirs. Development of policies to reduce mercury in the environment has been hindered by lack of underestanding 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.

OBJECTIVES:

  • Understand the sources, chemical cycling, 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;
  • Application of biogeochemical box models to better understand the cycling of mercury between reservoirs;
  • Interpretation of mercury observations in the atmosphere and oceans;
  • Projection of the effects of future changes in global anthropogenic emissions and climate;
  • Investigation of the fate of mercury in commercial products and their entry into the global biogeochemical cycle.

PEOPLE: Helen Amos, Bess Corbitt, Asif Qureshi, Hannah Horowitz

REFERENCES:

  • Amos, H. M., D. J. Jacob, C. D. Holmes, J. A. Fisher, Q. Wang, R. M. Yantosca, E. S. Corbitt, E. Galarneau, A. P. Rutter, M. S. Gustin, A. Steffen, J. J. Schauer, J. A. Graydon, V. L. St. Louis, R. W. Talbot, E. S. Edgerton, and E. M. Sunderland, Gas-Particle Partitioning of Atmopsheric Hg(II) and Its Effect on Global Mercury Deposition, submitted to Atmos. Chem. Phys., 2011.[PDF]

  • Corbitt, E.S., D.J. Jacob, C.D. Holmes, D.G. Streets, and E.M. Sunderland, Global source-receptor relationships for mercury deposition under present-day and 2050 emissions scenarios, Environ. Sci. Technol., accepted. [PDF] [SI]

  • Mercury in the environment: from smokestack to stomach, Weston Roundtable Series Lecture by Daniel J. Jacob at the University of Wisconsin, Madison, December 9, 2010. [pdf]

SUPPORT: NSF ATM (PIs Daniel Jacob and Elsie Sunderland), EPA (PI Elsie Sunderland)

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MERCURY IN THE ARCTIC

BACKGROUND:

The Arctic Ocean contains unusually high levels of mercury that endanger the health of Arctic wildlife and indigenous populations. We need to understand the origin of this mercury in order to develop strategies for mitigating it. We also need to understand how the rapid climate change presently taking place in the Arctic will affect mercury loadings.

OBJECTIVES:

  • Use observations in the Arctic atmosphere and ocean to constrain the sources of mercury to the Arctic;
  • Examine how climate change over the past 30 years has affected mercury loadings in the Arctic Ocean.

APPROACH:

  • Evaluate the GEOS-Chem global mercury model with observations to better understand how mercury levels in the Arctic Ocean are affected by atmospheric deposition, sea ice, riverine inflow, and other processes;
  • Conduct a GEOS-Chem simulation of the 1980-2010 period to determine how climate change has contributed to the accumulation of mercury in the Arctic;
  • Improve the GEOS-Chem model to include lateral flow in the Arctic Ocean.

PEOPLE: Jenny Fisher, Anne Soerensen

REFERENCES:

  • Fisher, J.A., D.J. Jacob, A.L. Soerensen, H.M. Amos, A. Steffen, and E.M. Sunderland, Large mercury evasion from the Arctic Ocean in summer: a source from circumpolar rivers?, submitted to Nature Geosci., 2011.

SUPPORT: NSF OPP (PIs Daniel Jacob and Elsie Sunderland), EPA (PI Elsie Sunderland)

soaFORCING OF ARCTIC CLIMATE CHANGE BY AEROSOLS AND OZONE

BACKGROUND:

The Arctic has been warming very rapidly over the past decades. Climate models cannot explain this warming, suggesting that they are missing important processes. Short-lived climate forcing agents including aerosols, ozone, and black carbon (soot) deposited on snow could possibly play a major role in driving Arctic warming. These agents originate from northern mid-latitudes pollution and from boreal fires. The large body of atmospheric observations collected over the Arctic during the International Polar Year (2007-2008) provides an opportunity to better understand the sources and radiative forcings from these short-lived agents, and from there to understand Arctic climate response.

OBJECTIVES:

  • Determine the sources of aerosols and ozone in the Arctic atmosphere and of black carbon (BC) deposited to snow;
  • Quantify the radiative forcings from these short-lived agents over the Arctic and the corresponding trends over the 1980-2010 period;
  • Determine the implications for 1980-2010 trends in Arctic climate.

