Language：Japanese   Publisher：Japan Society of Civil Engineers  

The wind spectrum of the atmospheric boundary layer is composed of the two well-known energy peaks. These are, the high frequency peak due to convection in the boundary layer, and the low frequency peak due to baroclinic instability. While the high-frequency peak has been well studied in many previous studies, the low-frequency peak has not been examined as often. This is because long-term data is required to investigate low-frequency phenomena, and data collection is difficult. In this study, the characteristics and formulation of the inertial range that appears from 5 to 24 hours in the wind spectrum were examined. Wind data from meteorological observation towers were used to analyze wind spectrum for up to 17 years. The results show that the interannual variation of the wind speed spectrum is linked to the interannual variation trend of the annual mean wind speed, and that the energy dissipation rate depends on the mean wind speed.

DOI： 10.2208/jscejj.24-16192

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

This study uses machine learning to develop a model for estimating turbulence statistics in an urban area using building height, vegetation distribution, and elevation as input. Machine learning generally requires a large amount of training data. Therefore, we used a database of the turbulent statistics within an urban district which covers the entire Tokyo 23 wards in 2 m resolution. This database enables us to learn several thousands of 320 x 320 m² areas. The results show that the horizontal distributions of mean streanwie velocity, spanwise wind velocity, and turbulent kinetic energy at a height of 2 m above the ground can be estimated with significant accuracy. In addition, the spatial mean values of within the test area be estimated with higher accuracy. On the other hand, the accuracy of the estimation for open space with no building or vegetaion was not good, which may be due to the influence of the outside of the test area is more strongly reflected.

DOI： 10.2208/jscejj.24-16196

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.jweia.2024.105783

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

This study aims to create a database of turbulent flow statistics within the urban district based on an urban turbulent boundary layer simulation. The inflow turbulence gradually loses its characteristics while progressing and developing the turbulent boundary layer. Turbulence finally becomes well-adjusted to the local surface conditions that are generally represented by massive obstacles in urban districts. This concept allows for the decomposition of a huge computational domain and a reconstruction of the simulation results of the decomposed simulation pieces. We apply this to create a mean flow database in the urban canopy layer of the Tokyo 23 wards. The simulation domain was decomposed in spanwise and streamwise directions. This resulted in the mean wind speed distributions being generally reconstructable after friction velocity normalization without any additional adjustments. On the other hand, if organized turbulent structures develop and stay for significant time above the building canopy, the mean flow structure is disturbed, and the quality of the reconstruction worsen.

DOI： 10.2208/jscejj.23-16100

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Other Link： https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-20H02253/

Publishing type：Research paper (scientific journal)   Publisher：Wiley  

<jats:title>Abstract</jats:title><jats:p>In this study, multi‐year near‐surface observations were conducted at two sites in Jakarta, Indonesia to analyse seasonal sea breeze variation. Seasonal length was defined using observed zonal wind components, the rainy season was defined as December–March, and the dry season was defined as May–September. We found that the sea breeze in Jakarta started earlier, propagated more rapidly, and lasted for a shorter period of time during the rainy than dry season. Variation in the air temperature difference between urban and coastal areas of Jakarta was the major factor driving sea breeze seasonal variation. During the rainy season, night‐time cloud downwelling decreased this air temperature difference, causing earlier sea breeze onset and more rapid sea breeze propagation due to a weaker land breeze. By contrast, during the dry season, intense night‐time radiative cooling inland caused a strong negative temperature difference that produced a stronger land breeze, thus, slowing sea breeze propagation. Seasonal differences in urban surface heating and urban heat island circulation may also affect sea breeze onset and propagation speed. Discrepancies in thermal properties between urban core and coastal areas of Jakarta also prolonged positive temperature differences after sunset, thus extending the sea breeze duration in the dry season.</jats:p>

DOI： 10.1002/joc.8139

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Other Link： https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-19KK0105/

Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s10546-022-00764-z

DOI： 10.2208/jscejj.23-16100_references_DOI_37Op5dKx7SeNG2QRHG3N3Z5w5gc

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Other Link： https://link.springer.com/article/10.1007/s10546-022-00764-z/fulltext.html

J-GLOBAL

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Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

DOI： 10.2208/jscejhe.78.2_i_325

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Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

