北海道大学大学院　地域気候システム研究室 - Regional Climate System Research Group

【研究室セミナーのお知らせ】Seminar (17:30-, Jun. 11, C204-1)
1. Jinyuan Ma
Title: Machine Learning Prediction of Mesoscale Convective Systems Integrating Spatial and Temporal Land Surface Temperature Features: A Regional Comparative Study in East Asia
2. Xukai Liu
Title: Paper Review on Wildfire Smoke Transport to Hokkaido: Evidence Chain and Synoptic Background
1. Jinyuan Ma
Abstract: This research aims to improve the prediction of Mesoscale Convective Systems (MCSs) in East Asia by integrating spatial and temporal Land Surface Temperature (LST) features. Building upon the successful preliminary results obtained from Himawari satellite data, the study period has been expanded to a long-term, 30-year dataset spanning from 1995 to 2015. In this seminar, I will present the key findings and challenges encountered while processing this 30-year climate data series. Furthermore, I will share the preliminary machine learning results trained on this long-term dataset, including a comparative analysis across different sub-regions in East Asia.
2. Xukai Liu
Abstract: This presentation summarizes my recent paper review on long-range wildfire smoke transport from eastern part of Eurasian continent to Hokkaido. The first paper introduces how wildfire-smoke influence should be identified using multiple evidence, including PM2.5 observations and reanalysis dataset. The second paper offers the idea of selecting pollution episodes and organizing them by synoptic weather types. Based on these papers, I discuss a possible future direction: identifying Hokkaido smoke transport events by evidence chain and examining favorable synoptic-scale background fields.
[Paper information]
[1]Yasunari, T. J., et al., 2018: Extreme air pollution events in Hokkaido, Japan, traced back to early snowmelt and large-scale wildfires over East Eurasia: Case studies. Scientific Reports, 8, 6413, DOI: 10.1038/s41598-018-24335-w
[2]Ryu, Y.-H., and Min, S.-K., 2024: Anthropogenic warming degrades spring air quality in Northeast Asia by enhancing atmospheric stability and transboundary transport. npj Climate and Atmospheric Science, 7, 69, DOI: 10.1038/s41612-024-00603-7

【研究】大雨をもたらす「大気の川」の強化に関する筑波大学 釜江先生との共同研究の成果がClimate Dynamnics誌に掲載され、プレスリリースを行いました。詳しくはこちらをご覧ください。
https://www.hokudai.ac.jp/news/pdf/260522_pr3.pdf
https://link.springer.com/article/10.1007/s00382-026-08189-x

www.hokudai.ac.jp

【研究室セミナーのお知らせ】Seminar (16:30-, Jun. 4, C204-1)
1. Haruka Kobayashi
Title: Paper review of “Predictability of Heavy Snowfall Days in Western Hokkaido from JMA Operational 1-Month Ensemble Predictions Using Self-Organizing Maps”.
2. Mai Nakazawa
Title: Overview of Pyrocumulonimbus (PyroCb) Research
3. Yuji Oda
Title: Investigating the temporal evolution of the structure of polar mesocyclones using the cyclone phase space
1. Haruka Kobayashi
Abstract: Providing accurate, long-lead heavy snowfall forecasts is crucial, but sub-seasonal prediction of these events remains challenging. This study investigated the sub-seasonal predictability of heavy snowfall events in Iwamizawa, Hokkaido, using the JMA’s 1-month ensemble predictions and the self-organizing map (SOM) technique. By identifying multiple weather patterns and projecting them onto the prediction model, forecast accuracy was improved up to approximately 10 days for both the 2019 and 2020 winters. These results highlight the potential benefit of incorporating multiple weather patterns to forecast heavy snowfall.
[Paper Information]
Kawazoe, S. and Inatsu, M., 2022: Predictability of Heavy Snowfall Days in Western Hokkaido from JMA Operational 1-Month Ensemble Predictions Using Self-Organizing Maps. SOLA, 18, 147-153, DOI:10.2151/sola.2022-024

