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Hajime Okamoto Last modified date:2022.11.11

Graduate School
Other Organization
Administration Post
Director of the Research Institute for Applied Mechanics

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Main topics of atmospheric physics group are aerosol, clouds, precipitation related physics. .
Academic Degree
Dr. of science
Country of degree conferring institution (Overseas)
Field of Specialization
Satellite remote sensing, cloud physics, aerosols, atmospheric physics, light scattering
Outline Activities
I focus on remote sensing of clouds and aerosols, atmospheric radiation and water cycle in the climate system. We develop algorithms for global analyses of clouds and aerosols. Observational tools include cloud profiling radar and lidar onboard satellite for better understanding of global energy and water cycle. We also play an active role in international satellite missions and also planning new satellite missions.
This group conducts the following researches;
(1) Analyses of cloud macroscale and microphysical properties from satellite remote sensing.
(2) Analyses of radiative properties of aerosols from lidar.
(3) Evaluation of numerical models.
(4) Light scattering by non-spherical particles
(5) Multiple scattering process of cloud particles for liar and radar remote sensing
(6) Development of algorithms for JAXA-ESA mission EarthCARE.
(7) Defining future satellite missions.
Research Interests
  • JAXA-EarthCARE mission project scientist.
    keyword : satellite, EarthCARE, cloud radar, Doppler, lidar、cloud, aerosol, radiation budget, water budget, climate change
  • co-chair of Japan-EU EarthCARE mission since July 2013.
    keyword : EarthCARE mission, Earth Observing Satellite
  • (1) Analyses of cloud macroscale and microphysical properties from satellite remote sensing.
    (2) Analyses of radiative properties of aerosols from lidar.
    (3) Light scattering by non-spherical particles
    (4) Multipel scattering due to cloud particles in radar and lidar remote sensing
    keyword : Clouds, aerosols, remote sensing, light scattering
Academic Activities
1. Sato Kaori, Okamoto Hajime, Takemura Toshihiko, Kumagai Hiroshi, Sugimoto Nobuo, Characterization of ice cloud properties obtained by shipborne radar/lidar over the tropical western Pacific Ocean for evaluation of an atmospheric general circulation model, J. Geophys. Res., 10.1029/2009JD012944, 115, 2010.08.
2. 萩原 雄一朗, Okamoto Hajime, Yoshida Ryo, Development of a combined CloudSat-CALIPSO cloud mask to show global cloud distribution, J. Geophys. Res., 10.1029/2009JD012344, 115, 2010.09, [URL].
3. Sato Kaori, Okamoto Hajime, Yamamoto, M. K., Fukao S., Kumagai Hiroshi, Ohno Yuichi, Horie Hiroaki, Abo M., 95-GHz Doppler radar and lidar synergy for simultaneous ice microphysics and in-cloud vertical air motion retrieval, J. Geophys. Res., doi:10.1029/2008JD010222, 114, D03203, doi:10.1029/2008JD010222, 2009 , 2009.02.
4. Okamoto, H., T. Nishizawa, T. Takemura, K. Sato, H. Kumagai, Y. Ohno, N. Sugimoto, A. Shimizu, I. Matsui, and T. Nakajima, Vertical cloud properties in the tropical western Pacific Ocean: Validation of the CCSR/NIES/FRCGC GCM by shipborne radar and lidar, J. Geophys. Res., doi:10.1029/2008JD009812, 113, D24213, doi:10.1029/2008JD009812, 2008. , 2008.10.
5. Nishizawa, T., H. Okamoto, T. Takemura, N. Sugimoto, I. Matsui, and A. Shimizu, Aerosol retrieval from two-wavelength backscatter and one-wavelength polarization lidar measurement taken during the MR01K02 cruise of the R/V Mirai and evaluation of a global aerosol transport model,, J. Geophys. Res., doi:10.1029/2007JD009640,, 113, D21201, doi:10.1029/2007JD009640, 2008. , 2008.10.
6. S. Iwasaki, Y. Tsushima, R. Shirooka, R. Katsumata, K. Yoneyama, I. Matsui, A. Shimizu, N. Sugimoto, A. Kamei, H. Kuroiwa, H. Kumagai, Okamoto Hajime, Subvisual cirrus cloud observations using a 1064-nm lidar, a 95 GHz cloud radar, and radiosondes in the warm pool region, Geophys. Res. Lett., 10.1029/2003GL019377, 31, 9, 31, L09103, doi: 10.1029/2003GL019377, 2004. , 2004.05.
