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 Aerosols And Clouds (329J): People
Vijay  Natraj's Picture
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Jet Propulsion Laboratory
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Curriculum Vitae:

Vijay Natraj

Dr. Vijay Natraj received bachelor and master degrees in chemical engineering from the National University of Singapore in 1998 and 2002, respectively, and a Ph.D. degree in chemical engineering from the California Institute of Technology in 2008.He is currently a scientist in the Aerosols and Clouds group at JPL, where he has been working since 2010. He has 15 years of experience in radiative transfer modeling with applications to retrievals of trace gases and atmospheric scatterers. As part of his graduate work, he developed a fast and accurate polarized radiative transfer model to account for polarization by the atmosphere and surface in the near-infrared. This model has been used operationally in retrievals of data from the Japanese GOSAT and the NASA OCO-2 satellites. He also developed an enhanced two-stream-enhanced single scattering model that is much more accurate than a standard two-stream model but just as fast. Recently, he developed a two-stream model for conservative scattering, which is relevant for shortwave flux computations in optically thick hot Jupiter type exoplanets. He is the Co-Chair of the Regional/Urban OSSE working group, comprised of scientists from JPL and other NASA centers and academic institutions, for the GEO-CAPE project. He also leads the retrieval algorithm team for the JPL PanFTS project. He pioneered the use of principal component analysis to speed up radiative transfer calculations and has published several peer-reviewed articles on the topic.

Dr. Natraj revised the famed Coulson-Sekera tables for Rayleigh scattering. For more than half a century, these tables have been the benchmark for testing the accuracy of radiative transfer codes. Dr. Natraj discovered errors in the tables and recomputed them with a thousand times more accuracy using a very elegant technique. Later, he extended the tables for applications to (optically thicker) planetary and extrasolar atmospheres.

Dr. Natraj leads a project to make a significant change in the way imaging spectroscopic retrievals are performed. This work, in collaboration with the AVIRIS-NG team, is enabling a move from atmospheric correction (and hence a loss of atmospheric information, particularly with respect to water vapor and aerosols) to accounting for a coupled atmosphere- surface system. This methodology will raise imaging spectroscopy science to the interpretability standards of atmospheric composition missions and is directly relevant to the surface geology and biology designated mission proposed by the 2017 Earth Science Decadal Survey.

Dr. Natraj leads several projects on using innovative RT techniques to understand aerosol vertical distribution, to profile temperature and water vapor in the planetary boundary layer using near- and thermal-infrared measurements and to improve diagnosis of clouds in climate models using mid-infrared satellite data. These efforts are directly related to important missions recommended by the 2017 Earth Science Decadal Survey (aerosols and clouds are in the designated mission category). In addition, he leads a project to utilize measurements of Earth's sunlit disk from Lagrangian orbit to model the Earth as a proxy exoplanet.

His research interests are in the areas of scattering, polarization, aerosol and cloud modeling, fast radiative transfer techniques, and information theoretical analysis. His expertise in the above fields led to him being invited to write a review paper in Light Scattering Reviews on fast radiative transfer techniques. He is writing a book (in collaboration with Dr. Alexander Kokhanovksy of EUMETSAT) on analytic methods in radiative transfer. He is the recipient of the best reviewer of the year award from JQSRT in 2009, the Richard M. Goody award for atmospheric radiation and remote sensing in 2014, and the JPL Voyager award for contributions to the field of atmospheric radiation and remote sensing in 2015, and the NASA Early Career Achievement Medal in 2016 for developing fast and accurate RT models needed for current and future atmospheric composition remote sensing missions, in addition to several team awards.


Research Interests
  • Scattering and polarization
  • Aerosol and cloud modeling
  • Fast radiative transfer techniques
  • Information theoretical analyses

Projects

Geo-Cape Icon Geo-Cape
Geostationary Coastal and Air Pollution Events

JIFRESSE Icon JIFRESSE
JIFRESSE is a scientific collaboration between UCLA and JPL to improve understanding and to develop future projections about global climate change.

