Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Nawo Eguchi Last modified date:2023.10.05

Associate Professor / Center for Oceanic and Atmospheric Research / Research Institute for Applied Mechanics

1. Kunihiko Kodera,Tomoe Nasuno, Seok-Woo Son, Nawo Eguchi and Yayoi Harada, Influence of the stratospheric QBO on seasonal migration of the convective center across
the Maritime Continent, Journal of the Meteorological Society of Japan, 2023.10.
2. Guangyu Liu, G., Toshihiko Hirooka, Nawo Eguchi and Kirstin Kruger, An Unusual Antarctic Sudden Stratospheric Warming in September 2019, Atmospheric Chemistry and Physics,, 2022.03, [URL].
3. Kodera, Kunihiko, Nawo Eguchi, Rei Ueyama, Beatriz M. Funatsu, Marco Gaetani, and Chris Taylor, The impact of tropical tropopause cooling on Sahelian extreme deep convection, Journal of Meteorological Society Japan,, 99, 4, 2021.08.
4. Kunihiko Kodera, Nawo Eguchi, Rei Ueyama, Yuhji Kuroda, Chiaki Kobayashi, Beatriz Miky Funatsu,and Chantal Claud,, Implication of tropical lower stratospheric cooling in recent trends in tropical circulation and deep convective activity, Atmospheric Chemistry and Physics, 10.5194/acp-19-2655-2019, 19, 4, 2665-2669, 2019.02.
5. Nawo Eguchi and Yukio Yoshida, A high-level cloud detection method utilizing the GOSAT TANSO-FTS water vapor saturated band, Atmospheric Measurement Technique, 10.5194/amt-12-389-2019, 12, 1, 389-403, 2019.01.
6. Kunihiko Kodera, Nawo Eguchi, Hitoshi Mukougawa, Tomoe Nasuno, and Toshihiko Hirooka, Stratospheric tropical warming event and its impact on the polar and tropical troposphere, Atmospheric Chemistry and Physics, 10.5194/acp-17-615-2017, 17, 1, 615-625, 2017.01.
7. Nawo Eguchi, Kunihiko Kodera, Beatriz M. Funatsu, Hisahiro Takashima, and Rei Ueyama, Rapid convective transport of tropospheric air into the tropical lower stratosphere during the 2010 sudden stratospheric warming, Scientific Online Letters on the Atmosphere, 10.2151/sola.12A-003, 12A, Special Edition, 13-17, 2016.08.
8. Kunihiko Kodera, Beatriz M. Funatsu, Chantal Claud, and Nawo Eguchi, The role of convective overshooting clouds in tropical stratosphere–troposphere dynamical coupling, Atmospheric Chemistry and Physics, 10.5194/acp-15-6767-2015, 15, 12, 6767-6774, 2015.06.
9. Nawo Eguchi, Kunihiko Kodera, and Tomoe Nasuno, A global non-hydrostatic model study of a downward coupling through the tropical tropopause layer during a stratospheric sudden warming, Atmospheric Chemistry and Physics, 10.5194/acp-15-297-2015, 15, 1, 297-304, 2015.01.
10. Chihiro Iida, Toshihiko Hirooka, and Nawo Eguchi, Circulation changes in the stratosphere and mesosphere during the stratospheric sudden warming event in January 2009, Journal of Geophysical Research-Atmospheres, 10.1002/2013JD021252, 119, D12, 7104-7115, 2014.06, [URL].
11. Nawo Eguchi, Tadahiro Hayasaka, and Masahiro Sawada, Maritime-Continental Contrasts in the Properties of Low-Level Clouds: A Case Study of the Summer of the 2003 Yamase, Japan, Cloud Event, Advances in Meteorology, 10.1155/2014/548091, 2014, 548091, 1-16, 2014.03.
