(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 70, No. 1, pp. 5-11, 2023
An automatic hydrometer classification system was constructed, and the result was opened on the Web site. The classification system used optical disdrometer observations of the size-fall speed distribution of precipitation particles and collocated temperature observations. The observed size-fall speed distributions were converted into a pair of representative size and fall speed and used for classification into several kinds of solid precipitation, sleet, and rain, using a diagram and temperature thresholds.
The classification system showed that the solid hydrometeor classes of six observation sites were different according to geographical location and altitude during heavy snowfall in the Niigata Prefecture on January 8, 2021. The classification method of wet particles will be improved in future studies.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 70, No. 2, pp. 65-76, 2023
In this study, statistical analyses were conducted in order to clarify the relationship between outbreaks of cold airmass and heavy snowfall on the Japan-Sea side in winter seasons from December 1981 to March 2020. Data used were daily snowfall amounts, JRA-55 reanalysis data, and sea surface temperature (SST). Outbreaks of cold airmass were quantified as cold airmass, horizontal cold airmass flux (FLCA), and mean wind of cold airmass (VEL). The cold airmass is given by the pressure difference (DP) between the ground surface and the isentropic surface with a threshold potential temperature of 280K, and FLCA is calculated by vertically integrating horizontal wind vectors between those two surfaces. VEL is obtained by dividing FLCA by DP. The largest DP appeared around Japan from January to February, and outbreaks of cold airmass from Vladivostok were remarkable in distributions of FLCA and VEL from December to February. Statistical analyses were conducted for four points in plain regions (Akita, Nigata, Fukui, and Matsue) and four points in mountainous regions (Kakunodate, Tokamachi, Ono, and Akana). As a result, it was found that DP=300hPa was one of criteria for the occurrence of heavy snowfall. VEL in heavy snowfall events was larger in mountainous regions than in plains, indicating the characteristic difference between mountain-snowfall and plain-snowfall types. A weak to medium negative correlation between SST and DP was found in the top 75 daily snowfall amounts for all the eight points. DP and FLCA for each meteorological disturbance or pressure pattern that brought about heavy snowfall events were investigated for the top 25 daily snowfall amounts for each point. DP was relatively low for heavy snowfall events caused by a low-level convergence and a front or low-level trough. In contrast, DP was high for heavy snowfall events caused by a meso-scale disturbance, and both DP and FLCA were high for those by longitudinal-mode clouds.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 70, No. 6, pp. 251-255, 2023
The large-scale features during the Kyusyu intense rainfalls in 22-24 July 1982 were studied based on trajectory analysis. In 22-23 July, the trajectories at 850hPa surface arriving in eastern Japan from the Japan Sea area maintained the dry area to the east of the intense rainfall area. In the peak period of the intense rainfalls around 12 UTC 23 July, the trajectories from the South China Sea and the southern part of China to the intense rainfall area sustained the low-level moist currents.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 70, No. 9, pp. 419-423, 2023
The seasonal change of airmass movement toward the Japan Islands in July 1982 (Baiu period) is studied based on the backward trajectory analysis. The seasonal change of trajectory is significant on 850hPa surface. In the early period of July, trajectories from cool Pacific area arrived north and eastern parts of Japan. In the later period of July, trajectories from South China Sea and southern part of China arrived many areas of Japan. The seasonal change of trajectory is also seen on 500hPa surface. In the early period of July, trajectories from the subpolar areas arrived over major part of Japan. In the later period of July, the trajectories from the Asian monsoon region and the subtropical Pacific arrived over the major parts of Japan.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 70, No. 10, pp. 487-500, 2023
The risk of frost damage to three deciduous fruit trees (peach "AKATSUKI", Japanese pear "KOUSUI", and apple "FUJI") was predicted and the accuracy was verified using observation data. Since the risk of frost damage to trees varies depending on their developmental stages, we first predicted the dates of budding, leaf development, and flowering of the trees using several growth prediction models. Then, we conducted the prediction of frost damage risk for the period when the large-scale frost damage was occurred in the Fukushima Basin in April 2021. The predicted risk was consistent with the observed damage data in several locations in the basin. It was found that the high frost hazard areas were distributed in the lowland areas along the river outside of the urban area. Possible reasons for the distribution of the damaged areas include the effect of higher nighttime temperatures due to the heat island (lower risk) and the effect of cold air lakes corresponding to the small topography within the basin (higher risk).
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 70, No. 12, pp. 569-575, 2023
Present status of university classes that incorporate surface meteorological observations into their curricula are explained. Based on the observational contents practicing at the College of Geosciences, University of Tsukuba, transitions of instruments since the 1980s, composition of classes to integrate real-time weather variations as teaching materials, and lessons from the online classes during the COVID-19 pandemic are introduced.