Japan Weather Association

Tokyo, Japan

Japan Weather Association

Tokyo, Japan
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Okada Y.,Meijo University | Yoshihisa K.,Meijo University | Higashi K.,Japan Weather Association | Nishimura N.,Kansai Electric Power Co.
Acoustical Science and Technology | Year: 2016

Field measurements of noise generated from two different wind turbines, one with an upwind rotor and one with a downwind rotor, have been performed. To examine the radiation characteristics of wind turbine noise, some receiving points were set around each wind turbine and the apparent A-weighted sound power levels were calculated from the obtained data at 200 ms intervals under various wind conditions. Wind turbine operational data were collected at 1 s intervals along with corresponding acoustic data. Additionally, a simple empirical formula for the sound directivity was proposed, assuming the directivity pattern of aerodynamic and mechanical sound to be bi- and omnidirectional, respectively. The results showed that the horizontal directivity of the A-weighted sound pressure level at the ground level for the two different wind turbines is almost the same, whereas the frequency dependence of the sound directivity is different for the individual wind turbines. Furthermore, obtaining data of the rotor rotational speed, output power, and nacelle direction is strongly recommended to assess the characteristics of noise emission, such as the changes in the sound power level, sound directivity, and tonal components of wind turbine noise. © 2016 The Acoustical Society of Japan.

Kato R.,Resilience | Shimizu S.,Resilience | Shimose K.-i.,Resilience | Maesaka T.,Resilience | And 2 more authors.
Quarterly Journal of the Royal Meteorological Society | Year: 2017

The development and verification of a forecast method for localized, meso-γ-scale (2-20km), extreme heavy rainfall (MγExHR) is important, because it can cause urban flash flooding and inundation with accompanying damage and potential loss of life. Although previous studies have examined the predictability of precipitation at a very short range (≤1h) using extrapolation-based nowcasts, they did not specifically focus on MγExHR. In this study, we examine the predictability of 23 selected events of MγExHR (1h rainfall accumulation ≥50mm) that occurred during the warm season of 2014 in Japan using High-Resolution Precipitation Nowcasts (HRPNs) provided by the Japan Meteorological Agency, which are extrapolation-based nowcasts. Traditional grid-scale verification using the equitable threat score shows that the HRPNs usefully predict the heavy rainfall areas of ≥20mmh-1 for at least 12min at the grid scale of 1km. Neighbourhood verification using fractions skill scores shows that HRPNs usefully predict the areas of ≥20mmh-1 up to 29min by tolerating 11km displacement errors. After 30min, a useful forecast cannot be obtained, even if the 11km displacement errors are tolerated for the ≥20mmh-1 areas. This result suggests that a numerical weather prediction (NWP) model, whose accuracy is useful after ∼30min, is necessary to seamlessly provide useful forecasts for heavy rainfall areas of ≥20mmh-1 for MγExHR with ∼10km displacement errors, by blending the extrapolation-based nowcast with NWP. © 2017 Royal Meteorological Society.

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.

Arai N.,Japan Weather Association | Iwakuni M.,Japan Weather Association | Watada S.,University of Tokyo | Imanishi Y.,University of Tokyo | And 2 more authors.
Geophysical Research Letters | Year: 2011

Atmospheric pressure changes caused by the 2011 Off the Pacific Coast of Tohoku, Japan earthquake (Mw = 9.0) are investigated. Sensitive microbarographs in and around Japan recorded unequivocal signals associated with the tsunami. We identify them as atmospheric boundary waves excited by the uplift and subsidence of the ocean surface, on the basis of the waveform characteristics as well as similarity with the data from ocean-bottom pressure gauges. Potential usefulness of an observation network of atmospheric pressure is discussed regarding the improvement of the tsunami warning system. © 2011 by the American Geophysical Union.

Ishii T.,Japan National Institute of Advanced Industrial Science and Technology | Otani K.,Japan National Institute of Advanced Industrial Science and Technology | Itagaki A.,Japan Weather Association | Utsunomiya K.,Japan Weather Association
Japanese Journal of Applied Physics | Year: 2012

Various photovoltaic (PV) technologies are commercially available today. The effect of solar spectrum on the performance of PV modules should be evaluated quantitatively in order to estimate the module performance with high accuracy and precision. Average photon energy (APE) has been frequently applied to evaluate the effect of solar spectrum. The purpose of this study is to enhance the precision and accuracy by introducing other indexes. In this study, we select solar spectra, the integrated spectral irradiance (ISI) and APE of which are equivalent to those of the standard AM1.5G spectrum. There is a slight difference in shape, although the shapes are approximately similar. We introduce one more index, which defines the spectral irradiance at the atmospheric window or the depth of the water absorption band. The introduction would further improve the accuracy and precision of the evaluation of the effect of solar spectrum. © 2012 The Japan Society of Applied Physics.

