著者

Mizuki Konagaya Teruo Ohsawa Takaya Inoue Toshinari Mito Hideki Kato Kazuhiro Kawamoto

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.234-238, 2021 (Released:2021-12-18)

参考文献数

13

被引用文献数

1

---

To develop offshore wind energy, we investigated nearshore wind conditions, notably the land–sea contrast, using the coastal area of Mutsu-Ogawara, Aomori Prefecture as a case study. We found that wind conditions were substantially different between onshore (MT-A1) and offshore (MT-B) sites, even when the latter were only 1.5 km apart. The mean wind speed at 55 m above sea level at MT-B was higher than that at the onshore site by up to 20% monthly and 12% annually. For winds from the landward side, the Iref value (turbulence intensity at a mean wind speed of 15 m/s) at MT-B was 37% lower than that at MT-A1. Because such high wind speeds and low turbulence conditions are preferable for the operation of wind turbines, an offshore wind farm would have advantageous wind conditions, even if placed close to the coastline. Moreover, we found that the land–sea contrast is caused not only by mechanical factors, such as roughness length, but also by thermodynamic factors such as seasonal variations of atmospheric stability over land and sea.

著者

Yoshifumi Ota Miho Sekiguchi Yousuke Sato

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.228-233, 2021 (Released:2021-12-16)

参考文献数

19

---

A three-dimensional (3D) atmospheric radiative transfer (RT) model based on the Monte Carlo method was developed to evaluate the cloud-resolving radiation budget. The simulation data of stratocumulus (open and closed cell types) stimulated by a large eddy simulation model were used to obtain a detailed cloud field dataset at different spatial resolutions between 100 m and 1 km orders. By applying the 3D RT model offline to a multiscale cloud field dataset, the 3D distribution and magnitude of the solar radiative heating rate were estimated for each spatial resolution. The results showed that the magnitude of the local solar radiative heating effect significantly changes in the range of spatial resolution between 100 m and 1 km. The solar radiative heating rate can reach 6 K/hr locally in the case of the spatial resolution at 100-m order, whereas it is approximately 1 K/hr at most in the case of the spatial resolution at 1-km order. However, the domain-averaged values of the solar radiative heating rates were almost invariant at different spatial resolutions. The results indicate that a radiation scheme for the cloud-resolving model needs to be constructed while considering spatial resolutions, along with cloud parameterization.

著者

Shin Fukui Akihiko Murata

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.207-212, 2021 (Released:2021-11-25)

参考文献数

40

---

This study statistically investigated sensitivities of simulated precipitation to horizontal resolution of a regional climate model, instead of focusing on particular cases. We performed long-term integrations of models with horizontal grid spacings of 20, 5, 2, 1, and 0.5 km over Kyushu in the Baiu seasons of 2009-2020. The 2-km grid model improves simulated precipitation to the 5-km grid models with and without cumulus parameterization. Further decreasing the gird spacing from 2 km to 1 and 0.5 km reduces the dependency of the frequency biases on intensities of hourly precipitation and mitigates the excessive concentration of heavy precipitation in small scale, approaching that of the radar/raingauge analysis. The features of individual deep moist convections, specifically the horizontal scale of updrafts, the representation of downdrafts, and the number of convections, start to converge when the grid spacing is reduced from 1 to 0.5 km. The results suggest models with grid spacing of 1 km or less are needed to resolve deep moist convections and to represent the resulting precipitations. The 2-km grid models can partly resolve the deep moist convections, but their effective resolution is still insufficient, requiring some parameterizations to simulate convective precipitations appropriately.