OCO-2 - Orbiting Carbon Observatory Icon OCO-2 - Orbiting Carbon Observatory
The Orbiting Carbon Observatory-2 (OCO-2) is a mission designed to make precise, time-dependent global measurements of atmospheric carbon dioxide (CO2) from an Earth orbiting satellite.

Megacities Carbon Project Icon Megacities Carbon Project
The Megacities Carbon Project is being established for the megacities of Los Angeles and Paris.

AVIRIS Icon AVIRIS
Airborne Visible / Infrared Imaging Spectrometer


Professional Experience
  • Scientist, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, USA (2010 - Present)
  • Visitor in Planetary Science, California Institute of Technology, Pasadena, USA (2010 - Present)
  • Associate Project Scientist, Joint Institute for Regional Earth System Science and Engineering, University of California at Los Angeles, Westwood, USA (2015 - Present)
  • Visiting Assistant Researcher, Joint Institute for Regional Earth System Science and Engineering, University of California at Los Angeles, Westwood, USA (2012 - 2014)
  • Researcher, California Institute of Technology, Pasadena, USA (2007 - 2010)
  • Co-mentor, Summer Undergraduate Research Fellowship (SURF) Program (2006 - Present)
  • Research Assistant, California Institute of Technology, Pasadena, USA (2001 - 2007)
  • Research Engineer, National University of Singapore (NUS), Singapore (1998 - 2001)
  • Internship Trainee, ESSO Singapore Pte. Ltd., Singapore (1997)

Selected Awards
  • NASA Early Career Achievement Medal for developing fast and accurate RT models needed for current and future atmospheric composition remote sensing missions (2016)
  • JPL Voyager award for contributions to the field of Atmospheric Radiation and Remote Sensing (2015)
  • Richard M. Goody award for Atmospheric Radiation and Remote Sensing  (2014)
  • JPL/NASA team bonus awards (2010, 2012, 2014, 2015, 2016)
  • JQSRT best reviewer (2009)
  • "Turning Coal into Diamonds" award for OCO retrieval algorithm development (2003)
  • Caltech departmental fellowship (2001)

