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In 2022, intense heat waves occur all around the world. In this study, we project these heat waves into the future with futuristic projection of hourly varying spatially distributed anthropogenic heat for three megacities—Delhi, London, and Tokyo. Different future climate forcing (CMIP5 and CMIP6) was also compared. We found that if similar heat waves occur in the future, they may be 0.8 to 1.5 °C hotter than the past events, on average. Urbanization in Delhi may severely worsen the heat wave, while projected decrease in energy usage in London and Tokyo may make the heat waves less severe. For the concerned heat wave events, urbanization effect was also found to be stronger in nighttime than daytime and exhibits large spatial heterogeneity and dependence on background climate forcing. Difference between CMIP5 and CMIP6 was significant but was much less than the difference between CMIP5/CMIP6 and the present.

DOI： 10.2208/journalofjsce.23-16120

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Historical land cover data is crucial for understanding urbanization dynamics, climate modeling, and monitoring water resources. Following recent advancements in deep learning for processing Landsat archive data, prior studies have released high-resolution historical land cover maps on a global scale. However, these works often present prediction results limited to specific periods of coverage, which hinders their utility in conducting time series analysis across different urban agglomerations. To address this issue, we propose deep-learning models for land cover classification from Landsat images at a 30-meter spatial resolution. Our models are specifically designed for urban areas and are trained to be compatible with the sensors used in the Landsat series from 1972 to the present. Experimental results demonstrate that our models are highly effective in predicting land cover maps in new cities, particularly in built-up land and water regions. Our research provides pretrained models for land cover classification, facilitating future studies in related fields.

DOI： 10.2208/journalofjsce.23-16151

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DOI： 10.1016/j.scs.2023.104442

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Cities warm up due to two main factors: global climate change and urbanization-induced warming (so-called, urban heat island effect). In the projection of future climate, coarse-resolution global climate models are not suitable for looking into the heterogeneous urban surface and their changes. On the other hand, regional climate models, which are capable of looking into cities in detail, have never been used to investigate the global urban climate. Here we show that urbanization significantly increases exposure to extreme warming for megacity residents. We reflect urbanization between the 2010s and the 2050s into our model by considering the spatiotemporal change in urban surface (buildings and anthropogenic heat emissions) induced by urban population and economic growth. We found that in the 2050s, under the worst-case scenario, 78 percent of megacity residents will be exposed to 2.5 °Cwarming, much higher than the projection of 65 percent when urban warming is left out. Our results highlight the importance of accounting for local urbanization in future global urban climate projection.

DOI： 10.1016/j.heliyon.2023.e15511

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DOI： 10.20965/jdr.2022.p0516

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

There is growing concern about the health risks posed by global warming and the heat island effect. In order to properly assess health risks, it is important to evaluate them in terms of thermal comfort. This study evaluated the long-term trend of the Universal Thermal Climate Index (UTCI) in Japan in summer from 1980 to 2020, and the relationship between UTCI and the number of heat stroke patients. Regarding the long-term trend of UTCI, increasing trends were detected at 109 out of 140 AMeDAS sites. Thermal comfort had worsen since the rise in air temperatures, MRT, and decreasing wind speeds. Regarding the relationship between UTCI and the number of heat stroke cases, we found that the UTCI threshold at which the number of heat stroke cases drastically increase differs across cities geographically and lower in northern cities than southern cities.

DOI： 10.2208/jscejhe.78.2_i_79

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Other Link： https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-21K14249/

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DOI： 10.1038/s41597-021-00850-w

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The Global Scientist and Engineers Program (GSEP) is Tokyo Institute of Technology’s purely English instruction-based undergraduate program in transdisciplinary science and engineering specifically designed for international students with minimal to no Japanese communication ability. The program faces multiple challenges not just those relating to multiculturalism but also in providing education in a newly emerging academic field. This research evaluates the program through questionnaires, mind mapping workshop, and focus group discussion conducted with the program’s first cohort who graduated in March 2020. The program was evaluated on how well the graduating students have gained confidence in important areas relevant to their field of study and the amount of support they received while in the program. The first cohort showed satisfaction being graduates of the program, expressed confidence in their transdisciplinary knowledge, and see themselves as global citizens. With enhanced engagement with Japanese students, the program has the potential to become a top-notched international undergraduate engineering degree program based in Tokyo.