12. Sergey Oshchepkov, Andrey Bril, Tatsuya Yokota, Isamu Morino, Yukio Yoshida, Tsuneo Matsunaga, Dmitry Belikov, Debra Wunch, Paul Wennberg, Geoffrey Toon, Christopher O'Dell, André Butz, Sandrine Guerlet, Austin Cogan, Hartmut Boesch, Nawo Eguchi, Nicholas Deutscher, David Griffith, Ronald Macatangay, Justus Notholt, Ralf Sussmann, Markus Rettinger, Vanessa Sherlock, John Robinson, Esko Kyrö, Pauli Heikkinen, Dietrich G. Feist, Tomoo Nagahama, Nikolay Kadygrov, Shamil Maksyutov, Osamu Uchino, and Hiroshi Watanabe, Effects of atmospheric light scattering on spectroscopic observations of greenhouse gases from space: Validation of PPDF-based CO2 retrievals from GOSAT, Journal of Geophysical Research Atmosphere, 10.1029/2012JD017505, 117, 12, D12305 1-18, 2012.06, [URL].
13. Nawo Eguchi, YukioYoshida, Isamu Morino, Nobuyuki Kikuchi, Tazu Saeki, Makoto Inoue Osamu Uchino, Shamil Maksyutov, Hiroshi Watanabe, and Tatsuya Yokota, Seasonal variations of greenhouse gas column-averaged dry air mole fractions retrieved from SWIR spectra of GOSAT TANSO-FTS, 2011 IEEE International Geoscience and Remote Sensing Symposium, 10.1109/IGARSS.2011.6049986, 3542-3545, 2011.10.
14. Hiroyuki Oguma, Isamu Morino, Hiroshi Suto, Yukio Yoshida, Nawo Eguchi, Akihiko Kuze, and Yasuhiro Yokota, First Observations of CO2 absorption spectra in 2005 using the airship-born FTS (GOSAT TANSO-FTS BBM) in SWIR spectral region, International Journal of Remote Sensing, 10.1080/01431161.2010.535864, 32, 24, 9033-9049, 2011.10, is article describes the results of a field experiment performed to confirm the feasibility of measuring the solar spectra absorbed by carbon dioxide (CO(2)) using a short wavelength infrared Fourier transform spectrometer (SWIR-FTS) installed onboard an airship. These airship-borne observations, conducted on 7 April 2005, represent the first aircraft-borne spectroscopic experiment on greenhouse gases (GHGs) in Japan and were performed as part of the Greenhouse Gases Observing Satellite (GOSAT) project. To develop and demonstrate an effective retrieval algorithm to derive CO(2) column amounts from spectroscopic observations, ground-surface scattered solar absorption spectra were observed by SWIR-FTS installed onboard the airship. This instrument is a breadboard model (BBM) of the Thermal and Near-infrared Sensor for Carbon Observation (TANSO) of GOSAT, which was successfully launched on 23 January 2009. The spectra of CO(2) observed using the BBM were compared with the simulated spectra calculated by a radiative transfer code based on airship-borne in situ measurement data, which were obtained at the time of FTS measurements. The two sets of spectra are in agreement within 5%, and we identified solutions to several technical problems related to the FTS instrument, thereby improving the signal-to-noise ratio (SNR)..
15. Nawo Eguchi, Tadahiro Hayasaka, and Masahiro Sawada, CHARACTERISTICS OF “YAMASE” CLOUD, 한국기상학회 학술대회 논문집, 178-178, 2011.10.
16. Kunihiko Kodera, Nawo Eguchi, Jae. N. Lee, Yuhji Kuroda and, Seiji Yukimoto, Sudden Changes in the Tropical Stratospheric and Tropospheric circulation during January 2009, Journal of the Meteorological Society of Japan, 10.2151/jmsj.2011-308, 89, 3, 283-290, 2011.06, [URL], In mid-January 2009, sudden changes in circulation occurred in the tropical troposphere and stratosphere. Convective activity situated over the equatorial Maritime Continent showed an abrupt weakening, whereas that over the South American to African sectors became stronger. Changes also occurred in the latitudinal structure; convective activity in the Northern Hemisphere became weaker, whereas that in the Southern Hemisphere became stronger. The change in convective activity took place in association with a change in tropical circulation, from east west to north south type (i.e., from Walker- to Hadley-type circulation). Almost simultaneously with these events in the troposphere, a change in meridional circulation occurred in the stratosphere during a record-breaking stratospheric sudden warming event in January 2009. Stratospheric tropical temperature showed a decrease in response to a strengthening of the hemispherical meridional circulation. In the present study, we show how the stratospheric and tropospheric circulation changes are dynamically coupled..