<title>Abstract</title>A double-distribution-function lattice Boltzmann model for large-eddy simulations of a passive scalar field in a neutrally stratified turbulent flow is described. In simulations of the scalar turbulence within and above a homogeneous plant canopy, the model’s performance is found to be comparable with that of a conventional large-eddy simulation model based on the Navier–Stokes equations and a scalar advection–diffusion equation in terms of the mean turbulence statistics, budgets of the second moments, power spectra, and spatial two-point correlation functions. For a top-down scalar, for which the plant canopy serves as a distributed sink, the variance and flux of the scalar near the canopy top are predominantly determined by sweep motions originating far above the canopy. These sweep motions, which have spatial scales much larger than the canopy height, penetrate deep inside the canopy and cause scalar sweep events near the canopy floor. By contrast, scalar ejection events near the canopy floor are induced by coherent eddies generated near the canopy top. The generation of such eddies is triggered by the downward approach of massive sweep motions to existing wide regions of weak ejective motions from inside to above the canopy. The non-local transport of scalars from above the canopy to the canopy floor, and vice versa, is driven by these eddies of different origins. Such non-local transport has significant implications for the scalar variance and flux budgets within and above the canopy, as well as the transport of scalars emitted from the underlying soils to the atmosphere.

DOI： 10.1007/s10546-021-00633-1

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

Thermal Image Velocimetry (TIV) is the method to measure the 2-dimentional wind field tracking the temperature displacement caused by advected turbulent heat exchange using TIR camera. So far, this method has been applied to the surface whose heat capacity is low so as to easily capture the turbulence-caused temperature displacement. We applied TIV to the high-heat-capacity asphalt road within urban canopy for the first time. As a result, we could conduct TIV observation even to the asphalt surface, observing complex wind field within the uraban canopy. Then we need to conduct temporal filtering with larger filter than the cycle of the random noise, which can be estimated by the spectral analysis of the displacement of the surface temperature. Even low performance TIR camera can conduct TIV observation if we set the large temporal filter enough compared to that of high performance TIR camera. And we found the possibility that we can change the size of tracking turbulent structure by changing the filter size,

DOI： 10.2208/jscejhe.77.2_i_1297

DOI： 10.2208/jscejj.24-16191_references_DOI_ItZlse8H8pyclahUioZGLu7rFIW

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Other Link： https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-20H02253/

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

Simulation of seven sea-breeze days (SBD) during dry season in tropical megacity of Jakarta was carried out using WRF with detailed urban representation. Model simulations were evaluated using satellite derived cloud line and high-temporal-resolution meteorological data obtained from observation campaign in 2017 and 2018. Results shows that WRF with detailed urban representation was able to simulate sea-breeze features and the associative boundary layer development. In the early stage of sea-breeze, model convergence line associated with sea-breeze front were matched against cloud line derived from satellite imagery. WRF tend to produce earlier sea-breeze occurrence due to overestimation of shortwave radiation and underestimation of latent heat flux. In general, simulated wind speed, temperature and relative humidity shows good agreement with observed values. Model also able to well simulate sea-breeze features, including lower boundary layer over Jakarta associated with thermal induced boundary layer (TIBL). Sea-breeze TIBL is influenced by coastal form of Jakarta and might plays important factor in air quality over the city.

DOI： 10.2208/jscejhe.77.2_i_1309

DOI： 10.1002/joc.8139_references_DOI_N3xXElQp6f3LLAxclqhsYAJKPSZ

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Other Link： https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-19KK0105/

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media B.V.  

DOI： 10.1007/s10546-021-00674-6

Scopus

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s10546-020-00519-8

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Other Link： https://link.springer.com/article/10.1007/s10546-020-00519-8/fulltext.html

Publishing type：Research paper (scientific journal)   Publisher：Copernicus GmbH  

Abstract. In this paper, we describe the PALM model system 6.0. PALM (formerly an abbreviation for Parallelized Large-eddy Simulation Model and now an independent name) is a Fortran-based code and has been applied for studying a variety of atmospheric and oceanic boundary layers for about 20 years. The model is optimized for use on massively parallel computer architectures. This is a follow-up paper to the PALM 4.0 model description in Maronga et al. (2015). During the last years, PALM has been significantly improved and now offers a variety of new components. In particular, much effort was made to enhance the model with components needed for applications in urban environments, like fully interactive land surface and radiation schemes, chemistry, and an indoor model. This paper serves as an overview paper of the PALM 6.0 model system and we describe its current model core. The individual components for urban applications, case studies, validation runs, and issues with suitable input data are presented and discussed in a series of companion papers in this special issue.

