My research is centered at remote sensing of the environment, with a focus on the use of satellite for mapping and monitoring terrestrial ecosystem dynamics under the changing climate and land use. Most of my work, linking remote sensing data, mathematic model and ground survey, aims to characterize spatial-temporal changes of 3D vegetation structure and its impact on nature and human society. The ever increasing monitoring and analyzing capacity helps bridge global sustainable development goals and local initiatives and requirements, and clear many uncertainties in design, planning and implementation of current climate-change and conservation projects.

Prior to joining NUS, I was a remote sensing scientist at University of Maryland and most of my research was related to the Earth Science Division of National Aeronautics and Space Administration (NASA). I have been PI and Co-I for multiple NASA research grants and a recipient of NASA Earth and Space Science fellow (NESSF) and New (Early Career) Investigator Program. I am on the science team of NASA's Carbon Monitoring System (CMS) - a program to support stakeholder needs for Monitoring, Reporting, and Verification (MRV) of carbon stocks and fluxes; and also, a Science Team Member and Product Lead of NASA's Global Ecosystem Dynamics Investigation (GEDI) mission - the first high resolution laser ranging of Earth’s forests and topography from the International Space Station. For more information visit https://gedi.umd.edu

GE4214 Remote Sensing of Environment
GE3216 Applications of GIS and Remote Sensing 

National Research Foundation of Singapore, Carbon Integrity SG, 1/Jan/2023 – 31/Dec/2027 (PI: LP Koh, Co-Is: H Tang, Y Zeng)

Ministry of Education (MOE) for AcRF Tier 2, Validating and Improving Satellite-based Forest Carbon Estimation in Southeast Asia, 28/Feb/2023 - 27/Feb/2026 (PI: H Tang)

Economic Development Board /Office for Space Technology and Industry (OSTIn), Space Technology Development Programme Thematic Grant Call on Space Technologies, New Techniques for Monitoring Carbon Stock and Flux in Southeast Asia using Spaceborne SAR and LiDAR Observations, 1/Jul/2022 – 30/Jun/2024 (Lead-PI: Sang-Ho Yun NTU, Co-PI: H Tang)

NASA, Carbon Monitoring System (CMS), High-Resolution Forest Carbon Monitoring and Modeling: Continued Prototype Development and Deployment to National and Global Scales and Science Team Lead, (PI: G Hurtt, Co-I: H Tang)

NASA, Global Ecosystem Dynamics Investigation (GEDI) Science Team, Enhanced calibration and validation of GEDI footprint-level products by refining footprint geolocation accuracy over North America, 01/01/2021 - 12/31/2023, (PI: H Tang)

NASA, Global Ecosystem Dynamics Investigation (GEDI) Science Team, Improved mapping and monitoring of vertical canopy profile metrics from GEDI for quantifying ecosystem dynamics, 01/01/2021 - 12/31/2023, (PI: J Armston, Co-I: H Tang)

NASA, Global Ecosystem Dynamics Investigation (GEDI) Science Team, Using GEDI to improve biomass estimates and understand recent biomass change in the tallest, highest biomass forests in the world, 01/15/2021 - 01/14/2024, (PI: C Doughty, NAU; Co-Is: G Koch–NAU, H Tang)

NASA, Advancing Collaborative Connections for Earth System Science, Spatio-temporal Machine Learning and Cloud Computing for Predicting Dynamics of Global Vegetation Structure from Active Satellite Sensors, 05/01/2020 - 04/30/2023, (PI: Sassan Saatchi, JPL; Co-Is: Gary Doran, Lukas Mandrake, Liang Xu, Yifan Xu–JPL, H Tang)

Microsoft, AI for Earth Microsoft Azure Compute Grant, Forest carbon mapping and individual tree delineation in the state of Maryland, 08/08/2019 (PI: H Tang).

NASA, New (Early Career) Investigator Program in Earth Science, Integrating Space-Borne Lidar Observations to Characterize Vegetation Structure Dynamics across Tropical Forests, 04/01/2018 - 03/31/2021 (PI: H Tang).