17. Yukio Yoshida, Yoshifumi Ota, Nawo Eguchi, Nobuyuki Kikuchi, Koji Nobuta, Ha Tran, Isamu Morino, and Tatsuya Yokota, Retrieval algorithm for CO2 and CH4 column abundances from short-wavelength infrared spectral observations by the Greenhouse gases observing satellite, Atmospheric Measurement Technique, 10.5194/amt-4-717-2011, 4, 4, 717-734, 2011.04.
18. Nawo Eguchi and Kunihiko Kodera, Impacts of stratospheric sudden warming event on tropical clouds and moisture fields in the TTL : A case study, scientific online letters on the atmosphere, 10.2151/sola.2010-035, 6, 1, 137-140, 2010.10, The impact of stratospheric sudden warming event in September 2007 on the tropics was investigated based on satellite data (CALIOP, MLS and TRMM PR). Equatorial temperature and water vapor at 100 hPa decreased by about 1 K and 1 ppmv within 10 days, respectively. Changes in tropical clouds are observed together with the occurrence of the SSW as i) frequent formation of higher-level cirrus clouds over the Maritime Continent, to where water vapor was transported from Asian Monsoon and where the lowest temperature occurred, ii) intensification of deep convective activity in the TTL over African continent, and iii) southward shift of the convective clouds over South American continent..
19. Hisahiro Takashima, Nawo Eguchi, and William Read, A short-duration cooling event around the tropical tropopause and its effect on water vapor, Geophysical Research Letters, 10.1029/2010GL044505, 37, 20, L20804 1-4, 2010.10, For the 2008/2009 winter, extremely low temperatures near the tropical tropopause (similar to 83 hPa) were observed at the beginning of February 2009 by COSMIC over the western Pacific and over eastern Pacific-South America in association with a wave response to the tropical heat source. At the same time, the water vapor field at 83 hPa detected from Aura MLS recorded a minimum, with a higher frequency of cirrus cloud observed by CALIOP. Although the temperature minima rapidly disappeared after the event, one possible interpretation is that the low water-vapor concentration remained at this level and spread gradually over the entire tropics, finally impacting on the cold phase of the atmospheric tape recorder. However, further study is required to establish a link between the large-scale reduction in water vapor and the dehydration that occurred during the cold event in early February..
20. Nawo Eguchi, Ryu Saito, Tazu Saeki, Yumiko Nakatsuka, Dmitry Belikov, and Shamil Maksyutov, A priori covariance estimation for CO2 and CH4 retrievals, Journal of Geophysical Research-Atmosphere, 10.1029/2009JD013269, 115, D10, D10215 1-16, 2010.05, We derive the a priori covariance matrices of CO2 and CH4 for the retrieval of their profiles and columns from satellite spectral data. The monthly a priori covariance matrices of CO2 and CH4 at each grid cell (0.5° × 0.5°) on the globe are calculated using simulated data from the atmospheric tracer transport model. The a priori covariance matrix is defined as the sum of the bias and noise components, where the bias is obtained from the difference in seasonal cycle between simulated data and observation-based reference data, and the noise is defined as synoptic and interannual variations. The use of simulated data as well as observation-based reference data enables realistic variance and covariance values to be obtained for each temporal component. The seasonal bias is approximately 2 ppm for CO2 and 20 ppb for CH4. A large difference in synoptic variations is obtained between simulated and reference data over the source region, especially over land. The interannual variances derived from the reference data show maximum values (4 ppm2 for CO2 and 220 ppb2 for CH4) in northern midlatitudes. Global data sets of a priori covariance matrices for CO2 and CH4 are now available for the retrieval of concentrations using satellite spectral data. Furthermore, the data set has the potential to be applied in studies in other fields, including estimates of CO2 flux error using inverse modeling and planning for ground-based observation networks..
