Papers by Toyoshi Shimomai
Earth, Planets and Space, Jun 1, 2007
We have developed three airglow temperature photometers with cooled-CCD detectors. The photometer... more We have developed three airglow temperature photometers with cooled-CCD detectors. The photometers measure rotational temperatures using the airglow emissions of OH and O 2 near the mesopause region (altitude: 80-100 km). The photometers also measure six other airglow and auroral lines at wavelengths of 557.7, 630.0, 777.4, 589.3, 427.8, and 486.1 nm. The CCD detectors are used to distinguish the emission lines in these airglow bands, similarly to those used by the Spectral Airglow Temperature Imagers (SATI). In this paper, we describe the configuration of the photometers, their calibration, the data processing to extract rotational temperatures and emission intensities from the measured airglow spectra, as well as the initial deployment at Platteville, Colorado (40.2 • N, 255.3 • E), when their observations were compared with the concurrent and nearly collocated observations by a sodium lidar. We obtain a good correlation and some systematic difference of temperatures from the photometers and the lidar, and discuss possible causes of the temperature difference.
Journal of Disaster Research, 2008
The Hydrometeorological ARray for Isv-Monsoon AUtomonitoring (HARIMAU), a 5-year project under th... more The Hydrometeorological ARray for Isv-Monsoon AUtomonitoring (HARIMAU), a 5-year project under the Japan EOS Promotion Program (JEPP) contributing to the Global Earth Observation System of Systems (GEOSS), has begun in 2005 to set up a radar-profiler network for observing the world's most active convective activities over the Indonesian Maritime Continent (IMC). Rainfall and wind distributions are displayed in nearly real time on the internet. Both scientific understanding and practical concepts on intraseasonal variations (ISVs) interacting with larger (seasonal and interannual) and smaller (diurnal or local) scale phenomena will be established. These are expected to contribute greatly and directly to climatic disaster prevention over the IMC and to global climate change assessment through studies on the global effects of the IMC-induced variations such as El Nino, and through construction of the first climatic database over the IMC.
We have been studying the turbidity estimation for Lakes Shinji and Nakaumi, Shimane Prefecture J... more We have been studying the turbidity estimation for Lakes Shinji and Nakaumi, Shimane Prefecture Japan using satellite sensors. Recently, we have developed a turbidity monitoring system for this area using near-real-time MODIS 250-m resolution band reflectance data which have been provided from Japan Aerospace Exploration Agency (JAXA). MODIS sensors on-board the Terra and Aqua satellites visit this area almost once or twice a day, so the limitation of sparse visit is solved to some extent (the limitation of cloud cover still remains). Since thin cloud and occasionally sand storm cover the ocean and/or lake areas, some threshold techniques are applied to remove the data or to issue warning flags. Empirical formulas adjusted for each lake (Lakes Shinji and Nakaumi) are used to estimate the turbidity from the Band 1 reflectance. The resulting turbidity distribution map is now published on our web site for general users. In this presentation, an outline of this system will be introduced...
2011 IEEE International Geoscience and Remote Sensing Symposium, 2011
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Remote Sensing of the Atmosphere, Clouds, and Precipitation IV, 2012
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2007 6th International Conference on Information, Communications & Signal Processing, 2007
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Radio Science, 2006
1] The diurnal variability of raindrop size distribution (DSD) in precipitating clouds over Kotot... more 1] The diurnal variability of raindrop size distribution (DSD) in precipitating clouds over Kototabang, West Sumatra, Indonesia (0.20°S, 100.32°E), is studied using three types of Doppler radars, operated at VHF (47 MHz), UHF (1.3 GHz), and X band (9.4 GHz) frequencies. Two precipitation events from 5 to 6 May 2004 in the first observation campaign of the first Coupling Processes in the Equatorial Atmosphere (CPEA-I) project reveal a difference between clouds precipitating in the early afternoon and clouds precipitating in the nighttime. In the early afternoon, the precipitating clouds were dominated by shallow convective types with high rainfall rate at the surface. In the nighttime, precipitating clouds were dominated by stratiform types with small rainfall rate at the surface. A diurnal variation of horizontal wind was observed over this area. The westerly in the lower troposphere and the easterly in the middle troposphere began to be enhanced in the afternoon (1400-1700 LT). DSD parameters were retrieved from VHF band Doppler radar data. A modified gamma distribution was used to model DSD parameters. The shape parameter (m) was larger during stratiform precipitation than during shallow convective precipitation events, as shown by previous studies. During stratiform rain events on 5 May 2004, the median volume diameter (D 0 ) was dominantly greater than 1 mm, which is larger than D 0 during shallow convective rain events. Results presented in this paper indicate that DSD has a diurnal cycle over the mountainous region of Sumatra.
