著者
Kentaro Araki Teruyuki Kato Yasutaka Hirockawa Wataru Mashiko
出版者
Meteorological Society of Japan
雑誌
SOLA (ISSN:13496476)
巻号頁・発行日
pp.2021-002, (Released:2020-12-24)
被引用文献数
1

This study investigated characteristics of atmospheric environmental fields in the occurrence of quasi-stationary convective bands (QSCBs) in Kyushu, western Japan during the July 2020 heavy rainfall event. We performed case studies of extreme rainfall subevents in the Kumamoto and Kagoshima prefectures on 3-4 July (2020KK) and northern Kyushu on 6-7 July 2020 (2020NK), compared with two heavy rainfall events in northern Kyushu in 2017 and 2018.Nine QSCBs were objectively extracted during the July 2020 heavy rainfall event, causing hourly precipitation amounts exceeding 100 mm twenty times. In 2020KK, the environmental field with extremely large precipitable water due to low-level and middle-level humidity was affected by the upper-level cold airflow, which resulted in favorable condition for the deep convection development. Consequently, the lightning activity became high, and cloud tops were the highest in comparison to previous events. QSCBs in 2020KK and 2020NK were located along a low-level convergence line/zone associated with an inflow that had extremely large water vapor flux on the south side of the mesoscale Baiu frontal depressions. In most of the QSCB cases in 2020, mesoscale depressions were observed and enhanced horizontal winds, which led to extremely large low-level water vapor flux to produce short-term heavy rainfall.
著者
Yasutaka Hirockawa Teruyuki Kato Kentaro Araki Wataru Mashiko
出版者
Meteorological Society of Japan
雑誌
SOLA (ISSN:13496476)
巻号頁・発行日
pp.2020-044, (Released:2020-12-10)

In early July 2020, an extreme rainfall event generated precipitation exceeding 1000 mm in Kyushu district, southwestern Japan. Especially, an elongated and stagnated mesoscale convective system formed around the Kuma River in central Kyushu district produced localized heavy rainfall with precipitation over 600 mm in 13 hours. Characteristics of this extreme rainfall event were investigated using distributions of radar/raingauge-analyzed precipitation amounts (RAP) that were statistically compared with those during the warm seasons (April–November) in 2009-2019. The results are as follows: (1) nine heavy rainfall areas of linear-stationary type (LS-HRAs) were extracted, (2) spatial and temporal scales of two LS-HRAs among the nine exceeded 270 km and 10 hours, respectively, (3) the maximum RAP exceeding 100 mm in LS-HRAs were comparable to those in previous extreme rainfall events, (4) large accumulated three-hour precipitation amounts exceeding 200 mm were more frequently observed than those in previous events, and (5) the accumulated five-day precipitation amount integrated around Kyushu Island was the largest since 2009. This study also showed that a large area-integrated precipitation amount was produced mainly from widespread precipitation systems associated with the Baiu front, while the nine LS-HRAs significantly contributed to localized heavy rainfall.
著者
Yasutaka Hirockawa Teruyuki Kato Kentaro Araki Wataru Mashiko
出版者
Meteorological Society of Japan
雑誌
SOLA (ISSN:13496476)
巻号頁・発行日
vol.16, pp.265-270, 2020 (Released:2020-12-24)
参考文献数
25

An extreme rainfall event brought precipitation amounts exceeding 1000 mm in Kyushu district, southwestern Japan, in early July 2020. Especially, an elongated and stagnated mesoscale convective system formed around the Kuma River in central Kyushu district produced localized heavy rainfall with precipitation amounts larger than 600 mm in 13 hours. Characteristics of this extreme rainfall event were investigated using distributions of radar/raingauge-analyzed precipitation amounts (RAP) and statistically compared with those during the warm seasons (April–November) in 2009-2019. The results are shown as follows; (1) nine heavy rainfall areas of linear-stationary type (LS-HRAs) were extracted, (2) spatial and temporal scales of two LS-HRAs among them respectively exceeded 270 km and 10 hours, (3) the maximum RAP exceeding 100 mm in LS-HRAs were comparable to those in previous extreme rainfall events, (4) large accumulated three-hour precipitation amounts exceeding 200 mm were more frequently observed than those in the previous events, and (5) the accumulated five-day precipitation amount integrated around Kyushu Island was the largest since 2009. This study also showed that the large area-integrated precipitation amount was produced mainly from widespread precipitation systems associated with the Baiu front, while the nine LS-HRAs significantly contributed localized heavy rainfall.
著者
Hiroshige TSUGUTI Teruyuki KATO
出版者
(公社)日本気象学会
雑誌
気象集誌. 第2輯 (ISSN:00261165)
巻号頁・発行日
vol.92, no.2, pp.163-183, 2014 (Released:2014-05-16)
参考文献数
32
被引用文献数
4 11

