12 results on '"OKUYAMA, Arata"'
Search Results
2. Examination of all‐sky infrared radiance simulation of Himawari‐8 for global data assimilation and model verification.
- Author
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Okamoto, Kozo, Hayashi, Masahiro, Hashino, Tempei, Nakagawa, Masayuki, and Okuyama, Arata
- Subjects
DIURNAL cloud variations ,RADIANCE ,DATA modeling ,WEATHER forecasting ,RADIATIVE transfer ,QUALITY control ,KALMAN filtering - Abstract
The systematic difference between observations and simulation from weather forecast model hampers effective data assimilation and model improvement. The purpose of this study is to identify the characteristics and cause of the systematic difference or observation‐minus‐background (O − B) bias for all‐sky infrared radiances of the Himawari‐8 satellite, and propose data assimilation preprocessings and model verification. The O − B bias in cloudy scenes showed substantial negative values because of the shortage of high‐altitude clouds generated in the forecast model. Additionally, a positive bias appeared for thin ice clouds because of the excessive absorption of radiative transfer models (RTMs). These biases were traced based on a bottom‐up approach investigating individual uncertainty of RTMs, observation calibration, and the forecast model using two RTMs, reference hyperspectral sounders and synergetic measurements of CloudSat and CALIPSO. Based on these findings, data assimilation preprocessing such as quality‐control procedures excluding samples that models poorly reproduced was developed. Although the quality controls reduced the number of biased samples, non‐negligible O − B biases remained. Possible problems and treatments for the biases were discussed, including bias correction, observation error inflation, and correction of the cloud effect parameter. The O–B statistics also suggested insufficient representation of the diurnal variation in the cloud fraction in the tropics. Modified physical processes in the forecast model to increase ice clouds were tested to help improve the model bias and develop data assimilation. This trial indicated the difficulty in improving both O − B bias and variance and the necessity of adjusting the cloud effect parameters in data assimilation. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
3. Estimation of radiation budget using geostationary satellites
- Author
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TAKENAKA, Hideaki, YAMAMOTO, Munehisa K., HAYASAKI, Masamitu, HIGUCHI, Atsushi, SAITOH, Naoko, KUZE, Hiroaki, NISHIO, Fumihiko, TAKAMURA, Tamio, FUKUDA, Satoru, NAKAJIMA, Teruyuki, OKUYAMA, Arata, KOSAKA, Yuki, NAKAYAMA, Ryuichiro, OWADA, Hiromi, DATE, Kenji, and ONO, Tomoaki
- Abstract
[ABSTRACT]SW radiation budget is estimated using geostationary satellites (GMS-5, GOES-8, GOES-10, METOSAT-5, METEOSAT-7). Each satellite data are calibrated, and optics properties of the cloud are retrieved. An accurate calibrated data propose the better accuracy for analysis of cloud and radiation budget. In this study, cloud and SW radiation budget analysis are done by CAPCOM algorithm and EXAM SYSTEM. On the other hand, aerosol optical thickness is retrieved by L-REAP algorithm. We discuss the possibility of aerosol-cloud-radiation interaction in north Pacific ocean and north Atlantic ocean.
- Published
- 2010
4. Estimation of Radiation budget using Geostationary Satellites Formation of a virtual laboratory for diagnosing the Earth's climate system
- Author
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TAKENAKA, Hideaki, YAMAMOTO, Munehisa K., HAYASAKI, Masamitsu, HIGUCHI, Atsushi, NISHIO, Fumihiko, KUZE, Hiroaki, TAKAMURA, Tamio, OKUYAMA, Arata, KOSAKA, Yuki, NAKAYAMA, Ryuichiro, OWADA, Hiromi, DATE, Kenji, and ONO, Tomoaki
- Abstract
[ABSTRACT]In this study, we develop a vicarious calibration technique and estimation algorithm of radiation budget for the global analysis. The vicarious calibration technique using three components ( clear sky sea surface, clear sky land surface, uniform cloud top) is applied to the geostationary satellites. This vicarious calibration technique is based on radiative transfer calculations and it has each optical properties (aerosol, cloud, surface BRDF/albedo) in three compon_~ntsT. he quality of three geostationary satellites (GMS-5, GOES-10, GOES-8) visible channel fixed accurately for global analysis. An accurate calibrated data set propose the better accuracy for analysis of cloud and radiation budget. Thus, cloud and radiation budget analysis algorithm are applied to new calibrated data set for global analysis. This is first result of trial for global analysis.