NASA, Determining Tropical Rain Forest Successional States Using Vertical Leaf Area Index (LAI) Profiles, 09/01/2012 - 08/31/2016 (PI: Ralph Dubayah; Student-PI: H Tang).

My research focuses on remote sensing of Earth's environment - I am interested in using satellite data to map and monitor the structure and function changes of terrestrial ecosystems towards the changing global environments. The overall research question I seek to answer is:

What are the structure, function and biodiversity of Earth's ecosystems, and how and why are they changing in time and space?”

My research is placed within a consistent framework that links ecological theory, remote sensing data record, as well as mathematical models. It has greatly extended applications of remote sensing on terrestrial ecology and ecosystem monitoring, particularly over tropical forests, by integrating 3-dimensional forest structure observations on the ground, in the air and from space. The 3-dimentional monitoring technology, known as Lidar, goes beyond the conventional 2-dimensional imaging paradigm, and provides accurate information and innovative implications for environmental, biodiversity, and conservation policies.  It has also helped advance our capacity of using spatiotemporal data in monitoring forest structure dynamics to discover and demonstrate ecological and biodiversity hypothesis. More detailed reseach work can be found in my Google Scholar.

ARTICLES IN JOURNAL

• • Ma, L., Hurtt, G., Tang, H., Lamb, R., Lister, A., Chini, L., Dubayah, R., Armston, J., Campbell, E., Duncanson, L., Healey, S., O’Neil-Dunne, J., Ott, L., Poulter, B., Shen, Q., 2023. Spatial heterogeneity of global forest aboveground carbon stocks and fluxes constrained by spaceborne lidar data and mechanistic modeling. Global Change Biology. 00, 1–17.
  • Tang, H., Stoker, J., Luthcke, S., Armston, J., Lee, K., Blair, B., Hofton, M., 2023. Evaluating and mitigating the impact of systematic geolocation error on canopy height measurement performance of GEDI. Remote Sensing of Environment. 291, 113571.
  • Hakkenberg, C.R., Tang, H., Burns, P., Goetz, S.J., 2023. Canopy structure from space using GEDI lidar. Front. Ecol. Environ. 21, 55–56. https://doi.org/10.1002/FEE.2585
  • Cobb, A. R., Dommain, R., Sukri, R. S., Metali, F., Bookhagen, B., Harvey, C. F., & Tang, H. (2023). Improved terrain estimation from spaceborne lidar in tropical peatlands using spatial filtering. Science of Remote Sensing, 7, 100074.
  • Dubayah, R., Armston, J., Healey, S.P., Bruening, J.M., Patterson, P.L., Kellner, J.R., Duncanson, L., Saarela, S., Ståhl, G., Yang, Z., Tang, H., Blair, J.B., Fatoyinbo, L., Goetz, S., Hancock, S., Hansen, M., Hofton, M., Hurtt, G., Luthcke, S., 2022. GEDI launches a new era of biomass inference from space. Environ. Res. Lett. 17, 095001
  • Qin, Y., Xiao, X., Wigneron, J.P., Ciais, P., Canadell, J.G., Brandt, M., Li, X., Fan, L., Wu, X., Tang, H., Dubayah, R., Doughty, R., Crowell, S., Zheng, B., Moore, B., 2022. Large loss and rapid recovery of vegetation cover and aboveground biomass over forest areas in Australia during 2019–2020. Remote Sensing of Environment. 278, 113087.
  • Ma, L., Hurtt, G., Ott, L., Sahajpal, R., Fisk, J., Lamb, R., Tang, H., Flanagan, S., Chini, L., Chatterjee, A., Sullivan, J., 2022. Global evaluation of the Ecosystem Demography model (ED v3.0). Geosci. Model Dev. 15, 1971–1994.
