文献一覧: Kozo Okamoto (著者)

5 0 0 0 OA Assessment of the Potential Impact of a Hyperspectral Infrared Sounder on the Himawari Follow-On Geostationary Satellite

著者: Kozo Okamoto Hiromi Owada Tadashi Fujita Masahiro Kazumori Michiko Otsuka Hiromu Seko Yoshifumi Ota Naotaka Uekiyo Hiroshi Ishimoto Masahiro Hayashi Haruma Ishida Akiyoshi Ando Masaya Takahashi Kotaro Bessho Hironobu Yokota
出版者: Meteorological Society of Japan
雑誌: SOLA (ISSN:13496476)
巻号頁・発行日: vol.16, pp.162-168, 2020 (Released:2020-09-05)
参考文献数: 21
被引用文献数: 14

To discuss the feasibility of the Himawari follow-on program, impacts of a hyperspectral sounder on a geostationary satellite (GeoHSS) is assessed using an observing system simulation experiment. Hypothetical GeoHSS observations are simulated by using an accurate reanalysis dataset for a heavy rainfall event in western Japan in 2018. The global data assimilation experiment demonstrates that the assimilation of clear-sky radiances of the GeoHSS improves the forecasts of the representative meteorological field and slightly reduces the typhoon position error. The regional data assimilation experiment shows that assimilating temperature and relative humidity profiles derived from the GeoHSS improves the heavy rainfall in the Chugoku region of western Japan as a result of enhanced southwesterly moisture flow off the northwestern coast of the Kyushu Island. These results suggest that the GeoHSS provides valuable information on frequently available vertically resolved temperature and humidity and thus improves the forecasts of severe events.

2020-09-15 17:07:25
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2 0 0 0 OA Assessment of the potential impact of a hyperspectral infrared sounder on the Himawari follow-on geostationary satellite

著者: Kozo Okamoto Hiromi Owada Tadashi Fujita Masahiro Kazumori Michiko Otsuka Hiromu Seko Yoshifumi Ota Naotaka Uekiyo Hiroshi Ishimoto Masahiro Hayashi Haruma Ishida Akiyoshi Ando Masaya Takahashi Kotaro Bessho Hironobu Yokota
出版者: Meteorological Society of Japan
雑誌: SOLA (ISSN:13496476)
巻号頁・発行日: pp.2020-028, (Released:2020-07-10)
被引用文献数: 14

2020-07-15 19:57:12
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2 0 0 0 OA Feasibility Study for Future Spaceborne Coherent Doppler Wind Lidar, Part 2: Measurement Simulation Algorithms and Retrieval Error Characterization

著者: Philippe BARON Shoken ISHII Kozo OKAMOTO Kyoka GAMO Kohei MIZUTANI Chikako TAKAHASHI Toshikazu ITABE Toshiki IWASAKI Takuji KUBOTA Takashi MAKI Riko OKI Satoshi OCHIAI Daisuke SAKAIZAWA Masaki SATOH Yohei SATOH Taichu Y. TANAKA Motoaki YASUI
出版者: (公社)日本気象学会
雑誌: 気象集誌. 第2輯 (ISSN:00261165)
巻号頁・発行日: vol.95, no.5, pp.319-342, 2017 (Released:2017-10-04)
参考文献数: 42
被引用文献数: 10

A feasibility study of tropospheric wind measurements using a coherent Doppler lidar aboard a super low altitude satellite is being conducted in Japan. The considered lidar uses a 2.05 μm laser light source of 3.75 W. In order to assess the measurement performances, simulations of wind measurements were conducted. The mission definition is presented in a companion paper (Part 1) while, in this paper, we describe the measurement simulator and characterize the errors on the retrieved line-of-sight (LOS) winds. Winds are retrieved from the Doppler-shift of the noisy backscattered signal with a horizontal resolution of 100 km along the orbit track and a vertical resolution between 0.5 and 2 km. Cloud and wind fields are the pseudo-truth of an Observing System Simulation Experiment while aerosol data are from the Model-of-Aerosol-Species-IN-the-Global-AtmospheRe (MASINGAR) constrained with the pseudo-truth wind. We present the results of the analysis of a full month of data in summer time for a near-polar orbiting satellite and a LOS nadir angle of 35°. Below ≈ 8 km, the ratio of good retrievals is 30-55 % and the median LOS wind error is better than 0.6 m s−1 (1.04 m s−1 for the horizontal wind). In the upper troposphere, the ratio is less than 15 % in the southern hemisphere and high-latitudes. However, the ratio is still 35 % in the northern Tropics and mid-latitudes where ice-clouds frequently occur. The upper-tropospheric median LOS-wind measurement error is between 1-2 m s−1 depending on the latitude (1.74-3.5 m s−1 for the horizontal wind). These errors are dominated by uncertainties induced by spatial atmospheric inhomogeneities.