Selected Publications
  1. Somkuti, P., H. Bösch, V. Natraj, and P. Kopparla (2017), Application of a PCA-based Fast Radiative Transfer Model to XCO2 Retrievals in the Shortwave Infrared, J. Geophys. Res., 122(19), 10268-10287, doi:10.1002/2017JD027013.
  2. Kopparla, P., V. Natraj, et al. (2017), PCA-Based Radiative Transfer: Improvements to Aerosol Scheme, Vertical Layering and Spectral Binning, J. Quant. Spectrosc. Radiat. Transfer, 198, 104-111, doi:10.1016/j.jqsrt.2017.05.005.
  3. Chang, K.-W., T. S. L'Ecuyer, B. H. Kahn, and V. Natraj (2017), Information Content of Visible and Midinfrared Radiances for Retrieving Tropical Ice Cloud Properties, J. Geophys. Res., 122, doi:10.1002/2016JD026357.
  4. Zeng, Z.-C., Q. Zhang, V. Natraj, et al. (2017), Aerosol Scattering Effects on Water Vapor Retrievals over the Los Angeles Basin, Atmos. Chem. Phys., 17(4), 2495-2508, doi:10.5194/acp-17-2495-2017.
  5. Eldering, A., V. Natraj, et al. (2017), The Orbiting Carbon Observatory-2: First 18 Months of Science Data Products, Atmos. Meas. Tech., 10(2), 549-563, doi:10.5194/amt-10-549-2017.
  6. Zoogman, P., V. Natraj, et al. (2017), Tropospheric Emissions: Monitoring of Pollution (TEMPO), J. Quant. Spectrosc. Radiat. Transfer, 186, 17-39, doi:10.1016/j.jqsrt.2016.05.008.
  7. Kopparla, P., V. Natraj, R. J. D. Spurr, R.-L. Shia, Y. L. Yung, and D. Crisp (2016), A Fast and Accurate PCA Based Radiative Transfer Model: Extension to the Broadband Shortwave Region, J. Quant. Spectrosc. Radiat. Transfer, 173, 65-71, doi:10.1016/j.jqsrt.2016.01.014.
  8. Kopparla, P., V. Natraj, X. Zhang, M R. Swain, S. J. Wiktorowicz, and Y. L. Yung (2016), A Multiple Scattering Polarized Radiative Transfer Model: Application to HD189733b, Astrophys. J., 817(1), doi:10.3847/0004-637X/817/1/32.
  9. Fu, D., K. W. Bowman, H. M. Worden, V. Natraj, et al. (2016), High-Resolution Tropospheric Carbon Monoxide Profiles Retrieved from CrIS and TROPOMI, Atmos. Meas. Tech., 9(6), 2567-2579, doi:10.5194/amt-9-2567-2016.
  10. Bousserez, N., V. Natraj, et al. (2016), Constraints on Methane Emissions in North America from Future Geostationary Remote Sensing Measurements, Atmos. Chem. Phys., 16(10), 6175-6190, doi:10.5194/acp-16-6175-2016.
  11. Colosimo, S. F., V. Natraj, S. P. Sander, and J. Stutz (2016), A Sensitivity Study on the Retrieval of Aerosol Vertical Profiles Using the Oxygen A-band, Atmos. Meas. Tech., 9(4), 1889-1905, doi:10.5194/amt-9-1889-2016.
  12. Su, Z., X. Xi., V. Natraj, K.-F. Li, R.-L. Shia, C. E Miller, and Y. L. Yung (2016), Information-Rich Spectral Channels for Simulated Retrievals of Partial Column-Averaged Methane, Earth Space Sci., 3, doi:10.1002/2015EA000120.
  13. Zhang, Q., V. Natraj, et al. (2015), Accounting for Aerosol Scattering in the CLARS Retrieval of Column Averaged CO2 Mixing Ratios, J. Geophys. Res., 120(14), 7205-7218, doi:10.1002/2015JD023499.
  14. Kokhanovsky, A. A., A. B. Davis, V. Natraj, et al. (2015), Space-Based Remote Sensing of Atmospheric Aerosols: The Multi-Angle Spectro-Polarimetric Frontier, Earth Sci. Rev., doi:10.1016/j.earscirev.2015.01.012.
  15. Xi, X., V. Natraj, et al. (2015), Simulated Retrievals for the Remote Sensing of CO2, CH4, CO and H2O from Geostationary Orbit, Atmos. Meas. Tech., 8(11), 4817-4830, doi: 10.5194/amt-8-4817-2015.
  16. Hache, E., J.-L. Attié, V. Natraj, et al. (2014), The Added Value of a Visible Channel to a Geostationary Thermal Infrared Instrument to Monitor Ozone for Air Quality, Atmos. Meas. Tech., 7(7), 2185–2201, doi:10.5194/amt-7-2185-2014.