  • Duncanson, L., Kellner, J.R., Armston, J., Dubayah, R., Minor, D.M., Hancock, S., Healey, S.P., Patterson, P.L., Saarela, S., Marselis, S., Silva, C.E., Bruening, J., Goetz, S.J., Tang, H., Hofton, M., Blair, B., Luthcke, S., Fatoyinbo, L., …[Data contributors], 2022. Aboveground biomass density models for NASA’s Global Ecosystem Dynamics Investigation (GEDI) lidar mission. Remote Sensing of Environment. 270, 112845.
  • Liu, X., Su, Y., Hu, T., Yang, Q., Liu, B., Deng, Y., Tang, H., Tang, Z., Fang, J., Guo, Q., 2022. Neural network guided interpolation for mapping canopy height of China’s forests by integrating GEDI and ICESat-2 data. Remote Sensing of Environment.. 269, 112844.
  • Bruening, J.M., Fischer, R., Bohn, F.J., Armston, J., Armstrong, A.H., Knapp, N., Tang, H., Huth, A., Dubayah, R., 2021. Challenges to aboveground biomass prediction from waveform lidar. Environ. Res. Lett. 16, 125013.
  • Qin, Y., Xiao, X., Wigneron, J.-P., Ciais, P., Canadell, J. G., Brandt, M., Li, X., Fan, L., Wu, X., Tang, H., Dubayah, R., Doughty, R., Chang, Q., Crowell, S., Zheng, B., Neal, K., Celis, J. A., & Moore, B. (2021). Annual Maps of Forests in Australia from Analyses of Microwave and Optical Images with FAO Forest Definition. Journal of Remote Sensing, 2021, 9784657, 11
  • Fatoyinbo, T., Armston, J., Simard, M., Saatchi, S., Denbina, M., Lavalle, M., Hofton, M., Tang, H., Marselis, S., Pinto, N., Hancock, S., Hawkins, B., Duncanson, L., Blair, B., Hansen, C., Lou, Y., Dubayah, R., Hensley, S., Silva, C., Poulsen, J.R., Labrière, N., Barbier, N., Jeffery, K., Kenfack, D., Herve, M., Bissiengou, P., Alonso, A., Moussavou, G., White, L.T.J., Lewis, S., Hibbard, K., 2021. The NASA AfriSAR campaign: Airborne SAR and lidar measurements of tropical forest structure and biomass in support of current and future space missions. Remote Sensing of Environment. 264, 112533.
  • Chen, X., Ciais, P., Maignan, F., Zhang, Y., Bastos, A., Liu, L., Bacour, C., Fan, L., Gentine, P., Goll, D., Green, J., Kim, H., Li, L., Liu, Y., Peng, S., Tang, H., Viovy, N., Wigneron, J., Wu, J., Yuan, W., Zhang, H., 2021. Vapor pressure deficits and sunlight explain seasonality of leaf phenology and photosynthesis across Amazonian evergreen broadleaved forest. Global Biogeochem. Cycles 35, e2020GB006893.
  • Lamb, R.L., Hurtt, G., Boudreau, T.J., Campbell, E., Sepúlveda Carlo, E., Chu, H.-H., de Mooy, J., Dubayah, R.O., Gonsalves, D., Guy, M., Hultman, N.E., Lehman, S., Leon, B., Lister, A., Lynch, C., Ma, L., Martin, C.R., Robbins, N.P., Rudee, A., Silva, C.E., Skoglund, C., Tang, H., 2021. Context and future directions for integrating forest carbon into sub-national climate mitigation planning in the RGGI region of the U.S. Environmental Research Letters. 16, 63001.
  • Ma, L., Hurtt, G., Tang, H., Lamb, R., Campbell, E., Dubayah, R., Guy, M., Huang, W., Lister, A., Lu, J., O’Neil-Dunne, J., Rudee, A., Shen, Q., & Silva, C. (2021). High-resolution forest carbon modelling for climate mitigation planning over the RGGI region, USA. Environmental Research Letters, 16(4), 45014.
  • Tang H, Ma L, Lister A, O’Neill-Dunne J, Lu J, Lamb R L, Dubayah R and Hurtt G 2021 High-resolution forest carbon mapping for climate mitigation baselines over the RGGI region, USA. Environmental Research Letters. 16 35011.