著者

Tshencho Dorji Bhenjamin Jordan L Ona Srivatsan V Raghavan

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.202-206, 2021 (Released:2021-11-25)

参考文献数

32

被引用文献数

2

---

This study examines the observed seasonal and annual rainfall trend and variability in Bhutan from 1996-2017. Using standard statistical methods, we utilized Mann-Kendall test and Sen's slope estimator to determine the trends in the seasonal rainfall of Bhutan. We analyzed the temporal variability and spatial pattern of rainfall by using the principal component analysis (PCA), Rainfall Anomaly Index (RAI), and Precipitation Concentration Index (PCI). Our results indicate that the summer season contributed to the 73% of the total rainfall in Bhutan while winter season contributed only 1%. Results from the PCI indicate that the rainfall distribution in the northeast part of the country is moderately concentrated while the south to the northwest portion experienced high fluctuation in rainfall distribution. PCA explains the 90.1% of the total variance is linked to the variability of Asian monsoon. The influences of ENSO/La Niña are possible causes for the variability of rainfall in Bhutan though this necessitates more investigations to corroborate.

著者

Akihito Umehara Toru Adachi Wataru Mashiko Hiroshi Yamauchi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.196-201, 2021 (Released:2021-11-25)

参考文献数

19

被引用文献数

2

---

The tornadic debris signatures (TDSs) of the Ichihara Tornado associated with Typhoon Hagibis (2019) were observed using two operational C-band dual-polarization weather radars and an X-band phased-array weather radar (PAWR). This TDS observation was the first to be made over Japan in a typhoon environment. The TDS bins spread over time, and the maximum vertical and aerial extents reached 2.4 km and 9.41 km2, respectively. The estimated rise velocity of the TDS was 8 m s−1. The first TDS was detected ∼1 min before damage reporting began. The TDSs became clearer along with the rotational velocity of the near-surface vortex detected by PAWR. The copolar correlation coefficient reached a minimum (0.27) ∼1 min after the tornado passed the most severely damaged area and increased gradually over 4 min. This suggests that heavy and/or dense debris was lofted and immediately fell out and/or diffused, whereas light debris remained aloft for ≥ 4 min. By comparing the PAWR-detected vortex signatures with aerial photographs, we inferred that the first TDS comprised vegetated debris, the clearest TDS mainly comprised destroyed manmade structures. These results indicate that TDS detection is effective both for investigating damage and for recognizing tornado's occurrence even in a typhoon environment.

著者

Tsubasa Kohyama Hiroaki Miura Shoichiro Kido

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-043, (Released:2021-11-09)

---

A modified version of the principal component analysis (PCA) is introduced by reconsidering statistical degrees of freedom in spatial dimensions based on spatial auto-correlations. In the conventional PCA, data points that represent equal areas are assumed to have equal amount of information. In our new method, the intensive variability extraction (IVE), data points correlated with less other data points are weighted more before performing PCA. Hence, variability with independent information is emphasized, even if the variability is confined to small areas.Sea surface temperature (SST) data at each grid in the tropics are shown to have fewer spatial statistical degrees of freedom than that in the extratropics. Tropical SSTs exhibit covariability with large areas, because oceanic equatorial waves and atmospheric gravity waves share temperature information with surrounding areas. As to the extratropics, grids along the western boundaries of oceanic basins are more independent than those in the east, following dynamical requirement of the Earth's rotation.Using IVE, climate modes that involve interscale covariability are extracted. IVE performed for the Pan-Pacific SSTs extracts the Pacific Decadal Oscillation assuming the aforementioned a priori dynamical expectation. Using extratropical SSTs, it is demonstrated that IVE detects synchronicity of small-scale variability between distant narrow regions.

著者

Mizuki Konagaya Teruo Ohsawa Takaya Inoue Toshinari Mito Hideki Kato Kazuhiro Kawamoto

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-041, (Released:2021-10-27)

被引用文献数

1

---

To develop offshore wind energy, we investigated nearshore wind conditions, notably the land–sea contrast, using the coastal area of Mutsu-Ogawara, Aomori Prefecture as a case study. We found that wind conditions were substantially different between onshore (MT-A1) and offshore (MT-B) sites, even when the latter were only 1.5 km apart. The mean wind speed at 55 m above sea level at MT-B was higher than that at the onshore site by up to 20% monthly and 12% annually. For winds from the landward side, the Iref value (turbulence intensity at a mean wind speed of 15 m/s) at MT-B was 37% lower than that at MT-A1. Because such high wind speeds and low turbulence conditions are preferable for the operation of wind turbines, an offshore wind farm would have advantageous wind conditions, even if placed close to the coastline. Moreover, we found that the land–sea contrast is caused not only by mechanical factors, such as roughness length, but also by thermodynamic factors such as seasonal variations of atmospheric stability over land and sea.

