Sciences and Exploration Directorate

Krzysztof Wargan



Org Code: 610.1

Mail Code: 610.1
Greenbelt, MD 20771


Research Interests

Stratospheric composition and transport

Earth Science: Atmospheric Chemistry


Constituent data assimilation

Solar System: Atmospheres



Chief Research Scientist

Science Systems and Applications - Global Modeling and Assimilation Office NASA Goddard Space Flight Center Greenbelt, MD 20771 USA

February 2012 - Present


Research Scientist

Science Applications International Corporation - Global Modeling and Assimilation Office NASA Goddard Space Flight Center Greenbelt, MD 20771 USA

September 2010 - January 2012


Research Assistant

Imperial College London - Department of Physics Imperial College London London United Kingdom

June 2009 - August 2010


Support scientist

Science Applications International Corporation - Global Modeling and Assimilation Office NASA Goddard Space Flight Center Greenbelt, MD 20771 USA

January 2002 - February 2009



 2001: PhD in mathematics, the George Washington University. Washington, DC

1994: Master's degree in mathematics, University of Gdańsk, Gdańsk, Poland

Professional Service

  • 2022 WMO/UNEP Scientific Assessment of Ozone Depletion: Coauthor of Chapter 4
  • 7th SPARC General Assembly 2022: Member of the organizing committee
  • Co-organizer of the 21st Conference on Middle Atmosphere (January 2022)
  • Member of the AMS Middle Atmosphere Committee
  • 2018 WMO/UNEP Scientific Assessment of Ozone Depletion: reviewer
  • SPARC Reanalysis Intercomparison Project (S-RIP): point of contact for NASA reanalyses
  • SPARC Reanalysis Intercomparison Project (S-RIP): Coauthor of Chapters 2, 4, and 7 of the S-RIP Report


A New Look at Stratospheric Chemistry With Multispecies Chemical Data Assimilation

Modeling Analysis and Prediction 16-MAP16-0165 - NASA - Awarded: 2017-04-20

Dates:  - 

Selected Publications


Kelp, M. M., C. A. Keller, K. Wargan, B. M. Karpowicz, and D. J. Jacob. 2023. Tropospheric ozone data assimilation in the NASA GEOS composition forecast modeling system (GEOS-CF v2.0) using satellite data for ozone vertical profiles (MLS), total ozone columns (OMI), and thermal infrared radiances (AIRS, IASI) Environmental Research Letters [10.1088/1748-9326/acf0b7]

Millán, L. F., G. L. Manney, H. Boenisch, et al. M. I. Hegglin, P. Hoor, D. Kunkel, T. Leblanc, I. Petropavlovskikh, K. Walker, K. Wargan, and A. Zahn. 2023. Multi-parameter dynamical diagnostics for upper tropospheric and lower stratospheric studies Atmospheric Measurement Techniques 16 (11): 2957-2988 [10.5194/amt-16-2957-2023]

Wargan, K., B. Weir, G. L. Manney, et al. S. E. Cohn, K. E. Knowland, P. A. Wales, and N. J. Livesey. 2023. M2‐SCREAM: A Stratospheric Composition Reanalysis of Aura MLS Data With MERRA‐2 Transport Earth and Space Science 10 (2): e2022EA002632 [10.1029/2022ea002632]

Chipperfield, M. P., M. L. Santee, S. P. Alexander, et al. A. J. de Laat, D. E. Kinnison, J. Kuttippurath, U. Langematz, and K. Wargan. 2023. Polar Stratospheric Ozone: Past, Present, and Future, Chapter 4 in Scientific Assessment of Ozone Depletion GAW Report No. 278, 509 pp., WMO, Geneva, 2022.

Coy, L., P. A. Newman, K. Wargan, et al. G. Partyka, S. Strahan, and S. Pawson. 2022. Stratospheric Circulation Changes Associated with the Hunga Tonga‐Hunga Ha'apai Eruption Geophysical Research Letters 49 [10.1029/2022gl100982]

Manney, G. L., L. F. Millán, M. L. Santee, et al. K. Wargan, A. Lambert, J. L. Neu, F. Werner, Z. D. Lawrence, M. J. Schwartz, N. J. Livesey, and W. G. Read. 2022. Signatures of Anomalous Transport in the 2019/2020 Arctic Stratospheric Polar Vortex Journal of Geophysical Research: Atmospheres 127 (20): [10.1029/2022jd037407]

