- Ph.D., Harvard University, 2003
- Ph.D.,Hong Kong Polytechnic University, 1998
- M.Sc., Peking University, 1993
- B.Sc., Peking University, 1990
- Research Fellow, NIA / NASA Langley Research Center, 2016-present
- Associate Research Fellow, NIA / NASA Langley Research Center, 2009-2016
- Senior Research Scientist, NIA / NASA Langley Research Center, 2004-2008
- Visiting Scientist, Geophysical Fluid Dynamics Laboratory / NOAA, 2005-2006
- Staff Scientist, NIA / NASA Langley Research Center, 2003-2004
- Staff Scientist, ICASE / NASA Langley Research Center, 2002
- Effects of aerosols and clouds on tropospheric composition and photochemistry
- Transport and wet removal of trace gases and aerosols
- Tropospheric ozone distribution and budget
- Asian pollution transport, outflow and global impact
- Aerosol-Cloud-Chemistry-Climate Interactions
Cloud scavenging of aerosols in the NASA GEOS model
Cloud scavenging is the dominant removal process for a range of aerosols in the troposphere, but model parameterizations of this process are highly uncertain. We have recently evaluated the aerosol wet deposition scheme in the NASA GEOS model using lead-210 (a radionuclide aerosol tracer). We are currently developing more physically-based parameterizations of wet scavenging and studying the impact of their uncertainties on aerosol burden, lifetime, and direct and indirect effects in GEOS.
Aerosol Cloud meteorology Interactions oVer the western Atlantic Experiment (ACTIVATE)
ACTIVATE is a NASA Earth Venture Suborbital-3 mission (2019-2023) to study aerosol-cloud-meteorology interactions over the western North Atlantic Ocean through extensive in situ and remote sensing airborne measurements in conjunction with multi-scale models. We will (1) support flight planning by conducting pre-mission model and data analysis of tropospheric aerosol and cloud variability, and seasonal aerosol sources in the ACTIVATE study region using MERRA-2 and GEOS-Chem, (2) provide customized aerosol, chemical, and weather forecast products during the ACTIVATE field deployments, using the near real-time NASA GEOS forecasts, (3) conduct FLEXPART trajectory calculations to assist science team with the analyses of aerosol sources and aging history associated with aircraft measurements, (4) quantify the sources and variability of tropospheric aerosols and examine transport pathways during the ACTIVATE missions, and place the ACTIVATE aerosol measurements in seasonal and interannual contexts, using the GEOS-Chem model driven by MERRA-2 reanalysis, and (5) use the ACTIVATE measurements to constrain and improve the parameterization of cloud scavenging of aerosols in the NASA GEOS model.
Tropospheric aerosol variability and sources over the North Atlantic
The North Atlantic Aerosols and Marine Ecosystems Study (NAAMES) is a five-year Earth-Venture Suborbital-2 Mission of NASA to characterize the plankton ecosystems and their influences on remote marine aerosols, boundary layer clouds, and their implications for climate in the North Atlantic. While marine-sourced aerosols have been shown to make important contributions to surface aerosol loading, cloud condensation nuclei and ice nuclei concentrations over remote marine and coastal regions, it is still a challenge to differentiate the marine biogenic aerosol signal from the strong influence of continental pollution outflow. We examine here the spatiotemporal variability and quantify the sources of tropospheric aerosols over the North Atlantic during the first two phases (November 2015 and May-June 2016) of NAAMES using the GEOS-Chem chemical transport model. The model includes sulfate-nitrate-ammonium aerosol thermodynamics coupled to ozone-NOx-hydrocarbon-aerosol chemistry, mineral dust, sea salt, elemental and organic carbon aerosols, and especially a recently implemented parameterization for the marine primary organic aerosol emission. We use the model to quantify the relative contributions of terrestrial and oceanic sources to the aerosol loading, aerosol optical depth, and their variability over the North Atlantic.
Radiative impact of clouds on global tropospheric composition and chemistry
The objective of this project is to improve our understanding of the global and regional impacts of clouds on tropospheric composition and chemistry via the modification of solar radiation that determines photolysis rates of trace gases. Using A-Train satellite observations of clouds, we determine the impact of model biases in cloud optical depths and spatial distributions on simulated key tropospheric oxidants (hydroxyl radical (OH) and ozone) and related species. We extend and improve our previous estimates of radiative effects of clouds on tropospheric oxidants by constraining the model cloud distributions and optical depths with satellite observations.