著者

Yoshifumi Ota Miho Sekiguchi Yousuke Sato

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-040, (Released:2021-10-26)

---

A three-dimensional (3D) atmospheric radiative transfer (RT) model based on the Monte Carlo method was developed to evaluate the cloud-resolving radiation budget. The simulation data of stratocumulus (open and closed cell types) stimulated by a large eddy simulation model were used to obtain a detailed cloud field dataset at different spatial resolutions between 100 m and 1 km orders. By applying the 3D RT model offline to a multiscale cloud field dataset, the 3D distribution and magnitude of the solar radiative heating rate were estimated for each spatial resolution. The results showed that the magnitude of the local solar radiative heating effect significantly changes in the range of spatial resolution between 100 m and 1 km. The solar radiative heating rate can reach 6 K/hr locally in the case of the spatial resolution at 100-m order, whereas it is approximately 1 K/hr at most in the case of the spatial resolution at 1-km order. However, the domain-averaged values of the solar radiative heating rates were almost invariant at different spatial resolutions. The results indicate that a radiation scheme for the cloud-resolving model needs to be constructed while considering spatial resolutions, along with cloud parameterization.

著者

Teruhisa Shimada

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.191-195, 2021 (Released:2021-10-22)

参考文献数

18

---

This study investigated the distributions of strong surface winds in the vicinity of Cape Erimo and the synoptic conditions favorable for inducing the strong winds by using scatterometer wind measurements and atmospheric reanalysis data. The wind around Cape Erimo is highly constrained by the topography, and the prevailing wind directions are split between westerly to west-northwesterly winds during the cool season and the easterly to northeasterly winds during the warm season. The zonal wind components in the region surrounding Cape Erimo are significantly correlated with the east–west sea level pressure gradient, which works as an index for the strong winds in the vicinity of Cape Erimo. Using composite analysis based on the index, the following atmospheric fields are presented. The low-pressure system passing over the Okhotsk Sea induces the northwesterly winds to the south of Cape Erimo during the cool season. The well-organized southwesterly winds are observed in the east of Cape Erimo when the southwesterly winds dominate during the warm season. The low-pressure system passing over Japan enhances the easterly winds around Cape Erimo during the cool season. The developed Okhotsk high induces strong winds to the southwest of Cape Erimo during the warm season.

著者

Syuichi Itahashi Junichi Kurokawa Toshimasa Ohara Itsushi Uno Shin-ichi Fujita

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.184-190, 2021 (Released:2021-10-14)

参考文献数

44

被引用文献数

1

---

Precipitation chemistry was observed at the remote background site at Ryori, Ofunato in northeastern Japan, from 1976 to 2011 as the part of World Meteorological Organization-Global Atmospheric Watch (WMO-GAW). During this period, anthropogenic emissions in East Asia varied widely, which affected the precipitation chemistry. The precipitation amount also affects the wet deposition amount. Thus, to eliminate the effect of the precipitation amount, we used the ratio of nitrate (NO3−) to non-sea-salt sulfate (nss-SO42−) concentration in precipitation on an equivalent basis (Ratio). The historical trend of NO3− and nss-SO42− concentrations in precipitation was not clear; however, Ratio showed a strong increase in the 1990s, a sudden drop in 2001, and an increase again after 2007. Based on the analysis of the historical emission dataset, the increases in Ratio during the 1990s and after 2007 were attributed to anthropogenic emission changes in Japan and China. The drop in Ratio in 2001 was explained by the massive SO2 release from Miyakejima volcano from mid-August 2000, rather than by anthropogenic emissions. The 36-year historical record analysis of precipitation chemistry at Ryori detected both anthropogenic and natural emission changes and indicated the transition from local to transboundary air pollution in Japan.

