Welcome to Rokjin J. Park's homepage

Febrary 07, 2012

 

ROKJIN J. PARK
School of Earth and Environmental Sciences
San 56-1, Daehak-dong, Gwanak-gu,
Seoul National University, Seoul, 151-747, Korea
Phone: +82-2-880-6715, Fax: +82-2-883-4972, email: rjpark at snu.ac.kr
URL: http://airchem.snu.ac.kr/rjpark

Global simulation of tropospheric ozone and its radiative forcing

BACKGROUND:

A 3-D global chemical transport model is an essential tool to examine the changes in chemical composition in the atmosphere where those consequences range from regional air pollution to global climate change. We developed a global 3-D chemical transport model to investigate tropospheric ozone chemistry especially focusing on the role of deep convective pumping of anthropogenic emissions from the surface to the upper troposphere in photochemical ozone production and its radiative forcing. Ozone is one of greenhouse gases having the third highest contribution to positive radiative forcing and its enhancement in concentrations caused by processes above has a significant implication for global climate.

OBJECTIVES:

  • Examine the role of deep convection in the tropospheric ozone chemistry
  • Quantify the enhancement in ozone concentrations and its radiative forcing
  • Quantify export efficiency of tropospheric ozone and its precursors from pbl

REFERENCES:

  • Park, R. J., K. E. Pickering, D. J. Allen, G. L. Stenchikov, and M. S. Fox-Rabinovitz (2004), Global simulation of tropospheric ozone using the University of Maryland Chemical Transport Model (UMD-CTM): 1. Model description and evaluation, J. Geophys. Res., 109, D09301, doi:10.1029/2003JD004266. [Full Text (pdf)]

  • Park, R. J., K. E. Pickering, D. J. Allen, G. L. Stenchikov, and M. S. Fox-Rabinovitz (2004), Global simulation of tropospheric ozone using the University of Maryland Chemical Transport Model (UMD-CTM): 2. Regional transport and chemistry over the Central United States using a stretched grid, J. Geophys. Res., 109, D09303, doi:10.1029/2003JD004269. [Full Text (pdf)]

  • Park, R. J., G. L. Stenchikov, K. E. Pickering, R. R. Dickerson, D. J. Allen, S. Kondragunta (2001), Regional air pollution and its radiative forcing: Studies with a single column chemical and radiation transport model, J. Geophys. Res., 106, 28,751-28,770. [Full Text (pdf)]

NATURAL VISIBILITY IN THE UNITED STATES AND THE EFFECT OF TRANSBOUNDARY POLLUTION

BACKGROUND:

The EPA Regional Haze Rule aims to achieve "natural visibility conditions" in national wilderness areas by 2064. In the Phase 1 implementation of the Rule, states have to show how they will decrease emissions over the 2004-2018 period in order to follow a linear trajectory of improved visibility toward that 2064 endpoint. Visibility is limited by aerosols, and implementation of the Regional Haze Rule is thus critically dependent on knowledge of natural aerosol concentrations in the United States. We are working to improve this knowledge, and also examine how transport of aerosol pollution from outside U.S. borders could compromise visibility in a way over which we have no domestic control.

OBJECTIVES:

  • To determine natural aerosol concentrations in the United States;
  • To determine the contributions from transboundary transport of pollution in degrading visibility in the United States.

APPROACH:

  • Analysis of data from aerosol observation networks, in particular the IMPROVE network;
  • Simulations with the GEOS-CHEM model for present-day conditions and for different emission scenarios.

REFERENCES: 

Export of black carbon aerosol

BACKGROUND:

Black carbon (BC) aerosol has complex climate implications because of its unique light absorbing property different from other aerosols. It is operationally defined as the light-absorbing fraction of carbonaceous aerosols and emitted to the atmosphere by combustion. Its source, transport, and scavenging are still poorly quantified. In particular, BC scavenging efficiency has major consequences for climate forcing, since outflow from source regions to the free troposphere mainly takes place by wet processes including warm conveyor belts (WCBs) and convection. Once in the free troposphere, BC can be transported on a global scale because precipitation is infrequent. We are presently examining BC scavenging in Asian outflow using aircraft observations during the TRACE-P and its consequences for the global burden of BC and the deposition of BC to the Arctic. The latter could make an important contribution to climate warming by decreasing the albedo of the snow. We plan to extend our work to examine BC scavenging in different regions of the atmosphere, both through observations and through improved models.