Sorooshian, A., B. Anderson, S. E. Bauer, R. A. Braun, B. Cairns, E. Crosbie, H. Dadashazar, G. Diskin, R. Ferrare, R. C. Flagan, J. Hair, C. Hostetler, H. H. Jonsson, H. Liu, A. B. MacDonald, A. McComiskey, R. Moore, D. Painemal, L. M. Russell, J. H. Seinfeld, M. Shook, W. L. Smith Jr., K. Thornhill, G. Tselioudis, H. Wang, X. Zeng, B. Zhang, L. Ziemba, P. Zuidema, Aerosol–cloud–meteorology interaction airborne field investigations: Using lessons learned from the US west coast in the design of ACTIVATE off the east coast, Bulletin of the American Meteorological Society, in review, 2019.
Behrenfeld, M.J., R.H. Moore, C.A. Hostetler, J. Graff, P. Gaube, L. Russell, G. Chen, S.C. Doney, S. Giovannoni, H. Liu, C. Proctor, L. Bolaños, N. Huynh, C. Davie-Martin, T. Westberry, T.S. Bates, T.G. Bell, K.D. Bidle, E.S. Boss, S.D. Brooks, B.Cairns, C. Carlson, K. Halsey, E.L. Harvey, C. Hu, L. Karp-Boss, M. Kleb, S. Menden-Deuer, F. Morison, P. K. Quinn, A.J. Scarino, B. Anderson, J. Chowdhary, E. Crosbie, R. Ferrare, J.W. Hair, Y. Hu, S. Janz, J. Redemann, E. Saltzman, M. Shook, D.A. Siegel, A. Wisthaler, and L. Ziemba, The North Atlantic Aerosol and Marine Ecosystem Study (NAAMES): Science motive and mission overview, Frontiers in Marine Science, in press, 2019.
Vernier, J.-P., T. D. Fairlie, T. Deshler, M. Venkat Ratnam, H. Gadhavi, B. S. Kumar, M. Natarajan, A. K. Pandit, S. T. Akhil Raj, A. Hemanth Kumar, A. Jayaraman, A. K. Singh, N. Rastogi, P. R. Sinha, S. Kumar, S. Tiwari, T. Wegner, N. Baker, D. Vignelles, G. Stenchikov, I. Shevchenko, J. Smith, K. Bedka, A. Kesarkar, V. Singh, J. Bhate, V. Ravikiran, M. Durga Rao, S. Ravindrababu, A. Patel, H. Vernier, F. G. Wienhold, H. Liu, T. N. Knepp, L. Thomason, J. Crawford, L. Ziemba, J. Moore, S. Crumeyrolle, M. Williamson, G. Berthet, F. Jégou, and J.-B. Renard, BATAL: The Balloon Measurement Campaigns of the Asian Tropopause Aerosol Layer, Bulletin of the American Meteorological Society, Vol. 99(5), doi:10.1175/BAMS-D-17-0014.1, 2018.
Choi, H.-D., Liu, H., Crawford, J. H., Considine, D. B., Allen, D. J., Duncan, B. N., Horowitz, L. W., Rodriguez, J. M., Strahan, S. E., Zhang, L., Liu, X., Damon, M. R., and Steenrod, S. D.: Global O3–CO correlations in a chemistry and transport model during July–August: evaluation with TES satellite observations and sensitivity to input meteorological data and emissions, Atmos. Chem. Phys., 17, 8429-8452, https://doi.org/10.5194/acp-17-8429-2017, 2017.
Brattich, E., Liu, H., Tositti, L., Considine, D. B., and Crawford, J. H.: Processes controlling the seasonal variations in 210Pb and 7Be at the Mt. Cimone WMO-GAW global station, Italy: a model analysis, Atmos. Chem. Phys., 17, 1061-1080, https://doi.org/10.5194/acp-17-1061-2017, 2017.
Liu, H., D.B. Considine, L.W. Horowitz, J.H. Crawford, J.M. Rodriguez, S.E. Strahan, M.R. Damon, S.D. Steenrod, X. Xu, J. Kouatchou, C. Carouge, and R.M. Yantosca, Using beryllium-7 to assess cross-tropopause transport in global models, Atmos. Chem. Phys., 16, 4641-4659, doi:10.5194/acp-16-4641-2016, 2016.
Huang, J., H. Liu, J.H. Crawford, C. Chan, D.B. Considine, Y. Zhang, X. Zheng, C. Zhao, V. Thouret, S.J. Oltmans, S.C. Liu, D. Jones, S. Steenrod, and M. Damon, Origin of springtime ozone enhancements in the lower troposphere over Beijing: In situ measurements and model analysis, Atmos. Chem. Phys., 15, 5161-5179, doi:10.5194/acp-15-5161-2015, 2015.
