著者

JUDT Falko KLOCKE Daniel RIOS-BERRIOS Rosimar VANNIERE Benoit ZIEMEN Florian AUGER Ludovic BIERCAMP Joachim BRETHERTON Christopher CHEN Xi DÜBEN Peter HOHENEGGER Cathy KHAIROUTDINOV Marat KODAMA Chihiro KORNBLUEH Luis LIN Shian-Jiann NAKANO Masuo NEUMANN Philipp PUTMAN William RÖBER Niklas ROBERTS Malcolm SATOH Masaki SHIBUYA Ryosuke STEVENS Bjorn VIDALE Pier Luigi WEDI Nils ZHOU Linjiong

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2021-029, (Released:2021-01-21)

被引用文献数

26

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Recent progress in computing and model development has initiated the era of global storm-resolving modeling and with it the potential to transform weather and climate prediction. Within the general theme of vetting this new class of models, the present study evaluates nine global-storm resolving models in their ability to simulate tropical cyclones (TCs). Results show that, broadly speaking, the models produce realistic TCs and remove longstanding issues known from global models such as the deficiency to accurately simulate TC intensity. However, TCs are strongly affected by model formulation, and all models suffer from unique biases regarding the number of TCs, intensity, size, and structure. Some models simulated TCs better than others, but no single model was superior in every way. The overall results indicate that global storm-resolving models are able to open a new chapter in TC prediction, but they need to be improved to unleash their full potential.

著者

NAKANO Masuo CHEN Ying-Wen SATOH Masaki

出版者

公益社団法人 日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2023-013, (Released:2023-02-24)

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Typhoon Krosa (2019) formed in the eastern part of the Philippine Sea and ∼ 1400 km east of another typhoon Lekima on 6 August and made landfall in the western part of Japan's mainland on 15 August. The operational global model forecasts, which were initialized just after Krosa's formation, showed a very large uncertainty and totally failed to predict the actual track of Krosa. In this study, we investigated the causes of this large uncertainty through 101-member ensemble forecast experiments by using a 28-km mesh global nonhydrostatic model. The experiments initialized at 1200 UTC 6 August, showed a large uncertainty. An ensemble-based lagged correlation analysis indicated that the western North Pacific Subtropical High (WNPSH) retreated further east in the members with large track forecast errors than in the members with small errors. For the members with a large track forecast error for Krosa, Krosa and Lekima approached each other by 250 km and Krosa moved northward faster than the observation in 36 hours from the initialization time. For the members with a small track forecast error for Krosa, two typhoons approached each other by only 50 km, and the northward moving speed was comparable with that of the observation. The typhoon-center relative composite analysis exhibited that at the initialization time, the members with a large Krosa track forecast error had a larger horizontal size of Krosa and the difference in Krosa's size was kept during the forecast period. This difference in size led to a stronger interaction between the two typhoons and retreatment of the WNPSH, thus resulting in a fast northward moving speed for the members with a large Krosa track error.

著者

SHIBUYA Ryosuke NAKANO Masuo KODAMA Chihiro NASUNO Tomoe KIKUCHI Kazuyoshi SATOH Masaki MIURA Hiroaki MIYAKAWA Tomoki

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2021-046, (Released:2021-04-08)

被引用文献数

5

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In this study, we assessed the prediction skill of the Boreal Summer Intra-Seasonal Oscillation (BSISO) mode of one-month simulations using a global non-hydrostatic atmospheric model (NICAM) with explicit cloud microphysics and with a grid spacing of 14 km. The simulations were run as a series of hindcast experiments every day of August during 2000-2014; a total of 465 simulations were run with a 13950-day integration. On using forecast skill scores for statistical measurements, it was found that the model showed an overall BSISO prediction skill of approximately 24 days. The prediction skill tended to be slightly higher (∼ 2 days) when BSISO events began in the initial phases 7 to 1, which corresponded to the re-initiation phase of the BSISO, where a major convective center over the Philippine Sea decayed and a new convective envelope began aggregating over the western Indian Ocean. The phase speed and the evolution of the amplitude of the BSISO were well simulated by the model with a clear northwestward-southeastward tilted outgoing longwave radiation (OLR) structure over the Maritime continent and the western Pacific. However, the propagation speed was slower during phases 6-7, and the amplitude of the BSISO largely decayed during phases 8-1, which was likely to have been associated with the stagnant behavior of the convective cells over the Philippines. This stagnation of the propagation over the Philippines may be largely attributed to the small background southerlies bias in the model over the Philippines based on regression coefficient analysis using the moist static energy. The bias in the large-scale circulation was likely to have been associated with the bias in the moisture field and the associated background monsoonal circulation. We concluded that the model physics controlling the background fields are important factors for improving the BSISO prediction skill.

著者

FUJITA Mikiko SATO Tomonori YAMADA Tomohito J. KAWAZOE Sho NAKANO Masuo ITO Kosuke

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2019-022, (Released:2018-12-17)

被引用文献数

4

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We investigated extremely heavy precipitation that occurred around the Kinugawa River, Japan, in September 2015, and the probability of extreme precipitation occurrence, using data from a large ensemble forecast more than 1,000 members that were dynamically downscaled to 1.6 km horizontal grid spacing. The observed event was statistically rare among simulated cases and 3-day accumulated precipitation around the target area was equivalent to the 95th percentile among all simulated ensemble members. Our results show that this extreme precipitation event occurred under specific conditions: two coexisting typhoons at close proximity that produces a high atmospheric instability, and water vapor transport from the Pacific Ocean. We also assessed the probability of extreme precipitation in mountainous areas other than the Kinugawa River case. Heavy precipitation also occurred southwest of the Kinugawa River region due to two typhoons, similar to the Kinugawa River case. The tracks of these typhoons shifted marginally; however, there was a difference in the water vapor supplied to the area, causing heavy precipitation. The large-ensemble downscaled data used in this study hence enable us to evaluate the occurrence probability of a torrential rainfall event that was rarely observed, which may contribute to updating a disaster mitigating plan for possible similar disasters in future.