著者

Sho Kawazoe Masaru Inatsu Tomohito J. Yamada Tsuyoshi Hoshino

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-039, (Released:2020-10-28)

被引用文献数

11

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Synoptic circulation patterns associated with heavy snowfall events in Sapporo are examined using large ensemble simulation with 60-km global climate experiments. For snowfall, a 5-km dynamically downscaled model from the 20-km regional simulation is utilized. To identify synoptic circulation patterns, self-organizing maps (SOMs) are applied, and their response to a warming climate is examined. The authors find that heavy snow events predominantly occur due to low pressure anomalies to the north/east of Hokkaido or over central Japan, and by high pressure anomalies over the Siberian continent. The 4 K warming climate shows robust decreases in heavy snowfall amounts associated with low pressure anomalies over central Japan and increases in heavy snowfall amounts under patterns with high pressure anomalies over Siberia. This is attributed to surface air temperature characteristics in future climates, as precipitation in the former with surface winds transporting warm, moist air from the south and east, develops predominantly above 0°C in the +4 K climate, while the latter, often resulting in intense snow band events, continues to be dominated by temperatures near or below zero.

著者

Sho Kawazoe Masaru Inatsu

出版者

公益社団法人 日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.18, pp.147-153, 2022 (Released:2022-07-17)

参考文献数

23

被引用文献数

2

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We investigated the sub-seasonal predictability of heavy snowfall events in Iwamizawa, Hokkaido, using the Japan Meteorological Agency's 1-month ensemble predictions. First, the self-organizing map (SOM) technique was applied to the Japanese 55-year Reanalysis sea-level pressure anomalies to identify weather patterns resulting in heavy snowfall. It revealed that heavy snowfall developed in SOM nodes (weather patterns) with low-pressure centers to the east/northeast of Hokkaido and Siberian high to the west, resulting in westerly to northwesterly monsoon winds traversing the Sea of Japan towards western Hokkaido. Next, ensemble forecasts were projected onto the SOM map to determine the predictability of weather patterns up to a month in advance. For winter 2019, there was relatively low probability of projecting a high number of ensembles in SOM nodes to those observed in the reanalysis. In contrast, much higher probability was seen in 2020 to ∼10 forecast days. When considering multiple SOM nodes that contribute to heavy snowfall in the forecast, both winters saw more ensemble members predicting heavy snowfall to ∼10 forecast days. We also saw a higher probability of heavy snowfall beyond 10-days in 2020. These results highlight the potential benefit of incorporating multiple weather patterns to forecast heavy snowfall.

著者

Sho Kawazoe Masaru Inatsu

出版者

公益社団法人 日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2022-024, (Released:2022-06-08)

被引用文献数

2

---

We investigated the sub-seasonal predictability of heavy snowfall events in Iwamizawa, Hokkaido, using the Japan Meteorological Agency's 1-month ensemble predictions. First, the self-organizing map (SOM) technique was applied to the Japanese 55-year Reanalysis sea-level pressure anomalies to identify weather patterns resulting in heavy snowfall. It revealed that heavy snowfall developed in SOM nodes (weather patterns) with low-pressure centers to the east/northeast of Hokkaido and Siberian high to the west, resulting in westerly to northwesterly monsoon winds traversing the Sea of Japan towards western Hokkaido. Next, ensemble forecasts were projected onto the SOM map to determine the predictability of weather patterns up to a month in advance. For winter 2019, there was relatively low probability of projecting a high number of ensembles in SOM nodes to those observed in the reanalysis. In contrast, much higher probability was seen in 2020 to ∼10 forecast days. When considering multiple SOM nodes that contribute to heavy snowfall in the forecast, both winters saw more ensemble members predicting heavy snowfall to ∼10 forecast days. We also saw a higher probability of heavy snowfall beyond 10-days in 2020. These results highlight the potential benefit of incorporating multiple weather patterns to forecast heavy snowfall.

著者

Sho Kawazoe Masaru Inatsu Tomohito J. Yamada Tsuyoshi Hoshino

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.233-239, 2020 (Released:2020-12-05)

参考文献数

30

被引用文献数

11

---

Synoptic circulation patterns associated with heavy snowfall events in Sapporo are examined using large ensemble simulation with 60-km global climate experiments. For snowfall, a 5-km dynamically downscaled model from the 20-km regional simulation is utilized. To identify synoptic circulation patterns, self-organizing maps (SOMs) are applied, and their response to a warming climate is examined. The authors find that heavy snow events predominantly occur due to low pressure anomalies to the north/east of Hokkaido or over central Japan, and by high pressure anomalies over the Siberian continent. The 4 K warming climate shows robust decreases in heavy snowfall amounts associated with low pressure anomalies over central Japan and increases in heavy snowfall amounts under patterns with high pressure anomalies over Siberia. This is attributed to surface air temperature characteristics in future climates, as precipitation in the former with surface winds transporting warm, moist air from the south and east, develops predominantly above 0°C in the +4 K climate, while the latter, often resulting in intense snow band events, continues to be dominated by temperatures near or below zero.

著者

Shiori Sugimoto Rui Ito Koji Dairaku Hiroaki Kawase Hidetaka Sasaki Shingo Watanabe Yasuko Okada Sho Kawazoe Takeshi Yamazaki Takahiro Sasai

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.46-51, 2018 (Released:2018-04-01)

参考文献数

32

被引用文献数

7

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To evaluate the influence of spatial resolution in numerical simulations on the duration of consecutive dry days (CDDs) and near-surface temperature over the central mountains in Japan, a regional climate model was used to conduct two experiments with horizontal resolutions of 5 and 20 km. Compared with observations, the spatial and temporal features of the CDDs were simulated well in the 5 km experiment, whereas in the 20 km simulation they were overestimated over the mountains and underestimated in the surrounding regions. The accuracy in the simulated CDDs affected the near-surface temperature in the model. In years with a difference of more than five days in the CDDs between the 5 and 20 km experiments, near-surface temperatures over the mountains were 0.2-0.3 K lower in the 5 km simulation compared with the 20 km simulation. This was due to the lower number of CDDs in 5 km simulation causing active cloud convection and reduced net radiation at the ground, resulting from a large decrease in the solar radiation at the ground. In addition, a land surface wetness controls a spatial heterogeneity of temperature difference between two experiments.