Development and application of urban climate-building-energy model

Global warming will accelerate urban heat island effect, which causes serious increases of heatstroke and energy consumption. To contribute in solving the social problems, AIST has been developing an urban climate-building-energy model. We have improved the model’s reproducibility of electricity consumption and expanded the regions can be simulated by the model, which enabled us to assess the effectiveness of global warming adaptation strategies. For example, we estimated the impact of COVID-19 (i.e., changes in human behavior) on air temperature and electricity consumption using real-time human population data (see figure). We have also developed a method to incorporate a contribution of urban vegetation into the model. In addition, we have carried out a new study to evaluate carbon budgets of terrestrial biosphere using our original forest fire model.

Press releases (in Japanese)

https://www.aist.go.jp/aist_j/press_release/pr2020/pr20201106/pr20201106.html

https://www.aist.go.jp/aist_j/new_research/2022/nr20220603/nr20220603.html

https://www.aist.go.jp/aist_j/press_release/pr2023/pr20231129/pr20231129.html

Evaluation of carbon/oxygen cycles and climate change based on precise observations of major atmospheric components

High-precision simultaneous measurements of atmospheric O₂/N₂ ratio, Ar/N₂ ratio, CO₂ concentration, stable isotopic ratios of N₂, O₂, and Ar are useful not only to estimate global and local CO₂ budgets but also to detect signals of climate change such as ocean heat content and atmospheric circulation. We have continued long-term and wide-area observations of the components, and started to apply them to evaluate some techniques to mitigate atmospheric CO₂ increase. We have also succeeded to develop highly precise gravimetric standard gas for O₂/N₂ ratio in collaboration with NMIJ.

Press releases (in Japanese)

https://www.aist.go.jp/aist_j/press_release/pr2020/pr20200515/pr20200515.html

https://www.aist.go.jp/aist_j/press_release/pr2021/pr20210730/pr20210730.html

https://www.aist.go.jp/aist_j/press_release/pr2024/pr20240214/pr20240214.html

https://www.aist.go.jp/aist_j/press_release/pr2025/pr20250225/pr20250225.html

JSPS KAKENHI Grant-in-Aid for Scientific Research (S)

Assessment of carbon cycle in terrestrial ecosystems

We have developed assessment methods of the carbon cycle in terrestrial ecosystems. At an observation site in a deciduous forest in Takayama, Japan, we have conducted observations of net CO₂ uptake by the forest ecosystem (NEP: Net Ecosystem Production), atmospheric CO₂ concentration, and various meteorological parameters since 1993; the NEP data are the longest in Asia and among the longest in the world. We have also conducted observations at Sakerat and Maeklong, Thailand. Using the long-term data, we have been analyzing the variations and the trends of NEP and CO₂ and their environmental factors and examining impacts of climate change on the carbon cycle in the forest in collaboration with researchers in ecology and remote sensing. The obtained data have been registered in databases and widely used by researchers in various fields.

Observations of nitrogen oxides, carbonyl sulfide, and aerosols and their application to carbon cycle study

The use of concentrations and stable isotope ratios of nitrogen oxides (NOₓ), which share some emission sources with CO₂, and carbonyl sulfide (OCS), which is taken up by plants during photosynthesis, is expected to improve the accuracy of identifying CO₂ emission sources and quantifying photosynthetic carbon fixation. Our group is developing analytical methods for these measurements and conducting observations. Atmospheric aerosols have been observed for a better understanding of health effects, visibility degradation, and regional-scale climate. We observed simultaneous increases of CO₂ and fine size fraction of aerosols (PM2.5) in Tokyo, and found a method to estimate the source of atmospheric aerosols and that of CO₂ can be used in a complementary manner. By integrating these observations, we aim to improve estimations of CO₂ sources and sinks.