著者

Hiroshi Takagi Akihiko Ito Heon-Sook Kim Shamil Maksyutov Makoto Saito Tsuneo Matsunaga

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-037, (Released:2021-10-13)

被引用文献数

2

---

Numerous wetlands, including the world's two largest contiguous wetlands, lie along the free-flowing Paraná and Paraguay Rivers that travel the length of subtropical South America (SSA) region. These wetlands are floodplains that are inundated with rising river water in flood events; their morphology and area are highly changeable with flooding extent. The long-term variability of methane emission from this wetland hotspot and its sensitivity to meteorological conditions are not well known. We herein explore this unknown using space-based estimates of methane flux for SSA region between 2009 and 2015 along with data of water balance. We find that methane emission from this region coherently varies with precipitation and inundation areal extent.

著者

Fumiaki Fujibe Jun Matsumoto

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-038, (Released:2021-10-13)

被引用文献数

4

---

Using vital statistics data from 1995 to 2019, the relationships among interannual variations of total mortality, heat-stroke mortality, and temperature in summer were assessed in an attempt to estimate excess deaths in hot summer years in Japan. The number of deaths in July and August increased by 1.1% for each 1°C increment of summer mean temperature over Japan, with an eight-fold larger range of interannual variation than the more narrowly defined heat-stroke deaths. This fact implies that excess deaths due to heat are about eight times more prevalent than heat-stroke deaths and can be on the order of 10,000 in a hot summer year. Analyses by age group and cause of death indicated that excess deaths are largely associated with cardiovascular and respiratory diseases among elderly people.

著者

Tshencho Dorji Bhenjamin Jordan L. Ona Srivatsan V. Raghavan

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-035, (Released:2021-10-05)

被引用文献数

2

---

This study examines the observed seasonal and annual rainfall trend and variability in Bhutan from 1996-2017. Using standard statistical methods, we utilized Mann-Kendall test and Sen's slope estimator to determine the trends in the seasonal rainfall of Bhutan. We analyzed the temporal variability and spatial pattern of rainfall by using the principal component analysis (PCA), Rainfall Anomaly Index (RAI), and Precipitation Concentration Index (PCI). Our results indicate that the summer season contributed to the 73% of the total rainfall in Bhutan while winter season contributed only 1%. Results from the PCI indicate that the rainfall distribution in the northeast part of the country is moderately concentrated while the south to the northwest portion experienced high fluctuation in rainfall distribution. PCA explains the 90.1% of the total variance is linked to the variability of Asian monsoon. The influences of ENSO/La Nina are possible causes for the variability of rainfall in Bhutan though this necessitates more investigations to corroborate.

著者

Hiromitsu Kanno Hiroshi Matsuyama

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.170-176, 2021 (Released:2021-10-05)

参考文献数

34

---

In the Western North Pacific, there is little meteorological data available for the 19th century. We found historical documents at Chichi-jima in the Ogasawara (Bonin) Islands that report routine meteorological observations and weather conditions before 1906. In 1906, Japan Meteorological Agency began observations at Ohmura in the northwestern part of the island. The Home Ministry in Japan conducted the observations until 1906 at Ohgiura, the central part of Chichi-jima, which is 3 km away from Ohmura. We analyzed precipitation data at Ohgiura and Ohmura from 1975 to 2020 and found that the former is systematically greater than the latter. Therefore, we corrected pre-1906 precipitation at Ohgiura to ensure correlation with post-1906 precipitation at Ohmura. No discontinuous changes in the data were found around 1906. A previous study reported that annual precipitation at Ohmura for 1907-1944 was higher than that after World War II. We found that in some years from 1882 to 1906, the precipitation was less than that for 1907-1944, which agrees with the reported higher atmospheric pressure around Chichi-jima before 1906. Our study suggests that the trend of decreasing precipitation at Chichi-jima in the 20th century is not monotonous but a part of longer-scale temporal variations.