  17. O’Brien, D. M., I. Polonsky, V. Natraj, et al. (2013), Testing the Polarization Model for TANSO-FTS on GOSAT against Clear-sky Observations of Sun-glint over the Ocean, IEEE Trans. Geosci. Remote Sens., 51(12), 5199–5209, doi:10.1109/TGRS.2012.2232673.
  18. Natraj, V. (2013), A Review of Fast Radiative Transfer Techniques (invited review paper), in Light Scat. Rev. 8, 475–504, Springer: Berlin, doi:10.1007/978-3-642-32106-1_10.
  19. Spurr, R. J. D., V. Natraj, C. Lerot, M. Van Roozendael, and D. Loyola (2013), Linearization of the Principal Component Analysis Method for Radiative Transfer Acceleration: Application to Retrieval Algorithms and Sensitivity Studies, J. Quant. Spectrosc. Radiat. Transfer, 125, 1–17, doi:10.1016/j.jqsrt.2013.04.002.
  20. Sanghavi, S., and V. Natraj (2013), Using Analytical Derivatives to Assess the Impact of Phase Function Fourier Decomposition Technique on the Accuracy of a Radiative Transfer Model, J. Quant. Spectrosc. Radiat. Transfer, 119, 137–149, doi:10.1016/j.jqsrt.2012.12.028.
  21. Fu, D., J. R. Worden, X. Liu, S. S. Kulawik, K. W. Bowman, and V. Natraj (2013), Characterization of Ozone Profiles Derived from Aura TES and OMI Radiances, Atmos. Chem. Phys., 13(6), 3445–3462, doi:10.5194/acp-13-3445-2013.
  22. Kuai, L., J. Worden, V. Natraj, et al. (2013), Profiling Tropospheric CO2 using the Aura TES and TCCON instruments, Atmos. Meas. Tech., 6(1), 63–79, doi:10.5194/amt-6-63-2013.
  23. Thompson, D. R., V. Natraj, et al. (2012), C. E. Miller, Atmospheric Validation of High Accuracy CO2 Absorption Coefficients for the OCO-2 Mission, J. Quant. Spectrosc. Radiat. Transfer, 113(17), 2265–2276, doi:10.1016/j.jqsrt.2012.05.021.
  24. Crisp, D., B. M. Fisher, C. O'Dell, C. Frankenberg, V. Natraj, et al. (2012), The ACOS CO2 Retrieval Algorithm - Part II: Global XCO2 Data Characterization, Atmos. Meas. Tech., 5(4), 687-707, doi:10.5194/amt-5-687-2012.
  25. O'Dell, C. W., B. Connor, H. Bösch, D. O'Brien, C. Frankenberg, V. Natraj, et al. (2012), The ACOS CO2 Retrieval Algorithm - Part 1: Description and Validation against Synthetic Observations, Atmos. Meas. Tech., 5(1), 99-121, doi:10.5194/amt-5-99-2012.
  26. Fishman, J., L. T. Iraci, V. Natraj, et al. (2012), The United States' Next Generation of Atmospheric Composition and Coastal Ecosystem Measurements: NASA's Geostationary Coastal and Air Pollution Events (GEO-CAPE) Mission, Bull. Am. Meteorol. Soc., doi:10.1175/BAMS-D-11-00201.1.
  27. Line, M. R., X. Zhang, G. Vasisht, V. Natraj, P. Chen, and Y. L. Yung (2012), Information Content of Exoplanetary Transit Spectra: An Initial Look, Astrophys. J., 749(1), 93, doi: 10.1088/0004-637X/749/1/93.
  28. Natraj, V., and J. W. Hovenier (2012), Polarized Light Reflected and Transmitted by Thick Rayleigh Scattering Atmospheres, Astrophys. J., 748(1), 28, doi: 10.1088/0004-637X/748/1/28.
  29. Natraj, V., X. Liu, S. Kulawik, K. Chance, R. Chatfield, D. P. Edwards, A. Eldering, G. Francis, T. Kurosu, K. Pickering, R. Spurr, and H. Worden (2011), Multi-spectral Sensitivity Studies for the Retrieval of Tropospheric and Lowermost Tropospheric Ozone from Simulated Clear-sky GEO-CAPE Measurements, Atmos. Environ., 45(39), 7151-7165, doi: 10.1016/j.atmosenv.2011.09.014.