7. Okamoto Hajime, An algorithm for retrieval of cloud microphysics using 95-GHz cloud radar and lidar., J. Geophys. Res., doi:10.1029/2001JD0001225, 108(D7, 4226), doi:10.1029/2001JD0001225, 2003., 2003.10.
8. Okamoto, H, Information content of the 95-GHz cloud radar signals: Theoretical assessment of effects of nonsphericity and error evaluation of the discrete dipole approximation, J. Geophys. Res., 10.1029/2001JD001386, 107, D22, 107 (D22, 4628) , doi: 10.1029/2001JD001386, 2002. , 2002.11.
9. Iwasaki, S., and H. Okamoto, Analysis of the enhancement of backscattering by nonspherical particles with flat surfaces, Appl. Opt.,, 40(33), 6121-6129, 2001., 2001.10.
10. Horie, H., T. Iguchi, H. Hanado, H. Kuroiwa, H. Okamoto and H. Kumagai, Development of A 95-GHz airborne cloud profiling radar (SPIDER) -- Technical aspects --, IEICE Trans. Commun,, E83-B, 2010-2020, 2000. , 2000.10.
11. Murayama, T; Okamoto, H; Kaneyasu, N; Kamataki, H; Miura, K, Application of lidar depolarization measurement in the atmospheric boundary layer: Effects of dust and sea-salt particles, J. Geophys. Res., 104, D24, 31781-31792, 104, 31781-31792, 1999., 1999.12.
12. Okamoto, H; Xu, YL, Light scattering by irregular interplanetary dust particles, Earth, Planets and Space, 50, 6-7, 577-585, 1998.01.
13. Lemke, H., H. Okamoto, and M. Quante, Comments on error analysis of backscatter from discrete dipole approximation for different ice particle shapes, Atmos. Res., 49, 189-197, 1998., 1998.10.
14. Okamoto, H., A.Macke, M.Quante, E.Raschke, Modeling of backscattering by non-spherical ice particles for the interpretation of cloud radar signals at 94GHz., Contr. Atmos. Phys., 68, 319-334, 1995. , 1995.10.
15. Okamoto, H., Light scattering by clusters : the a1-term method, Optical Review, 2, 407-412, 1995., 1995.10.
1. Okamoto, Hajime, EarthCARE mission : move the global models to next levels, 7th JAPAN-EU workshop (第7回日EU気候変動研究ワークショップ), 2016.04.
2. Okamoto, Hajime, Sato Kaori, Takano, Toshiaki, Nishizawa,Tomoaki, Sugimoto, Nobuo, Jin, Yoshitaka, Development of multiple scattering polarization lidar to observe depolarization ratio of optically thick low- level clouds
, IRS2016, 2016.04.
3. Okamoto, Hajime, Sato Kaori, Hagihara, YuichiroYuichiro, Ishimoto, Hiroshi, Relationship between ice supersaturation and ice microphysics inferred from CloudSat, CALIPSO and AIRS
, IRS 2016, 2016.04.
4. Okamoto, Hajime, Sato Kaori, Ishimoto, H., Hagihara, Y., Global analysis of generation mechanism of ice microphysics inferred from space-borne active sensors and infrared sounder, AGU fall meeting , 2015.12.
5. Okamoto, Hajime, Sato Kaori, Hagihara, Y., Ishimoto, H., Borovoi, A., Konoshonkin, A., Kusutoba, N., Evaluation of retrieval algorithms for ice microphysics using CALIPSO/CloudSat and EarthCARE, 27th International Laser Radar Conference, 2015.07.
6. Okamoto, Hajime, Sato Kaori, Makino, T., Nishizawa, T., Jin, Y., Sugimoto, N., Shimizu, A., Depolarization ratio of clouds measured by multiple-field of view multiple scattering polarization lidar, 27th International Laser Radar Conference, 2015.07.