21. Nikolay Kadygrov, Shamil Maksyutov, Nawo Eguchi, Tadao Aoki, Takakiyo Nakazawa, Tatsuya Yokota and Gen Inoue, Role of simulated GOSAT total column CO2 observations in surface CO2 flux uncertainty reduction, Journal of Geophysical Research-Atmosphere, 10.1029/2008JD011597, 114, D21, D21208 1-12, 2009.11, We investigated the utility of Greenhouse Gases Observing Satellite (GOSAT) column CO(2) observations in surface CO(2) flux estimation. We addressed two key issues in carbon flux estimation from satellite data: (1) reduction of the CO(2) flux uncertainty and (2) bias in the constrained surface fluxes. Our results showed that GOSAT data with 1.7 ppm precision (monthly mean, land observation only) had the same utility as observational data from the existing surface network. By adding satellite observations with 2.5 ppm single-shot random error and a bias of 1 ppm, it was possible to reduce the mean regional flux uncertainty by approximately 30%. Unbiased data with 2.5 ppm single-shot precision (0.8 ppm for the monthly mean) halved the flux uncertainty. The aerosol-dependent bias in satellite data with 1 ppm mean variance led to significant absolute errors in the surface CO(2) fluxes, highlighting a need for the accurate detection and rejection of biased data..
22. Tatsuya Yokota, Yukio Yoshida, Nawo Eguchi, Yoshifumi Ota, Tomoaki Tanaka, Hiroshi Watanabe and Shamil Maksyutov, Global Concentrations of CO2 and CH4 Retrieved From GOSAT: First Preliminary Results, Scientific Online Letters on the Atmosphere, 10.2151/sola.2009‒041, 5, 1, 160-163, 2009.10, The Greenhouse Gases Observing Satellite (GOSAT) was launched on January 23, 2009, to monitor global atmospheric levels of CO2 and CH4 from space. GOSAT started initial operation of its instruments after an initial satellite system check. Although the radiant data obtained by the GOSAT instruments are currently in the preliminary stages of calibration and validation, the spectral absorption features of CO2 and CH4 are clearly identifiable. An initial retrieval of these gaseous concentrations was performed for measurement scenes of cloud-free conditions over land. These results showed that column-averaged dry air mole fractions of both CO2 and CH4 in the northern hemisphere were higher than those in the southern hemisphere. These latitudinal differences agree with data obtained from groundbased sources and other satellite observations; however, the absolute values of the gaseous concentrations from GOSAT data seem to have been underestimated. Calibrations as well as validation should be conducted to improve the quality of GOSAT retrievals..
23. Nawo Eguchi and Tatsuya Yokota, Investigation of clear-sky occurrence rate estimated from CALIOP and MODIS observations, Geophysical Research Letters, 10.1029/2008GL035897, 35, 23,  L23816 1-5, 2008.12, We derived the global distribution of the clear-sky occurrence rate during the daytime using Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and Moderate-resolution Imaging Spectrometer (MODIS) data. Our goal was to estimate the frequency of likely successful CO(2) and CH(4) column concentration retrievals by the Greenhouse gases Observing Satellite (GOSAT). Clear-sky regions over land were frequently found around desert regions throughout the year, and at northern mid-latitudes in the winter hemisphere. Overall, clear-sky regions covered approximately 11% of the globe annually, on average. From a comparison of the CALIOP and MODIS cloud data for June 2007, we found that MODIS overestimated the clear-sky ratio by approximately 5%, except for in the tropics..
24. Hiroshi Watanabe, Hironari Ishihara,Kenji Hayashi, Fumie Kawazoe, Nobuyuki Kikuchi, Nawo Eguchi, Tsuneo Matsunaga, and Tatsuya Yokota, Detailed design of the GOSAT DHF at NIES and data acquisition/processing/ distribution strategy, Sensors, Systems, and Next-Generation Satellites XII, 10.1117/12.801238, 7106, 71060N, 2008.10.