DOI： 10.20549/jseeen.2021.0_6

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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

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

Language：English   Publishing type：Research paper (scientific journal)   Publisher：{MDPI} {AG}  

DOI： 10.3390/su12176801

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DOI： 10.1038/s41598-020-66288-z

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Heat-risk evaluations are needed by societies for adapting to and mitigating the social/health impacts attributed to climate change and urbanization. Meanwhile, big data and numerical models are advancing.

 In this study, we propose an integrated approach to utilize both big data and existing models for estimating heat-related risk. By combining products of a 3D-City irradiance model and Google big data services, a geospatial framework for mapping heat-related risks(Hazard×Exposure×Vulnerability) was developed .Hazard and exposure(individual HR factor) were estimated using thresholds of wetbulb globe temperature(WBGT) and mobility from frequented locations to nearest station exits; Vulnerability(HR probability factor) was estimated using popular times of frequented locations. Through this framework, multiple perspectives for understanding heat risks may be observed at various districts. For example, ATMs were found to have high heat risks mainly because of its high HR probability factor.

DOI： 10.2208/jscejhe.76.2_i_283

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Urbanization is an essential, yet underrepresented, parameter when investigating futuristic climate change of cities. The change in 2 m air temperature in August between the 2006–2015 period and the 2046–2055 period for 33 megacities and 10 emerging megacities under RCP8.5 emission forcing and SSP3 was projected with the consideration of both global climate change (using pseudo-global warming method) and local urbanization (using global urban sprawling map, distributed urban morphological parameters, and hourly anthropogenic heat emission dataset).

 In newly urbanized area, the urbanization effect will be significant, accounting for (13.5 ± 5.9) % of the total temperature change. In existing urban areas, the effect will vary depending on the current degree of urbanization. When viewed over a regional scale, the effect will be rather insignificant. It was observed in some cities that urbanization effect originating from urban area was advected by the wind to non-urban area located kilometers downwind.

DOI： 10.2208/jscejhe.76.2_i_103

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Language：Japanese   Publisher：東京 : 土木学会  

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Other Link： http://id.ndl.go.jp/bib/030806402

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Other Link： http://id.ndl.go.jp/bib/030805852

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DOI： 10.1016/j.uclim.2019.100482

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DOI： 10.1038/s41597-019-0048-z

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Institute of Life Cycle Assessment, Japan  

In Asian megacities, not only climate change but also heat island phenomena are expected to pose air temperature increase. Therefore, effective adaptation measures to alleviate health damage caused by temperature increase are becoming more crucial. The objective of this study is to evaluate the effect of air conditioner on health damages using disability-adjusted life year（DALY）and considering an adverse effect from temperature increase accompanied by exhaust heating from outdoor units and uncertainty of the effect caused by interannual variability in temperature in Jakarta, Indonesia. Health damages to be assessed were sleep disturbance and fatigue. By increasing the usage rate of air conditioners, it was estimated that the DALY reduction per person per month in August of the average temperature year is 2.48 × 10^-4 years for sleep disturbance, 1.43 × 10^-5 years for fatigue, and totally 2.62 × 10^-4 years. It corresponded with 29.8% reduction from the present situation. The effect of interannual variability in temperature was not large, which was 7.94 × 10^-5 years at most. Air conditioner will be one of effective adaptations throughout the year considering small monthly variability in temperature and the residents’thermal perception.

DOI： 10.3370/lca.15.2

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In order to analyze the effects of urban warming, it is essential to estimate Urban Heat Island (UHI) and elucidate its mechanism. However, the method to estimate UHI, which has been studied by previous numerical simulation, is simplified by replacing land use before urbanization with vegetation not necessarily representing the background climate of the region. This leads to inaccurate UHI estimates

 In this study, we construct a land use global database representing pre-urbanization for an improved numerical modeling of the UHI. This database makes it possible to compare urban meteorological conditions using current land use and those utilizing typical land use before urbanization for any city around the world. This study demonstrates the usage of the global database by comparing two simulation cases for 35 large cities and examining the tendency of UHI. Temperature rises are seen in both cities during the daytime and nighttime in many cities. The current work also hints the possible dependence of UHI on topography, building geometry, etc.