2. Mai Nakazawa
Abstract: While studying fire whirls associated with wildfires, I became interested in the phenomenon known as pyrocumulonimbus (PyroCb). PyroCb is a cumulonimbus cloud generated by intense wildfire activity and is known to produce various hazardous phenomena, including rapid fire spread, downbursts, lightning-induced new fires, hail, and fire tornadoes. In addition, PyroCb can transport large amounts of smoke and aerosols from the upper troposphere into the lower stratosphere, potentially causing large-scale smoke transport and climatic impacts. I was attracted to this topic because PyroCb research is a relatively new field with many unresolved questions. This presentation begins with the introduction of the formation processes of PyroCb, followed by the review of PyroCb researches from early satellite-based observational studies to recent machine learning approaches for prediction.

3. Yuji Oda
Title: Investigating the temporal evolution of the structure of polar mesocyclones using the cyclone phase space
Abstract: Polar mesocyclones developing over the sea west of Hokkaido occasionally cause severe snowfall, such as a 24-hour snowfall total of 53 cm, the largest on record for January, observed from 24 to 25 January 2026. These mesocyclones exhibit a variety of physical structures, and thus their development mechanisms are complex. This study focuses on a case in January 2024 to investigate the structural evolution of a polar mesocyclone using cyclone phase space analysis. The results suggest that the structure of the polar mesocyclone may evolve from an extratropical-cyclone-like structure to a tropical-cyclone-like structure during its lifetime. Given that SST in the Sea of Japan has increased in recent years, future work is expected to investigate how SST affects the structure of polar mesocyclones through the analysis of more cases.

【研究室セミナーのお知らせ】Seminar (16:30-, May. 21, C204-1)
1. Kazuya Wakao
Title: Water v***r transport and heavy rainfall over Kyushu, western Japan in July as a response to delayed ENSO influence
2. Xiling Zhou
Title: Impacts of Arctic Sea Ice Loss on Heavy Snowfall in Japan: A Preliminary Analysis Based on PAMIP Datasets
1. Kazuya Wakao
Abstract: The El Niño–Southern Oscillation (ENSO) is known to modulate the structure and distribution of the North Pacific High (NPH). Previous studies have shown that the ENSO’s influence remains even after its winter peak, as evidenced by its alteration of water v***r transport and summer precipitation over East Asia, thereby making it a useful predictor for East Asian precipitation. However, the extent to which such a delayed ENSO influence affects synoptic-scale water v***r transport patterns as well as their impacts on local precipitation remains poorly understood. Focusing on Kyushu, where heavy rainfall is closely linked to moisture transport regulated by the NPH, this study examines moisture transport patterns and precipitation responses to the delayed ENSO influence based on a synoptic-scale circulation classification. We selected daily heavy rainfall events during the summer season (June–September) for 1979–2024 using in-situ precipitation data. Atmospheric circulation was then classified using a Self-Organizing Map based on JRA-3Q sea level pressure and the u-and v-components of water v***r transport at 850 hPa. A significant correlation is observed between the interannual variations of the frequency of the NPH pattern (i.e., southwesterly moisture transport along the periphery of the NPH) and SST anomalies in the central tropical Pacific from the preceding winter to spring. A significant correlation is also found between the interannual frequency of the NPH pattern and heavy rainfall events over northern Kyushu. Interestingly, the influence of delayed ENSO on the NPH appears to be significant in July. The analysis shows supporting evidence that the NPH tends to shift westward over the ocean south of Japan during late July in the post-El Niño summer.
2. Xiling Zhou
Abstract: At the end of January 2026, heavy snowfall affected the Sea of Japan coast, severely disrupting transportation and resulting in a death toll exceeding 40 in Japan. This disastrous snowfall event was linked to Arctic cold-air outbreaks, whose interannual frequency may be associated with the rapid loss of Arctic sea ice. Moreover, the Sea of Japan coast experiences substantial snowfall due to the East Asian winter monsoon, which may also be influenced by Arctic sea ice loss. Since the Arctic is warming faster than the global mean and this amplified warming is projected to persist in the future, it is imperative to determine the contribution of Arctic warming to heavy snowfall in Japan and to clarify the associated dynamical processes. This study utilizes datasets from the Polar Amplification Model Intercomparison Project (PAMIP), which consists of coordinated large-ensemble climate model simulations performed by multiple climate models. The HadGEM3 model shows increased precipitation and more frequent heavy precipitation days along the Sea of Japan coast in January in response to past Arctic sea ice loss. However, this increase is not robust across all climate models. Meanwhile, among-model agreement is found concerning that future Arctic sea ice loss strengthens the East Asian winter monsoon.

