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Yamaguchi N.M.,University of Tokyo | Yamaguchi N.M.,Nagasaki University | Arisawa Y.,Weather Information and Communication Service Ltd. | Shimada Y.,Japan Weather Association | Higuchi H.,University of Tokyo
Journal of Ethology | Year: 2012

Many animals seasonally travel between their breeding and wintering grounds. With their advanced mobility, birds often migrate over thousands of kilometres. Recently, satellite-tracking studies have revealed peculiar migration routes for some avian species at a global scale. However, the adaptability of such migration routes has not been clearly demonstrated. Using satellite-tracking data for 33 individuals, we show that the Japanese population of Oriental honey-buzzards (Pernis ptilorhynchus) directly crosses the 650-km-wide East China Sea during their autumn migration, although they fly a longer route around the sea rather than directly crossing it during their spring migration. By applying aerodynamic theory, we show that the buzzards could cross the sea by soaring and gliding flight. Moreover, using a high-resolution meteorological-prediction analysis, we demonstrate that the migratory trajectory of the birds strongly depends on the wind direction at their estimated locations. In the area, northeastern tailwinds blow stably only during autumn. Thermals were abundant ca. 500-1,000 m over the East China Sea in autumn, but that was not the case in spring. We suggest that the autumn-migration route across the East China Sea is likely to have evolved in response to the specific weather conditions over the sea. Animations showing movements of Oriental honey-buzzards and temporal change in weather conditions are available at: http://www.momo-p.com/showdetail-e.php? movieid=momo110822oh01a, http://www.momo-p.com/sh owdetail-e.php?movieid=momo110822oh02a, http://www. momo-p.com/showdetail-e.php?movieid=momo110822oh 04a, http://www.momo-p.com/showdetail-e.php?movieid= momo110822oh05a, http://www.momo-p.com/showdetail-e. php?movieid=momo110822oh06a, and http://www.momo-p. com/showdetail-e.php?movieid=momo110822oh07a. © 2011 Japan Ethological Society and Springer.

Lacanna G.,University of Florence | Ichihara M.,University of Tokyo | Iwakuni M.,Japan Weather Association | Takeo M.,University of Tokyo | And 2 more authors.
Journal of Geophysical Research: Solid Earth | Year: 2014

The effects of topography and atmospheric structures on infrasonic wave propagation from a volcanic source were investigated using observations and numerical modeling. This paper presents the first long-term observational data set showing spatiotemporal variations in patterns of infrasound propagation at distances of up to 60 km from a persistently active infrasound source (Sakurajima Volcano, Japan). The data show that the amplitudes of infrasonic waves received at distant stations relative to those received at a reference station close to the source can vary up to an order of magnitude over short time intervals and short distances and that they do not follow the theoretical geometric decay expected for homogeneous media. Moreover, waveforms also change significantly in both time and space. Numerical simulations were performed using a two-dimensional finite difference time domain (2-D FDTD) method. Effects of atmospheric structure and topography are included in a vertical section parallel to the wave propagation direction. The simulation successfully reproduced the variations of amplitudes and waveforms. Results are interpreted in terms of wave refraction due to sound and wind speed gradients and wave diffraction at topographic barriers. Our numerical results indicate that both atmospheric and topographic propagation effects are nonnegligible. To evaluate the propagation effects and determine source processes in spatially and temporally varying infrasound data, atmospheric data with a time resolution higher than is currently available are required. If the data are available, the present results suggest that the propagation effects could be evaluated using 2-D FDTD modeling at realistic calculation times. ©2014. American Geophysical Union. All Rights Reserved.