- Published
- 2009
5. Geostationary lmager Visible Recalibration
- Author
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OKUYAMA, Arata, HASHIMOTO, Toru, NAKAYAMA, Ryuichiro, TAHARA, Yoshihiko, KURINO, Toshiyuki, TAKENAKA, Hideaki, FUKUDA, Satoru, NAKAJIMA, Takashi Y., HIGURASHI, Akiko, SEKIGUCHI, Miho, TAKAMURA, Tamio, and NAKAJIMA, Teruyuki
- Abstract
[ABSTRACT]The re-construction of the GMS-5 visible channel calibration table is examined. It is based on the comparison of satellite observation with reference. To obtain the reference, satellite radiance is simulated over various reference targets of clear sea area, clear land area and cloud top as dark, medium and bright references, respectively. Parameters necessary to compute the radiance are prepared independently from GMS-5 observations. The recalibrated visible table improves the GMS-5 data. That is confirmed from the improvement of aerosol and cloud products retrieved from the GMS-5 data.
- Published
- 2008
6. Geostationary Satellite Re-Analysis -Estimation of radiation budget
- Author
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TAKENAKA, Hideaki, FUKUDA, Satoru, OKUYAMA, Arata, HASHIMOTO, Toru, NAKAYAMA, Ryuichiro, TAHARA, Yoshihiko, NAKAJIMA, Takashi Y., HIGURASHI, Akiko, SEKIGUCHI, Miho, TAKAMURA, Tamio, and NAKAJIMA, Teruyuki
- Abstract
[ABSTRACT]In this study, we analyze Refined -Visible and Infrared Spin-Scan Radiometer (R-VISSR) data set. An accurate calibrated data propose the better accuracy for analysis of cloud and radiation budget. Therefore, in Asian Atmospheric Particle Environmental Change Studies (APEX) -E2 period, diffuse component and aerosol optical thickness showed the pattern that looked like well. Thus, analysis of 12 months of 2001 was executed that the results indicate a feature trend of the direct and the diffuse component of downward solar radiation from East Asia to North Pacific Ocean. Moreover, contrast is clear between East Asia and South side of Australia in direct and diffuse components.
- Published
- 2008
7. MTSAT-1R Infrared Infrared lntercalibration on GSICS
- Author
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TAHARA, Yoshihiko, KATO, Koji, OKUYAMA, Arata, NAKAYAMA, Ryuichiro, KURINO, Toshiyuki, TAKENAKA, Hideaki, and SEKIGUCHI, Miho
- Abstract
[ABSTRACT]MTSAT-1R infrared intercalibration with the hyper sounder AIRS and IASI is operated at MSC. Comparison methodology is on the basis of algorithm determined in GSICS, one of the components of WMO. To match-up data of two sensors, observation time difference, satellite zenith angle difference and environment uniformity are checked. To adjust spectral response difference, a super channel is generated from hyper sounder to have the same SRF as a MTSAT-1R infrared channel. In case that there are spectral gaps or failed channels in hyper sounder, their radiances are estimated with good accuracy by using observations and beforehand simulated radiances of hyper sounder. The intercalibration is examined once a day, and results are posted on the MSC webpage (http ://mscweb.kishou.go.jp/ monitoring/calibration.htm).
- Published
- 2008
8. MTSAT-1R Visible Imager Point Spread Correction Function, Part I: The Need for, Validation of, and Calibration With.
- Author
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Doelling, David R., Khlopenkov, Konstantin V., Okuyama, Arata, Haney, Conor O., Gopalan, Arun, Scarino, Benjamin R., Nordeen, Michele, Bhatt, Rajandra, and Avey, Lance
- Subjects
REMOTE sensing by radar ,SPECTRORADIOMETER ,IMAGING systems ,NOISE measurement ,ALGORITHM research - Abstract
The multifunctional transport satellite (MTSAT)-1R imager was launched in 2005 and is operated by the Japan Meteorological Agency (JMA). A nonlinear behavior in the MTSAT-1R visible sensor response is observed when the instrument is intercalibrated with coincident moderate resolution imaging spectroradiometer (MODIS) ray-matched radiances. Analysis reveals that the nonlinear behavior is not a result of imager navigation, sensor spectral response difference, nor scan pattern. Examination of coincident MTSAT-1R and MTSAT-2 images reveals that MTSAT-1R dark ocean radiances are affected by neighboring bright clouds, whereas large regions of dark ocean radiances are not impacted. Although the IR and visible optical paths are shared, the MTSAT-1R brightness temperatures are not affected. A dust contaminant coating the mirror, which only affects certain wavelengths, may be one explanation. To address the nonlinearity, a pixel point spread function (PSF) correction algorithm is implemented, wherein most of the radiance contribution is from the pixel field of view itself, as well as including a small contribution from all pixels within a radii of several hundred kilometers. The application of the PSF-corrected ~80% of the affected pixel radiances. After application, a near linear response is observed between the coincident MTSAT-1R and Aqua-MODIS ray-matched radiances, and the intercept is now near the predicted space count of zero. The monthly calibration gain noise is reduced by one-third when compared with the non-PSF-corrected gains. The monthly gains are the most erratic during the first two years of operation, and the MTSAT-1R visible sensor is degrading at ~1.9 % decade. [ABSTRACT FROM PUBLISHER]