APPROACH:

  • Apply the GEOS-Chem model to understand the sources of aerosols, ozone, and snow BC in the Arctic during the International Polar Year (2007-2008), including extensive comparison to aircraft, sonde, and surface observations;
  • Reconstruct and interpret 1980-2010 trends in aerosols, ozone and snow BC in the Arctic;
  • Use the archived GEOS-Chem concentration fields of aerosols and ozone to drive simulations of 1980-2010 climate change with the Community Earth System Model (CESM);
  • Conduct fully coupled aerosol-chemistry-climate simulations of the 1980-2010 period with CESM to investigate climate feedbacks.

PEOPLE:  Tom Breider, Loretta Mickley, Qiaoqiao Wang

COLLABORATORS: Cecilia Bitz, Sarah Doherty (University of Washington)

REFERENCES:

  • Wang, Q., D.J. Jacob, J.A. Fisher, J. Mao, E.M. Leibensperger, C.C. Carouge, P. Le Sager, Y. Kondo, J.L. Jimenez, M.J. Cubison, and S.J. Doherty, Sources of carbonaceous aerosols and deposited black carbon in the Arctic in winter-spring: implications for radiative forcing, Atmos. Chem. Phys., in press. [PDF]

  • Fisher, J.A., D.J. Jacob, Q. Wang, R. Bahreini, C.C. Carouge, M.J. Cubison, J.E. Dibb, T. Diehl, J.L. Jimenez, E.M. Leibensperger, Z. Lu, M.B.J. Meinders, H.O.T. Pye, P.K. Quinn, S. Sharma, D.G. Streets, A. van Donkelaar, and R.M. Yantosca, Sources, distribution, and acidity of sulfate-ammonium aerosol in the Arctic in winter-spring, Atmos. Environ., 45, 7301-7318, 2011. [PDF]

SUPPORT: NSF EASM (PIs Loretta Mickley and Daniel Jacob)

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broTROPOSPHERIC BROMINE CHEMISTRY

BACKGROUND:

Bromine radicals in the troposphere originate from the degradation of bromocarbons and from debromination of sea salt. They may provide the main atmospheric sink of elemental mercury and also a significant sink of tropospheric ozone. Bromine chemistry is generally not included in global models because atmospheric observations are few, but this situation is rapidly changing with new BrO data sets from satellite, aircraft, and ground stations.

OBJECTIVES:

  • Improve satellite retrievals of tropospheric BrO;
  • Use these together with other observations as constraints for our understanding of tropospheric bromine chemistry;
  • Assess the implications for mercury, ozone, and other species.

APPROACH:

  • Retrieve BrO tropospheric columns from the GOME-2, OMI and SCIAMACHY (limb and nadir) satellite instruments through spectral fitting and application of air mass factors;
  • Implement tropospheric bromine chemistry in the GEOS-Chem global model of atmospheric composition, and test the simulation with the ensemble of BrO observations from satellite and other platforms.

PEOPLE: Justin Parrella

COLLABORATORS: Kelly Chance (Harvard/SAO)

SUPPORT: NASA ACMAP (PI Daniel Jacob)

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GTE GLOBAL AND NORTH AMERICAN BUDGETS OF METHANE

BACKGROUND:

Methane is the second most important anthropogenic greenhouse gas after CO2. It was rising for most of the 20th century at the rate of 1-2 %/yr. The growth halted in the past decade but the past few years show an uptick. We don't understand these trends. Sources of methane are very poorly quantified. There is evidence that the EPA anthropogenic emission inventory for the US may be too low by more than a factor of two. We are analyzing methane observations from aircraft and satellite to better understand and quantify methane sources in North America and on the global scale.

OBJECTIVES:

  • Determine the value of different satellite data sets as constraints for methane sources through inverse analyses:
  • Integrate observations from aircraft, satellite, and ground-based platforms to constrain methane emissions in North America;
  • Broaden the investigation to the global sources of methane.

APPROACH:

  • Validate satellite observations of methane with aircraft observations from the HIPPO campaign across the Pacific;
  • Conduct adjoint inverse analyses of North American methane sources using methane observations from satellite (GOSAT, TES, SCIAMACHY) and aircraft (INTEX, HIPPO);
  • Extend these analyses to the global scale.