Kusaka H.,University of Tsukuba | Nawata K.,University of Tsukuba | Nawata K.,Taiho Pharmaceutical Co | Suzuki-Parker A.,University of Tsukuba | And 3 more authors.
Journal of Applied Meteorology and Climatology | Year: 2014

This study examines how urbanization affects the precipitation climatology in Tokyo, Japan. Aunique aspect of this study is that an ensemble, regional climatological simulation approach is used with sensitivity experiments to reduce uncertainty arising fromnonlinearity in the precipitation simulations.Another aspect is that the robustness of the precipitation response is tested with ''stress response'' simulations with increasing urban forcing. The results show that urbanization causes a robust increase in the amount of precipitation in the Tokyo metropolitan area and a reduction in the inland areas. These anomalies are statistically significant at the 95% and 99%levels in some parts. There is no measureable change in the surrounding rural and ocean areas. These precipitation responses are attributed to an increase of surface sensible heat flux inTokyo,which destabilizes the atmosphere and induces an anomalous surface low pressure pattern and the convergence of grid-scale horizontal moisture flux. The anomalous convergence of grid-scale horizontal moisture flux is a consequence of urbanization modifying the sea breeze. © 2014 American Meteorological Society.

Okada Y.,Meijo University | Yoshihisa K.,Meijo University | Higashi K.,Japan Weather Association | Nishimura N.,Kansai Electric Power Co.
Acoustical Science and Technology | Year: 2015

In Japan, the development of large-scale wind power generation facilities has been promoted since about 2000. Nationwide investigations of the acoustic characteristics of wind turbine noise have been conducted at various wind farms. In this study, to examine the horizontal and vertical radiation characteristics of noise generated from wind turbines, field measurements of noise from a single wind turbine with a rated power of 1.5MW have been performed. Some receiving points were set circularly around the wind turbine and mounted on a nearby lightning tower. Meteorological and associated wind turbine operational data were collected at 1 s intervals along with corresponding acoustic data. In addition, the sound pressure level distributions at distances of 50m to 200m from the wind turbine were investigated. Results revealed distinguishable horizontal directivity of wind turbine noise. The A-weighted sound pressure levels in the crosswind direction are almost 5 dB lower than those in the up- and downwind directions. Furthermore, it has been found that the sound directivity around the wind turbine could be expressed by a simple empirical formula, assuming the wind turbine to be a point source with combined bi- and omnidirectional patterns. © 2015 The Acoustical Society of Japan.

Shimadera H.,Osaka University | Hayami H.,Japan Central Research Institute of Electric Power Industry | Chatani S.,Toyota Central R&D Labs. | Morino Y.,Japan National Institute of Environmental Studies | And 4 more authors.
Journal of the Air and Waste Management Association | Year: 2014

Improvement of air quality models is required so that they can be utilized to design effective control strategies for fine particulate matter (PM2.5). The Community Multiscale Air Quality modeling system was applied to the Greater Tokyo Area of Japan in winter 2010 and summer 2011. The model results were compared with observed concentrations of PM2.5 sulfate (SO4 2-), nitrate (NO3 -) and ammonium, and gaseous nitric acid (HNO3) and ammonia (NH3). The model approximately reproduced PM2.5 SO4 2- concentration, but clearly overestimated PM2.5 NO3 - concentration, which was attributed to overestimation of production of ammonium nitrate (NH4NO3). This study conducted sensitivity analyses of factors associated with the model performance for PM2.5 NO3 - concentration, including temperature and relative humidity, emission of nitrogen oxides, seasonal variation of NH3 emission, HNO3 and NH3 dry deposition velocities, and heterogeneous reaction probability of dinitrogen pentoxide. Change in NH3 emission directly affected NH3 concentration, and substantially affected NH4NO3 concentration. Higher dry deposition velocities of HNO3 and NH3 led to substantial reductions of concentrations of the gaseous species and NH4NO3. Because uncertainties in NH3 emission and dry deposition processes are probably large, these processes may be key factors for improvement of the model performance for PM2.5 NO3 -. The Community Multiscale Air Quality modeling system clearly overestimated the concentration of fine particulate nitrate in the Greater Tokyo Area of Japan, which was attributed to overestimation of production of ammonium nitrate. Sensitivity analyses were conducted for factors associated with the model performance for nitrate. Ammonia emission and dry deposition of nitric acid and ammonia may be key factors for improvement of the model performance. © 2014 Copyright © 2014 A&WMA.

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