Manney, G. L., A. H. Butler, K. Wargan, and J. Grooß. 2022. Introduction to Special Collection “The Exceptional Arctic Stratospheric Polar Vortex in 2019/2020: Causes and Consequences” Journal of Geophysical Research: Atmospheres 127 (18): [10.1029/2022jd037381]

Ziemke, J. R., N. A. Kramarova, S. M. Frith, et al. L. Huang, D. P. Haffner, K. Wargan, L. N. Lamsal, G. J. Labow, R. D. McPeters, and P. K. Bhartia. 2022. NASA Satellite Measurements Show Global‐Scale Reductions in Free Tropospheric Ozone in 2020 and Again in 2021 During COVID‐19 Geophysical Research Letters 49 (15): [10.1029/2022gl098712]

Manney, G. L., A. H. Butler, Z. D. Lawrence, K. Wargan, and M. L. Santee. 2022. What's in a Name? On the Use and Significance of the Term “Polar Vortex” Geophysical Research Letters 49 (10): [10.1029/2021gl097617]

Knowland, K. E., C. A. Keller, P. A. Wales, et al. K. Wargan, L. Coy, M. S. Johnson, J. Liu, R. A. Lucchesi, S. D. Eastham, E. Fleming, Q. Liang, T. Leblanc, N. J. Livesey, K. A. Walker, L. E. Ott, and S. Pawson. 2022. NASA GEOS Composition Forecast Modeling System GEOS‐CF v1.0: Stratospheric composition Journal of Advances in Modeling Earth Systems 14 (e2021MS002852): [10.1029/2021ms002852]

Petropavlovskikh, I., K. Miyagawa, A. McClure-Beegle, et al. B. Johnson, J. Wild, S. Strahan, K. Wargan, R. Querel, L. Flynn, E. Beach, G. Ancellet, and S. Godin-Beekmann. 2022. Optimized Umkehr profile algorithm for ozone trend analyses Atmospheric Measurement Techniques 15 (6): 1849-1870 [10.5194/amt-15-1849-2022]

Thompson, A. M., R. M. Stauffer, K. Wargan, et al. J. C. Witte, D. E. Kollonige, and J. R. Ziemke. 2021. Regional and Seasonal Trends in Tropical Ozone From SHADOZ Profiles: Reference for Models and Satellite Products Journal of Geophysical Research: Atmospheres 126 (22): [10.1029/2021jd034691]

Karpowicz, B. M., W. McCarty, and K. Wargan. 2021. Investigating the utility of hyperspectral sounders in the 9.6 μm band to improve ozone analyses Quarterly Journal of the Royal Meteorological Society [10.1002/qj.4198]

Kramarova, N. A., J. R. Ziemke, L.-K. Huang, et al. J. R. Herman, K. Wargan, C. J. Seftor, G. J. Labow, and L. D. Oman. 2021. Evaluation of Version 3 Total and Tropospheric Ozone Columns From Earth Polychromatic Imaging Camera on Deep Space Climate Observatory for Studying Regional Scale Ozone Variations Frontiers in Remote Sensing 2 [10.3389/frsen.2021.734071]

Manney, G. L., M. L. Santee, Z. D. Lawrence, K. Wargan, and M. J. Schwartz. 2021. A Moments View of Climatology and Variability of the Asian Summer Monsoon Anticyclone Journal of Climate 1-69 [10.1175/jcli-d-20-0729.1]

Wargan, K., B. Weir, G. L. Manney, S. E. Cohn, and N. J. Livesey. 2020. The Anomalous 2019 Antarctic Ozone Hole in the GEOS Constituent Data Assimilation System With MLS Observations Journal of Geophysical Research: Atmospheres 125 (18): [10.1029/2020jd033335]

Orbe, C., K. Wargan, S. Pawson, and L. D. Oman. 2020. Mechanisms Linked to Recent Ozone Decreases in the Northern Hemisphere Lower Stratosphere Journal of Geophysical Research: Atmospheres 125 (9): [10.1029/2019jd031631]

Wargan, K., N. Kramarova, B. Weir, S. Pawson, and S. M. Davis. 2020. Toward a Reanalysis of Stratospheric Ozone for Trend Studies: Assimilation of the Aura Microwave Limb Sounder and Ozone Mapping and Profiler Suite Limb Profiler Data Journal of Geophysical Research: Atmospheres 125 (4): [10.1029/2019jd031892]