7. Okamoto, Hajime, Sato Kaori, Ishimoto, Hiroshi, Tanaka, Kenta, Global analysis of ice microphysics and ice super-saturation from CloudSat, CALIPSO and AIRS, 26th IUGG General Assembly, 2015.06.
8. Okamoto, Hajime, Development of level 2 algorithms for CPR, CPR-ATLID and CPR-ATLID-MSI, Joint PI meeting of Global Environment Observation Mission 2014, 2015.01.
9. Okamoto, Hajime, Sato, K., Hagihara, Yuichiro, Tanaka, Kenta, Ishimoto, Hiroshi, Makino, Toshiyuki, Nishizawa, Tomoaki, Sugimoto, Nobuo, Evaluation of ice cloud retrievals using CloudSat/CALIPSO/MODIS/AIRS and EarthCARE, AGU Fall Meeting, 2014.12.
10. Okamoto, Hajime, Satellite remote sensing of cloud properties and generation mechanism, GRENE-AWI workshop on Atmospheric Research 2014, 2014.10.
11. Okamoto, Hajime, Global analysis of cloud microphysics by space-borne active sensors from A-Train to EarthCARE, Tohoku-DLR Workshop, 2014.10.
12. Okamoto Hajime, EarthCARE science towards understanding nature of clouds, aerosols, radiation and cloud motion, EarthCARE Workshop 2014, 2014.09, すでに軌道上にあるCloudSat衛星、CALIPSO衛星等のA-train衛星群によって解析された結果と、現状の課題、EarthCARE衛星で期待されるプロダクト、そこから期待される新しいサイエンスに関するサマリーを行った。.
13. Okamoto Hajime, JAXA science status 2013-2014, EarthCARE JMAG meeting, 2014.01.
14. 岡本 創, 佐藤 可織, 萩原 雄一朗, Development of level 2 algorithms for CPR, CPR-ATLID, and CPR-ATLID-MSI, Joint PI workshop of environment observation mission 2014, 2014.01.
15. Okamoto Hajime, EarthCARE mission : Development of algorithms, The 3rd International Symposium of Atmospheric Light Scattering and Remote Sensing (ISALSaRS'13), 2013.07, JAXA and ESA joint mission, EarthCARE, will carry the four instruments in the same plat form. Among them, there are two next generation active instruments; 95GHz-Doppler radar (CPR) and 355 nm-high spectral resolution lidar (ATLID) and there are also multispectral imager with seven channels (MSI) and broad band radiometer (BBR). The EarthCARE is expected to start observations in late 2015.
The EarthCARE CPR and ATLID might be regarded as extended version of CloudSat 95GHz radar and CALIPSO lidar, respectively. The CPR has higher sensitivity than CloudSat radar and also has the first Doppler capability in space. The ATLID can provide robust profile of backscattering coefficient by the high spectral resolution mechanism. Due to these new features, more complete picture of clouds and aerosols will be obtained.
The CloudSat and CALIPSO have provided the vertical profiles of clouds and aerosols for more than six years. In order to retrieve detail information of cloud and aerosol microphysics, we have developed series of algorithms, e.g., cloud detection, cloud particle type classification, cloud microphysics, aerosol detection, aerosol types and aerosol extinctions algorithms (Hagihara et al., 2010, Yoshida et all.,2010, Okamoto et al, 2010, Sato and Okamoto 2011. The retrieved products from CloudSat and CALIPSO data have been distributed to many institutes and universities for the validation of the GCM and regional models.
The EarthCARE algorithms are developed using the heritage of the algorithms for the CloudSat and CALIPSO. We first review these algorithms and also demonstrated the retrieved cloud and aerosol products from CloudSat and CALIPSO. Some current limitations in the analyses are also discussed. Then we will show the improved algorithms for the EarthCARE and introduce plans of the new cloud and aerosol products.
Finally we describe new ground-based radar and lidar experiments towards the better understanding of the observed signals obtained from the spaceborne active sensors.
16. Okamoto Hajime, JAXA science status 2013, EarthCARE Joint Mission Advisory Group meeting, 2013.07.
17. Okamoto Hajime, Sato Kaori, Hagihara Yuichiro, CPR-ATLID/CPR-ATLID-MSI products and algorithms, EarthCARE Joint Algorithm Development Endeavor meeting, 2013.07.