PEOPLE:  Kevin Wecht

COLLABORATORS: John Worden (JPL), Eric Kort and Steve Wofsy (Harvard)

REFERENCES:

  • Wecht, K.J., D.J. Jacob, S.C. Wofsy, E.A. Kort, J.R. Worden, S.S. Kulawik, D.K. Henze, M. Kopacz, and V.H. Payne, Validation of TES methane with HIPPO aircraft observations: implications for inverse modeling of methane sources, submitted to Atmos. Chem. Phys.,, 2011. [PDF]

SUPPORT: NASA Graduate Fellowship to Kevin Wecht, NASA ACMAP (PI Daniel Jacob), NSF HIPPO (Daniel Jacob subcontract to Steve Wofsy)

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GTENUMERICAL METHODS FOR GLOBAL CHEMICAL TRANSPORT MODELS

BACKGROUND:

Global 3-D models of atmospheric composition such as GEOS-Chem represent a grand computational challenge. One has to describe the 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.

OBJECTIVE:

  • To develop efficient numerical methods for global 3-D models of atmospheric composition.

APPROACH:

  • Increase efficacy of chemical solvers through spatial reduction algorithms;
  • Improve the model representation of transport for pollution plumes transported on global scales;
  • Optimize operator splitting in the solution of the differential equations for chemical evolution.

PEOPLE: Mauricio Santillana

COLLABORATOR: Michael Brenner (Harvard)

REFERENCES:

  • Santillana M., P. Le Sager, D. J. Jacob, and M. P. Brenner, An adaptive reduction algorithm for efficient chemical calculations in global atmospheric chemistry models. Atmos. Environ., 44, 4426-4431, 2010.[PDF]

  • Rastigejev, Y., R. Park, M.P. Brenner, and D.J. Jacob, Resolving intercontinental pollution plumes in global models of atmospheric transport , J. Geophys. Res., 115, D02302, 2010. [PDF]

SUPPORT:NASA MAP (PI Daniel Jacob)

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GTE GRID-INDEPENDENT GEOS-Chem FOR CHEMICAL DATA ASSIMILATION AND EARTH SYSTEM MODELING

BACKGROUND:

"Off-line" chemical transport models such as GEOS-Chem simulate global atmospheric composition using archived meteorological data generated by a model of atmospheric dynamics (general circulation model). An "on-line" simulation where the chemical transport is coupled to the dynamics would provide better fidelity, enable joint chemical and meteoroloical data assimilation, allow study of chemistry-climate interactions, and avoid the need for tedious and error-prone meteorological data archiving. A limitation to the development of on-line models has been the difficulty of integrating the chemical and dynamical codes in a flexible way that allows for model improvements to be seamlessly exchanged between the different components of the on-line model.

OBJECTIVES:

  • Develop a flexible on-line interface between GEOS-Chem and the Goddard Earth Observing System (GEOS) meteorological model from the NASA Global Modeling and Assimilation Office (GMAO) using the Earth System Modeling Framework (ESMF);
  • Use this on-line capability for joint chemical and meteorological data assimilation.

APPROACH:

  • Develop a grid-independent version of GEOS-Chem to interface with the GEOS data assimilation system;
  • Contribute to the chemical data assimilation capability at GMAO.

PEOPLE:  Mike Long, Bob Yantosca

COLLABORATORS: Steven Pawson (NASA/GSFC)

SUPPORT: NASA MAP (PI Daniel Jacob)

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GTEEMISSIONS AND CHEMISTRY OF BIOGENIC HYDROCARBONS

BACKGROUND:

Emission of hydrocarbons from vegetation is a major driver for the formation of organic aerosols and tropospheric ozone. This emission is highly sensitive to changes in land cover and in climate. Satellite observations of formaldehyde and glyoxal (both produced in the atmosphere by hydrocarbon oxidation) offer a unique resource to constrain biogenic hydrocarbon emissions in a selective manner and determine the dependences of these emissions on environmental variables. Improved understanding of the hydrocarbon oxidation mechanisms is needed to take full advantage of this resource and more generally to assess the implications of hydrocarbon emissions for aerosols and ozone.