Tegtmeier, S., J. Anstey, S. Davis, et al. R. Dragani, Y. Harada, I. Ivanciu, R. Pilch Kedzierski, K. Krüger, B. Legras, C. Long, J. S. Wang, K. Wargan, and J. S. Wright. 2020. Temperature and tropopause characteristics from reanalyses data in the tropical tropopause layer Atmospheric Chemistry and Physics 20 (2): 753-770 [10.5194/acp-20-753-2020]

Lawrence, Z. D., G. L. Manney, and K. Wargan. 2018. Reanalysis intercomparisons of stratospheric polar processing diagnostics Atmospheric Chemistry and Physics 18 (18): 13547-13579 [10.5194/acp-18-13547-2018]

Wargan, K., C. Orbe, S. Pawson, et al. J. R. Ziemke, L. D. Oman, M. A. Olsen, L. Coy, and K. E. Knowland. 2018. Recent decline in extratropical lower stratospheric ozone attributed to circulation changes Geophysical Research Letters [10.1029/2018gl077406]

Levelt, P. F., J. Joiner, J. Tamminen, et al. J. P. Veefkind, P. K. Bhartia, D. C. Stein Zweers, B. N. Duncan, D. G. Streets, H. Eskes, R. van der A, C. McLinden, V. Fioletov, S. Carn, J. de Laat, M. T. Deland, S. Marchenko, R. McPeters, J. Ziemke, D. Fu, X. Liu, K. Pickering, A. Apituley, G. González Abad, A. Arola, F. Boersma, C. Chan Miller, K. Chance, M. de Graaf, J. Hakkarainen, S. Hassinen, I. Ialongo, Q. Kleipool, N. Krotkov, C. Li, S. V. Martchenko, P. Newman, C. Nowlan, R. Suleiman, L. G. Tilstra, O. Torres, and K. Wargan. 2018. The Ozone Monitoring Instrument: overview of 14 years in space Atmospheric Chemistry and Physics 18 (8): 5699-5745 [10.5194/acp-18-5699-2018]

Nielsen, J. E., S. Pawson, A. Molod, et al. B. Auer, A. M. da Silva, A. R. Douglass, B. Duncan, Q. Liang, M. Manyin, L. D. Oman, W. Putman, S. E. Strahan, and K. Wargan. 2017. Chemical Mechanisms and Their Applications in the Goddard Earth Observing System (GEOS) Earth System Model Journal of Advances in Modeling Earth Systems [10.1002/2017ms001011]

Jaeglé, L., R. Wood, and K. Wargan. 2017. Multi-year composite view of ozone enhancements and stratosphere-to-troposphere transport in dry intrusions of northern hemisphere extratropical cyclones Journal of Geophysical Research: Atmospheres [10.1002/2017jd027656]

Davis, S. M., M. I. Hegglin, M. Fujiwara, et al. R. Dragani, Y. Harada, C. Kobayashi, C. Long, G. L. Manney, E. R. Nash, G. L. Potter, S. Tegtmeier, T. Wang, K. Wargan, and J. S. Wright. 2017. Assessment of upper tropospheric and stratospheric water vapor and ozone in reanalyses as part of S-RIP Atmospheric Chemistry and Physics 17 (20): 12743-12778 [10.5194/acp-17-12743-2017]

Manney, G. L., M. I. Hegglin, Z. D. Lawrence, et al. K. Wargan, L. F. Millán, M. J. Schwartz, M. L. Santee, A. Lambert, S. Pawson, B. W. Knosp, R. A. Fuller, and W. H. Daffer. 2017. Reanalysis comparisons of upper tropospheric–lower stratospheric jets and multiple tropopauses Atmospheric Chemistry and Physics 17 (18): 11541-11566 [10.5194/acp-17-11541-2017]

Knowland, K. E., L. E. Ott, B. N. Duncan, and K. Wargan. 2017. Stratospheric intrusion-influenced ozone air quality exceedances investigated in the NASA MERRA-2 Reanalysis Geophysical Research Letters 44 (10): 691–10,701 [10.1002/2017gl074532]