DOI： 10.5194/gmd-13-1335-2020

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

Abstract Sea breeze is closely related to the living environment in coastal-urban regions. Therefore, the framework for sea-breeze detection is crucial. We proposed a framework to derive a two-dimensional distribution of sea-breeze front (SBF) using geostationary satellite images. The framework includes the application of morphological snake algorithm into visible band images for automated detection of the cumulus cloud-lines associated with SBF. The verification was undertaken by comparing the passage time of the cloud-line with the arrival time of the SBF estimated from ground observation. The results show that the cloud-line was reasonably able to represent the arrival time of the SBF with a bias time of 20 min and within a distance of 3 km. The mean penetration speed obtained from the cloud-lines passage was slightly slower than that estimated from the arrival time of SBF (1.4 ms−1 and 1.5 ms−1, respectively). In certain cases, the cloud-lines passage was found to be behind the SBF more than 5 km, particularly in the city center. This indicated the enhanced updraft due to urban-heat-island circulation potentially caused the delayed of cloud-line propagation in certain prevailing wind condition.

DOI： 10.1016/j.uclim.2020.100586

DOI： 10.2208/jscejhe.77.2_i_1309_references_DOI_3569yEH8JxqlqUYQ2swVgglFvq4

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

Hight-resolution pollutant model embedded into Lattice Boltzmann method (LBM) is constructed. We focuse on Particle pollutants. Flow field is calculated using D3Q27 model of LBM and particle is calculated by Lagrangian method. Using this model, we discuss the change in concentration distribution when there is a huge building (GARUDA) in Jakarta as a application.

 As a result, we can find the relation of differences in particle density and differences in flow velocity due to GARUDA. When the velocity in the case w/o GARUDA is faster than the other, particle velocity in the case w/o GARUDA is reduced. The reverse is also possible. And also, we can find the velocity near the solid boundary is underestimated and the particle density is higher than theoretical value. However, this model is valid far away from the solid boundary.

DOI： 10.2208/jscejhe.76.2_i_253

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

This study developed a method to measure spatial distribution of the surface sensible heat flux by means of the thermal image velocimetry (TIV) and bulk transfer coefficient. TIV reproduced a spatial distribution of horizontal wind speed near the ground surface. This velocity distribution is used to calculate the sebsible heat flux by multiplying the bulk transfer coefficient of heat. This method is tested in Saitama 2002 stadium, which has a natural turf ground for the football. The method can make accurate measurements of the velocity and the sensible heat flux near the ground as as validated in the ground-based observations. In addition, the method can clarify the spatial heterogeneity of the wind speed and sensible heat flux on the identical soccer ground.

DOI： 10.2208/jscejhe.76.2_i_247

DOI： 10.2208/jscejhe.77.2_i_1297_references_DOI_Vj2oGKSWNYfIF20TCAR1GmRpqR7

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

Large-eddy simulation based on lattice-Boltzmann method has been conducted, using different inflow conditions, over a realistic urban geometry including high-rise building area in Shinjuku. Three types of inflow conditions regarding the boundary-layer height and turbulence intensities were reproduced by extending fetch with roughness blocks. The effect of boundary-layer development on mean air flow fields under neutral atmospheric condition has been investigated in a target domain with identical building geometries. The ratio of mean wind speed at the same positions in the different cases corresponded well with the ratio of the friction velocities. This means that mean wind speed within the urban canyon normalized by a bulk friction velocity is solely determined by the building geometry. Therefore, we can reproduce a three dimensional mean wind distribution within the urban canyon diagnostically by referencing a regionally representative velocity scale, which is the friction velocity, and the preprocessed microscale simulation of the target urban district.

DOI： 10.2208/jscejhe.76.2_i_265

DOI： 10.2208/jscejj.24-16198_references_DOI_EUeMhoMluMhQFXTKXO582uKP2w0

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Meteorological Society of Japan  

The similarity of the turbulence intensity profile with the inner-layer (i.e. from the ground to the top of the logarithmic layer) and the outer-layer (i.e. from the top of the inner layer to top of the boundary layer) scalings were examined for an urban boundary layer using numerical simulations. The simulations consider a developing neutral boundary layer over realistic building geometry with and without a slightly upsloping terrain. The computational domain covers an 19.2 km by 4.8 km and extends up to a height of 1 km, and is resolved by 2-m grids. Several turbulence intensity profiles are defined locally in the computational domain. The inner- and outer-layer scalings work well reducing the scatter of the turbulence intensity within the inner- and outer-layers, respectively, regardless of the surface geometry. Although the main scatters among the scaled profiles are attributed to the mismatch of the parts of the layer (i.e. inner or outer) and the scaling parameters, their behaviours can also be explained by introducing a non-dimensional parameter which consists of the ratio of the inner- and outer-layer parameters for length (the boundary-layer height over the roughness length), or velocity (the external free stream velocity over the friction velocity).