  • Potapov P, Li X, Hernandez-Serna A, Tyukavina A, Hansen M C, Kommareddy A, Pickens A, Turubanova S, Tang H, Silva C E, Armston J, Dubayah R, Blair J B and Hofton M 2021 Mapping global forest canopy height through integration of GEDI and Landsat data. Remote Sensing of Environment. 112165.
  • Marselis, S.M., Abernethy, K., Alonso, A., Armston, J., Baker, T.R., Bastin, J.-F., Bogaert, J., Boyd, D.S., Boeckx, P., Burslem, D.F.R.P., Chazdon, R., Clark, D.B., Coomes, D., Duncanson, L., Hancock, S., Hill, R., Hopkinson, C., Kearsley, E., Kellner, J.R., Kenfack, D., Labrière, N., Lewis, S.L., Minor, D., Memiaghe, H., Monteagudo, A., Nilus, R., O’Brien, M., Phillips, O.L., Poulsen, J., Tang, H., Verbeeck, H., Dubayah, R., 2020. Evaluating the Potential of Full-waveform Lidar for Mapping Pan-Tropical Tree Species Richness. Global Ecology and Biogeography. 29(10), 1799– 1816.
  • Dubayah, R., Blair, J.B., Goetz, S., Fatoyinbo, L., Hansen, M., Healey, S., Hofton, M., Hurtt, G., Kellner, J., Luthcke, S., Armston, J., Tang, H., Duncanson, L., Hancock, S., Jantz, P., Marselis, S., Patterson, P., Qi, W., Silva, C., 2020. The Global Ecosystem Dynamics Investigation: High-resolution laser ranging of the Earth’s forests and topography. Science of Remote Sensing. 1, 100002.
  • Boucher, P.B., Hancock, S., Orwig, D.A., Duncanson, L., Armston, J., Tang, H., Krause, K., Cook, B., Paynter, I., Li, Z., Elmes, A., Schaaf, C., 2020. Detecting change in forest structure with simulated GEDI lidarwaveforms: A case study of the hemlock woolly adelgid (HWA; adelges tsugae) infestation. Remote Sensing. 12(8), 1304.
  • Rödig, E., Knapp, N., Fischer, R., Bohn, F., Dubayah, R., Tang. H, Huth A. (2019) From small-scale forest structure to Amazon-wide carbon estimates. Nature Communications. 10, 5088.
  • Marselis, M., Tang, H., Armston, J., Abernethy, K., Alonso, A., Barbier, N., Bissiengou, P., Jeffery, K., Kenfack, D., Labrière N.… (2019) Exploring the relation between remotely sensed vertical canopy structure and tree species diversity in Gabon. Environmental Research Letters. 14(9), 094013.
  • Tang, H., Armston, J.D., Hancock, S., Marselis, S.M., Goetz, S., Dubayah, R., (2019). Characterizing global forest canopy cover distribution using spaceborne lidar. Remote Sensing of Environment. 231, 111262.
  • Huang, W., Dolan, K., Swatantran, A., Johnson, K., Tang, H., O’Neill Dunne, J., Dubayah, R., Hurtt, G. (2019). High-resolution mapping of above ground biomass for forest carbon monitoring system in the tri-state region Maryland, Pennsylvania, Delaware, USA. Environmental Research Letters. 14(9), 095002.
  • Hurtt, G., Zhao, M., Sahajpal, R., Armstrong, A., Birdsey, R., Campbell, E., Dolan, K., Dubayah, R., Fisk, J.P., Flanagan, S., Huang, C., Huang, W., Johnson, K., Lamb, R., Ma, L., Marks, R., O’Leary, D., O’Neil-Dunne, J., Swatantran, A., Tang, H., (2019). Beyond MRV: high-resolution forest carbon modeling for climate mitigation planning over Maryland, USA. Environmental Research Letters. 14(4), 045013.
  • Tang, H., Song, XP., Zhao, F., Strahler, A.H., Schaaf, C.L., Goetz, S., Huang, C., Hansen, M., Dubayah, R., (2019) Definition and measurement of tree cover: A comparative analysis of field-, lidar-and landsat-based tree cover estimations in the Sierra national forests, USA. Agricultural and Forest Meteorology. 268, 258-268.