【研究室セミナーのお知らせ】Seminar (16:30-, May. 7, C204-1)
1. Yuji Oda
Title: Investigating the temporal evolution of the structure of polar mesocyclones using the cyclone phase space
2. Hiroto Fukushima
Title: Evaluation of the impact of anthropogenic global warming on downburst events in mid-July 2023 using an analogue-based approach
1. Yuji Oda
Abstract: Polar mesocyclones developing over the sea west of Hokkaido occasionally cause severe snowfall, such as a 24-hour snowfall total of 53 cm, the largest on record for January, observed from 24 to 25 January 2026. These mesoscale cyclones exhibit a variety of physical structures, and thus their development mechanisms are complex. This study focuses on a case in January 2024 to investigate the structural evolution of a polar mesocyclone using cyclone phase space analysis.
2. Hiroto Fukushima
Abstract: Atmospheric instability is projected to worsen in future global warming scenarios, which may increase the likelihood of severe weather events because cumulonimbus clouds favor unstable conditions. Meanwhile, it is poorly understood whether human-induced global warming has increased the risk of such events. This study focuses on multiple downburst events that occurred in the northern Kanto region in mid-July 2023. This presentation will report progress, including the identification of analogue cases based on the classification of synoptic-scale pressure patterns, and preliminary results on the influence of anthropogenic global warming on atmospheric stability in these analogue cases.

【研究室セミナーのお知らせ】Seminar (16:30-, Apr. 30, C204-1)
1. Kazushi Kikuchi
Title: Evaluation of the impact of global warming on heavy rainfall associated with Baiu front: findings from master's research and future research plans
2. Noa Kashiwazaki
Title: Analysis of the extremely low precipitation in February 2025 in the Tohoku region, Japan, along the Pacific coast as a potential environmental factor for wildfire

1. Kazushi Kikuchi
Abstract: Studies have revealed the contribution of global warming to the recent increase in the frequency of heavy rainfall in Japan. My master's thesis research examined the July 2020 heavy rainfall event in western Japan using an analogue-based event attribution approach. The results showed that global warming intensified heavy precipitation through increased atmospheric water v***r content and enhanced low-level water v***r flux, leading to increased convective instability. I plan to investigate whether such changes in water v***r flux and convective instability represent common responses of heavy precipitation events associated with the Baiu front.
2. Noa Kashiwazaki
Abstract: There has been increasingly impacts of wildfires worldwide. In February 2025, a severe wildfire that lasted for more than a month occurred in Ofunato City, causing extensive damage to forests and residential areas. One possible meteorological factor for this event is the widespread precipitation deficit observed across the Pacific coastal region of the Tohoku region. However, it remains unclear whether this dry condition was caused by natural variability or whether there is any contribution of human-induced climate change. This presentation reports an initial assessment of the low precipitation in February 2025 based on Standardized Precipitation Index using 50 years of AMeDAS observations.

