著者

Seika Tanji Masaru Inatsu

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.32-36, 2019 (Released:2019-02-13)

参考文献数

31

被引用文献数

2 4

---

Blowing snow potential is diagnosed for typical cases around Sapporo, Japan, as snow concentration and visibility based on dynamically downscaled data with 1-km resolution. The results are consistent with the blowing-snow records on time and place of traffic disruption, when the dynamical downscaling (DDS) reproduced wind speed well for a case. The diagnosis with mesoscale model analysis with 5-km resolution does not reproduce the blowing snow events in most area, however. Hence, the DDS potentially, not perfectly, adds the value to estimate blowing snow potential, despite a large scale-gap from an explicit representation of small-scale turbulence related to blowing snow. Sensitivity tests clarify that blowing snow requires strong wind and freezing temperature at the surface.

著者

Yuta Katsuyama Masaru Inatsu

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-006, (Released:2021-01-27)

被引用文献数

2

---

This study developed a volume scan-type disdrometer and investigated the size distribution of solid-precipitation particles observed by flux- and volume-scan type disdrometers, installed in 2016-2017 winter in Sapporo, Japan. The former disdrometer detected particles, by line sensors, of which frequency is proportional to the particle number per area. On the other hand, the latter directly observed the particle number per volume using an image sensor. The flux-scan data are known to have the bias of more frequency in higher-speed (or larger-size) particles, but this bias was hardly corrected due to the error of estimated particles' velocity. It was first validated that the volume scan-type disdrometer could observe particle size between 0.5 mm and 13 mm, consistently with the flux scan-type one. Then, we examined how many events showed the difference of the size distribution between the two disdrometers with the Kolmogorov-Smirnov test. The result showed that 84% of the total events examined fell into the class where they were significantly different, partially due to fast-falling graupels.

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

10

---

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

Makoto Kondo Yousuke Sato Masaru Inatsu Yuta Katsuyama

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-012, (Released:2021-03-12)

被引用文献数

4

---

The performances of bulk microphysical schemes were evaluated through comparisons with observations, including a new volume scanning video disdrometer targeting one of a typical snowfall event in Hokkaido, Japan. For the evaluation, downscaling experiments using three bulk microphysical schemes were conducted: a two-moment bulk scheme, a one-moment bulk scheme, and an improved version of the one-moment bulk scheme coupled with an identical dynamical core. The two-moment scheme successfully simulated the measured relationship between particle size and terminal velocity distribution (PSVD). On the other hand, the one-moment scheme overestimated the graupel frequency, its terminal velocity, and underestimated the particle diameter. The improved version of the one-moment bulk scheme reduced the overestimation of the terminal velocity of hydrometeors, but still overestimated the graupel frequency. We improved the overestimation of terminal velocity and the frequency of graupel in the one-moment scheme by modifying the assumption of the velocity–diameter relationship and the intercept parameter of the size distribution of graupel based on the results of the new disdrometeor. The observation of the new disdrometer would give us hints to improve the microphysics schemes in snowfall cases.

著者

Kuniyasu Sugawara Masaru Inatsu Seiji Shimoda Keach Murakami Tomoyoshi Hirota

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-004, (Released:2021-01-04)

被引用文献数

4

---

While global warming may expand suitable places for potato cultivation in cold regions, it may reduce the yield due to the increase of hot days during the tuber growth period. This study evaluated the effects of global warming on potato cultivation over Hokkaido by dynamically-downscaled ensemble experiments called d4PDF and assessed applicability of possible adaptive measures. In this study, we define the suitable area based on the accumulated temperature and deduced a relationship between the potato yield per unit area and the number of hot days (maximum temperature > 28°C) from crop statistic data. In a warming environment with 2K or 4K increase in global-mean temperature relative to the present climate (1981-2010), the accumulated temperatures likely satisfied the criterion on potato production almost over Hokkaido. The risk of growth delay due to cold weather was projected to reduce. However, hot days in the tuber growth period would increase, reducing potato yield by 7% in a plus 2-K climate and 16% in a plus 4-K climate. This risk of yield loss would not be avoidable by moving up planting by 30 days, and the development of varieties that are tolerant to 31-33°C would be a possible way to adaptation.

著者

Ken Hirata Miho Sekiguchi Yousuke Sato 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.19, pp.50-56, 2023 (Released:2023-03-23)

参考文献数

22

---

This study investigated biases of diffuse radiation in a look-up table approach, which pre-computed the sequential ray tracing to avoid heavy computation in full three-dimensional radiative transfer calculation. We introduced corrections that enhanced directionality of radiative propagation in the solar angle and horizontal direction. By comparing irradiance calculations with and without the corrections for cloudy field in an idealized atmospheric simulation, it was found that the corrections helped mitigate vertically localized false signals by diffuse irradiance. The results suggested that the two types of directionalities are important to accurately represent the three-dimensional transfer of diffuse radiation in an inhomogeneous atmosphere.

著者

Ken Hirata Miho Sekiguchi Yousuke Sato 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.2023-007, (Released:2023-01-30)

---

This study investigated biases of diffuse radiation in a look-up table approach, which pre-computed the sequential ray tracing to avoid heavy computation in full three-dimensional radiative transfer calculation. We introduced corrections that enhanced directionality of radiative propagation in the solar angle and horizontal direction. By comparing irradiance calculations with and without the corrections for cloudy field in an idealized atmospheric simulation, it was found that the corrections helped mitigate vertically localized false signals by diffuse irradiance. The results suggested that the two types of directionalities are important to accurately represent the three-dimensional transfer of diffuse radiation in an inhomogeneous atmosphere.