Gelaro, R., W. McCarty, M. J. Suárez, et al. R. Todling, A. Molod, L. Takacs, C. Randles, A. Darmenov, M. G. Bosilovich, R. Reichle, K. Wargan, L. Coy, R. Cullather, C. Draper, S. Akella, V. Buchard, A. Conaty, A. da Silva, W. Gu, G.-K. Kim, R. Koster, R. Lucchesi, D. Merkova, J. E. Nielsen, G. Partyka, S. Pawson, W. Putman, M. Rienecker, S. D. Schubert, M. Sienkiewicz, and B. Zhao. 2017. The Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2) Journal of Climate 30 5419–5454 [10.1175/jcli-d-16-0758.1]

Wargan, K., G. Labow, S. Frith, et al. S. Pawson, N. Livesey, and G. Partyka. 2017. Evaluation of the Ozone Fields in NASA’s MERRA-2 Reanalysis Journal of Climate 30 (8): 2961–2988 [10.1175/jcli-d-16-0699.1]

Liu, J., J. M. Rodriguez, S. D. Steenrod, et al. A. R. Douglass, J. A. Logan, M. A. Olsen, K. Wargan, and J. R. Ziemke. 2017. Causes of interannual variability over the southern hemispheric tropospheric ozone maximum Atmospheric Chemistry and Physics 17 (5): 3279-3299 [10.5194/acp-17-3279-2017]

Fujiwara, M., J. S. Wright, G. L. Manney, et al. L. J. Gray, J. Anstey, T. Birner, S. Davis, E. P. Gerber, V. L. Harvey, M. I. Hegglin, C. R. Homeyer, J. A. Knox, K. Krüger, A. Lambert, C. S. Long, P. Martineau, B. M. Monge-Sanz, M. L. Santee, S. Tegtmeier, S. Chabrillat, D. G. Tan, D. R. Jackson, S. Polavarapu, G. P. Compo, R. Dragani, W. Ebisuzaki, Y. Harada, C. Kobayashi, W. McCarty, K. Onogi, S. Pawson, A. Simmons, K. Wargan, J. S. Whitaker, and C.-Z. Zou. 2017. Introduction to the SPARC Reanalysis Intercomparison Project (S-RIP) and overview of the reanalysis systems Atmospheric Chemistry and Physics 1-52 [10.5194/acp-2016-652]

Olsen, M. A., K. Wargan, and S. Pawson. 2016. Tropospheric column ozone response to ENSO in GEOS-5 assimilation of OMI and MLS ozone data Atmos. Chem. Phys. 16 (11): 7091-7103 [10.5194/acp-16-7091-2016]

Ott, L. E., B. N. Duncan, A. M. Thompson, et al. G. Diskin, Z. Fasnacht, A. O. Langford, M. Lin, A. M. Molod, J. E. Nielsen, S. E. Pusede, K. Wargan, A. J. Weinheimer, and Y. Yoshida. 2016. Frequency and impact of summertime stratospheric intrusions over Maryland during DISCOVER-AQ (2011): New evidence from NASA's GEOS-5 simulations J. Geophys. Res. Atmos. [10.1002/2015jd024052]

Coy, L., K. Wargan, A. M. Molod, W. R. McCarty, and S. Pawson. 2016. Structure and Dynamics of the Quasi-Biennial Oscillation in MERRA-2 J. Climate 29:14 5339-5354 [10.1175/jcli-d-15-0809.1]

Wargan, K., and L. Coy. 2016. Strengthening of the Tropopause Inversion Layer During the 2009 Sudden Stratospheric Warming: A MERRA-2 Study Journal of the Atmospheric Sciences [10.1175/jas-d-15-0333.1]

Wargan, K., S. Pawson, M. A. Olsen, et al. J. C. Witte, A. R. Douglass, J. R. Ziemke, S. E. Strahan, and J. E. Nielsen. 2015. The Global Structure of Upper Troposphere-Lower Stratosphere Ozone in GEOS-5: A Multi-Year Assimilation of EOS Aura Data J. Geophys. Res. - Atmos 120 2013-2036 [10.1002/2014JD022493]

Ziemke, J. R., M. A. Olsen, J. C. Witte, et al. A. R. Douglass, S. E. Strahan, K. Wargan, X. Liu, M. Schoeberl, K. Yang, T. Kaplan, S. Pawson, B. N. Duncan, P. Newman, P. K. Bhartia, and M. K. Heney. 2014. Assessment and applications of NASA ozone data products derived from Aura OMI/MLS satellite measurements in context of the GMI chemical transport model J. Geophys. Res. Atmos. 119 (9): 5671-5699 [10.1002/2013JD020914]