25. Nawo Eguchi, Tatsuya Yokota, and Gen Inoue, Characteristics of cirrus clouds from the ICESat/GLAS observations, Geophysical Research Letters, 10.1029/2007GL029529, 34, 9, L09810 1-6, 2007.05, [URL], Cloud observations from the Geoscience Laser Altimeter System (GLAS) revealed characteristics of cirrus clouds in boreal autumn 2003. The vertical distribution of the central altitude of cirrus peaks 2 km below the climatological tropopause, which is 14.5 km in the tropics and 9.5 km in the northern midlatitudes. The mean location of the peak in deep convection is north of the Equator (7.5 degrees N) but the top of zonally averaged cirrus is almost constant at 14.5 km in the tropics. This suggests that the height of tropical cirrus is closely linked to anvil cirrus from deep convection and lower temperatures in the tropopause symmetric with respect to the Equator. Cirrus clouds in the midlatitudes have a greater optical depth than those at other latitudes. The zonally averaged thickness of cirrus is about 1.6 km regardless of latitude..
26. Nawo Eguchi and Kunihiko Kodera, Impact of the 2002, Southern Hemisphere, stratospheric warming on the tropical cirrus clouds and convective activity, Geophysical Research Letters, 10.1029/2006GL028744, 34, 5, L05819 1-5, 2007.03, Tropical cirrus cloud variation associated with the southern hemisphere stratospheric sudden warming (SSW) in September 2002 was investigated using data from MODIS/Terra. During the SSW, enhanced wave forcings induced upwelling in the tropical stratosphere, which further extended into the equatorial troposphere. This initial perturbation of the tropospheric upwelling developed in the southern tropical troposphere through increased mass- and water vapor convergence in the lower level leading to deep convection. Cirrus cloud was first formed by the low temperature due to upwelling associated with the SSW, and it persisted for a few weeks after the end of SSW due to the low temperature associated with the Kelvin-wave response to a deep convection triggered by the SSW..
27. Nawo Eguchi and Masato Shiotani, Intraseasonal variations of water vapor and cirrus clouds in the tropical upper troposphere, Journal of Geophysical Research-Atmosphere, 10.1029/2003JD004314, 109, D12, D12106 1-11, 2004.06, Space-time variations of tropical upper tropospheric water vapor and cirrus clouds associated with the intraseasonal oscillation (ISO) are investigated using data from the Microwave Limb Sounder (MLS) and the Cryogenic Limb Array Etalon Spectrometer (CLAES) on board the Upper Atmosphere Research Satellite (UARS). Composite moisture and meteorological fields based on five ISO events selected in two boreal winters (1991–1993) are analyzed using 20–80 day band-pass-filtered data. At 215 and 146 hPa, wet anomalies with frequent appearance of cirrus clouds exist over the convective system and move eastward from the Indian Ocean to the central Pacific, suggesting a direct effect of convective activity up to this level. At 100 hPa, however, the moisture field seems to be indirectly affected by convective activity through the dynamical response to the convective heating. Dry anomalies are observed over the Indian Ocean around the developing stage and over the eastern Pacific around the mature-to-decaying stage of the ISO. Cirrus clouds are frequently found over the cold region located to the east of the convective system. These structures around the tropopause level are closely related to the eastward moving Kelvin and Rossby wave responses to the convective heating with the equatorial cold anomaly and with the subtropical anticyclonic gyres. Between the two gyres the easterly wind blowing through the equatorial cold region may cause dehydration through cirrus formation when the convective system develops over the Indian Ocean and the western Pacific. As the northern gyre intensifies, tropical dry air is transported to the subtropical Pacific and eventually to the equatorial eastern Pacific. It is suggested that the temperature and flow variations due to the coupled Kelvin-Rossby wave structure play an important role in dehydrating air in the tropical and subtropical tropopause region..