Zhang, Y., H. Liu, J.H. Crawford, D.B. Considine, C.Y. Chan, S.J. Oltmans, and V. Thouret, Distribution, variability and sources of tropospheric ozone over South China in spring: Intensive ozonesonde measurements at five locations and modeling analysis, vol.117, D12304, doi:10.1029/2012JD017498, J. Geophys. Res., 2012.
Lin, J.-T., Z. Liu, Q. Zhang, H. Liu, J. Mao, and G. Zhuang, Modeling uncertainties for tropospheric nitrogen dioxide columns affecting satellite-based inverse modeling of nitrogen oxides emissions, Atmos. Chem. Phys., 12, 12255-12275, doi:10.5194/acp-12-12255-2012, 2012.
Zhang, L., Q.B. Li, L.T. Murray, M. Luo, H. Liu, J.H. Jiang, Y. Mao, D. Chen, M. Gao, and N. Livesey, A tropospheric ozone maximum over the equatorial southern Indian Ocean, Atmos. Chem. Phys., 12, 4279-4296, doi:10.5194/acp-12-4279-2012, 2012.
Zhang, L., Q.B. Li, J. Jin, H. Liu, N. Livesey, J.H. Jiang, Y.H. Mao, D. Chen, M. Luo, and Y. Chen, Impacts of 2006 Indonesian fires and dynamics on tropical upper tropospheric carbon monoxide and ozone, Atmos. Chem. Phys., 11, 10929-10946, doi:10.5194/acp-11-10929-2011, 2011.
Liu, H., J.H. Crawford, D.B. Considine, S. Platnick, P. Norris, B.N. Duncan, R.B. Pierce, G. Chen, and R.M. Yantosca, Sensitivity of photolysis rates and key tropospheric oxidants in a global model to cloud vertical distributions and optical properties , J. Geophys. Res., 114, doi:10.1029/2008JD011503, 2009.
Liu, H., J.H. Crawford, R.B. Pierce, P. Norris, S.E. Platnick, G. Chen, J.A. Logan, R.M. Yantosca, M.J. Evans, C. Kittaka, Y. Feng, and X. Tie, Radiative effect of clouds on tropospheric chemistry in a global three-dimensional chemical transport model, J. Geophys. Res., 111, D20303, doi:10.1029/2005JD006403, 2006.
Considine, D.B., D.J. Bergmann, and H. Liu, Sensitivity of Global Modeling Initiative chemistry and transport model simulations of radon-222 and lead-210 to input meteorological data, Atmos. Chem. Phys., 5, 3389-3406, 2005.
Oltmans, S.J., B.J. Johnson, J.M. Harris, A.M. Thompson, H. Liu, C.Y. Chan, H. Vomel, T. Fujimoto, V.G. Brackett, W.L. Chang, J.-P. Chen, J.H. Kim, L.Y. Chan, and H.-W. Chang, Tropospheric ozone over the North Pacific from ozonesonde observations, J. Geophys. Res., 109(D15), D15S01, 10.1029/2003JD003466, 2004.
Liu, H., D.J. Jacob, J.E. Dibb, A.M. Fiore, and R.M. Yantosca, Constraints on the sources of tropospheric ozone from 210Pb-7Be-ozone correlations, J. Geophys. Res., 109, D07306, doi:10.1029/2003JD003988, 2004.
Fiore, A.M., D.J. Jacob, H. Liu, R.M. Yantosca, T.D. Fairlie, and Q. Li, Variability in surface ozone background over the United States: Implications for air quality policy, J. Geophys. Res., 108(D24), 4787, doi:10.1029/2003JD003855, 2003.
Liu, H., Asian outflow of ozone and carbon-monoxide to the Pacific: Origins and pathways, PhD thesis, Dept. of Earth and Planetary Sciences, Harvard University, Cambridage, MA, 2003. (Advisor: Prof. Daniel J. Jacob)
Liu, H., D.J. Jacob, I. Bey, R.M. Yantosca, B.N. Duncan, and G.W. Sachse, Transport pathways for Asian pollution outflow over the Pacific: Interannual and seasonal variations, J. Geophys. Res., 108(D20), 8786, doi:10.1029/2002JD003102, 2003.