DOI： 10.2151/sola.2020-021

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Publishing type：Research paper (scientific journal)   Publisher：Meteorological Society of Japan  

DOI： 10.2151/sola.2020-033

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Publisher：Elsevier BV  

International audience

DOI： 10.1016/j.rse.2018.05.004

DOI： 10.1016/j.ufug.2020.126630_references_DOI_Zz5Tnupi3z1OlQrxXbv4YmzsKaf

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

This study discussed about the characteristics of long-term period variation of surface wind speed by using surface observations data. We analyzed this data which is one-minute data of three-year length and got from 155 Japanese weather stations that almost covering the whole area of Japan. The results show that all of these 155 spectra from observation sites have a local minimum value, which is called spectral gap at about period of 30 min or the existence of an inflection point. Also we find that if we plot the spectrum in log-log scale, in the lower frequency side, there is also a range showing that the spectral intensity is linearly decreasing with the frequency increasing, just being similar with the inertia subrange in the microscale. The value of this slope from all observation sites is between -1.2~-2.0, which is bigger than the value of -3 derived from the two-dimensional turbulence theory. Moreover, we can find a clear relationship between the slope and the annual mean wind speed. According to this relationship, we tried to model this slope in the mesoscale of spectrum of wind speed. In addition to the above analyses, we also discussed about the difference in the spectrum of different seasons and years.

DOI： 10.2208/jscejhe.74.5_i_1195

DOI： 10.2208/jscejj.24-16192_references_DOI_5373GpgSAxRPAUGQDA6YoODaNe8

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

Recently, temperature in urban areas continue to rise as an effect of climate change and urbanization. Asian megacities are projected to expand rapidly resulting to serious in the future atmospheric environment. Thus, detailed analysis of urban meteorology for Asian megacities is needed to prescribe optimum countermeasure for these warming. A building-resolving large eddy simulation (LES) offline coupled with an energy balance model is conducted for a highly urbanized district in central Jakarta on typical daytime hours. Six cases were considered; two cases which utilized present urban scenario and four cases represent different urban configurations in 2050. The present case was used for validation by comparison with a moving observation of wet bulb temperature (WBGT). Meteorological inputs of the other present case and four future cases were acquired from a downscaling model. The future configurations were based on representative concentration pathways (RCP) and shared socio-economic pathways (SSP). Using the standard new effective temperature (SET^*), thermal comfort in urban area in Jakarta was calculated and analyzed. Construction of dense high-rise buildings can reduce SET^* (thermal comfort) due to increased shading throughout the district during daytime. Near-surface winds and temperatures were affected by the projected changes in morphology. For example, homogeneous high-rise buildings (case 3 and 4) prevented cooler downdrafts thereby maintaining high potential temperature within the street canyons.

DOI： 10.2208/jscejhe.74.i_259

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Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

DOI： 10.2208/jscejhe.74.i_253

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Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

DOI： 10.2208/jscejhe.74.i_247

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s10546-017-0249-y

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Other Link： http://link.springer.com/content/pdf/10.1007/s10546-017-0249-y.pdf

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s10546-017-0233-6

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s10546-016-0213-2

Web of Science

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Language：Japanese  

CiNii Books

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

Identifying the pre-convective condition of the atmospheric boundary layer plays an important role in the prediction of extreme weather events. To achieve this, acquisition of low-level flow fields is necessary. Latest available wind vector dataset, called Atmospheric Motion Vector (AMV), is still incapable for estimating near-ground level fields. We investigated the possibility applying the Thermal Image Velocimetry (TIV) method to Himawari-8 satellite retrievals to estimate near-ground level fields in cloud-free areas, identified during days of calm weather with sea-breeze penetration.<br> A sea-breeze day event on August 4,2015 was selected. Average sea-breeze inland penetration speed was estimated to be ~3.6 m/s and ~1.8 m/s from Sagami Bay and Tokyo Bay, respectively. The derived motion vector of advection flow from TIV revealed the general pattern of near-surface atmospheric flow due to sea-breeze phenomena.