DOI： 10.2208/jscejhe.75.2_i_1039

DOI： 10.2208/jscejhe.76.2_i_103_references_DOI_Cv8REbTy4YBDZQ2XXWP9sCdc0R1

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The urban heat island (UHI) is caused by the progress of urbanization, but is considered to be influenced by various factors that differ depending on the cities, such as the geography and the background climate. However, the comprehensive mechanism is not clear yet. In this study, we tried to clarify the influence of not only urbanization, but geography and background climate by comparing the heat island phenomena of multiple cities in the world using numerical simulation. The wind speed is the main contributor to the urban heat island intensity; the heat of the city is transferred more effectively to the surrounding area as the wind speed is stronger. The wind speed is considered to be a comprehensive indicator reflecting the effect of geography around the city, and the roughness of the buildings.

DOI： 10.2208/jscejhe.75.2_i_37

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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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Language：Japanese   Publisher：東京 : 土木学会  

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Other Link： http://id.ndl.go.jp/bib/028903132

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Other Link： http://id.ndl.go.jp/bib/029394852

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DOI： 10.1038/s41612-018-0042-8

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A systematic method to project the future distribution of population in megacities is introduced. Two general steps were discussed: (1) estimation of urban sprawl by an urban growth model, SLEUTH; (2) estimation of population distribution by a logistic model with variable empirical coefficients. Predicting the annual change from 2014 to 2050, Jakarta megacity was used as a benchmark urban agglomeration. The key inputs are historical land cover and geographic information, transportation networks, high-spatial resolution population density, and country-level projection of population as defined by various shared socio-economic pathways (SSP). Coefficients were modified in SLEUTH to predict urban sprawling (and auxiliary probability map) compatible with a suitable SSP faced by the encompassing country. Utilizing the predicted annual probability of urbanization and the key inputs into a discrete logistic model with empirical coefficients fitted to minimize the difference of total predicted population with that provided by SSP, population distribution of the target urban agglomeration, Jakarta, was obtained.

DOI： 10.2208/jscejhe.74.i_223

DOI： 10.2208/jscejhe.76.2_i_103_references_DOI_YrDoPBq8eUnxeG0ICm0rKUz3D18

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The contribution of anthropogenic heat (AH) to the surface energy budget is well known. However, further investigation of realistic AH emissions in cities and their interactions with its surrounding atmospheric environment is still limited. Furthermore, past studies are site-specific providing limited insight to general impacts of AH. In this study, a realistic, high-spatiotemporal AHE dataset was used as surface boundary input into a weather model. With monthly-representative typical diurnal climatic pattern from 2006 to 2015 as lateral boundary, weather simulation of atmospheric environment of 15 large Asian cities included in the world’s top 30 largest cities declared by the United Nations was conducted. Results suggest that the effect of AH per location is sensitive to the background climate. An empirical equation is introduced to approximate the amount of temperature increase for any city of a given AH and background monthly temperature.

DOI： 10.2208/jscejhe.74.5_i_1177

DOI： 10.2208/jscejhe.75.2_i_1039_references_DOI_W2cE0n60hvsDXUcnLd96nAh3bMG

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DOI： 10.1016/j.uclim.2017.07.001

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DOI： 10.1016/j.atmosenv.2016.11.040

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Despite increasing utilization and accuracy of models to predict the future climate and hydrology at higher resolutions, urban areas are still underrepresented. A method to determining future distribution of urban parameters in accordance with the global climate and socio-ecoonomic pathways of the future is proposed. An urban growth model was used to project the expansion of urban areas in 2050 of Jakarta. From shared socio-economic pathways (SSP), total population in the future was acquired. Using historical population distribution data, spatial distribution of population was projected until the year 2050. From empirical relationships acquired from population with nighttime lights adjustment, actual urban parameters, and GDP, futuristic urban parameters were calculated. Finally, the calculated future distribution of urban parameters was used in downscaling the future climate of Jakarta using the pseudo-global warming method.