Li, Q., D.J. Jacob, T.D. Fairlie, H. Liu, R.M. Yantosca, and R.V. Martin, Stratospheric versus pollution influences on ozone at Bermuda: Reconciling past analyses, J. Geophys. Res., 107(D22), 4611, doi:10.1029/2002JD00213, 2002.
Martin, R.V., D.J. Jacob, J.A. Logan, I. Bey, R.M. Yantosca, A.C. Staudt, Q. Li, A.M. Fiore, B.N. Duncan, H. Liu, P. Ginoux, and V. Thouret, Interpretation of TOMS observations of tropical tropospheric ozone with a global model and in-situ observations, J. Geophys. Res., 107(D18), 4351, doi:10.1029/2001JD001480, 2002.
Liu, H., D.J. Jacob, L.Y. Chan, S.J. Oltmans, I. Bey, R.M. Yantosca, J.M. Harris, B.N. Duncan, and R.V. Martin, Sources of tropospheric ozone along the Asian Pacific Rim: An analysis of ozonesonde observations, J. Geophys. Res., 107(D21), 4573, doi:10.1029/2001JD002005, 2002.
Li, Q., D.J. Jacob, I. Bey, R. M. Yantosca, B.D. Field, H. Liu, J. A. Logan, A. M. Fiore, R. V. Martin, and B. N. Duncan, Sources of ozone over the North Atlantic and trans-Atlantic transport of pollution: A global model perspective, IGACtivities Newsletter, NARE special issue, No. 24, p12-15, August 2001.
Li, Q., D. J. Jacob, J. A. Logan, I. Bey, R. M. Yantosca, H. Liu, R. V. Martin, A. M. Fiore, B. D. Field, B. N. Duncan, and V. Thouret, A tropospheric ozone maximum over the Middle East, Geophys. Res. Lett., 28, 3235-3238, 2001.
Bey, I., D. J. Jacob, R. M. Yantosca, J. A. Logan, B. Field, A. M. Fiore, Q. Li, H. Liu, L. J. Mickley, and M. Schultz, Global modeling of tropospheric chemistry with assimilated meteorology: Model description and evaluation, J. Geophys. Res., 106, 23,073-23,096, 2001.
Liu, H., D.J. Jacob, I. Bey, and R.M. Yantosca, Constraints from 210Pb and 7Be on wet deposition and transport in a global three-dimensional chemical tracer model driven by assimilated meteorological fields, J. Geophys. Res., 106(D11), 12,109-12,128, 2001.
Chan, L.Y., C.Y. Chan, H.Y. Liu, S.A. Christopher, S.J. Oltmans, and J.M.Harris, A case study on the biomass burning in southeast Asia and enhancement of tropospheric ozone over Hong Kong, Geophys. Res. Lett., 27(10), 1479-1482, 2000.
Liu, H., W.L. Chang, S.J. Oltmans, L.Y. Chan, and J.M. Harris, On springtime high ozone events in the lower troposphere from southeast Asian biomass burning, Atmos. Environ., 33(15), 2403-2410, 1999.
Chan, L.Y., H.Y. Liu, K.S. Lam, T. Wang, S.J. Oltmans, and J.M.Harris, Analysis of the seasonal behavior of tropospheric ozone at Hong Kong, Atmos. Environ., 32(2), 159-168, 1998.
Lam, K.S., T. Wang, L.Y. Chan, and H.Y. Liu, Observation of surface ozone and carbon monoxide at a coastal site in Hong Kong, in Atmospheric Ozone: proceedings of the XVIII Quadrennial Ozone Symposium (L’Aquila, Italy, 12-21 September 1996), edited by Rumen D. Bojkov and Guido Visconti, Vol.1, 395-398, 1998.
Chan, L.Y., H.Y. Liu, K.S. Lam, and T. Wang, Observations of total column ozone and vertical ozone distribution at subtropical Hong Kong, in Atmospheric Ozone: proceedings of the XVIII Quadrennial Ozone Symposium (L’Aquila, Italy, 12-21 September 1996), edited by Rumen D. Bojkov and Guido Visconti, Vol.1, 107-110, 1998.
Liu, H., Variation of total ozone and characteristics of vertical ozone distribution over Hong Kong, research degree thesis, Dept. of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hong Kong, 1998.
Liu, H., Application of Maximum Entropy Method in the calculation of turbulence spectrum and a study of coherent structures in the surface layer, MSc thesis, Center of Environmental Sciences, Peking University, P.R. China, 1993.
Liu, H., Similarities and differences in the turbulent mixing below and above the forest-net canopy, BSc thesis, Dept. of Geophysics, Peking University, P.R. China, 1990.