(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 46, No. 3, pp. 205-218, 1999
Distributions of precipitation over the Kyoto Prefecture during
the winter monsoon of 1988-1994 are statistically analyzed.
A principal component analysis is applied to the radar echo data.
Echo patterns over the region are classified into three types;
coastal, normal, and inland type.
We examine the synoptic situations of the coastal and inland type.
Wind directions, depths of convective mixed layer, and positions
of troughs and upper cold air mass differ between the coastal
and inland type.
Growth rates of radar echoes are also calculated by using displacement
of echoes. Multiple regression analysis reveals that the correlation
between the growth rates and orographic elements is low in the
coastal type, while it is high in the inland type. It is concluded
that the orographic lifting intensify the precipitation cloud
of the inland type.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
The down-slope wind during the night (nocturnal drainage wind,
NDW) was investigated based on the observations made on the south
foot of Mt.Kujyu, Naoiri, Oita, Japan in September, 1997.
After sunset, the speed of the NDW increased with time as the
ground temperature inversion developed, while the thickness of
the NDW was kept constant all night, which was about 25 m.
The wind speed varied approximately as the square root of the
vertical gradient of potential temperature in the NDW. This suggests
that NDWs observed on the present hillslope were the equilibrium
flow; that is, gravity which drives the NDW was balanced by the
frictional forces exerted on its top and bottom
surfaces.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
Diurnal variations of ascent curves, and development
of heat thunderstorm are investigated at Somagahara in a foot
of Mount Haruna in Gunma prefecture with Omega rawinsonde in
two days, Aug. 4 and 9, 1997. The results show that the mixing
depth increased and the level of free convection(LFC) lowered
in the day with the thunderstorm on 4 August. The convective
inhibition(CIN) took the minimum values and it showed good condition
for a convection to take place when the thunderstorms were
observed. Moreover, no considerable stable layer which was expected
to hinder development of a high convective cloud was observed
over the LFC.
On 9 August, the day without heat thunderstorms, the mixing
depth increased also. But there was no LFC owing to warm air
over the notable stable layer in the middle atmosphere. Therefore,
convection clouds did not developed to thunderstorms though some
convective clouds were observed.
Showalter stability index reduced till the evening in the
two days regardless thunderstorm development.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
In Japan, the phrase "sea breeze" is often used as a generic term of onshore wind in the daytime. The "sea breeze" in this usage can be driven by various mechanisms in addition to land-sea thermal contrast, and is often accompanied by warm advection at its onset. In order to find the climatological features of such apparent "sea breezes", a statistical analysis was made on the temperature distribution at the onset of daytime onshore wind in the Kanto and the Tokachi-Konsen regions by using data from the AMeDAS network for 18 years (1979-96). It is shown that more than ten percent of daytime onshore winds are of the warm-advection type. They tend to occur under relatively weak sunshine in cloudy weather or just after sunrise, with synoptic pressure increasing seaward.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
Automobile traverses were used 153 times to gather air temperature data in Obuse, Nagano, which is surrounded by a large number of paddy fields and orchards in order to make clear the feature of urban heat island. Using the horizontal pattern of air temperature and the monthly average and the monthly maximum of heat island intensity, the roles of rural land coverage such as paddy fields, orchards and mixed-use lands in the appearance of heat islands were investigated. In the nighttime, paddy fields had the lowest air temperature area in the snowy season, but orchards had the lowest air temperature from May to July and from October to December. The effect which snow coverage on rural and urban areas and irrigation of paddy fields have on seasonal variation of heat island intensities was not seen. The daytime heat island intensities are almost similar to those in the nighttime in summer. The maximum heat island intensity of 5.4 ℃ in settlements whose population is at least twelve thousand, was significantly larger than that of the same-sized cities in Japan shown by Fukuoka (1983) and Park (1987), and nearly equal to that of North American settlements pointed out by Oke (1973).
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
Observation of daily minimum and maximum temperature at meteorological stations in Japan is currently made for the 24 hours between 0000 and 2400 JST (Japan Standard Time), whereas it was made for 2200-2200 JST at many stations until 1939, and for 0900-0900 JST as to minimum temperature from 1953 to 1963. In order to evaluate the bias arising from different observation times, hourly data at 830 AMeDAS stations for 1979-1997 were analyzed. The results are summarized as follows: (1) The 0900-0900 minimum temperature tends to deviate positively from the 0000-2400 value. The bias is 0.41℃ on the annual average over the whole country. (2) The 2200-2200 minimum temperature, which has been believed to be unbiased so far, has also some positive bias. The annual average bias over the whole country is 0.17℃. (3) The bias has considerable seasonal and spatial differences according to the diurnal and synoptic temperature variations. At some stations and in some seasons, the bias can exceed twice of the average values mentioned above. (4) The bias of 0900-0900 and 2200-2200 maximum temperatures are generally small. It is also shown that the 2200-2200 bias can be more serious than the 0900-0900 bias in evaluating the rising rate of minimum temperature during the last hundred years, with a maximum possible error of 0.4℃/(100 years).