DOI： 10.2208/jscejhe.73.i_463

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s00704-015-1556-1

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

We proposed a new height parameter which explicitly and uniquely specifies the potential range of surface layer regardless of daytime mixed layer, nocturnal stable layer, or indoor free stream topped on it. This parameter is defined as the level where the momentum flux becomes zero by extrapolating the momentum flux profile within the surface layer to the top. We conducted multi-point Doppler lidar observations in Tokyo to test this parameter. Two Doppler lidars were used to measure the vertical distribution of the momentum flux at two locations to test the new parameter proposed in this study. The other one is used to measure the height of the atmospheric boundary layer for comparison. When the mixed-layer is well developed, the height of surface layer reached about 15% of the mixed layer height, which is consistent with the conventional estimates. It is also observed that the diurnal variations of the height of surface layer and mixed layer are negatively correlated.

DOI： 10.2208/jscejhe.72.i_79

DOI： 10.2208/jscejhe.78.2_i_325_references_DOI_IBPbmVwu5FrNkWAV3N97yrvpKqd

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Other Link： https://ndlsearch.ndl.go.jp/books/R000000004-I027165502

Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Hydrology and Water Resources  

DOI： 10.3178/jjshwr.29.186

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Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s10546-015-0019-7

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Other Link： http://link.springer.com/article/10.1007/s10546-015-0019-7/fulltext.html

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s10652-013-9322-3

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Other Link： http://link.springer.com/article/10.1007/s10652-013-9322-3/fulltext.html

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

We conducted continuous observation for three months using Doppler lidar to investigate characteristic of the spacing of streaky coherent structures which include horizontal roll vortex and streak above urban area, Tokyo. The spacing of streaky coherent structures was estimated from the power spectrum density of horizontal velocity fluctuation. The spacing normalized by boundary layer height decreases with decreasing atmospheric stability In stable condition, and varies in a wide range under weakly unstable condition. A remarkable finding is that normalized local wind shear can consistently explain the normalized spacing of streaky coherent structures developed under stable, neutral and unstable conditions. In other words, local wind shear plays a significant role to decide spacing of such streaky coherent structures as horizontal roll vortex and streak.

DOI： 10.2208/jscejhe.71.i_415

DOI： 10.3130/aije.86.185_references_DOI_4wXLbKKt6WuQuTXe1tPYHf20FIY

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Other Link： https://ndlsearch.ndl.go.jp/books/R000000004-I026333489

Language：English  

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

Several methods are established for measuring two-dimensional horizontal velocity distribution for outdoor flow field. Yet, a method to measure the turbulent structure of 10~100 meter scale is lacking.TIV (Thermal Image Velocimetry), which is introduced in this paper is adequate to the range and has quantitatively measured dust devil like vortex and upward flow near the wall in the past researches. However, advection velocity of TIV and wind speed relation is not yet clarified. In this research, horizontal surface wind speed distribution in an outdoor artificial turf football field were estimated from a TIV observation experiment that took place during sunny daytime in Sep. 2013. Two dimensional horizontal advection speed vector estimated from thermal camera and wind speed measured by 5 sonic anemometers were compared for all 21 observation cases by 10 minute intervals.

DOI： 10.2208/jscejhe.71.I_427

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

Large Eddy Simulation (LES) with realistic three-dimensional building geometries have been performed for both neutral conditions and unstable thermal conditions. Parallelized Large-Eddy Simulation (PALM) has been implemented for LES modelling. Heterogeneous three-dimensional sensible heat fluxes over impervious urban surfaces at five metres resolution in Shinjuku have been calculated by an urban outdoor-indoor multi-patch energy balance model (3D-City Irradiance). This can calculate sophisticated radiation exchange processes. These values have then been inputted into PALM by the setting of Neumann boundary conditions. The effect of buoyancy from surface heating on turbulent structures within the urban atmospheric boundary layer and the urban canopy layer has generally been investigated. Moreover, special attention has been paid to streaky mechanical and thermal turbulent structures above high-rise buildings, which have been considerably altered.