著者

Kazuto Takemura Hitoshi Mukougawa

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.164-169, 2021 (Released:2021-09-25)

参考文献数

24

被引用文献数

4

---

This study presents a possible large-scale factor of tropical cyclogenesis over the western North Pacific, which is triggered by Rossby wave breaking to the east of Japan. More than half of the wave breaking cases is accompanied by the tropical cyclogenesis. Results from a composite analysis for the wave breaking cases indicate that the genesis and development of tropical cyclones are dominant over the southwest quadrant of the wave breaking center, where an intrusion of the upper-level potential vorticity caused by the wave breaking and the consequent enhanced convection are seen. The number of tropical cyclones in the wave breaking cases exponentially increases in time during the developing stage of the wave breaking. The results of composite analysis further indicate that lower-level strong wind convergence and the associated enhanced convection, which are resulting from the wave breaking, is favorable conditions for the tropical cyclogenesis. An enhanced monsoon trough accompanied by the Pacific–Japan pattern resulting from the enhanced convection can regulate tracks of the tropical cyclones. These results show that the Rossby wave breaking can trigger the tropical cyclogenesis over the western North Pacific, through the southwestward intrusion of the upper-level potential vorticity and the consequent enhanced convection.

著者

Teruhisa Shimada

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-033, (Released:2021-09-29)

---

This study investigated the distributions of strong surface winds in the vicinity of Cape Erimo and the synoptic conditions favorable for inducing the strong winds by using scatterometer wind measurements and atmospheric reanalysis data. The wind around Cape Erimo is highly constrained by the topography, and the prevailing wind directions are split between westerly to west-northwesterly winds during the cool season and the easterly to northeasterly winds during the warm season. The zonal wind components in the region surrounding Cape Erimo are significantly correlated with the east–west sea level pressure gradient, which works as an index for the strong winds in the vicinity of Cape Erimo. Using composite analysis based on the index, the following atmospheric fields are presented. The low-pressure system passing over the Okhotsk Sea induces the northwesterly winds to the south of Cape Erimo during the cool season. The well-organized southwesterly winds are observed in the east of Cape Erimo when the southwesterly winds dominate during the warm season. The low-pressure system passing over Japan enhances the easterly winds around Cape Erimo during the cool season. The developed Okhotsk high induces strong winds to the southwest of Cape Erimo during the warm season.

著者

Ayako Seiki Yu Kosaka Satoru Yokoi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-031, (Released:2021-09-02)

被引用文献数

3

---

The relationship between the boreal summer intraseasonal oscillation (BSISO) in the tropics and the summertime tropical-extratropical teleconnection called the Pacific-Japan (PJ) pattern is investigated. The positive correlation between the BSISO and intraseasonal PJ pattern peaks during BSISO phase 8 when the convective center of the BSISO reaches the vicinity of the Philippines. A composite analysis based on the BSISO events shows that intraseasonal responses to the migration of the BSISO extend to the midlatitudes and form circulation anomalies reminiscent of the PJ pattern. During phases 7-8, cyclonic wind anomalies with low-pressure signals drastically intensify north of the Philippines and southeasterly wind anomalies blow into midlatitude East Asia, influencing the summer climate. Other apparent intraseasonal signals in pressure and surface air temperature are found over the midlatitude central Pacific and eastern Eurasia, respectively. The intraseasonal variability in the PJ pattern associated with the BSISO undergoes strong interannual modulations, with enhanced intraseasonal signals in summers of the positive seasonal-mean PJ pattern and suppressed signals in those of the negative PJ pattern. This asymmetry between the positive and negative PJ summers highlights the importance of cross-scale interactions for a better understanding of summer climate in East Asia.