18. Okamoto Hajime, Sato Kaori, Hagihara Yuichiro, CPR-only level2a product for EarthCARE, EarthCARE Joint Algorithm Development Endeavor meeting, 2013.07.
19. Okamoto Hajime, Sato Kaori, Hagihara Yuichiro, Ishimoto Hiroshi, Ice particle type and microphysics in high latitudes by spaceborne active sensors : regional characteristic and annual variability , Davos-Atmosphere and Cryosphere Assembly, 2013(DACA-13) , 2013.07, [URL], We examined ice particle types and microphysics in high latitudes by using space-borne active sensors between 2006 and 2012. We developed series of algorithms to retrieve cloud properties by using 95GHz cloud radar on CloudSat and dual-wavelength polarization lidar on CALIPSO. By combining these information, the cloud particle types were classified as three-dimensional ice particles (3D-ice), horizontally oriented ice plates (2D-plate), water and solid and liquid precipitation. The fraction of 2D-plates was larger in high latitude regions than in other regions. Ice microphysics was also studied by combined use of radar reflectivity factor from CloudSat, and lidar backscattering coefficient and depolarization ration from CALIPSO. The vertical and latitudinal distribution of ice particle types and microphysics and their annual variability were also examined. The maximum altitude of clouds is about 10km in high latitudes and that for super cooled water is about 5km. IWC decreased as altitude decreased and zonal mean of the maximum IWC and effective radius were 0.05 g/m^3 and 150µm, respectively. The large particles >100µm were found below 5km in high latitude (>70 degrees north). Land-ocean differences were also noticeable. The IWC was smaller over ocean than over land and ice effective radius was larger over ocean. These properties were further analyzed in relation to temperature and water vapor amount as well as super saturation using ECMWF and AIRS data in order to reveal the formation mechanism of ice particles and its variability. .
20. Okamoto Hajime, Sato Kaori, Hagihara Yuichiro, CPR/CPR-ATLID/CPR-ATLID-MSI products and algorithms, EarthCARE science meeting, 2013.06.
21. Okamoto Hajime, Sato Kaori, 萩原 雄一朗, Development of level 2 algorithms for CPR/CPR-ATLID/CPR-ATLID-MSI, EarthCARE PI workshop, 2013.01.
22. Okamoto Hajime, Sato Kaori, 萩原 雄一朗, Multi-year analysis of ice microphysics derived from CloudSat and CALIPSO, American Geophysical Union fall meeting 2012, 2012.12, We conducted multi-year analyses of ice microphysics using CloudSat and CALIPSO data. Inter-annual variability, land-ocean differences and seasonal changes of ice microphysical properties were reported for the observation periods from 2006 to 2009. CALIPSO changed the laser tilt angle from 0.3 degrees to 3 degrees off nadir direction on November 2007 and the zonal mean properties of backscattering coefficient and depolarization ratio were significantly decreased and increased, respectively, for low altitude after November 2007. This could be explained by the different backscattering behavior of horizontally oriented ice crystals for the different laser tilt angles.
On the other hand, inter-annual variability of zonal mean properties of reflectivity factor observed by CloudSat showed the very similar characteristics during the four years. In addition, the lidar observables were similar when the monthly mean properties were compared for different years before November 2007 and also the same was true for the comparisons after November 2007. These analyses of observables suggested that the inter-annual variability of zonal mean properties of ice microphysics could be considered to be similar. Application of the radar-lidar algorithm showed that the change of the laser tilt angle introduced the large gap between the ice microphysical properties before and after November 2007, if the proper treatment of the oriented ice crystals were not conducted in the retrievals. Global analysis of cloud particle types showed that the frequent occurrence of oriented ice crystals were identified in the temperature range between -10 to -20 degrees C. It is also noted that the significant overestimation of ice water content and significant underestimation of ice effective radius were found if the scattering properties of the horizontally oriented ice particles were not considered. Therefore it is highly demanded that the realistic ice orientation model is implemented in the look up tables used in the retrieval algorithm for CloudSat and CALIPSO.
