(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 48, No. 3, pp. 151-158, 2001
Automobile traverses were used to gather 111 times water vapor
pressure distributions in Obuse, Nagano, in which rural there
are paddy fields and orchards from September 1996 to October 1997.
The water vapor pressure in urban is lower than that in rural
at day and night. The urban / rural water vapor pressure difference
is the maximum at daytime in summer. The difference of water vapor
pressure between urban and paddy field is roughly twice as large
as that between urban and orchard. The effect of selection of
rural sites in water vapor pressure difference can't be seen at
night. There is low water vapor pressure island over urban area,
similar to heat island, with steep water vapor pressure gradients
between paddy field and urban, which can be seen in 11 cases among
21 summer daytime cases. Winds have emerged as an important parameter
in controlling the urban/rural water vapor pressure difference.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 48, No. 4, pp. 219-226, 2001
An analysis was made on changes in observed wind speed at JMA observatories due to installation of the JMA-80 type equipment in the 1980's. It was found that daily mean wind speed increased by 8.7% and nighttime wind speed increased by 13-14% on the average over the 110 stations. The rate of increase is larger for lower wind speed, so that it exceeded 30% for daily mean wind speed and 50-70% for nighttime wind speed at some inland stations where nighttime wind is very weak. It is also shown that the percentage of calm condition, defined by wind speed of 0.2m/s or less, decreased to a quarter of the value before the installation of the JMA-80 type equipment.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 48, No. 4, pp.231-237 , 2001
Accuracy of estimated monthly temperature and precipitation
amount using diaries is examined. Using two sets of personal diaries,"Takahashi-ke
Nikki"and "Kobayashi-ke Nikki",number of rainy
days for a month is counted by descriptions about rainfall and
snowfall. This number of rainy days is highly correlated to official
observation made near by Nagano local meteorologicaI observatory
in Apr., Jul., Sep., and Oct.Relations among number of rainy days
and mean temperature,Precipitation amount are examined using official
data.Estimations are not so good for some months in year,but quaIitative
evaluation,extremely above or below normal, is applicable.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 48, No. 5, pp.305-311 , 2001
This paper presents the discussion about causes of the heat
island. The data employed in this study were air temperature distributions
in and around Obuse town (Sakakibara, 1999), the mountain-top
temperatures, and the wind speeds at the nearest observatory.
Two methods were used in order to compare the effect of heating
from urban surface with that of mechanical mixing of urban atmosphere
to heat island: One is to compare the correlation coefficient
of meteorological parameters such as the gradient of the vertical
potential temperature over the surrounding rural area alpha and
the square root of alpha divided by wind speed. The other is to
compare the changing patterns of heat island intensity as wind
speed increases. The results suggest that the mechanical mixing
of urban atmosphere contributes to nighttime heat island more
than the heating from surface in the small and middle cities.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 48, No. 6, pp.383-391 , 2001
Statistical approaches were applied to the heat island phenomena
occurring in urban and suburban Tokyo areas in order to clarify
how the temperatures change according to time and locations. Analyses
were focused on temperature changing patterns within a day. Temperature
data that were measured every hour at 100 locations in mid-summer
were used. Principal component analysis was applied to the data
and three principal components were obtained. Close examination
on the components revealed their meanings as daily average temperature,
daily temperature range, and speed in temperature changes. 100
measuring locations were grouped into 7 groups each of which had
own characteristics. Also, the validity of the analyses was checked
using AMeDAS data of the same period.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 48, No. 8, pp.547-559 , 2001
In order to investigate the possibilities for snow pack augmentation
by cloud seeding, the cooperative, orographic snow cloud project
has been carried out by Meteorological Research Institute, Japan
Meteorological Agency and Tone River Dams Integrated Control Office,
Ministry of Construction in three winters since 1994.
Appearance frequency of snow clouds with high seedability, that
is, high possibilities that the cloud seeding would cause an enhancement
of total snowfall amount (snow clouds of type 1) or a shift of
snowfall area downwind (snow clouds of type 2), is examined over
the Echigo Mountains during the winter season from Nov. 1994 through
Mar. 1995. Monthly means of surface temperatures were about 1degree
higher than usual so that we could call the winter a mild one.