2017-10-06 09:34:29
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2 0 0 0 OA Feasibility Study for Future Space-Borne Coherent Doppler Wind Lidar, Part 1: Instrumental Overview for Global Wind Profile Observation

著者: Shoken ISHII Philippe BARON Makoto AOKI Kohei MIZUTANI Motoaki YASUI Satoshi OCHIAI Atsushi SATO Yohei SATOH Takuji KUBOTA Daisuke SAKAIZAWA Riko OKI Kozo OKAMOTO Toshiyuki ISHIBASHI Taichu Y. TANAKA Tsuyoshi T. SEKIYAMA Takashi MAKI Koji YAMASHITA Tomoaki NISHIZAWA Masaki SATOH Toshiki IWASAKI
出版者: (公社)日本気象学会
雑誌: 気象集誌. 第2輯 (ISSN:00261165)
巻号頁・発行日: vol.95, no.5, pp.301-317, 2017 (Released:2017-10-04)
参考文献数: 57
被引用文献数: 15

A working group is studying the feasibility of a future Japanese space-borne coherent Doppler wind lidar (CDWL) for global wind profile observation. This study is composed of two companion papers: an instrumental overview of the space-borne CDWL for global wind profile observation (Part 1), and the wind measurement performance (error and bias) investigated using a full-fledged space-borne CDWL simulator (Part 2). This paper aims to describe the future space-borne CDWL in terms of technical points and observation user requirements. The future mission concept is designed to have two looks for vector wind measurement with vertical resolutions of 0.5 (lower troposphere: 0-3 km), 1 (middle troposphere: 3-8 km), and 2 km (upper troposphere: 8-20 km) and horizontal resolution of < 100 km along a satellite. The altitude and orbit of the satellite are discussed from a scientific viewpoint. The candidate altitude and orbit of the satellite are 220 km and an inclination angle of 96.4° (polar orbit) or 35.1° (low-inclination-angle orbit). The technical requirements of the space-borne CDWL are a single-frequency 2-μm pulse laser with an average laser power of 3.75 W, two effective 40-cm-diameter afocal telescopes, a wide-bandwidth (> 3.4 GHz) detector, a high-speed analog-to-digital converter, and a systematic lidar efficiency of 0.08. The space-borne CDWL looks at two locations at a nadir angle of 35° at two azimuth angles of 45° and 135° (225° and 315°) along the satellite track. The future space-borne CDWL wind profile observation will fill the gap of the current global wind observing systems and contribute to the improvement of the initial conditions for numerical weather prediction (NWP), the prediction of typhoons and heavy rain, and various meteorological studies.

2017-10-06 09:34:28
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1 0 0 0 OA Air-Sea Coupled Data Assimilation Experiment for Typhoons Kilo, Etau and the September 2015 Kanto-Tohoku Heavy Rainfall with the Advanced Microwave Scanning Radiometer 2 Sea Surface Temperature

著者: Akiyoshi WADA Hiroshige TSUGUTI Kozo OKAMOTO Naoko SEINO
出版者: Meteorological Society of Japan
雑誌: 気象集誌. 第2輯 (ISSN:00261165)
巻号頁・発行日: vol.97, no.3, pp.553-575, 2019 (Released:2019-06-05)
参考文献数: 62
被引用文献数: 4

The September 2015 Kanto-Tohoku heavy rainfall event occurred in a stationary linear convective system between Typhoons Kilo and Etau. We investigated the influence of sea surface temperature (SST) on the local heavy rainfall event using a regional air-sea strongly coupled data assimilation system based on the local ensemble transform Kalman filter (LETKF) and a nonhydrostatic atmosphere model (NHM) coupled with an ocean-surface wave model and a multilayer ocean model with an Advanced Microwave Scanning Radiometer 2 (AMSR2) level 2 (L2) SST product. From the validation of SST analyzed by the coupled data assimilation system with the Japanese geostationary multi-functional transport satellite 2 hourly SST product and in-situ observations at a moored buoy, we demonstrated that the coupled system with the AMSR2 L2 SST led to an improvement in the SST analysis. Based on the verification using radiosonde observations and radar-rain gauge rainfall analysis, the analysis of the lower-atmospheric components was improved by the air-sea coupled NHM-LETKF. The local torrential rainfall event that occurred around 37°N in the Tochigi prefecture was embedded in a stationary linear convective system. The location of the linear convective system corresponded to the synoptic-scale convergence area between the cyclonic circulation associated with Etau and easterly lower-tropospheric winds. Strong southerly winds associated with Etau caused a periodic enhancement of local convection along the convergence area on the upwind side of the linear convective system and resulted in a wave-like train of the total water content around an altitude of 4-8 km on the leeward side. The improvement of SST analysis could not only change the transition of Etau to the extratropical cyclone but also the lower-tropospheric wind field and thereby the location of the stationary linear convective system with embedded local torrential rain.

2019-06-05 14:58:18
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