  30. Zoogman, P., D. J. Jacob, K. Chance, L. Zhang, P. Le Sager, A. M. Fiore, A. Eldering, X. Liu, V. Natraj, and S. S. Kulawik (2011), Ozone Air Quality Measurement Requirements for a Geostationary Satellite Mission, Atmos. Environ., 45(39), 7143-7150, doi: 10.1016/j.atmosenv.2011.05.058.
  31. Spurr, R. J. D., and V. Natraj, (2011), A Linearized 2-Stream Radiative Transfer Code for Fast Approximation of Multiple-Scatter Fields, J. Quant. Spectrosc. Radiat. Transfer, 112(16), 2630-2637, doi: 10.1016/j.jqsrt.2011.06.014.
  32. Kuai, L., V. Natraj, R.-L. Shia, C. E. Miller, and Y. L. Yung (2010), Channel Selection using Information Content Analysis: A Case Study of CO2 Retrieval from Near Infrared Measurements, J. Quant. Spectrosc. Radiat. Transfer, 111(9), 1296-1304, doi: 10.1016/j.jqsrt.2010.02.011.
  33. Natraj, V., R.-L. Shia, and Y. L. Yung (2010), On the use of Principal Component Analysis to Speed up Radiative Transfer Calculations, J. Quant. Spectrosc. Radiat. Transfer, 111(5), 810-816, doi: 10.1016/j.jqsrt.2009.11.004.
  34. Natraj, V., K.-F. Li, and Y. L. Yung (2009), Rayleigh Scattering in Planetary Atmospheres: Corrected Tables Through Accurate Computation of X and Y Functions, Astrophys. J., 691(2), 1909-1920, doi: 10.1088/0004-637X/691/2/1909.
  35. Natraj, V., H. Bösch, R. J. D. Spurr, and Y. L. Yung (2008), Retrieval of XCO2 from Simulated Orbiting Carbon Observatory Measurements using the Fast Linearized R-2OS Radiative Transfer Model, J. Geophys. Res., 113, D11212, doi: 10.1029/2007JD009017.
  36. Natraj, V., and R. J. D. Spurr (2007), A Fast Linearized Pseudo-Spherical Two Orders of Scattering Model to Account for Polarization in Vertically Inhomogeneous Scattering-Absorbing Media, J. Quant. Spectrosc. Radiat. Transfer, 107(2), 263-293, doi: 10.1016/j.jqsrt.2007.02.011.
  37. Natraj, V., R. J. D. Spurr, H. Bösch, Y. Jiang, and Y. L. Yung (2007), Evaluation of Errors from Neglecting Polarization in the Forward Modeling of O2 A Band Measurements from Space, with Relevance to CO2 Column Retrieval from Polarization-Sensitive Instruments, J. Quant. Spectrosc. Radiat. Transfer, 103(2), 245-259, doi: 10.1016/j.jqsrt.2006.02.073.
  38. Guo, X., V. Natraj, D. R. Feldman, R. J. D. Spurr, S. P. Sander, R.-L. Shia, and Y. L. Yung (2007), Retrieval of Ozone Profile from Ground-Based Measurements with Polarization: A Synthetic Study, J. Quant. Spectrosc. Radiat. Transfer, 103(1), 175-192, doi: 10.1016/j.jqsrt.2006.05.008.
  39. Bösch, H., G. C. Toon, B. Sen, R. A. Washenfelder, P. O. Wennberg, M. Buchwitz, R. de Beek, J. P. Burrows, D. Crisp, M. Christi, B. J. Connor, V. Natraj, and Y. L. Yung (2006), Space-based Near-infrared CO2 Measurements: Testing the Orbiting Carbon Observatory Retrieval Algorithm and Validation Concept using SCIAMACHY Observations over Park Falls, Wisconsin, J. Geophys. Res., 111, D23302, doi: 10.1029/2006JD007080.
  40. Natraj, V., X. Jiang, R.-L. Shia, X. Huang, J. S. Margolis, and Y. L. Yung (2005), Application of Principal Component Analysis to High Spectral Resolution Radiative Transfer: A Case Study of the O2 A Band, J. Quant. Spectrosc. Radiat. Transfer, 95(4), 539-556, doi: 10.1016/j.jqsrt.2004.12.024.
  41. Natraj, V., and S. B. Chen (2003), Diffusion Coefficient of a Charged Porous Sphere, Chem. Eng. Sci., 58(16), 3621-3628, doi: 10.1016/S0009-2509(03)00252-5.
  42. Natraj, V., and S. B. Chen (2002), Primary Electroviscous Effect in a Suspension of Charged Porous Spheres, J. Coll. Interface Sci., 251(1), 200-207, doi: 10.1006/jcis.2002.8434.

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