著者

Shinta Seto

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2022-009, (Released:2022-02-10)

被引用文献数

2

---

For over 20 years, precipitation measurement has continued with spaceborne radars including the Precipitation Radar (PR) operating at 13.8 GHz on the Tropical Rainfall Measuring Mission and the Ku-band Precipitation Radar (KuPR) operating at 13.6 GHz on the Global Precipitation Measurement mission core satellite. PR and KuPR have essentially the same hardware designs and the same algorithm to make standard products (PRV8 and KuPRV06, respectively). The surface precipitation rate estimates (R) and related variables are statistically compared between PR and KuPR for a common observation area (within 35°N and 35°S) and period (April to September 2014). Due to the difference in sensitivity, the total precipitation amount recorded by KuPR is larger than recorded by PR by approximately 1.3%. For heavy precipitation, PR shows a smaller measured radar reflectivity factor (Zm) and a larger R than KuPR. Zm is affected by the attenuation and it is smaller for PR than KuPR, as the frequency is slightly higher. The attenuation corrected radar reflectivity factor is almost the same for PR and KuPR. However, the adjustment factor is larger for PR, which results in a larger R. Direct comparison between PR and KuPR during matchup cases demonstrates similar results.

著者

Yasutaka Hirockawa Teruyuki Kato

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.18, pp.13-18, 2022 (Released:2022-02-02)

参考文献数

23

被引用文献数

4

---

We propose a new application method in which radar/raingauge-analyzed precipitation amounts (RAP) produced by the Japan Meteorological Agency are spatially converted into 5km-resolution data, in addition to a three-hourly accumulation procedure, in order to statistically analyze localized heavy rainfall areas (HRAs) for a long period. A long-term trend and homogeneity in the appearance frequency of RAP with 5km-resolution converted by several methods, including the conventional method, are statistically evaluated in comparison with rain-gauge observations. The results indicate that the following application method is the most suitable to represent long-term variations in the appearance frequency of HRAs; (1) the converted value of RAP from 1 km to 5 km resolution is set to the 90th percentile value in 30 segments with 1km-resolution included in a grid with 5km-resolution, and (2) this spatial conversion is conducted after accumulating original RAP with 1km-resolution for three hours. Statistical analyses were performed for the appearance frequency of HRAs extracted from 5km-resolution RAP that were produced by the new application method, which indicates that the number of HRAs of the linear-stationary type could be increased without compromising the characteristics of HRAs extracted by the conventional method.

著者

Yuhji Kuroda Miho Toryu Hiroaki Naoe

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2022-008, (Released:2022-01-27)

---

This study examined the influence of stratospheric variability on the polar winter tropospheric climate. The winter-mean tropospheric condition can be well represented by a winter-mean stratospheric index (the Polar-night Jet Oscillation (PJO) index) defined from profiles of monthly polar temperature anomalies. In winters with a positive (negative) index, the winter-mean surface pressure anomaly tends to acquire a positive (negative) pattern resembling the Arctic Oscillation (AO). This tropospheric condition tends to become a persistent polarity of the AO index throughout the winter. This tendency is also found when the PJO index for each month is used. Although the PJO index in January shows the best results, those in early winter can be used as predictors for the entire winter troposphere. Use of the PJO index for the stratospheric effect on winter troposphere is compared with that associated with the occurrence of the major stratospheric sudden warmings. The origin of the decadal variability of the index is also discussed.

著者

Kenji Kai Kei Kawai Atsuya Ito Yuki Aizawa Yuki Minamoto Erdenebadrakh Munkhjargal Enkhbaatar Davaanyam

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-023, (Released:2021-06-18)

被引用文献数

5

---

The Gobi Desert is a dominant source of dust on the Asian continent. In this study, we analysed the characteristics of a typical Mongolian dust storm and identified a prominent dust hotspot in the Gobi Desert. During a field survey from Ulaanbaatar (the capital of Mongolia) to Dalanzadgad in the Gobi Desert, we encountered a typical dust storm on 28 April 2019, exhibiting a distinct dust wall. The head of the dust storm crossed the road several kilometres ahead of our vehicle. The head of the storm had a height of 600 m, and its structure suggested that the dust storm was induced by a gravity current. We entered the front of the dust storm and measured a maximum wind speed of 18.2 m/s and a visibility of less than 20 m. The normalized dust number concentration at 7 μm was 59 cm−3. Moreover, Himawari-8 Dust RGB imagery showed that the dust storm occurred in an orographic convergence zone. This zone connects two valleys that are sandwiched between three mountains in the Gobi Desert: the Khangai, Altai, and Gurvan Saikhan Mountains. Our results suggest that this zone is a remarkable dust hotspot in the Gobi Desert.

