(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 53, No. 3, pp. 185-196, 2006
The objective of this study is to clarify the long-term changes in snowfall depth and snowcover depth and the dependences of snowfall depth and snowcover depth on temperature and precipitation in Niigata, Yamagata, and Fukushima prefecture, and these were analyzed by using data observed at 14 railway stations from 1927 to 2005.
Annual snowfall depth, annual maximum snowcover depth, and annual maximum daily snowfall depth have a decreasing trend from 1927 to 2005. These also have decadal cyclic variations, and there were high before the middle 1940's, low from the late 1940's to the 1950's, high from the 1960's to the middle 1980's, and low after the late 1980's.
Annual snowfall depth and annual maximum snowcover depth show negative correlation with the winter (from December to February) mean temperature at all stations. Furthermore, in case of the winter mean temperature rising, the higher the winter mean temperature of the site, the larger the decreasing rates of annual snowfall depth and annual maximum snowcover depth become. Annual snowfall depth and annual maximum snowcover depth show positive correlation with the winter precipitation at most of the stations. Furthermore, in case of the winter precipitation increasing, the lower the winter mean temperature of the site, the larger the increase of annual snowfall depth and annual maximum snowcover depth become.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 53, No. 5, pp. 393-404, 2006
The cool island intensity (CII) on urban green space was investigated in Shinjyuku-Gyoen, that is one of the largest parks in Tokyo. A through-year measurement of ground level air temperature revealed seasonal variation and relationship to the atmospheric condition of CII. The temperature variation in the park and the reference downtown Tokyo was as same order as CII. The daytime CII is larger in summer than that in winter due to the leaf fall of the park trees. On the other hand, seasonal variation of nighttime CII is not so clear. The nighttime CII was large under the stable atmosphere or the strong nocturnal cooling.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 53, No. 6, pp. 479-484, 2006
Modifications of precipitation systems by the metropolitan area in and around Tokyo (MAT) are investigated using radar data for twelve years period. Lag composite analysis of precipitation frequency is carried out for 71 summer days when strong precipitation echo was detected over mountainous area of Okuchichibu without synoptic scale disturbances near Kanto area. Most of precipitation systems generated in the mountainous area move eastward and arrive at the MAT in 2.5 to 3.5 hours after the initiation. Precipitation frequency in the MAT is remarkably high compared with that in surrounding areas. The results indicate that the MAT affects the intensification of the precipitation systems.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 53, No. 7, pp. 551-563, 2006
Supposing that the cause of the trees damage discovered in the Sarukura peak of the Hakkouda mountain system of Aomori Prefecture on April 23, 2000 is due to the high wind generated on the same day, it is considered from a meteorological point of view. The cyclone accompanied by the cold front approached most the Aomori district on the morning of the same day, and it passed northeastward after that. Two foehn related to generating of the high wind were ascertained from the weather data of the Aomori Local Meteorological Observatory (Aomori city) located in about 24 km north-northwest from the Sarukura peak. That is, the first foehn on the morning was wet for the southwest wind to have blown in the rainfall of the northern part of Akita Prefecture and it is thought that the airflow which tends to converge into the east slope of Sarukura peak having the geographical feature, which situated on the exit of the saddle part of the adjoining mountains at the prevailing time of the southwest wind, was intensified locally. On the other hand, the dry air of the upper layer with few amounts of water vapor descended and spread behind the cold front, therefore the west wind accelerated, and the second foehn of an afternoon became the high wind over mountains. This wind direction was in agreement with the direction of east from the west where trees dispersed. From this analytical results, it can be concluded that high wind generated by foehn is main cause of the trees damage of Sarukura peak, and both the airflow influenced by geographical feature on the morning and the cross-barrier airflow over the mountain range on the afternoon act continuously so that the tree damage was occurred.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 53, No. 8, pp. 621-627, 2006
To clarify the early process of snowflake growth, characteristics of the aggregation of combination of bullets type snow crystals observed in the Arctic region were investigated by examining microphotographs of snowflakes composed of two to five crystals. The combined state of two crystals indicated that the smaller of the aggregated crystals is attached mainly in the region between the center and the periphery of the larger crystals.
An aspect ratio of snowflakes approached gradually to 0.5~0.6, when the size of snowflakes and the number of component of crystals increased. Like the case of dendritic type snow crystals, for a given number of component crystals, the larger the average size of the crystals, the larger the size of the snowflakes were. The size of snowflakes can be expressed as a power of the number of crystals with the average size of crystals as one of parameters.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 53, No. 10, pp. 773-784, 2006
Characteristics of strong northwesterly winds in the Tokachi Plain, Tokachi winds, are investigated by analyzing hourly meteorological observations at AMeDAS stations and upper air observations at Sapporo for the years 1992-2001. It is shown that the Tokachi winds are most frequently observed during the early winter(November-December)and the early spring(March and April)when strong northwesterly winds blow above Sapporo under synoptic meteorological conditions of a strong low pressure to the east of Hokkaido. At the same time, strong upper air winds blow over Sapporo being associated with a convective surface layer even in the early morning.
The Tokachi winds are found to show a clear diurnal variation with strong wind speeds in the early afternoon and weak speeds in the mid-night. In general, the northwesterly winds begin to blow from the Karikachi Pass to the Pacific in the early morning, and then the wind speed increases with time as they spread over the Tokachi Plain. On the other hand, higher wind speeds in the Tokachi Plain are accompanied with longer sunshine durations, implying that the air is unstable to cause vertical convection. Consequently, we may conclude that the Tokachi winds are caused by the transport of strong upper winds to the surface layer through the thermal convection over the Tokachi Plain during the daytime.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 53, No. 10, pp. 785-790, 2006
Climatological features of the dry period which occurs from late May to early June over the region from Kyushu to Honshu are described using daily data for 44 years(1961-2004). The dry period is centered around 24 May along the southern coast from Kyushu to Kinki and 1 June in the Tohoku district. The period is characterized by smaller precipitation amount and less precipitation days, as well as lower frequency of heavy precipitation(>=50 mm/day and>=100 mm/day)than preceding and following periods, while thunderstorms and hails in the eastern Honshu occur with a higher frequency. The analysis of equivalent potential temperature at the 850 hPa level confirms that the dry period corresponds to a short period of reduced meridional baroclinicity around Honshu.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 53, No. 11, pp. 857-861, 2006
The improvement of quantitative precipitation forecasts (QPF) is expected to contribute to the disaster mitigation. However, the economic and social impacts of warm-season QPF have not been quantified. The purpose of this study is to estimate for social impacts of available QPF using the warning lead time as the measure.
Such warnings as helpful to the decision making of evacuation counsel for disaster are focused in this study. The contribution of QPF to the warning lead time is estimated as 0.8~2.8 hours.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 53, No. 11, pp. 863-869, 2006
Heavy snowfall in the winter of 2005/2006 resulted in many disasters and accidents in Japan. The characteristics of the heavy snow were analyzed using the normalized maximum snow depth considering the year-by-year variation. The normalized maximum snow depth was large in some specific areas. It had a tendency to be larger in inland areas than in the coastal areas in and to the south of Yamagata and Miyagi Prefectures. Many snow and ice damages occurred in areas where significantly large values of normalized maximum snow depth were analyzed. The anomaly of the snow depth tended to be large in areas where 23-year mean of the maximum snow depth was large. On the other hand, a significant negative anomaly was analyzed in other areas. The uneven distribution of the normalized snow depth was also a characteristic of the 2005/2006 winter season.