DOI： 10.2208/jscejhe.71.i_433

DOI： 10.2208/jscejhe.74.i_259_references_DOI_46aD59Y64339k8j3FGalWRHLVVT

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Language：English   Publisher：Japan Society of Civil Engineers  

When simulating the turbulent flow around urban structures with large-eddy simulation models it is often necessary to use non-cyclic boundary conditions in streamwise direction. In such cases a turbulent inflow condition at the inlet is favored although it is highly difficult to obtain. A synthetic turbulence generator, modelling turbulence statistics and correlations, is used to generate a turbulent inflow for large-eddy simulations. Results are compared with simulations using laminar inflow. An artificial urban canopy consisting of aligned buildings with cubical shape was used. Two simulations contained one additional tall building located at the center of the domain. The turbulence statistics show a well-developed urban boundary layer above the building arrays for each simulation. Higher turbulence intensity was found when using the turbulence inflow method resulting in faster development of an urban boundary layer.

DOI： 10.2208/jscejhe.71.i_43

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Other Link： https://ndlsearch.ndl.go.jp/books/R000000004-I026324394

Language：Japanese   Publisher：Japan Society of Civil Engineers  

Horizontal turbulent flow fields within atmospheric boundary layer above an urban area (Tokyo, Japan) measured by Doppler lidar in autumn and winter were visually classified into six groups, Streak, No streak, Mixed, Fish net, Front, The others. The conditions of each flow occurrence were examined with observed surface meteorological data and related scaling parameters. The following results were obtained: (1)Streak dominates 64% of all valid data, while Fish net does only 2%. No streak and The others, look more laminar rather than turbulent, reach to 20% contribution in total. (2) Each flow patterns can be categorized by . and Re ( is boundary layer height, is the Monin Obukhov length. Re is Reynolds number, the length scale of which is .). (3) Each flow patterns can be categorized by . and Resurf (z is observation height. Resurf is Reynolds number, the length scale of which is .) as well as . and Re. (4) The diagrams of . and Re, and . and Resurf qualitatively illustrate the flow regimes.

DOI： 10.2208/jscejhe.70.I_325

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s10546-013-9832-z

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Other Link： https://projects.repo.nii.ac.jp/?action=repository_uri&item_id=377326

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s10546-013-9818-x

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Other Link： http://link.springer.com/article/10.1007/s10546-013-9818-x/fulltext.html

Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s10546-012-9790-x

Scopus

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Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

DOI： 10.2208/jscejhe.69.i_1753

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Language：Japanese   Publisher：Japan Association for Wind Engineering  

DOI： 10.5359/jawe.37.184

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：土木学会  

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Other Link： https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-21360233/

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s10546-011-9671-8

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

A new technology to estimate velocity fields very close to a ridged wall by using a sequence of thermal images of the wall is proposed. We call this method Thermal Image Velocimetry (TIV). The principle TIV is the same as PIV (Particle Image Velocimetry) but utilizing thermal images instead of particle images. Although TIV can potentially obtain highly fluctuated turbulent fields, the surface temperature (ST) of the target wall should be sensitive to the velocity fluctuation nearby. We apply TIV to a building wall and discuss the performance of TIV. Insulation panels, Styrofoam^TM, are attached on the target wall. Styrofoam^TM decreases the volumetric heat capacity of the surface thereby increasing the sensitivity of ST to velocity fluctuations. The wind variations estimated by TIV correlate very well with those observed by a sonic anemometer.

DOI： 10.2208/jscejhe.68.i_1753

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Other Link： https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-21360233/

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

This study focuses on the problem of "mosquito swarm" along urban rivers. Different from general biological methods (capture, counting and photograph), we adopted a fluid dynamical approach to investigate the temporal-spatial distribution of mosquito swarm. First, a novel device composed of multiple laser sheets is developed as a mosquito counter in order to quantify the density of the swarm. Second, filed observations are done in Nomi River by utilizing this laser device as well as the other conventional meteorological observations. The followings are the major results obtained: (1) Mosquito swarms are apparent only about 1 hours before the sunrise heavily on one-sided (sunlit side) along the river. (2) The hot-sopt of mosquite swarm seems to exist ; the cross sections of urban street perpendicular to the river. The locations were roughly fixed with slight perturbations. (3) The suitable temperature to make swarm is about 22.5ºC.

DOI： 10.2208/jscejhe.68.i_763

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Other Link： https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-21360233/

Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

DOI： 10.2208/jscejhe.68.i_1777

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

This report aims to propose a new aerodynamic parameterization of the urban land surface parameters for mesoscale weather prediction models. Aerodynamic parameters in build-up area are calculated from an output of the large eddy simulation in which the airflow within the building canopy was explicitly resolved with fine grid spacing. Real urban morphologies in Tokyo were implemented in the simulation. Drag coefficients, which were calculated from the numerical simulation, became significantly larger than those from the conventional morphological models widely used. The influence of relevant geometric parameters such as the maximum building height and the deviation of building height on the aerodynamic parameters are discussed. On the base of discussion above, a new simple aerodynamic parameterization is proposed.