  • Hancock, S., Armston, J., Hofton, M., Sun, X., Tang, H., Duncanson, L., Kellner, J., Dubayah, R. (2019) The GEDI Simulator: A Large‐Footprint Waveform Lidar Simulator for Calibration and Validation of Spaceborne Missions. Earth and Space Science. 6(2), 294-310. (TOP CITED ARTICLE 2018-2019)
  • Qi, W., Lee, SK., Hancock, S., Luthcke, S., Tang, H., Armston, J., Dubayah, R., (2019). Improved forest height estimation by fusion of simulated GEDI Lidar data and TanDEM-X InSAR data. Remote Sensing of Environment. 221, 621–634.
  • Marselis, S.M., Tang, H., Armston, J.D., Calders, K., Labrière, N., Dubayah, R., (2018). Distinguishing vegetation types with airborne waveform lidar data in a tropical forest-savanna mosaic: A case study in Lopé National Park, Gabon. Remote Sensing of Environment. 216, 626–634.
  • Tang, H., & Dubayah, R. (2017). Light-driven growth in Amazon evergreen forests explained by seasonal variations of vertical canopy structure. Proceedings of the National Academy of Sciences. 114(10), 2640-2644.
  • Tang, H., Swatantran, A., Barrett, T., DeCola, P., & Dubayah, R. (2016). Voxel-Based Spatial Filtering Method for Canopy Height Retrieval from Airborne Single-Photon Lidar. Remote Sensing. 8(9), 771.
  • Brolly, M., Simard, M., Tang, H., Dubayah, R. O., & Fisk, J. P. (2016). A Lidar-Radar Framework to Assess the Impact of Vertical Forest Structure on Interferometric Coherence. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, PP(99), 1–12.
  • Swatantran, A., Tang, H., Barrett, T., DeCola, P., & Dubayah, R. (2016). Rapid, High-Resolution Forest Structure and Terrain Mapping over Large Areas using Single Photon Lidar. Scientific Reports, 6, 28277.
  • Tang, H., Ganguly, S., Zhang, G., Hofton, M., Nelson, R., & Dubayah, R. (2016). Characterizing leaf area index (LAI) and vertical foliage profile (VFP) over the United States. Biogeosciences 13, 239-252.
  • Huang, W., Swatantran, A., Johnson, K., Duncanson, L., Tang, H., O'Neil Dunne, J., Hurtt, G., & Dubayah, R. (2015). Local discrepancies in continental scale biomass maps: a case study over forested and non-forested landscapes in Maryland, USA. Carbon Balance and Management, C7 - 19, 10, 1-16.
  • Tang, H., Brolly, M., Zhao, F., Strahler, A.H., Schaaf, C.L., Ganguly, S., Zhang, G., & Dubayah, R. (2014a). Deriving and validating Leaf Area Index (LAI) at multiple spatial scales through lidar remote sensing: A case study in Sierra National Forest, CA. Remote Sensing of Environment, 143, 131-141.
  • Tang, H., Dubayah, R., Brolly, M., Ganguly, S., & Zhang, G. (2014b). Large-scale retrieval of leaf area index and vertical foliage profile from the spaceborne waveform lidar (GLAS/ICESat). Remote Sensing of Environment, 154, 8-18.
  • Zhao, F., Yang, X.Y., Strahler, A.H., Schaaf, C.L., Yao, T., Wang, Z.S., Roman, M.O., Woodcock, C.E., Ni-Meister, W., Jupp, D.L.B., Lovell, J.L., Culvenor, D.S., Newnham, G.J., Tang, H., & Dubayah, R.O. (2013). A comparison of foliage profiles in the Sierra National Forest obtained with a full-waveform under-canopy EVI lidar system with the foliage profiles obtained with an airborne full-waveform LVIS lidar system. Remote Sensing of Environment, 136, 330-341.
  • Tang, H., Dubayah, R., Swatantran, A., Hofton, M., Sheldon, S., Clark, D.B., & Blair, B. (2012). Retrieval of vertical LAI profiles over tropical rain forests using waveform lidar at La Selva, Costa Rica. Remote Sensing of Environment, 124, 242-250.