著者

Hiromitsu Kanno Hiroshi Matsuyama

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-030, (Released:2021-09-01)

---

In the Western North Pacific, there is little meteorological data available for the 19th century. We found historical documents at Chichi-jima in the Ogasawara (Bonin) Islands that report routine meteorological observations and weather conditions before 1906. In 1906, Japan Meteorological Agency began observations at Ohmura in the northwestern part of the island. The Home Ministry in Japan conducted the observations until 1906 at Ohgiura, the central part of Chichi-jima, which is 3 km away from Ohmura. We analyzed precipitation data at Ohgiura and Ohmura from 1975 to 2020 and found that the former is systematically greater than the latter. Therefore, we corrected pre-1906 precipitation at Ohgiura to ensure correlation with post-1906 precipitation at Ohmura. No discontinuous changes in the data were found around 1906. A previous study reported that annual precipitation at Ohmura for 1907-1944 was higher than that after World War II. We found that in some years from 1882 to 1906, the precipitation was less than that for 1907-1944, which agrees with the reported higher atmospheric pressure around Chichi-jima before 1906. Our study suggests that the trend of decreasing precipitation at Chichi-jima in the 20th century is not monotonous but a part of longer-scale temporal variations.

著者

He Gong Mei Huang Zhaosheng Wang

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.151-157, 2021 (Released:2021-08-31)

参考文献数

29

---

The northern Eurasia is a region heavily affected by the Arctic polar vortex (APV). Understanding the vegetation responses to anomalous APV in this region is important for dealing with climate change. In this study, we investigated the impacts and mechanism of the anomalous APV phases on the vegetation dynamics in the northern Eurasia. The larger and smaller APV phases correspond to almost opposite atmospheric circulation patterns which result in opposite vegetation responses. The decreased (increased) solar radiation, the enhanced (weakened) northerly winds, together with the decreased (increased) water vapor divergence, caused the decreasing (increasing) of the air temperature, increasing (decreasing) of the precipitation and soil moisture in the study area during the larger (smaller) APV phase. The response of vegetation growth to the APV depends on climate change and vegetation sensitivity to it. In most parts of the study area, vegetation growth was positively associated with air temperature, and hence, vegetation was suppressed (promoted) during the larger (smaller) APV phase. In the northeast of the Caspian Sea (NCS), vegetation growth was sensitive to precipitation. Therefore, the increased (decreased) soil moisture in summer and autumn were responsible for the promoted (suppressed) vegetation growth during the larger (smaller) APV phase.

著者

Tana Bao Tao Gao Banzragch Nandintsetseg Mei Yong Erdemtu Jin

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.145-150, 2021 (Released:2021-08-27)

参考文献数

42

被引用文献数

12

---

In this study, we investigated the spatiotemporal variations of border-crossing dust events (DEs), including floating, blowing dust, and dust storms between Mongolia (MG) and Inner Mongolia (IM), China using the ground-based observations from 91 synoptic stations across the Mongolian Plateau during 1977-2018. We defined the intensity of DEs (progressive and recessive) depending on the dust impact area (number of stations affected by dust) by dividing them into three categories: DEs, transported dust events (T-DEs), and severe transported dust events (ST-DEs). The results revealed that during 1977-2018, the frequency of DEs in MG was two times higher than in IM. Simultaneously, the frequency of DEs (dominated by dust storms) increased in MG, whereas IM experienced a decrease in DEs (prevalent types of blowing dust). The T-DEs occurred 2.4 times higher than the ST-DEs over Mongolian Plateau. For the border-crossing DEs, transported dust storms were the dominant type. During 1977-1999, approximately 86% of DEs in IM originated from MG; however, this was decreased to 60% in the 2000s (2000-2018). The intensity of the border-crossing DEs originated from MG and the recessive T-DEs increased significantly since the 2000s, which were more significant than the progressive type.