著者

Takumi Honda Takemasa Miyoshi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.113-119, 2021 (Released:2021-06-01)

参考文献数

38

被引用文献数

1

---

In July 2018, record-breaking heavy precipitation caused catastrophic disasters in west Japan. This study investigated the predictability of this precipitation event using a regional ensemble data assimilation system. A series of daily ensemble forecast experiments showed that the forecast ensemble spread during the heavy precipitation event increased in the forecasts initialized on 1 July and 3 July. The first peak of the forecast ensemble spread was associated with the uncertain track forecast of Typhoon Prapiroon. Namely, about a half of the ensemble members predicted eastward recurvature of the typhoon, whereas the other members predicted that the typhoon stayed near China. The later peak was associated with the southern convective disturbances near the Ryukyu Islands. Composite analysis and ensemble-based correlations showed that more active convective activities corresponded to a stronger cyclonic circulation and pushed the main precipitation band northward. The results implied that Prapiroon and the southern convective disturbances played important roles in the July 2018 heavy rain event and largely contributed to its predictability.

著者

Masaki Katsumata Kyoko Taniguchi Tomoaki Nishizawa

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-022, (Released:2021-05-21)

---

This article is a correction to SOLA Vol.16A (2020) pp. 6-11.

著者

Biao Geng Ryuichi Shirooka

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.81-87, 2021 (Released:2021-05-07)

参考文献数

34

---

The internal structure and evolution of a monsoon trough (MT) and associated mesoscale convective systems (MCSs) in the western North Pacific were investigated, based mainly on radiosonde and a Doppler radar observations in Palau. The MT was observed on 15-16 June 2013, with the pre-existing disturbance of Typhoon Leepi (2013) being embedded in it. The large-scale circulation around the MT featured a pattern representing an active MT. Deep convection developed ahead and at the leading edge of the downward-sloping monsoonal flow, where intense low-level convergence was observed. Stratiform precipitation broadened rearward over the MT axis. A deep and wide layer of warm and moist air over the MT axis was undercut by a layer of cold air sloping downward from the trailing stratiform region to the leading convective region. An intense low-pressure zone formed in the interface between the warm layer above and cold layer below, with the westerly monsoonal and easterly trade flows being enhanced on its west and east sides, respectively, from the low to middle troposphere. The results suggest that a strengthening of the large-scale cyclonic circulation in response to the internal processes of the MCSs triggered by the MT is important for typhoon genesis.

著者

Kazuyo Murazaki Hirotaka Kamahori Chiaki Kobayashi Seiji Yukimoto

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.88-95, 2021 (Released:2021-05-07)

参考文献数

32

---

This study evaluated the effects of sea surface temperature (SST) resolution on dynamically downscaled daily surface air temperature (Tsrf) in the Kanto region during early summer. Two downscaling experiments and one additional experiment were conducted using different SST datasets for the months of June and July over a 10-year period. The results demonstrated that the Tsrf difference in the Kanto region between the high-resolution SST experiment (Run-H) and the low-resolution SST experiment (Run-C) correlates positively with the difference in surrounding SST. The impact of SST difference depends on the wind direction and speed. By comparing the results with observations at meteorological stations, the number of days with warm Tsrf bias in Run-C significantly reduces in Run-H, but the number of days with cold Tsrf bias still remains. These results suggest that SST resolution influences the downscaled Tsrf reproducibility over land, and it is worthwhile to pay attention to coastal SST.