IEICE Transactions on Communications, 2008
The performance of the adaptive scan for spaceborne rain radar, which uses a quick scan for rain ... more The performance of the adaptive scan for spaceborne rain radar, which uses a quick scan for rain search followed by a normal or con-centrated scan only for rainy areas, are studied through a simulation using TRMM (Tropical Rainfall Measuring Mission) Precipitation Radar (PR) data. Trade-off studies are performed to find an optimum quick-scan and rain search method to minimize rain
IEICE Transactions on Communications, 2011
Preliminary Study of Performance Evaluation of Adaptive Scan with Wide-Band Noise Modulation for ... more Preliminary Study of Performance Evaluation of Adaptive Scan with Wide-Band Noise Modulation for Spaceborne Rain Radar Based on Simulation
… 33rd Conference on Radar …, 2007
Earth, Planets and Space, 1999
Vertical wavenumber spectra are analyzed by using temperature, zonal wind and meridional wind dat... more Vertical wavenumber spectra are analyzed by using temperature, zonal wind and meridional wind data obtained with MU radar and radiosondes at the MU observatory in Shigaraki and with operational rawinsondes at five stations over Japan. The temperature and meridional wind spectral power densities of the dominant gravity wave increase with a decrease of latitude, whereas the zonal wind spectral power seems to have a maximum near the tropopausal jet stream axis. An analysis technique to estimate a characteristic value of intrinsic frequency from the wind and temperature vertical-wavenumber spectra is proposed. The different meridional distributions of spectral power densities for temperature, zonal wind and meridional wind possibly can be explained by a latitudinal distribution of the characteristic intrinsic frequency.
25th AIAA International Communications Satellite Systems Conference (organized by APSCC), 2007
Orthonormal wavelet analysis is applied for the first time to two-dimensional (time and height) d... more Orthonormal wavelet analysis is applied for the first time to two-dimensional (time and height) data obtained from three-week continuous MU radar observations in June-July, 1991. It is confirmed that monochromatic wave structures are generally localized both in time and in altitude. We find the dominant temporal scale of wave activity in this case study is 2-4 days. The dominant vertical wavelength seems to decrease from -4 km to -1 km, upwards through the tropopause-lower stratosphere region, which is almost independent of temporal scales in the 1-4 day range.
Monthly Weather Review, Jun 1, 2006
Multiscale aspects of convective systems over the Indonesian Maritime Continent in the convective... more Multiscale aspects of convective systems over the Indonesian Maritime Continent in the convectively active phase of an intraseasonal oscillation (ISO) during November 2002 are studied using Geostationary Meteorological Satellite infrared data and ground-based observational data from X-band rain radar, equatorial atmosphere radar, L-band boundary layer radar, and upper-air soundings at Koto Tabang (KT; 0.20°S, 100.32°E; 865 m above mean sea level), West Sumatera, Indonesia. In the analysis period, four super cloud clusters (SCCs; horizontal scale of 2000-4000 km), associated with an ISO, are seen to propagate eastward from the eastern Indian Ocean to the Indonesian Maritime Continent. The SCCs are recognized as envelopes of convection, composed of meso-␣-scale cloud clusters (M␣CCs; horizontal scale of 500-1000 km) propagating westward. When SCCs reach the Indonesian Maritime Continent, the envelopes disappear but M␣CCs are clearly observed. Over Sumatera, the evolution and structure of a distinct M␣CC is closely related to the organization of localized cloud systems with a diurnal cycle. The cloud systems are characterized by westward-propagating meso--scale cloud clusters (MCCs; horizontal scale of ϳ100 km) developed in eastern Sumatera, and an orographic cloud system formed over a mountain range in western Sumatera. Ground-based observations further revealed the internal structure of the orographic cloud system around KT. A meso--scale convective precipitation system with eastward propagation (E-MCP; horizontal scale of ϳ40 km) is found with the formation of the orographic cloud system. This is associated with a low-level wind change from easterly to westerly, considered to be local circulation over the mountain range. The E-MCP also indicates a multicell structure composed of several meso-␥-scale convective precipitation systems (horizontal scale of Ͻ10 km) with multiple evolution stages (formation, development, and dissipation).
Earth, Planets and Space, 2009
Vertical wind variations in the Upper Troposphere and Lower Stratosphere (UTLS) measured by the E... more Vertical wind variations in the Upper Troposphere and Lower Stratosphere (UTLS) measured by the Equatorial Atmosphere Radar (EAR) at Kototabang, Sumatra, between 2003 and 2005 but mainly in 2004, have been statistically analyzed to study the characteristics of wind variances associated with convective activity, which is related to gravity wave generation and propagation. The analyses are intended to characterize relatively short period disturbances of less than 12 hours and an energy propagation direction of a relatively high elevation angle, and to relate vertical wind variations to convective activity close to the EAR. Correlation analyses between vertical wind variations and rainfall show that the wind variances have a clear diurnal variation indicating probable effects of tropospheric convection. They also show some intraseasonal variation. However, there are no significant correlations with the Out-going Long-wave Radiation (OLR) anomaly. The correlations between variances at UT and LS suggest that the UTLS coupling of vertical wind variation through upward propagation of gravity wave is similarly evident in the afternoon during both the active and the inactive phase of OLR that is a proxy of large-scale convective activity.
Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering), 2009
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Papers by Toyoshi Shimomai