OBJECTIVES:

  • Quantify export and scavenging efficiency of BC
  • Examine BC long range transport and its deposition in the Arctic
  • Quantify East Asian BC sources

APPROACH:

  • Examine export efficiency of BC using aircraft observations and 3-D model simulation
  • Incorporate aerosol microphysics into GEOS-CHEM for better simulation of aging and mixing of BC
  • Model validation using ground-based, aircraft, and satellite measurements
  • Inverse model analysis of East Asian BC sources with aircraft observations

REFERENCES:

  • Park, R. J., D.J. Jacob, P.I. Palmer, A.D. Clarke, R.J. Weber, M.A. Zondlo, F.L. Eisele, A.R. Bandy, D.C. Thornton, G.W. Sachse, and T.C. Bond (2005), Export efficiency of black carbon aerosol in continental outflow: global implications, J. Geophys. Res., 110, D11205, doi:10.1029/2004JD005432. [PDF]

GLOBAL DISPERSAL OF MINERAL DUST

BACKGROUND:

Wind-blown mineral dust is the largest single source of aerosol in the Earth's atmosphere. Mineral dust is mobilized during strong wind events over arid soils. Major source regions include desert regions of North Africa, Asia, and the Middle East. There is clear evidence from satellites that wind-blown dust is transported across oceans. In particular, Asian dust can reach North America during transpacific transport. Yet, the contribution of overseas sources of mineral dust to aerosol concentrations over North America remains poorly quantified. In addition, the role of vegetation change and human activities in global mineral dust mobilization is a subject of current debate. Estimates of the anthropogenic contribution to the global dust budget range from near zero to as much as 50%.

OBJECTIVES:

  • Assess the contribution of overseas sources of mineral dust to aerosol levels over North America;
  • Assess the role of changing vegetation and human activity on the global dust loadings.

APPROACH:

  • Global 3-D modeling of mobilization, transport, and deposition of mineral dust;
  • Application of different dust mobilization schemes that take opposing sides of the debate on the role of vegetation;
  • Model validation using ground-based, aircraft, and satellite measurements

REFERENCES:

  • Fairlie, T. D., D. J. Jacob, and R. J. Park (2007), The impact of transpacific transport of mineral dust in the United States, Atmos. Environ., doi:10.1016/j.atmosenv.2006.09.048. [PDF]

QUANTIFYING AEROSOL SOURCES USING SATELLITE OBSERVATIONS OF AEROSOL OPTICAL DEPTH

BACKGROUND:

Aerosols have many important environmental impacts, from public health to climate change. Satellite observations of aerosol optical depth by solar backscatter provide an outstanding new opportunity to map aerosol concentrations and constrain aerosol sources. We recently explored the potential of the MISR instrument to estimate surface aerosol concentrations in the United States and are now focusing on the MODIS instrument for inversion of aerosol sources. We are particularly interested in South and East Asia, where aerosol sources are large and poorly quantified.

OBJECTIVES:

  • Quantify global aerosol sources using MODIS observations;
  • Correlate MODIS and other satellite information to improve constraints on anthropogenic sources;
  • Use MODIS to observe continental outflow and transboundary transport of aerosols from fires, dust, and pollution.

APPROACH:

  • Interpret MODIS aerosol optical depth observations using the GEOS-CHEM chemical transport model, accounting for the assumptions made in the MODIS retrieval regarding aerosol size distributions and optical properties;
  • Examine ability of MODIS to observe continental outflow and transboundary transport events

REFERENCES:

  • van Donkelaar, A., R. V. Martin, and R. J. Park (2006), Estimating ground-level PM2.5 using aerosol optical depth determined from satellite remote sensing, J. Geophys. Res., 111, D21201, doi:10.1029/2005JD006996. [PDF]

  • Li, Q., D. J. Jacob, R. Park, Y. Wang, C. L. Heald, R. Hudman, R. M. Yantosca, R. V. Martin, and M. Evans (2005), North American pollution outflow and the trapping of convectively lifted pollution by upper-level anticyclone, J. Geophys. Res., 110, D10301, doi:10.1029/2004JD005039. [ Full Text (pdf)]