DOI： 10.2208/jscejhe.73.i_103

DOI： 10.2208/jscejhe.76.2_i_103_references_DOI_PAEKG0Xpk2ZFy1oxqzfWtebTZxb

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Recent studies have proven the need for realistic urban representation in weather models. However, cities modeled using distributed urban parameters with updated urban parameterization are still few and limited to highly developed countries. Furthermore, real building datasets used to estimate the urban parameters are unavailable or lacking in other cities. This study was conducted to address both issues by expanding the advance weather model methodology to another megacity and utilizing global datasets to readily estimate a distribution of urban and other surface parameters. Sensitivity of the models to either real or global-estimated urban parameters was conducted; and the urban effect to a synoptic circulation over Istanbul was investigated. The simulation results for a typical summer day over Istanbul suggest that global datasets can be used as alternative to real building data for estimating distributed urban parameters.

DOI： 10.2208/jscejhe.72.i_91

DOI： 10.2208/jscejhe.74.5_i_1177_references_DOI_QRAOwPK8b5PinYZXi9Y6OgA9EIG

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DOI： 10.2208/jscejhe.72.i_91

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Weather models coupled with urban parameterizations require robust and realistic urban parameter inputs such as actual building distribution. Acquiring real building parameters often require huge amount of time and money. In this study, we introduce a simplified but precise approximation of urban parameters through a readily-available, high-resolution global dataset. Regression equations were derived from the spatial relationship of global 1-km population dataset adjusted by nightlight distribution to real urban parameters in Japan and Istanbul, Turkey. These equations can readily estimate urban parameters globally. Derived global urban parameters were incorporated into a weather model to investigate urban heat island in neighboring megacities in South and Southeast Asia. UHI phenomena of 5 mega cities depended a great deal on location and climate zone of each city.

DOI： 10.2208/jscejhe.72.i_97

DOI： 10.2208/jscejhe.74.5_i_1177_references_DOI_WPWjMHWElvF5fhF2PfZCZ8uIxgL

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DOI： 10.2208/jscejhe.72.i_97

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DOI： 10.1007/s10546-014-9985-4

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This paper analyzed the behavior of sea breeze (hereafter SB) penetration to urban area in Kanto. In order to analyze SB penetration, we proposed a new method for SB-front detection using very high-resolution-geostationary satellite images, or MTSAT-2 Rapid Scan, with 1 km-spatial and 5 min.-temporal resolution. From the images, the detailed behaviors of SB were successfully visualized. For the selected SB events, the penetrations to in-land from Tokyo bay and Sagami bay were discussed using the point data of AMeDAS and Atmospheric Environmental Regional Observation System (AEROS), and also a result from the meso-scale simulation, where the important urban effects were parameterized (e.g., actual aero-thermodynamic parameters, anthropogenic heat and vapor emission). Along Tokyo-Saitama line, SB stagnation occurred in every sea breeze event. The observed higher air temperature and convergence resulted in increased vertical mixing, leading to SB stagnation.

DOI： 10.2208/jscejhe.69.i_1741

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Other Link： http://id.ndl.go.jp/bib/024914646

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This paper highlights the application of Water and Energy Transfer Processes (WEP) Model to two highly urbanized watersheds within Tokyo, Japan; Nomikawa and Meguro watershed. Major model improvements include refinement of time-resolution input rainfall data from 1 hr. to 10 min. intervals, and addition of subroutine to accommodate weir/side-weir effects and rainfall input. 2007 heavy rainfall data from Tokyo AMESH were used in Nomikawa watershed simulation. 2008 heavy rainfall data from Tokyo Metropolitan Construction Bureau were also used to simulate runoffs for Meguro watershed. The improved model was validated using comparative analysis of previous and new model using simulated river discharges and actual gauge measurements. Results show the new model simulates rapid runoffs well.

DOI： 10.2208/jscejhe.67.i_25

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Global anthropogenic heat flux (AHF) with high spatial resolution is needed to deepen understanding of climate in cities. Existing datasets require improvements in the spatial estimation of AHF. Specifically, AHF point sources of industrial facilities, power plants, or oil refineries were not detected.

 In this study, we improved the spatial estimation of AHF globally by estimating the emissions of point sources using a coupling of short-wavelength infrared data measured by satellite (VIIRS-Nightfire) with conventional top-down approach methodology. Using VIIRS-Nightfire, we have validated the location of point sources and partitioned the bulk estimates of energy consumption in Japan. Most of the detected AHF from point sources were coming from either blast furnaces or thermal power plants.