Snow cloud of type 1 (2) are defined as having top temperatures
between -5 degree and -15 degree (-15 degree and -25 degree),
top height more than 2.5 km, cloud amount greater than 9/10, and
one-hour averaged liquid water path more than 0.2mm. Cloud top
temperatures, heights and cloud amounts are calculated by a new
algorithm, which is developed to detect relatively shallow clouds
over the mountain areas, with GMS-4 infrared window channel data,
surface temperature data from Automated Meteorological Data Acquisition
System (AMeDAS) and aerological data. Liquid water path (vertically
integrated cloud water contents) was measured with ground-based
microwave radiometers.
The results indicated that snow clouds of type 1 appeared in early
and late winter (Nov., Dec. and Mar.) while those of type 1 appeared
in mid winter (Dec., Jan. and Feb.). The appearance frequency
of the both types of snow clouds were high over the windward slope
of the mountains and the sum of appearance frequency of the both
types reached 15 - 20 % of the time during the winter season.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 48, No. 9, pp.661-671 , 2001
This paper aims at obtaining predictive indices of human thermal
sensation for the outdoor environment. Two indices are newly suggested:
one is named temperature load TL that is derived from the skin
and core temperatures estimated from two-nodes model of Gagge
et al (1971), and the other one is temperature sensation index
or TSI, which is a regressional function of wind
velocity and operative temperature. The applicability of suggested
indices, i.e. TL and TSI were tested along with other existing
indices such as SET*, the temperature humidity index THI and the
wind chill index WCI. The dataset on temperature sensation collected
for several cities in Japan were used to see the correlation with
thermal indices. For the summer condition, TL and TSI have
better correspondence with answered thermal sensation. It was
also shown that TSI can be practical measure to estimate temperature
sensation for winter as well. Finally, the sensitivity of air
temperature, humidity and wind velocity to thermal sensation was
investigated using TL-based temperature sensation.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 48, No. 9, pp.673-687 , 2001
A carrot-shaped cloud system developed to the south of Kyushu
Island was studied using TRMM
(Tropical Rainfall Measuring Mission) multi-sensor observations
by PR (Precipitation Radar), VIRS (Visible and Infrared Scanner)
, TMI (TRMM Microwave Imager), and LIS (Lightning Imaging Sensor).
We also utilized GMS (Geostationary Meteorological Satellite)
frequent IR observations and otherˇˇmeteorological data. Structure
of the cloud system is quite different between the tip portion
sharpened in the west and the eastern portion where the upper-level
cloud canopy extended continuously. In the tip portion, banded
cloud streaks extend almost perpendicular to the axis of the carrot-shaped
cloud system. Each cloud streak is an anvil extended from a deep
convective cell located at the northern end of the streak. The
anvils elongated along relative upper-level wind to
the cell motion. Since the extension of anvils is smaller for
the newer cells existed near the western tip, tapering shape of
the cloud system is maintained. In the eastern part of the cloud
system, a strong precipitation line composed of deep convective
cells appeared and upper-level anvil clouds widely spread to the
both sides of the line. In the southern side of the line, the
anvil clouds contain much precipitation-size ice particles, and
surface rain is scare due to evaporation of particles under the
cloud base, except several sporadic convective rainfalls. In the
northern side, fairly strong stratiform rain is found over a wide
area below the mid troposphere.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 48, No. 12, pp.885-892 , 2001
Two types of network structure and two types of output-layer
transfer function were tested for neural-network precipitation
amount forecasts. The neural network of 3-layer hybrid structure
(which has links combining input layer and output layer directly)
with sigmoid function as output-layer transfer function showed
the best skill score among four types of neural networks (including
a traditional 4-layer feed-forward network) and a linear multiple
regression model.
The result suggests that the neural network which is most skillful
for a specified problem cannot be given automatically but the
network structure or output-layer transfer function must be chosen
properly.