  • Liu, Y., R. J. Park, D. J. Jacob, Q. Li, V. Kilaru, and J. A. Sarnat (2004), Mapping Surface Concentrations of Fine Particulate Matter Using MISR Satellite Observations of Aerosol Optical Thickness , J. Geophys. Res., 109, D22206, 10.1029/2004JD005025. [ Full Text (pdf)]

GLOBAL TRANSPORT OF MERCURY COMPOUNDS

BACKGROUND:

Mercury is a toxic pollutant which is transported on a global scale. Mercury poses particular problems in the Arctic, where it accumulates in food chains and poses risks far from the locations of its emissions. Previous efforts to model mercury have had several limitations, including highly averaged meteorological and chemical mechanisms. We are presently investigating the global budget of mercury with the GEOS-CHEM model. Future work will assess the impact of changing climate on mercury pollution pathways to the Arctic.

OBJECTIVES:

  • Understand the pathways by which mercury travels in the global environment
  • Assess the sources and sinks of mercury in the Arctic

APPROACH:

  • 3-D modeling of mercury chemistry and transport using GEOS-CHEM

REFERENCES:

  • Swartzendruber, P. C., D. A. Jaffe, E. M. Prestbo, P. Weiss-Penzias, N. E. Selin, R. Park, D. Jacob, S. Strode, and L. Jaegle (2006), Observations of reactive gaseous mercury in the free-troposphere at the Mt. Bachelor observatory, J. Geophys. Res., 111, D24301, doi:10.1029/2006JD007415. [PDF].

  • Strode, S. A., L. Jaegle, N. E. Selin, D. J. Jacob, R. J. Park, R. M. Yantosca, R. P. Mason, F. Slemr (2007), Air-Sea Exchange in the Global Mercury Cycle, Global Biogeochem. Cycles, 21, GB1017, doi:10.1029/2006GB002766. [PDF]

  • Selin, N. E., D. J. Jacob, R. J. Park, R. M. Yantosca, S. Strode, L. Jaegle, and D. Jaffe (2007), Chemical cycling and deposition of atmospheric mercury: Global constraints from observations, J. Geophys. Res., 112, D02308, doi:10.1029/2006JD007450. [PDF]

OXYGEN ISOTOPE TRACERS OF SULFATE FORMATION PROCESSES

BACKGROUND:

Measurements of the mass-independent composition (D17O = d17O – 0.5d18O) of the oxygen isotopes of sulfate provide information on the relative importance of individual oxidants (OH, H2O2, O3) for sulfate formation, and the amounts of gas versus aqueous phase sulfate formation pathways. The relative partitioning of the latter is important for determining new particle sulfate formation which has implications for the indirect radiative forcing by sulfate aerosols. Measurement of the D17O of sulfate from ice cores provides means to study past variations in sulfur chemistry, and provides a potential proxy for past variations in the oxidants themselves.

OBJECTIVES:

APPROACH:

  • Global 3-D model simulations of sulfate including D17O for the present-day atmosphere;
  • Interpretation of ice core observations of D17O using global simulations with glacial climate meteorology from the GISS General Circulation Model.

REFERENCE:

PHASE TRANSFORMATIONS OF SULFATE AEROSOLS AND RADIATIVE EFFECTS

BACKGROUND:

Sulfate aerosols are the most important type of anthropogenic aerosols in the atmosphere. They scatter solar radiation back to space and thus have a major cooling effect on the Earth's surface, partly compensating for the effect of rising greenhouse gases. But are sulfate aerosol particles solid or liquid (aqueous)? Embarrassingly enough, we don't know. If they are aqueous, then they will grow to large sizes at high relative humidity, thus scattering solar radiation far more effectively than if they are solid.

OBJECTIVES:

  • Improve understading of the phase of sulfate aerosols on the global scale;
  • Assess the implications for radiative forcing of climate.

APPROACH:

REFERENCE:

  • Martin, S. T.; Hung, H. M.; Park, R. J.; Jacob, D. J.; Spurr, R. J. D.; Chance, K. V.; Chin, M. (2004), Effects of the Physical State of Tropospheric Ammonium-Sulfate Nitrate Particles on Global Aerosol Direct Radiative Forcing, Atmos. Chem. Phys., 4, 183-214. [ Full Text (pdf)]