DOI： 10.2208/jscejhe.74.5_i_1171

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Language：Japanese   Publisher：THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES  

<p>&emsp;Global urban climatology (GUC) is proposed as a subfield of urban climatology. The main focus of GUC is uniform understanding of urban climates across all cities, globally. By utilizing globally applicable methodologies to quantify and compare urban heat islands of cities with diverse backgrounds, including their geography, climate, socio-demography, and other factors, a universal understanding of the mechanisms underlying the formation of the phenomenon can be established. The implementation of GUC involves the use of globally acquired historical observation networks, gridded meteorological parameters from climate models, global geographic information system datasets, the construction of a distributed urban parameter database, and the development of techniques necessary to model the urban climate. Here, the GUC concept, the pathways through which GUC assessments can be undertaken, and current implementations are discussed together with some examples of its application.</p>

DOI： 10.3178/jjshwr.29.313

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This research focuses on the improvement of urban parameters for weather models. The distribution database – derived from a combination of recently-derived parameterisation, processed urban building geometry data, and open source satellite-acquired digital elevation maps – were incorporated into the urban canopy model of the Advance Weather Research and Forecasting Model. The focus of the study is on the importance of applying large eddy simulation-derived aerodynamic parameterisation into the model. The statistics of simulated wind speeds using new parameterisation reveal better accuracy than those using conventional roughness parameters. The modified model was used to understand actual building roughness effects on wind fields. On account of the increased roughness parameter values, surface drag became more apparent at urban areas. Consequently, the simulated spatial distribution of fronts matches well with ground observations and satellite imagery. The applications of the model cover an investigation of the interaction of sea breeze circulation and urban heat island in Tokyo and other major cities.

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Language：Japanese   Publisher：日本気象学会  

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Numerical weather prediction models for urban weather require various urban parameters such as urban geometry and anthropogenic heat emission. Preparing databases of these urban parameters is essential for better reproducibility of urban weather simulation.<br>In this paper, a database of urban geometric parameters for the whole Japan is created using a detailed building GIS. This database includes average, maximum, and standard deviation of building heights, plane and frontal area indices, roughness length for momentum, displacement height, and sky view factor. Furthermore, to expand this database to areas where detailed building GIS is not well prepared, methods of estimating the surface parameters are proposed. These methods require only a global digital elevation models and aerial imagery, which are now open to public inspection and easy to obtain. The results are compared with values derived from high-resolution building heights data.

DOI： 10.2208/jscejhe.70.I_331

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Numerical weather prediction models have been improved to adequately represent the growing influence of urban areas to surrounding weather. Recently, updated LES-derived empirical equations on the aero-dynamic urban surface parameters displacement height d, and roughness length for momentum z0m, have been introduced. Using a high spatial resolution d, z0m, and anthropogenic heat emission distribution, dry case simulation was conducted using Weather Research and Forecasting Model with domains covering Tokyo, Nagoya, and Osaka. It was found that default WRF generally underestimate roughness. Results were also compared with actual observations of 2 m air temperature and surface wind speed, and were found to be well represented in the model when detailed parameters were used.

DOI： 10.2208/jscejhe.70.I_175

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

Urban localized heavy rainfall has become a serious issue especially during summer in the Tokyo metropolitan area. In order to analyze its relationship with urbanization, improved urban parameters were implemented into WRF together with high spatial resolution sea surface temperature (SST). For the simulation, the aerodynamic parameters such as roughness length and displacement height were prepared using a new feedback parameterization derived from large eddy simulations of real urban morphology. Applying the new urban parameterization realized a more accurate simulation of localized heavy rainfall. The stagnation of heat and water vapor around city, and also the delay of sea breeze caused by the drag of urban geometry, increased heavy rain in Tokyo.

DOI： 10.2208/jscejhe.69.i_355

DOI： 10.3178/jjshwr.29.313_references_DOI_Mh49INl3IiNZtPODfz4KxyQerA

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Language：Japanese   Publisher：日本気象学会  

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J-GLOBAL

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