OTHERS

• 1. Ma, L., G.C. Hurtt, H. Tang, R. Lamb, E. Campbell, R.O. Dubayah, M. Guy, W. Huang, J. Lu, A. Rudee, Q. Shen, C.E. Silva, and A.J. Lister. 2022. Forest Aboveground Biomass and Carbon Sequestration Potential, Northeastern USA. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1922
  2. Dubayah, R.O., J. Armston, J.R. Kellner, L. Duncanson, S.P. Healey, P.L. Patterson, S. Hancock, H. Tang, M.A. Hofton, J.B. Blair, and S.B. Luthcke. 2021. GEDI L4A Footprint Level Aboveground Biomass Density, Version 1. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1907
  3. Tang, H., L. Ma, A.J. Lister, J. O'Neil-Dunne, J. Lu, R. Lamb, R.O. Dubayah, and G.C. Hurtt. 2021. LiDAR Derived Biomass, Canopy Height, and Cover for New England Region, USA, 2015. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1854
  4. Armston, J., H. Tang, S. Marselis, L. Duncanson, M. Hofton, J.B. Blair, T. Fatoyinbo, and R.O. Dubayah. 2020. AfriSAR: Gridded Forest Biomass and Canopy Metrics Derived from LVIS, Gabon, 2016. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1775
  5. Dubayah R., Luthcke, S., Blair, J. B., Hofton, M., Armston, J., Tang, H. (2020). GEDI L1B Geolocated Waveform Data Global Footprint Level V001 [Data set]. NASA EOSDIS Land Processes DAAC. https://doi.org/10.5067/GEDI/GEDI01_B.001
  6. Dubayah R., Hofton, M., Blair, J. B., Armston, J., Tang, H., Luthcke, S. (2020). GEDI L2A Elevation and Height Metrics Data Global Footprint Level V001 [Data set]. NASA EOSDIS Land Processes DAAC. https://doi.org/10.5067/GEDI/GEDI02_A.001
  7. Dubayah R., Tang, H., Armston, J., Luthcke, S., Hofton, M., Blair, J. B. (2020). GEDI L2B Canopy Cover and Vertical Profile Metrics Data Global Footprint Level V001 [Data set]. NASA EOSDIS Land Processes DAAC. https://doi.org/10.5067/GEDI/GEDI02_B.001
  8. Hurtt, G.C., M. Zhao, R. Sahajpal, A. Armstrong, R. Birdsey, E. Campbell, K. Dolan, R.O. Dubayah, J.P. Fisk, S. Flanagan, C. Huang, W. Huang, K. Johnson, R. Lamb, L. Ma, R. Marks, D. O'Leary III, J. O'Neil-Dunne, A. Swatantran, and H. Tang. 2019. Forest Aboveground Biomass and Carbon Sequestration Potential for Maryland, USA. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1660
  9. Tang, H., J. Armston, S. Hancock, M. Hofton, J.B. Blair, T. Fatoyinbo, and R.O. Dubayah. 2018. AfriSAR: Canopy Cover and Vertical Profile Metrics Derived from LVIS, Gabon, 2016. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1591
  10. Dubayah, R.O., A. Swatantran, W. Huang, L. Duncanson, K. Johnson, H. Tang, J.O. Dunne, and G.C. Hurtt. 2017. CMS: LiDAR-derived Aboveground Biomass, Canopy Height and Cover, Sonoma County, California, 2013. ORNL DAAC, Oak Ridge, Tennessee, USA.
  11. Dubayah, R.O., A. Swatantran, W. Huang, L. Duncanson, K. Johnson, H. Tang, J.O. Dunne, and G.C. Hurtt. 2016. CMS: LiDAR-derived Aboveground Biomass, Canopy Height and Cover for Maryland, 2011. ORNL DAAC, Oak Ridge, Tennessee, USA.

Associate Editor - Remote Sensing of Environment, an interdisciplinary journal emphasis on biophysical and quantitative approaches to remote sensing at local to global scales