著者

Arata Amemiya Takumi Honda Takemasa Miyoshi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.6-11, 2020 (Released:2020-01-28)

参考文献数

18

被引用文献数

7

---

The observation operator for the Phased Array Weather Radar in the SCALE-LETKF data assimilation system is revisited, and the impact of its improvement on the analyses and forecasts is examined. The observation operator provides a functional relationship between equivalent radar reflectivity factor (Ze) and hydrometeor mass density (W) of each precipitation particle category. The W–Ze relationship is obtained by a radar simulator. This study performs a radiation code calculation with the parameters regarding particle size distribution of graupel consistent with the cloud microphysics scheme in the SCALE model. The newly obtained observation operator provides much stronger sensitivity of graupel mixing ratio to observed Ze compared to the operator originally used in the model. To examine the impact on the SCALE-LETKF analyses and forecasts, an experiment on a 13 July 2013 heavy rain case is performed with the new observation operator and is compared with the previous study. The forecast initiated by the analysis using the new operator shows much more realistic evolution of Ze in the middle troposphere, where a large amount of graupel is located. The overestimation of forecast Ze is significantly alleviated by the new observational operator. The 30-minute forecast of surface precipitation rate is also improved.

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

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

pp.2021-008, (Released:2021-02-09)

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

Arata Amemiya Takumi Honda Takemasa Miyoshi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-002, (Released:2019-12-28)

被引用文献数

7

---

The observation operator for the Phased Array Weather Radar in the SCALE-LETKF data assimilation system is revisited, and the impact of its improvement on the analyses and forecasts is examined. The observation operator provides a functional relationship between equivalent radar reflectivity factor (Ze) and hydrometeor mass density (W) of each precipitation particle category. The W − Ze relationship is obtained by a radar simulator. This study performs a radiation code calculation with the parameters regarding particle size distribution of graupel consistent with the cloud microphysics scheme in the SCALE model. The newly obtained observation operator provides much stronger sensitivity of graupel mixing ratio to observed Ze compared to the operator originally used in the model. To examine the impact on the SCALE-LETKF analyses and forecasts, an experiment on a 13 July 2013 heavy rain case is performed with the new observation operator and is compared with the previous study. The forecast initiated by the analysis using the new operator shows much more realistic evolution of Ze in the middle troposphere, where a large amount of graupel is located. The overestimation of forecast Ze is significantly alleviated by the new observational operator. The 30-minute forecast of surface precipitation rate is also improved.