著者

Paula Maldonado Juan Ruiz Celeste Saulo

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.96-102, 2021 (Released:2021-05-19)

参考文献数

34

被引用文献数

4

---

This study investigates the impact of applying different types of initial and boundary perturbations for convective-scale ensemble data assimilation systems. Several observing system simulation experiments (OSSEs) were performed with a 2-km horizontal resolution, considering a realistic environment, taking model error into account, and combining different perturbations' types with warm/cold start initialization. Initial perturbations produce a long-lasting impact on the analysis's quality, particularly for variables not directly linked to radar observations. Warm-started experiments provide the most accurate analysis and forecasts and a more consistent ensemble spread across the different spatial scales. Random small-scale perturbations exhibit similar results, although a longer convergence time is required to up-and-downscale the initial perturbations to obtain a similar error reduction. Adding random large-scale perturbations reduce the error in the first assimilation cycles but produce a slightly detrimental effect afterward.

著者

Kazuto Takemura Hitoshi Mukougawa Shuhei Maeda

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-021, (Released:2021-05-18)

被引用文献数

2

---

Rossby waves propagating along the Asian jet frequently cause the breaking near the jet exit region. This study examines characteristics of oceanographic condition and atmospheric circulation associated with interdecadal variability of Rossby wave breaking frequency near Japan in August. Sea surface temperature during a period of the higher Rossby wave breaking frequency is cooler over the central part of the tropical North Pacific, compared with that during a period of the lower frequency. Convective activities are suppressed over the region consistent with the cooler sea surface temperature, contributing to an enhanced and southwestward extended mid-Pacific trough. Deceleration and diffluence of the Asian jet are stronger during the period of the higher frequency than that during the period of the lower one. The enhanced deceleration and diffluence of the jet are associated with the enhanced and southwestward extended mid-Pacific trough. The abovementioned dynamical influence is also shown by a numerical simulation using an atmospheric linear baroclinic model. These results indicate that the interdecadal variability of sea surface temperature over the central part of the tropical North Pacific has an impact on that of the Rossby wave breaking frequency near Japan, through the modulated convective activities and mid-Pacific trough.

著者

Paula Maldonado Juan Ruiz Celeste Saulo

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-015, (Released:2021-04-14)

被引用文献数

4

---

This study investigates the impact of applying different types of initial and boundary perturbations for convective-scale ensemble data assimilation systems. Several OSSEs were performed with a 2-km horizontal resolution, considering a realistic environment, taking model error into account, and combining different perturbations' types with warm/cold start initialization. Initial perturbations produce a long-lasting impact on the analysis's quality, particularly for variables not directly linked to radar observations. Warm-started experiments provide the most accurate analysis and forecasts and a more consistent ensemble spread across the different spatial scales. Random small-scale perturbations exhibit similar results, although a longer convergence time is required to up-and-downscale the initial perturbations to obtain a similar error reduction. Adding random large-scale perturbations reduce the error in the first assimilation cycles but produce a slightly detrimental effect afterward.

著者

Kazuyo Murazaki Hirotaka Kamahori Chiaki Kobayashi Yukimoto Seiji

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-014, (Released:2021-03-31)

---

This study evaluated the effects of sea surface temperature (SST) resolution on dynamically downscaled daily surface air temperature (Tsrf) in the Kanto region during early summer. Two downscaling experiments and one additional experiment were conducted using different SST datasets for the months of June and July over a 10-year period. The results demonstrated that the Tsrf difference in the Kanto region between the high-resolution SST experiment (Run-H) and the low-resolution SST experiment (Run-C) correlated positively with the difference in surrounding SST. The impact of SST difference depended on the wind direction and speed. By comparing the results with observations at meteorological stations, the number of days with warm Tsrf bias in Run-C significantly reduced in Run-H, but the number of days with cold Tsrf bias remained steady. These results suggest that SST resolution influences the downscaled Tsrf reproducibility over land, and it is worthwhile to pay attention to coastal SST.