Remsberg, E., M. Natarajan, T. Fairlie, et al. K. Wargan, S. Pawson, L. Coy, G. Lingenfelser, and G. Kim. 2013. On the inclusion of Limb Infrared Monitor of the Stratosphere version 6 ozone in a data assimilation system J. Geophys. Res. Atmos. 118 (14): 7982-8000 [10.1002/jgrd.50566]

Doughty, D. C., A. M. Thompson, M. R. Schoeberl, et al. I. Stajner, K. Wargan, and W. C. Hui. 2011. An intercomparison of tropospheric ozone retrievals derived from two Aura instruments and in-situ measurements in western North America in 2006 J. Geophys. Res. doi: 116 D06303 [10.1029/2010JD014703]

Wargan, K., S. Pawson, I. Stajner, and V. Thouret. 2010. Spatial structure of assimilated ozone in the upper troposphere and lower stratosphere J. Geophys. Res. 115 (D24): D24316 [10.1029/2010JD013941]

Stajner, I., K. Wargan, S. Pawson, et al. H. Hayashi, L. P. Chang, R. C. Hudman, L. Froidevaux, N. Livesey, P. Levelt, A. M. Thompson, D. W. Tarasick, R. Stuebi, S. B. Andersen, M. Yela, G. Koenig-Laslo, F. J. Schmidlin, and J. C. Witte. 2008. Assimilated Ozone from EOS-Aura: Evaluation of the Tropopause Region and Tropospheric Columns J. Geophys. Res.-Atmos. 113 D15S32 [doi:10.1029/2007JD008863]

Stajner, I., K. Wargan, L. Chang, et al. H. Hayashi, S. Pawson, and H. Nakajima. 2006. Assimilation of ozone profiles from the Improved Limb Atmospheric Spectrometer-II: Study of Antarctic ozone JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 111 (D11): [10.1029/2005JD006448]

Wargan, K., I. Stajner, S. Pawson, R. Rood, and W. Tan. 2005. Assimilation of ozone data from the Michelson Interferometer for Passive Atmospheric Sounding QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 131 (611): [10.1256/qj.04.184]

Stajner, I., and K. Wargan. 2004. Antarctic stratospheric ozone from the assimilation of occultation data GEOPHYSICAL RESEARCH LETTERS 31 (18): [10.1029/2004GL020846]


Mccarty, W. R., L. Coy, R. Gelaro, et al. A. Huang, D. Merkova, E. B. Smith, M. E. Sienkiewicz, and K. Wargan. 2016. MERRA-2 Input Observations: Summary and Assessment Technical Report Series on Global Modeling and Data Assimilation 46 (NASA/TM–2016-104606):

Bosilovich, M. G., S. R. Akella, L. Coy, et al. R. I. Cullather, C. S. Draper, R. Gelaro, R. M. Kovach, Q. Liu, A. M. Molod, P. M. Norris, K. Wargan, C. Yang, R. H. Reichle, L. L. Takacs, Y. V. Vikhliaev, S. C. Bloom, A. Collow, S. Firth, G. J. Labow, G. S. Partyka, S. Pawson, O. Reale, S. D. Schubert, and M. J. Suarez. 2015. MERRA-2: Initial Evaluation of the Climate NASA Technical Report Series on Global Modeling and Data Assimilation 43 (NASA/TM–2015–10) 139 pp.

Gelaro, R., W. M. Putman, S. Pawson, et al. C. S. Draper, A. M. Molod, P. M. Norris, L. E. Ott, N. C. Privé, O. Reale, D. Achuthavarier, M. G. Bosilovich, V. J. Buchard, W. C. Chao, L. Coy, R. I. Cullather, A. M. Da Silva, A. S. Darmenov, R. M. Errico, M. Fuentes, M.-J. Kim, R. D. Koster, W. R. Mccarty, J. Nattala, G. S. Partyka, S. D. Schubert, G. R. Vernieres, Y. V. Vikhliaev, and K. Wargan. 2015. Evaluation of the 7-km GEOS-5 Nature Run NASA Technical Report Series on Global Modeling and Data Assimilation 36 (NASA/TM-2014-104606):