DOI： 10.2208/jscejhe.68.i_1801

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s10546-011-9614-4

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Other Link： http://link.springer.com/article/10.1007/s10546-011-9614-4/fulltext.html

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s10546-011-9612-6

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Other Link： http://link.springer.com/article/10.1007/s10546-011-9612-6/fulltext.html

Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.ijheatmasstransfer.2011.04.020

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

Thermal boundary layers along the wall of a building were measured by using a thermocouple rake perpendicularly installed to the wall and a sonic anemometer with a high sampling frequency. In order to measure the temperature in the viscous layer, four thermocouples were set within 1mm from the wall surface. The Grashof number, Grx, which is a non-dimensional parameter of buoyant flows, was varied from 109 to 1012, to examine the scale effects. The boundary layer thickness normalized with similarity parameters for laminar natural convection was estimated, and the value is related to the fetch of heated wall. The measured temperature profiles were found to be composed of three layers. The layer closest to the wall is mainly controlled by the buoyancy flow due to heat from the wall, whereas in the farthest layer, the effects of the forced convection flows of the atmosphere become dominant. The middle layer is influenced by both the buoyancy flow and the forced convection flows.

DOI： 10.2208/jscejhe.67.i_337

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Other Link： https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-21360233/

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Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s10546-010-9477-0

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Other Link： http://link.springer.com/article/10.1007/s10546-010-9477-0/fulltext.html

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DOI： 10.2208/prohe.52.307

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Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

The present study investigated the relationship between the mean and instantaneous characteristics of turbulence within the atmospheric surface layer over urban like roughness. To make it, we compared the horizontal distribution of the turbulent fluctuations and the turbulent statistics, which are derived from the same data obtained in the facility of comprehensive outdoor scale model for urban climate (COSMO) .<BR>It is known that the turbulent motion within the atmospheric surface layer is composed of active and inactive eddies. The active eddy is originated from the surface under neutral stratification and relevant to the turbulent transport process. The inactive eddy is attributed the mixing in the atmospheric boundary layer and irrelevant to the turbulent transport process. To evaluate the characteristics of active turbulence which reflects the characteristics of roughness, we decomposed the turbulent fluctuation into the active and inactive components. This analysis revealed that the streaky structure observed in COSMO is attributed to the active turbulence.

DOI： 10.2208/prohe.52.253

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Other Link： https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-05J08562/

DOI： 10.1017/S0022112008003765

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DOI： 10.2208/prohe.52.313

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DOI： 10.5359/jawe.2008.299

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DOI： 10.1007/s10546-006-9133-x

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DOI： 10.2208/prohe.51.241

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Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

The present study investigated the vertical profiles of the turbulent statistics over the reduced urban scale model in a neutral stratification. The experiment was conducted under the planetary boundary layer so that the corrected data was always affected by the outer layer turbulence more or less. We compared the surface layer turbulence statistics in the scale model with that in urban, which are velocity spectra, momentum co-spectra and nondimensional velocity variances and so on. <BR>A scale effect was apparent in the statistics related with the horizontal velocity variance. The scale effect came from the discrepancy of the ratio of outer layer (i. e. planetary boundary layer) scale with the surface layer scale of the scale model and with that of urban. Although the former scale is always same order, the latter scale is different in urban and in the scale model. Therefore we considered that the scale effect is an evidence of the influence of the outer layer turbulence in the surface layer.

DOI： 10.2208/prohe.51.247

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Other Link： http://t2r2.star.titech.ac.jp/cgi-bin/publicationinfo.cgi?q_publication_content_number=CTT100601013

Language：Japanese   Publisher：The Japan Society of Fluid Mechanics  

DOI： 10.11426/nagare1982.26.361

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Meteorological Society of Japan  

DOI： 10.2151/jmsj.84.187

Scopus

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Other Link： https://ndlsearch.ndl.go.jp/books/R000000004-I7832608

Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

The vertical profiles and horizontal distribution of atmospheric turbulence were observed at an outdoor urban scale model site. The model dimensions were 50 x 100m, with 1.5-meter cubic roughness blocks arranged uniformly. Eight sonic anemometers were arranged vertically or horizontally in the site to obtain the vertical profiles or horizontal distribution. In this study, we focused on the atmospheric stability effect on the vertical profiles and the horizontal distribution of the turbulent structure over the model site.<BR>The quadrant analysis was conducted using the data set of the vertical distribution. The analysis showed the dependence of the turbulent motion on the atmospheric stability (z'/L). The sweep mode is mostly dominant at all height in the surface layer when the stability is stable. In case of the unstable atmospheric condition, the ejection mode can crossover the sweep mode at the higher portion in the surface layer.<BR>The streak pattern was observed in a turbulent flow over the building like roughness from the measurement of the horizontal distribution. The width was about 3 or 6 times larger than that of the blocks. This result strongly implies the importance of the horizontal distribution the turbulent structure over urban area.