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.

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.

Saito T.,Japan Weather Association | Hayasaka T.,Tohoku University
Journal of the Meteorological Society of Japan | Year: 2014

The effects of dust aerosol particles on the properties of clouds over East Asia and the Sahara are studied using moderate resolution imaging spectroradiometer observations from the Terra and Aqua satellites and simulation results of the chemical weather forecast system (CFORS) model. Dust-contaminated clouds are detected using the brightness temperature difference (BTD) method, in which dust or dust-bearing clouds are detected when the BTD between the 11 μm and 12 μm channels in the window region is negative, and by the CFORS model’s dust vertical profile. Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation data are also used to assess the above procedures. For the Sahara region, no obvious changes to effective particle radius (Re) are attributed to dust aerosols. However, for East Asia, dust aerosols are found to change the cloud microphysical properties, decreasing Re by 12 % and increasing the cloud optical depth by 27 % and the liquid water path by 9 %. Re is found to be negatively correlated with sulfate concentration by CFORS in dust-bearing clouds, but not in dust-free clouds, over East Asia. These findings indicate that mineral dust can act as effective cloud condensation nuclei in environments polluted by water-soluble aerosols such as sulfates. We also estimate the indirect radiative effect of dust aerosols in the East Asia region and determine, by radiative transfer calculation, that the net shortwave radiative flux at the top of the atmosphere decreases and the absorption of shortwave radiation by the atmosphere increases with changes in cloud properties due to dust aerosols. © 2014, Meteorological Society of Japan.

Akimoto H.,Asia Center for Air Pollution Research | Mori Y.,Japan Weather Association | Sasaki K.,Japan Weather Association | Nakanishi H.,Japan Weather Association | And 2 more authors.
Atmospheric Environment | Year: 2015

The puzzling increase of annual average mixing ratio of ozone (oxidant) in spite of the decrease of those of the ambient NOx and NMHC was analyzed using the twenty-one years monitoring data during 1990-2010 focusing on four high O3 areas in Japan, Tokyo Metropolitan Area (TMA), Nagoya Area (NA), Osaka/Kyoto Area (OKA) and Fukuoka Area (FA). During the period, the NOx and NMHC mixing ratios have decreased by 40-50 % and 51-54 %, respectively, in these areas. Nevertheless, the annual averaged increasing trends of O3 by linear regressions during the whole period are all positive, 1.23±0.09, 0.85±0.17, 1.41±0.12 and 1.42±0.17(1σ)%yr-1 for TMA, NA, OKA and FA, respectively. Three causes of long-term trends of O3 have been discussed: (1) the decrease of NO titration effect, (2) the increase of transboundary transport, and (3) the decrease of in situ photochemical production. The total ozone (TO) was defined by [TO]=[O3]+[NO2]-0.1[NOx] as an index to indicate the net O3 removing the perturbation by in situ NO titration. TO shows statistically significant annual increasing trends, 0.20±0.04 and 0.56±0.08%yr-1 only in OKA and FA, and the increase of TO is not discernible in TMA and NA. In springtime (March-May), TO shows larger increasing rates of 0.44±0.08, 0.59±0.09 and 0.96±0.18%yr-1 for TMA, OKA, and FA. The statistically significant increase of TO at higher rates in spring and western part of Japan suggests the increase of transboundary transport during the period. The reduction of domestic emissions of precursors was found to result the decreasing trend of the high mixing ratio range of 98-percentile most clearly in TMA, but is not enough yet to result in the decrease of annual mean mixing ratio of O3, which is compensated by the increase of transboundary transport and the decrease of the NO titration effect. The similar situation has been reported in Taiwan (Chou etal., 2006), and would apply more or less to other outflow region of Pacific rim, Korea and Hoang Kong, where the emission control started to reduce the O3 precursors. Further reduction of NOx emissions over a certain limit will negate the NO titration effect, and the decrease of net O3 due to the reduction of in situ photochemical production is expected. © 2014.

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.

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