We have tested several orientation models with various parameters such as Gauss distribution model (Sassen 1980) and Klett type distribution function (Klett 1985) to estimate the look up tables for the laser tilt angles of 0.3 and 3 degrees off nadir. And the best orientation model can be determined by minimizing the inter-annual variability of ice microphysics. The best model showed the inter-annual variability of ice microphysics are about 30% for the retrieved IWC and effective radius and about 60% for mass fraction of oriented ice particles in low altitude regions. And ice microphysics over land tended to be larger than the values over ocean and the differences between over land and ocean were much larger than the uncertainties that attributed to the ice particle orientation. The inter-relationship between IWC and effective radius turned out to be very consistent for different years and also for over land and ocean. The frequency distribution of IWC (and effective radius) was different over land and ocean.
23. Okamoto Hajime, Sato Kaori, 萩原 雄一朗, Synergy level 2b products Japan, EarthCARE JADE meeting, 2012.11.
24. Okamoto Hajime, Teruyuki Nakajima, JAXA science status, EarthCARE Joint Mission Advisory Group meeting , 2012.11.
25. Okamoto Hajime, Sato Kaori, 萩原 雄一朗, Hirakata Maki, CPR level 2a products Japan, EarthCARE JADE meeting, 2012.11.
26. Okamoto Hajime, Sato Kaori, 萩原 雄一朗, Tomoaki Nishizawa, Development of Level 2 Algorithms for EarthCARE CPR/ATLID, International Radiation Symposium 2012, 2012.08, [URL], We develop algorithms that can be applied to EarthCARE Cloud Profiling Radar (CPR) and Atmospheric backscatter LIdar (ATLID) and discuss about the expected products. EarthCARE will carry CPR and ATLID and these combination corresponds to the CloudSat and CALIPSO for the A-train. Due to the similarities between the EarthCARE and the A-train, it will be possible to apply the similar types of algorithms that have been already developed and extensively used for the analyses of the A-train satellites and it is therefore expected to obtain the similar cloud products for the EarthCARE. On the other hand, there are some differences between the EarthCARE and A-train satellites, e.g., the EarthCRAE CPR has better sensitivity compared with the CloudSat. And Doppler capability of the EarthCARE-CPR is a new element and is expected to provide the better constraint for the retrievals of cloud/precipitation microphysics. And the vertical air motion and sedimentation velocity of cloud particles will be inferred. .
27. Okamoto Hajime, Sato Kaori, 萩原 雄一朗, Takuya Matsumoto, Anatoli Borovoi, Retrieved ice microphysics from CALIPSO and CloudSat and horizontally oriented ice plates , 26th International laser radar conference (ILRC), 2012.06, We improved the radar and lidar algorithm that can be applied to CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) data to retrieve ice microphysics. The essential modification is the implementation of distribution of tilt angles of ice plates respect to the horizontal plane. We introduced the Gauss-type and Klett-type distribution functions in the improved version of the algorithm. The backscattering signatures in radar and lidar wavelengths were calculated for the same particle type and orientation by using the discrete dipole approximation and physical optics, respectively.
Introducing the distribution of orientations lead to the large reduction of lidar backscattering coefficient compared with that for perfectly oriented ice plates with same effective radius and mass but larger than that for spheres for the CALIPSO tilt angle of 0.3o.
The effective radius and ice water content were similar between the improved and old algorithms. Mass fraction of oriented crystals to the total IWC became much larger in the improved algorithms when the specular reflection was observed.
28. Okamoto Hajime, Sato Kaori, 萩原 雄一朗, Global Analyses of cloud Properties from CloudSat and CALIPSO and Development of the Level 2 Algorithms for EarthCARE, CloudSat-CALIPSO-EarthCARE joint workshop, 2012.06.
29. , [URL].
Membership in Academic Society
  • American Geophysical Union
  • American Meteorological Society
  • Japan Meteorological Society
Educational Activities
Education in Atmospheric Physics Laboratory, Research Institute for Applied Mechanics
and Department of Earth System Science and Technology, Interdisciplinary graduate school of engineering Sciences, Kyushu University
Other Educational Activities
  • 2014.09, Master course student, Toshiyuki Makino, received Hirono awards in the 32nd laser sensing symposium in September 2014. .
Professional and Outreach Activities
Science team member of CloudSat and CALIPSO satellites
ESA-JAXA mission EarthCARE Joint Mission Advisory Group (JMAG) member
ESA-JAXA mission EarthCARE co-chair.