On 20 October 2010, a heavy rainfall event occurred on Amami-Oshima Island, Japan, delivering a record 622 mm of rainfall in one day. To clarify the factors underlying this event, the supply mechanism and formation process of low-level humid air and the formation and maintenance mechanisms of the precipitation systems causing the heavy rainfall were examined using observation data, objective analysis data, and numerical simulation results. These investigations showed that low-level humid air, carried to Amami-Oshima Island during the rainfall event by strong east-northeasterly winds, originated more than 500 km to the east-northeast as low-level dry air on the northern side of a stationary front. This dry air was transformed into humid air on the way to the island by receiving large latent heat flux from the sea surface (air-parcel transformation). Warm sea surface temperatures around Amami-Oshima Island, about 2°C higher than the annual mean, contributed to this air-parcel transformation. At Amami-Oshima Island, the collision of the humid flows with a cold pool formed under earlier precipitation systems contributed significantly to the formation and maintenance of the precipitation systems, supplemented by topographic effects of the island.
著者
Masuo NAKANO Teruyuki KATO Syugo HAYASHI Sachie KANADA Yoshinori YAMADA Kazuo KURIHARA
出版者
(公社)日本気象学会
雑誌
気象集誌. 第2輯 (ISSN:00261165)
巻号頁・発行日
vol.90A, pp.339-350, 2012 (Released:2012-06-07)
参考文献数
32
被引用文献数
14 26

A 5-km-mesh nonhydrostatic cloud-system-resolving regional climate model (NHM-5km) has been developed at the Meteorological Research Institute (MRI) of the Japan Meteorological Agency (JMA) by improving upon the JMA operational mesoscale model (MSM). Three major changes have been made to MSM: the Kain-Frisch convective parameterization scheme has been improved to reduce the incidence of false predictions of rainfall areas along coastlines during the warm season, a spectral nudging method has been introduced to avoid phase-gap between the inner model (NHM-5km) and the outer model, and a Simple Biosphere model has been applied for sophisticated representation of land surface processes. This article presents details of the first two of these modifications.A present-day climate simulation is performed using NHM-5km by nesting within the results of a 20-kmmesh atmospheric global climate model (MRI-AGCM3.2S). Taylor’s skill score is used to compare the performances of NHM-5km and MRI-AGCM3.2S in terms of reproducing the spatial pattern of precipitation-based extreme indices over the Japanese Islands. The comparison shows that NHM-5km yields a significant improvement in reproducing the present-day climatology (e.g., the maximum number of consecutive dry days and the simple daily precipitation intensity index), suggesting that NHM-5km is a reliable tool for accurately predicting future changes in extreme weather at a fine spatial resolution.
著者
Teruyuki Kato Kohei Aranami
出版者
Meteorological Society of Japan
雑誌
SOLA (ISSN:13496476)
巻号頁・発行日
vol.1, pp.1-4, 2005 (Released:2005-01-07)
参考文献数
7
被引用文献数
28 32

Localized, band-shaped heavy rainfall was observed over the Niigata-Fukushima area on July 13th 2004 and the over Fukui area on July 18th 2004. Both areas are located on the Japan-Sea side of the Japan Islands. These heavy rainfall events were a result of an intensification of convective instability over the Baiu frontal zone, induced by the inflows of low-level humid air and middle-level dry air. The middle-level air was considerably warm, not colder than the surrounding air. This indicates that the formation factors of heavy rainfall should be examined using convective instability, rather than potential instability.Numerical simulations using a cloud-resolving model with a horizontal grid of 1.5 km were carried out in an attempt to reproduce these heavy rainfall events. The Niigata-Fukushima heavy rainfall was reproduced well, while the Fukui heavy rainfall was not. This failure of the Fukui case could be the result of the uncertain analysis of the wind field over the Sea of Japan that determined the movement of low-level humid air. edevelopment of new observation systems over the sea, where upper-air sounding is seldom operated, are required to improve heavy rainfall predictions and to prevent such failures.
著者
Teruyuki KATO
出版者
Meteorological Society of Japan
雑誌
Journal of the Meteorological Society of Japan. Ser. II (ISSN:00261165)
巻号頁・発行日
pp.2018-008, (Released:2017-12-08)
被引用文献数
8

This study investigated the representative height of low-level water vapor field that can be used to examine the occurrence possibility of heavy rainfall in East Asia. First, cloud base heights (CBHs) of moist convection were statistically examined by performing simulations with a 1-km-resolution numerical model during April–August 2008, with a focus on Kyushu and Shikoku Islands, western Japan. CBHs of moist convection with strong updrafts were simulated mainly around 500 and 300 m heights above sea level over land and over the ocean, respectively. This result indicates that low-level humid air below a height of 500 m is very important for the initiation of strong moist convection. Moreover, the equivalent potential temperature θe at the CBHs was examined to clarify θe values of lifted air parcels initiating cumulonimbus development. This result showed that below the CBHs, θe was usually around 355 K. Next, given these results for the CBHs, θe at 500 m height from 10-km-resolution objective analysis data was statistically compared with θe at various heights and pressure levels over the ocean south of 35 °N in East Asia during June–September 2008. These comparisons showed that analyses at the 850-hPa level could not represent the low-level water vapor field, while the θe field at 850 hPa in the Baiu season was strongly influenced by convective activity over the Baiu frontal zone. The θ e field at 925 hPa also could not adequately represent the low-level water vapor field, but the difference in θ e between heights of 250 and 500 m was very small. Because high θ e layers must have some thickness, data at 500 m height can be considered representative of the low-level water vapor field in analyses examining the initiation of moist convection leading to heavy rainfall.