著者

Yuka Kanamori Masaru Inatsu Ryoichi Tsurumaki Naoki Matsuoka Tsuyoshi Hoshino Tomohito J. Yamada

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.249-253, 2022 (Released:2022-11-26)

参考文献数

23

被引用文献数

1

---

A set of hydrological experiments for a flooding event on 11 September 2014 at Motsukisamu River in Sapporo were performed. Dynamical downscaling to 5-km resolution of a large-ensemble global simulation allowed us to estimate that a 99%-tile hourly precipitation in Sapporo would increase by 70% in a future climate, when the global-mean temperature increases by 4 K compared with the present climate. After developing a three-tank model of which parameters were optimized on the basis of the in-situ observation at the Motsukisamu River during the event period, the model was forced by hypothetical hyetographs of the event that would occur under the future climate. The results of this experiment suggested that the peak flow rate would increase by 75%. However, it was also revealed that an upstream aqueduct tunnel, just completed in autumn 2021, would effectively reduce the peak flow rate and mitigate the flooding risk even in extreme precipitation under the future climate.

著者

Yuka Kanamori Masaru Inatsu Ryoichi Tsurumaki Naoki Matsuoka Tsuyoshi Hoshino Tomohito J. Yamada

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.2022-040, (Released:2022-11-11)

被引用文献数

1

---

A set of hydrological experiments for a flooding event on September 11, 2014 at Motsukisamu River in Sapporo were performed. Dynamical downscaling to 5-km resolution of a large-ensemble global simulation allowed us to estimate that a 99%-tile hourly precipitation in Sapporo would increase by 70% in a future climate, when the global-mean temperature increases by 4 K compared with the present climate. After developing a three-tank model of which parameters were optimized on the basis of the in-situ observation at the Motsukisamu River during the event period, the model was forced by hypothetical hyetographs of the event that would occur under the future climate. The results of this experiment suggested that the peak flow rate would increase by 75%. However, it was also revealed that an upstream aqueduct tunnel, just completed in autumn 2021, would effectively reduce the peak flow rate and mitigate the flooding risk even in extreme precipitation under the future climate.

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

---

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

Makoto Kondo Yousuke Sato Masaru Inatsu Yuta Katsuyama

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.74-80, 2021 (Released:2021-04-24)

参考文献数

51

被引用文献数

4

---

The performances of bulk microphysical schemes were evaluated through comparisons with observations, including a new volume scanning video disdrometer targeting one of a typical snowfall event in Hokkaido, Japan. For the evaluation, downscaling experiments using three bulk microphysical schemes were conducted: a two-moment bulk scheme, a one-moment bulk scheme, and an improved version of the one-moment bulk scheme coupled with an identical dynamical core. The two-moment scheme successfully simulated the measured relationship between particle size and terminal velocity distribution (PSVD). On the other hand, the one-moment scheme overestimated the graupel frequency, its terminal velocity, and underestimated the particle diameter. The improved version of the one-moment bulk scheme reduced the overestimation of the terminal velocity of hydrometeors, but still overestimated the graupel frequency. We improved the overestimation of terminal velocity and the frequency of graupel in the one-moment scheme by modifying the assumption of the velocity–diameter relationship and the intercept parameter of the size distribution of graupel based on the results of the new disdrometeor. The observation of the new disdrometer would give us hints to improve the microphysics schemes in snowfall cases.

著者

Yuta Katsuyama Masaru Inatsu

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.35-40, 2021 (Released:2021-02-25)

参考文献数

24

被引用文献数

2

---

This study developed a volume scan-type disdrometer and investigated the size distribution of solid-precipitation particles observed by flux- and volume-scan type disdrometers, installed in 2016-2017 winter in Sapporo, Japan. The former disdrometer detected particles, by line sensors, of which frequency is proportional to the particle number per area. On the other hand, the latter directly observed the particle number per volume using an image sensor. The flux-scan data are known to have the bias of more frequency in higher-speed (or larger-size) particles, but this bias was hardly corrected due to the error of estimated particles' velocity. It was first validated that the volume scan-type disdrometer could observe particle size between 0.5 mm and 13 mm, consistently with the flux scan-type one. Then, we examined how many events showed the difference of the size distribution between the two disdrometers with the Kolmogorov-Smirnov test. The result showed that 84% of the total events examined fell into the class where they were significantly different, partially due to fast-falling graupels.

著者

Kuniyasu Sugawara Masaru Inatsu Seiji Shimoda Keach Murakami Tomoyoshi Hirota

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.24-29, 2021 (Released:2021-02-18)

参考文献数

31

被引用文献数

4

---

While global warming may expand suitable places for potato cultivation in cold regions, it may reduce the yield due to the increase of hot days during the tuber growth period. This study evaluated the effects of global warming on potato cultivation over Hokkaido by dynamically-downscaled ensemble experiments called d4PDF and assessed applicability of possible adaptive measures. In this study, we define the suitable area based on the accumulated temperature and deduced a relationship between the potato yield per unit area and the number of hot days (maximum temperature > 28°C) from crop statistic data. In a warming environment with 2K or 4K increase in global-mean temperature relative to the present climate (1981-2010), the accumulated temperatures likely satisfied the criterion on potato production almost over Hokkaido. The risk of growth delay due to cold weather was projected to reduce. However, hot days in the tuber growth period would increase, reducing potato yield by 7% in a plus 2-K climate and 16% in a plus 4-K climate. This risk of yield loss would not be avoidable by moving up planting by 30 days, and the development of varieties that are tolerant to 31-33°C would be a possible way to adaptation.

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

10

---

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.