OBJECTIVES:

  • Use satellite observations of formaldehyde and glyoxal from SCIAMACHY, OMI, and GOME-2 to better quantify the sources of biogenic hydrocarbons from vegetation, with particular focus on isoprene;
  • Improve understanding of isoprene chemistry and its implications for formation of organic aerosols and ozone.

APPROACH:

  • Use satellite observations of formaldehyde from OMI as constraint on isoprene emissions from Africa;
  • Test new isoprene oxidation mechanisms through simulation of atmospheric observations;
  • Interpret satellite and in situ measurements of glyoxal in terms of the constraints that they offer on hydrocarbon sources and organic aerosol formation.

PEOPLE: Eloise Marais, Chris Miller,Fabien Paulot, Lei Zhu

COLLABORATORS: Kelly Chance (Harvard/SAO)

SUPPORT: South African National Research Foundation Scholarship to Eloise Marais, Knox Fellowship to Chris Miller, HUCE postdoctoral fellowship to Fabien Paulot, NASA ACMAP (PI Daniel Jacob), NASA AQAST (PIs Daniel Jacob and Loretta Mickley)

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GTEROLE OF PEROXYACETYL NITRATE IN GLOBAL OXIDANT CHEMISTRY

BACKGROUND:

Peroxyacetyl nitrate (PAN) is produced in the atmosphere by the oxidation of nonmethane volatile organic compounds (NMVOCs) in the presence of nitrogen oxide radicals (NOx). It sequesters NOx during long-range transport to eventually release it in the remote atmosphere, with important implications for the global budgets of tropospheric ozone and OH (the main atmospheric oxidants). PAN chemistry is complicated and global models are not successful at reproducing observations. This affects radiative forcing estimates for a range of chemically active gases and is also relevant for ozone air quality.

OBJECTIVES:

  • To better understand the factors controlling PAN concentrations in the atmsophere and the role of PAN in global oxidant chemistry;
  • To better quantify the radiative forcings from NOx, methane, NMVOCs, and CO as modulated by PAN chemistry.

APPROACH:

  • Use the GEOS-Chem model to simulate PAN observations from remote sites and from aircraft campaigns;
  • Infer the factors controlling PAN concentrations and the dominant NMVOC precursors;
  • Examine the implications of PAN formation on global oxidant chemistry and intercontinental ozone pollution;
  • Improve radiative forcing estimates for NOx, methane, NMVOCs, and CO.

PEOPLE:  Emily Fischer

REFERENCES:

  • Fischer, E.V., D.J. Jacob, D.B. Millet, R.M. Yantosca, and J. Mao, The role of the ocean in the global atmospheric budget of acetone, Geophys. Res. Lett., in press. [PDF]

SUPPORT: Harvard University Committee on the Environment postdoctoral fellowship to Emily Fischer, NASA ACMAP (PI Daniel Jacob)

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GTECONSTRAINTS ON OZONE SOURCES FROM SATELLITE MEASUREMENTS OF OZONE-CO CORRELATIONS

BACKGROUND:

Tropospheric ozone is of central environmental importance as a greenhouse gas, as a surface air pollutant, and as the precursor of OH (the main atmospheric oxidant). Ozone is produced by complex chemistry and the factors controlling ozone concentrations are uncertain. Atmospheric observations show strong correlations (either positive or negative) with carbon monoxide (CO), a long-lived tracer of combustion. Satellite observations offer an opportunity to examine and interpret these correlations on a global scale as constraint on ozone sources. The OMI and AIRS satellite instruments aboard the NASA A-Train are of particular interest in that regard because they provide global daily converage of tropospheric ozone and CO respectively.

OBJECTIVES:

  • Exploit ozone-CO correlations observed from space as constraints to improve our understanding of tropospheric ozone.

APPROACH:

  • Construct ozone-CO correlation statistics from OMI and AIRS data;
  • Simulate these correlation statistics with the GEOS-Chem model and interpret their meaning using model sensitivity tests;
  • Resolve discrepancies between simulated and observed correlations through improved representation of model processes.

PEOPLE:  Sungshik Kim

COLLABORATORS: Xiong Liu (Harvard-SAO)

SUPPORT: NASA ACMAP (PI Daniel Jacob)

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