DOI： 10.2208/prohe.50.445

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Other Link： https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-05J08562/

DOI： 10.2208/prohe.49.343

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Language：English  

DOI： 10.1023/B:BOUN.0000007225.45548.7a

Web of Science

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Other Link： http://link.springer.com/article/10.1023/B:BOUN.0000007225.45548.7a/fulltext.html

DOI： 10.2208/prohe.47.37

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Publisher：Japan Society of Civil Engineers  

The spatial representativeness of turbulent fluxes on the basis of point measurements has been investigated through a theoretical approach and numerical experiments using Large Eddy Simulation (LES) Model. These investigations have been done for the daytime atmospheric boundary layers heated uniformly over the flat surface with no synoptic vertical motion under several geostrophic winds from 1 to 4 (ms^-1). The following results were obtained;<BR>(1) The spatial representativeness of turbulent fluxes based on the time-series analysis are shown to be problematic: Their horizontally averaged value has a negative imbalance irrespective of the density of measurements points, and their spatial variability increases, in accordance with averaging time, or under lower horizontal wind.<BR>(2) The imbalance intensities are closely related to turbulent organized structure (TOS). The points over the updraft regions are likely to have positive imbalance due to highly activated thermal plumes. The temporal and spatial change of TOS pattern cause low-frequency trends in time-series data, which can account for the large horizontal scatter of flux estimates.<BR>(3) High-pass filter excluding the temperature trend is theoretically useful to improve the representativeness of point measurements, although the filter choice actually needs a great care not to damage the turbulent components.

DOI： 10.2208/prohe.46.97

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：Japanese   Publisher：日本気象学会  

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Language：Japanese   Publisher：日本気象学会  

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Language：Japanese   Publisher：日本気象学会  

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Language：Japanese   Publisher：日本気象学会  

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Language：Japanese   Publisher：日本気象学会  

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Language：Japanese   Publisher：日本気象学会  

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Language：Japanese   Publisher：日本気象学会  

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Language：Japanese   Publisher：日本気象学会  

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Language：Japanese   Publisher：社団法人日本気象学会  

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Language：Japanese   Publisher：日本気象学会  

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Language：Japanese   Publisher：日本気象学会  

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Language：Japanese   Publisher：日本気象学会  

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Language：Japanese   Publisher：土木学会  

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Language：Japanese   Publisher：社団法人日本気象学会  

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Language：Japanese   Publisher：社団法人日本気象学会  

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Language：Japanese   Publisher：日本気象学会  

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Language：Japanese   Publisher：日本気象学会  

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Language：Japanese   Publisher：日本気象学会  

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Language：Japanese   Publisher：社団法人日本気象学会  

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Language：Japanese   Publisher：日本気象学会  

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Language：Japanese   Publisher：日本気象学会  

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Language：Japanese   Publisher：日本気象学会  

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Language：Japanese  

Turbulence similarity was investigated over an array of cubic roughness under atmospheric condition. The measurement was compared with the datasets obtained in cities, rural fields and laboratory experiments. It was observed that the inner-scaling similarity is valid through the various experimental fields. A nature of atmospheric flow, which is the prominent outer-layer disturbance, contaminated the similarity law in a low frequency region of spectra. To understand the role of outer-layer disturbance with inner-scaling, the scale of outer-turbulence and also that of roughness should be considered. In addition, the horizontal distribution of the velocity fluctuation was also examined.

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Language：Japanese   Publisher：日本気象学会  

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Language：Japanese   Publisher：日本気象学会  

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Language：Japanese   Publisher：日本気象学会  

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Language：Japanese   Publisher：日本気象学会  

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Language：Japanese  

J-GLOBAL

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Language：Japanese   Publisher：日本気象学会  

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Presentation type：Poster presentation  

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Presentation type：Poster presentation  

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