(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 69, No. 4, pp. 197-204, 2022
Upper tropospheric features over the Kyusyu heavy rainfall area on 23 July, 1982 are studied using observation data and reanalysis data. A Baiu-frontal mesoscale depression, which formed over China on 21 July, developed and moved eastward, and reached over the Tsushima Strait on 23 July. The cloud cluster formed in the warm-sector of the depression caused intense rainfalls. At 200hPa height, strong divergence and diffluence are formed over the heavy rainfall area. IR cloud images and cloud-top TBB (blackbody temperature) data show meso-scale features of the cloud cluster. The coldest TBB of -70ßC is found over the heavy rainfall area. Crescent-shaped areas of warm and relatively cold TBB are seen in the eastern outside of the coldest TBB area. The features of the present case are compared with features in previous reports on sever convective storms. Very cold TBB, upper tropospheric divergence and diffluence are commonly found in these cases. However, some differences are seen among the cases.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 69, No. 5, pp. 247-252, 2022
Past 45 years' long-term trend of the occurrence frequency of heavy rainfall events (HREs) in Japan was examined. The HREs were extracted using a threshold value of 130mm for three-hourly accumulated precipitation amounts observed at 1178 AMeDAS stations between 1976 and 2020; AMeDAS is the Automated Meteorological Data Acquisition System operated by the Japan Meteorological Agency. We also compared the results with the trend of the occurrence frequency for hourly accumulated precipitation amounts (P1H) of 68mm or more, which was determined to correspond to the number of the extracted HREs. Annual change of the occurrence frequency for the HREs and P1H>_68mm showed a long-term increasing trend at a significant level of 1%, and the increase rate was higher by about 10% for the HREs than for P1H>_68mm. For monthly changes, a long-term increasing trend for the HREs was remarkable during the rainy season (June and July) in Japan, especially the long-term increase rate during 45 years in July reached about 3.8 times at a significant level of 5%; it was about 2.8 times for P1H>_68mm. In August no significant increasing trend was found for the HREs, but the frequency of P1H>_68mm increased. Conversely no increasing trend was found for P1H>_68mm in September, but the HREs became more frequent.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 69, No. 6, pp. 319-325, 2022
Long-term changes in the newspaper coverage of terms related to meteorology and disaster were examined using online search systems of four major newspapers in Japan from 1990 to 2020. It was found that the number of articles containing terms related to severe weather and disaster has increased. However, the trend of change is different according to terms. For example, the coverage of "gou (torrential rain)" has increased significantly, while that of "shuchugou (localized torrential rain) has decreased. The coverage of meteorological terms that are not directly related to disasters tends to have remained unchanged or decreased.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 69, No. 7, pp. 365-378, 2022
To contribute to the predictions of short-term heavy rainfall, we extracted the cases of heavy rainfall in Tokyo from high-density observation data and analyzed the characteristics of the surface wind convergence that preceded the rainfall. The error in divergence due errors in the surface wind observations was evaluated, and the correspondence between the divergence and vertical flow near the ground was examined.
An index--"effective convergence"--the increase in the amount of convergence that precedes heavy rainfall was defined using the same method that was used to determine the effective rainfall, and the temporal change in the effective convergence was examined. An increase in convergence was observed in about 25%-40% of cases of heavy rainfall. In addition, the greater the effective convergence before the heavy rainfall, the greater is the cumulative and peak precipitation. There was a good correspondence between the areas where there was an increase in the effective convergence and the heavy rainfall. As a result of using the effective convergence to make predictions of heavy rainfall, it was found that the effective convergence reached the threshold value at least 60 mins earlier than the occurrence of rainfall in half of the cases where heavy rainfall was detected. Although the false alarm rate was high, it was suggested that monitoring the effective convergence would be useful in the predictions of short-term heavy rainfall.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 69, No. 7, pp. 379-385, 2022
This report studies intense rainfalls over Nagasaki area (northwestern area of Kyushu District) on 23 July 1982 using precipitation data at about 90 stations of Japan Meteorological Agency (JMA data) and other organizations (non-JMA data). Maximum 1-hour precipitation and its occurrence time over Nagasaki area are examined to confirm the time-spatial consistency of the observations. It is also shown that the standard-deviation of the maximum 1-hour precipitation (120-150mm/h) in data rich area of about 7km radius is about 10mm. Analysis of 1-hour precipitation including the non-JMA data revealed detailed variations of intense rainfall. The consistency of the 10-min precipitation data could not be examined because of the insufficient spatial density of the observations. The10-min precipitation data show a few peaks of 10-min precipitation within the strong rainfall period.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 69, No. 11, pp. 609-620, 2022
During the recent years, synoptic-scale water vapor flows have frequently caused widespread intense precipitation events over East Asia, including the heavy rain event of mid-August 2021. The elongated water vapor transport bands over the middle latitudes are called as "atmospheric rivers (ARs)". Previous studies found the relationship between the ARs and the warm-season heavy rainfall events over western and central Japan. Here we investigate climatological features of widespread intense precipitation events over Japan including cold seasons and over northern Japan by utilizing variable criteria of precipitation intensity between different regions and seasons. During winter, ARs have caused intense precipitation over the Pacific sides of western and central Japan. In June and July, heavy rainfalls lasting for several days have occurred over the Hokuriku District, Central Japan, and the Japan-Sea side of the Tohoku District, Northeast Japan, due to westerly water vapor flows associated with ARs along zonally-elongated fronts. Tropical cyclones located south of Japan in summer and autumn seasons often bring meridionally-elongated ARs and resultant heavy rainfall over wide areas of western to northern Japan.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 69, No. 12, pp. 671-677, 2022
Shikoku-Kii intense rainfalls in 24-25 July 1982 are studied by using observational data and reanalysis data. A Baiu frontal depression developed over the Tsushima Strait in 23-24 July. The successive development of mesoscale precipitation systems in the warm-sector of the depression caused intense rainfalls over Kyushu. The depression weakened gradually after 12 UTC 24th, and intense rainfall area shifted from Kyushu to Shikoku-Kii area. Low-level moist southwesterly flow was intensified to the south of the weakened depression. Belt of convection in the southwesterly flow caused intense rainfalls over coastal zone of Shikoku-Kii area. The Kyushu intense rainfalls occurred in the developing stage of the Baiu frontal depression, while the Shikoku-Kii intense rainfalls occurred in the weakening stage of the depression.