【研究】
研究室OBの中村さんの論文が4月21日にnpj Climate and Atmospheric Scienceに掲載されました。気象研・北大・名大から日本語プレスリリースも行っており、ABEMAニュースなどで紹介されています。
https://www.hokudai.ac.jp/news/pdf/260422_pr.pdf
https://www.nature.com/articles/s41612-026-01389-6
https://news.tv-asahi.co.jp/news_society/articles/000500097.htmlNatureInterlinks between sea-ice melting and continental wetting under a changing Arctic moisture transportnpj Climate and Atmospheric Science - Interlinks between sea-ice melting and continental wetting under a changing Arctic moisture transporthttps://www.nature.com/articles/s41612-026-01389-6テレ朝NEWS北極で進む温暖化　原因の水蒸気は夏と秋に増加　日本の研究チームの解析で判明　北極でも進む温暖化について、気象研究所は温暖化を引き起こす水蒸気が夏と秋に増加するメカニズムを世界で初めて明らかにしたと発表しました。　地球上で最も早く温暖化が進む北極では、気温の上昇が世界平均の2https://news.tv-asahi.co.jp/news_society/articles/000500097.html

news.tv-asahi.co.jp

【研究室セミナーのお知らせ】Seminar (16:30-, Apr. 23, C204-1)
1. Takehiro Morioka
Title: Day-to-day atmospheric circulation modulates the impact of marine heatwaves on heatstroke risk in Hokkaido in August 2023
2. Jinyuan Ma
Title: Machine Learning Prediction of Mesoscale Convective Systems Integrating Spatial and Temporal Land Surface Temperature Features: A Regional Comparative Study in East Asia
3. Xukai Liu
Title: About a long-distance fire smoke transport to Hokkaido, Japan

1. Takehiro Morioka
Abstract: High surface air temperature and humidity threaten high-latitude regions that are less adapted to heat. While marine heatwaves (MHWs) have the potential to rise air temperature and humidity over adjacent land areas, the modulation of these impacts by day-to-day atmospheric circulation remains poorly understood. This study focuses on Hokkaido, the northernmost prefecture in Japan, to investigate how daily atmospheric circulation regulates the distribution and intensity of MHW-related heatstroke risk during August 2023, when record numbers of heatstroke patients coincided with severe MHWs. Numerical experiments showed that MHWs increased the monthly-average wet bulb globe temperature by approximately 2 °C in southern coastal areas. Further analysis revealed that variable daily atmospheric circulations and SST patterns play a key role in coastal heatstroke risk on a daily timescale.
2. Jinyuan Ma
Abstract: My research aims to improve the prediction accuracy of Mesoscale Convective Systems (MCSs) in East Asia by integrating spatial and temporal Land Surface Temperature (LST) features. After identifying MCS genesis events, the atmospheric and land datasets adjacent to each genesis point, including spatial LST variance from geostationary satellite and atmospheric parameters from ERA5, were extracted. These datasets were then used to train a machine learning framework for MCS prediction. The presentation will report preliminary results obtained using Random Forest model, specifically how LST contributes to predicting convective initiation.
3. Mai Nakazawa
Abstract: This presentation summarizes recent studies on long-distance wildfire smoke transport that affected air pollution in Hokkaido. Based on Yasunari et al. (2018, Sci Rep), basic processes linking early snowmelt, wildfire activity, smoke emission, and eastward transportation will be discussed.

週末の暖かさで学院前の桜も４割ほど咲きました🌸

先日、新入生歓迎会をいたしました。
春を感じられる料理をいただきながら、会話に花が咲きました。
これからどうぞ宜しくお願いします。

日差しの力が増し、
北大内に積み上げられた雪ももうほとんどなくなってきました。
あちらこちらにフキノトウが顔を出し、
研究室前の桜の木の蕾もだいぶ膨らんできました。
日当たりの良い一部の蕾からはピンク色の花びらが少し見え始めています。
今週は週末に向かって日増しに暖かくなり、いよいよ札幌にも桜の開花の便りが届きそうです。