(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 67, No. 2, pp. 89-108, 2020
The characteristics of an optical disdrometer (OD), the Thies Laser Precipitation Monitor (LPM), were examined by switching the telegram to all-particle logging. Intensive tests were carried out using spherical bodies of known diameter, and field observations were used for further analysis. The LPM emits a parallel laser light beam over a single horizontal sheet-like detection area. The size (velocity) derived by typical operation of the LPM is the horizontal width (sphere-assumed velocity). Large sizes were truncated. The number of small particles less than~ 0.3mm in size was underestimated. The ratio of measured size to real size varied significantly, depending on the location of particles' fall within the detection area when using the tested sensor. The measured size distribution should be considered a convolution of the ratio and the natural size distribution of the particles. Over time, the particle size measured by the tested sensor decreased slightly, but the change in the overall ratio distribution pattern was not significant. Appropriate user calibration should be performed continuously for observations of precipitation.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 67, No. 3, pp. 149-162, 2020
The large- and meso-a-scale features of Baiu frontal zone, Baiu frontal cloud zone and Baiu frontal rain zone in July 1982 are studied using observation data and reanalysis data.
The cloud zone elongated from east side of the Tibetan Plateau to the Northwestern Pacific. It was sustained along the southern side of the subtropical jet stream and northern periphery of the Pacific subtropical anticyclone. The cloud zone coincides with the rain zone. The cloud zone was located in a weak baroclinic zone in ~35ßN zone. The cloud zone in 110-130ßE is characterized by large precipitation, strong meridional gradient of specific humidity and moist-unstable stratification, while the cloud zone over the Northwestern Pacific is characterized by stable stratification. The baroclinicity in 35-55ßN (north to the cloud zone) is weak over China and strong over the Northwestern Pacific. Japan is the transitional area between these regions. Meso-a-scale variations of the cloud-precipitation are large over Japan.
The 500hPa lows, troughs and surface depressions in northern zone (40-65ßN) have influence on Baiufrontal depressions. Many cloud-precipitation systems in the Baiu frontal zone are associated with the depressions.
The large-scale features found in this period are compared with these in previous reports. Although, large-scale features in this period are commonly found in other periods, some differences of large-scale features are seen among the periods. This report also shows that features of meso-scale systems varied depending on circumstances in periods and/or cases.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 67, No. 6, pp. 331-342, 2020
Synoptic- and meso-a-scale variations of Baiu frontal cloud-precipitation systems over Japan in July 1982 are studied using observation data to clarify the relationship between meso scale phenomena and synoptic fields.
The temperature variation at the 500hPa surface was large in middle latitude (to the north of the Baiu frontal zone). During the period of low temperature in mid-July, predominant upper troughs passed over Japan. Baiu frontal depressions, and cloud-precipitation systems also developed. Significant variations of cloud/precipitation systems with ~2 day period appeared in 5-20 July. In 23-24 July, after the cold period, record-breaking precipitation occurred in Kyushu.
The south-north gradient of the moist static energy, vertical stability in the frontal zone varied in association with passage of the major upper troughs. The Baiu frontal depressions, cloud systems in the frontal zone varied in association with these variations of the frontal zone.
Major troughs in the lower troposphere were accompanied with the major upper troughs. However, minor trough in the lower troposphere seen in 17 July was not associated with upper trough. Most of Baiu frontal depressions and cloud-precipitation systems developed under the influence of the troughs in the lower troposphere. However, the depression with intense precipitation in 23-24 July was not associated with significant trough. Features of the cloud-precipitation systems varied from case to case. In some cases, they formed "cloud system family in the Baiu frontal zone".
The synoptic-scale features found during July 1982 are compared with those in previous reports. Although, synoptic-scale features in this period are commonly found in other periods, some differences of features are seen among the periods. This report also shows that features of cloud-precipitation systems varied significantly depending on synoptic fields.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 67, No. 10, pp. 595-607, 2020
The climatological characteristics of the heavy rainfall event due to Typhoon Hagibis (1919), which caused landslides and floods in many places of eastern Japan in October 2019, was examined using daily precipitation data from the former JMA's Kunai (local) rainfall observations that were as dense as the current AMeDAS observation system. It was found that the rainfall distribution due to Hagibis was characterized by a heavy rain area over the Kanto Mountains extending northward to the eastern part of the Tohoku District, in a similar way to that of the Tropical Cyclone Kathleen case which caused severe floods in the Kanto Plain in 1947. An extreme value analysis for the two-day precipitation records indicated that area-averaged precipitation amounts in regions of heavy rainfalls due to both Hagibis and Kathleen had a return period of the order of a hundred years.