著者

James Taylor Arata Amemiya Takumi Honda Yasumitsu Maejima Takemasa Miyoshi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.48-56, 2021 (Released:2021-03-23)

参考文献数

28

被引用文献数

6

---

The predictability of the July 2020 heavy rainfall event that saw record-breaking rainfall over Western Japan in July 2020 is examined with the near real-time SCALE-LETKF numerical modelling system in a low resolution 18-km configuration setting. Ensemble-mean 5-day rainfall total forecasts showed close agreement with Japanese Meteorological Agency 1-km precipitation analyses in relation to the large-scale distribution of rainfall and to location of heaviest rainfall over Kyushu. Onset and duration of rainfall at specific sites across Kyushu were also well predicted by the forecasts. However, the precise prediction of heavy rainfall, including over the worst-hit Kumamoto and Kagoshima prefectures, was severely underestimated. Examination of the atmospheric conditions at the time of the heavy rainfall from reanalysis datasets and ensemble member forecasts showed very high humidity over central Kyushu with strong transport of moisture from the southwest to central regions. In addition, strong low-level convergence was observed to the west of Kyushu in both reanalysis and best performing member forecasts during the time of heavy rainfall, suggesting a potential contributing factor to the record-breaking rainfall.

著者

Biao Geng Ryuichi Shirooka

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-013, (Released:2021-03-18)

---

The internal structure and evolution of a monsoon trough (MT) and associated mesoscale convective systems (MCSs) in the western North Pacific were investigated, based mainly on radiosonde and a Doppler radar observations in Palau. The MT was observed on June 15-16, 2013, with the pre-existing disturbance of Typhoon Leepi (2013) being embedded in it. The large-scale circulation around the MT featured a pattern representing an active MT. Deep convection developed ahead and at the leading edge of the downward-sloping monsoonal flow, where intense low-level convergence was observed. Stratiform precipitation broadened rearward over the MT axis. A deep and wide layer of warm and moist air over the MT axis was undercut by a layer of cold air sloping downward from the trailing stratiform region to the leading convective region. An intense low-pressure zone formed in the interface between the warm layer above and cold layer below, with the westerly monsoonal and easterly trade flows being enhanced on its west and east sides, respectively, from the low to middle troposphere. The results suggest that a strengthening of the large-scale cyclonic circulation in response to the internal processes of the MCSs triggered by the MT is important for typhoon genesis.

著者

Akiyoshi Wada Johnny C. L. Chan

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17A, no.Special_Edition, pp.29-32, 2021 (Released:2021-03-18)

参考文献数

18

被引用文献数

9

---

In the 2019 tropical cyclone season in the western North Pacific, Typhoons FAXAI and HAGIBIS made landfall in Japan while keeping the intensity, resulting in serious disasters. This study addresses the influences of an increasing trend and variations in the upper ocean heat content above 26°C (tropical cyclone heat potential: TCHP) from January 1982 to June 2020 on FAXAI and HAGIBIS. TCHP underneath FAXAI and HAGIBIS in 2019 was higher than the climatological mean except for a part of mature phase of HAGIBIS due to HAGIBIS-induced sea surface cooling. TCHP significantly increased with the interannual oceanic variations (IOVs) in the subtropical (15°N-20°N, 140°E-150°E) and midlatitude (30°N-35°N, 130°E-140°E) areas where FAXAI and HAGIBIS intensified or kept the intensity. From an empirical orthogonal function (EOF) analysis of TCHP, we demonstrate that the leading three EOF modes of TCHP explain approximately 76.8% of total variance, but the increase in TCHP along the tracks of FAXAI and HAGIBIS particularly in the early intensification of HAGIBIS cannot be explained only by the IOVs included in the leading three EOF modes but rather by the warming trend irrespective of the IOVs.