- Published
- 2015
- Full Text
- View/download PDF
9. MTSAT-1R Visible Imager Point Spread Function Correction, Part II: Theory.
- Author
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Khlopenkov, Konstantin V., Doelling, David R., and Okuyama, Arata
- Subjects
IMAGE processing ,REMOTE-sensing images ,SPATIAL data structures ,IMAGE reconstruction algorithms ,IMAGING systems - Abstract
An image processing methodology is presented to recover the quality of the Multifunctional Transport Satellite (MTSAT)-1R visible channel data affected by spatial crosstalk. The slight blurring of the visible optical path is attributed to an imperfection in the mirror surface caused either by flawed polishing or a dust contaminant. The methodology assumes that the dispersed portion of the signal is small and distributed randomly around the optical axis, which allows the image to be deconvolved using an inverted point spread function (PSF). The PSF is described by four parameters, which are solved using a maximum-likelihood estimator using coincident collocated MTSAT-2 images as truth. A subpixel image matching technique is used to align the MTSAT-2 pixels into the MTSAT-1R projection and to correct for navigation errors and cloud displacement due to the time and viewing geometry differences between the two satellite observations. An optimal set of the PSF parameters is derived by an iterative routine based on the 4-D Powell's conjugate direction method that minimizes the difference between the PSF-corrected MTSAT-1R and the collocated MTSAT-2 images. The PSF parameters were found to be consistent over the 5 days of available daytime coincident and MTSAT-1R and MTSAT-2 images. After applying the PSF parameters, the visible sensor response is nearly linear, and the space count is close to zero. The overall linear regression standard error was reduced by 52%. Users can easily apply the PSF parameter coefficients to the MTSAT-1R imager pixel level counts to restore the original quality of the entire MTSAT-1R record. [ABSTRACT FROM PUBLISHER]
- Published
- 2015
- Full Text
- View/download PDF
10. Fractal Transition: Hierarchical Structure and Noise Effect.
- Author
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Gohara, Kazutoshi and Okuyama, Arata
- Subjects
- *
FRACTALS , *DYNAMICS - Abstract
A Sierpinski gasket with continuous trajectories is presented as an example of the fractal transition that characterizes the behavior of dissipative dynamical systems excited by external temporal inputs. Using this example, we investigate the fractal transition from two points of views, i.e. a hierarchical structure and a noise effect. Depending on internal and external parameters, the structure can be geometrically classified as one of three types, i.e. totally disconnected, just-touching, and overlapping. For the totally disconnected structure, continuous trajectories and their starting points can be characterized by a definite hierarchical tree structure. Even for the just-touching and overlapping structure, a similar hierarchy exists. White noise contaminating the external inputs breaks the hierarchy. In particular, small clustered structures are sensitive to the noise. In such a case, the difference between trajectories and starting points is remarkable in the hierarchy. [ABSTRACT FROM AUTHOR]
- Published
- 1999
- Full Text
- View/download PDF
11. Dynamical Systems Excited by Temporal Inputs: Fractal Transition between Excited Attractors.
- Author
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Gohara, Kazutoshi and Okuyama, Arata
- Subjects
- *
DIFFERENTIABLE dynamical systems , *ATTRACTORS (Mathematics) , *ITERATIVE methods (Mathematics) - Abstract
This paper presents a framework for dissipative dynamical systems excited by external temporal inputs. We introduce a set {I[sub l]} of temporal inputs with finite intervals. The set {I[sub l]} defines two other sets of dynamical systems. The first is the set of continuous dynamical systems that are defined by a set {f[sub l]} of vector fields on the hyper-cylindrical phase space M. The second is the set of discrete dynamical systems that are defined by a set {g[sub l]} of iterated functions on the global Poincaré section Σ. When the inputs are switched stochastically, a trajectory in the space M converges to an attractive invariant set with fractal-like structure. We can analytically prove this result when all of the iterated functions satisfy a contraction property. Even without this property, we can numerically show that an attractive invariant set with fractal-like structure exists. [ABSTRACT FROM AUTHOR]
- Published
- 1999
- Full Text
- View/download PDF
12. Intercalibration of the Advanced Microwave Scanning Radiometer-2 (AMSR2) level-1B dataset.
- Author
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Okuyama, Arata and Imaoka, Keiji
- Published
- 2014
- Full Text
- View/download PDF
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