著者

Hironobu Ueki Hisahiro Takashima Martina Michaela Friedrich

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-011, (Released:2021-03-03)

被引用文献数

1

---

To clarify three-dimensional (3-D) spatiotemporal variations and horizontal–vertical transport processes in nitrogen dioxide (NO2) over urban areas, combined NO2 profile observations by multiple Multi AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) and direct wind observations by 3-D coherent Doppler lidar were made over an urban area in Japan. MAX-DOAS measurements were conducted at Yakuin and Fukuoka University in Fukuoka urban area with high temporal resolution of four minutes.Enhanced NO2 concentrations were often observed over the city center. We conducted a case study on 29 November 2018 under clear sky conditions and NO2 profiles were well retrieved. Using MAX-DOAS at two locations, high NO2 concentrations were observed near the surface of the city center in the morning. Higher NO2 concentrations appearing gradually at higher altitudes over the city center and disappearing in the afternoon are explained using direct evidence of a 3-D wind field: an airmass with a high NO2 concentration was transported upward over the city center. Then, the airmass was advected landward by a sea breeze. Multiple MAX-DOAS combined with 3-D Doppler lidar constitutes a powerful tool for elucidating horizontal–vertical transport processes. It can contribute to the improvement of data retrieval by satellites for urban areas.

著者

Koichi Shiraishi Takashi Shibata

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.30-34, 2021 (Released:2021-02-23)

参考文献数

18

被引用文献数

2

---

Stratospheric aerosols over the high Arctic at Ny Ålesund, Svalbard (79°N, 12°E) were observed continuously for four years from March 2014 by a lidar system using the second harmonic wavelength (532 nm) of the Nd:YAG laser. Our observations reveal the seasonal features of stratospheric aerosols and the arrival of the smoke at the high Arctic from Canadian forest-fire in August 2017. We estimated the seasonal variation for three years before the Canadian forest-fire when there was no apparent volcanic effect. In the estimation, we removed polar stratospheric clouds by the threshold temperature of their formation. The seasonal variation for the three years is that the vertical profiles of the backscattering ratio take a maximum value of about 1.05-1.06 at altitudes between 13 and 16 km from December to March, and about 1.02-1.04 at altitudes between 17 and 20 km from April to November. These results are compared with the results observed at the low Arctic, northern Norway. We also present the increases in the backscattering ratio and the volume depolarization ratio from September to December 2017 caused by the smoke from the Canadian forest-fire.

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

Tomoe Nasuno

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.16-23, 2021 (Released:2021-02-18)

参考文献数

46

被引用文献数

1

---

Relationship between diurnal convection and the intraseasonal oscillation (ISO) over the western Maritime Continent (MC) was investigated by a case study of an ISO event that occurred during the Years of the Maritime Continent (YMC)-Sumatra 2017 campaign. Two sets of global cloud-permitting simulations using cloud microphysics settings for ISO prediction (CTL) and for climate simulation (MOD) were performed to clarify their impacts. CTL had biases of weaker diurnal variation and smaller precipitation amounts over land than in observations; these were reduced in MOD by higher probabilities of local intense convection in the middle troposphere and higher precipitation efficiency. The enhanced convection over land coincided with suppressed convection over the surrounding ocean, especially at the diurnal peak time of land convection. Exception is the onset period of the ISO convection, when upward moisture advection and precipitation increased also over ocean in MOD than in CTL at the diurnal peak time of oceanic convection. These results suggest that the enhancement of local convection over the MC by the cloud microphysical processes basically hinders the ISO convection by the activation of land convection, but it also favors the ISO convection development over ocean during the onset period.

著者

Hideo Shiogama Noriko N. Ishizaki Naota Hanasaki Kiyoshi Takahashi Seita Emori Rui Ito Toshiyuki Nakaegawa Izuru Takayabu Yasuaki Hijioka Yukari N. Takayabu Ryosuke Shibuya

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-009, (Released:2021-02-16)

被引用文献数

17

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Climate change impact assessment studies often use future projections of only a few global climate models (GCMs) due to limited research resources. Here we develop a novel method to select a small subset of GCMs that widely capture the uncertainty range of large ensemble. By applying this method, we select a subset of five GCM projections from the Coupled Model Intercomparison Project Phase 6 (CMIP6) ensemble for impact and adaptation studies in Japan. At first, we omit GCMs whose global warming projections have been evaluated to be overestimated in the recent literature. Then, we select a subset of five GCMs that widely captures the uncertainty ranges for 8 climate variables and have good performances in present-climate simulations. These selected GCM simulations will be used to provide better climate scenarios for impact and adaptation studies than those in the previous impact assessment project.