沙漠研究 19-1, 299- 303 (2009 )Journal of Arid Land Studies“Desert Technology IX ”
Refereed Paper

Changes of Local Meteorological Environment in particular Air Temperature
at Isahaya Bay Reclamation Area as a Naked Saline Flat Land
Taichi MAKI1, Kazuki URAYAMA2, Shinichiro YAMASHITA3, Kenji WAKIMIZU2, Hisashi YOSHIKOSHI2
Abstract: Isahaya Bay reclamation area (816 ha) was a flat saline naked land like a newdesertificated land. Land reclamation was carried out in Isahaya Bay for two reasons, toincrease the amount of flat land and to decrease meteorological disasters. Within several
years after salt is eliminated, the reclaimed land will become excellent arable land, and will
be available for many uses. It is necessary to perform continued meteorological research on
this land, which is intended for agricultural usage after reclamation is complete. The watertemperature of the artificial pond increased by the heat of solar radiation during the daytime
in summer, and the effect of increased air temperature at Yue and Azuma was obtained
when the wind was blowing toward them from the pond.
Keywords: Air temperature, Bank, Isahaya Bay, Meteorological environment, Reclamation

1. Introduction
Isahaya Bay reclamation area was a flat, saline and naked land for these 5 to 10 years. It was like a
new desertificated land. So it is necessary to observe and evaluate variations of wind and air temperature
for predicting and simulating the new climatic characteristics. The plan for the reclamation of Isahaya Bay
was initiated by the Kyushu Agricultural Administration Agency, Ministry of Agriculture, Forestry andFisheries (MAFF) in 1989. The meteorological observation of wind speed, wind direction, air temperatureand precipitation began on Jan. 1, 1989. The construction of reclaimed land in Isahaya Bay was started inNov. 1992. The reclamation area of Isahaya Bay included an artificial regulation or control pond that wascompletely and instantaneously separated from Isahaya Bay in the Ariake Sea on a day in Apr. 1997, andwork on this part of the project was finished in Mar. 1999. The reclamation project was continued and thereclamation was completed in 2007. The observation results of wind speed and wind direction around
Isahaya Bay were presented in arecent paper (Maki, 2007; Maki et al.,Kyogatake Mt.
Taradake Mt.
2008). The wind speed on thegroundsurfacewasslightly
decreased by resistance from theAriake Sea
Isahaya Bay front bank, and wind
Front bankdirection on the ground surface
YueOeareachanged to clockwise by about 20
P3
Artificial control pond
degrees in the prevailing wind
IsahayaBay
Central area
P1
direction.
Nishisato

2. Observational and Analytical
Methods of Meteorological Data
Figure 1 shows the satellite
image of the topography andmeteorological observation of 4
pointsaroundtheIsahaya
reclamation area.
Around theIsahaya reclamation area, Azuma
and Yue are located at the foot ofUnzen (1359 m), and the foot of both
1W

P2

W:
Observation
pointforwindbreaknetOnojima

Azuma

Unzendake Mt.
Tachibana BayFig. 1. Topography of the Ariake Sea, Isahaya Bay and thereclamation area in Nagasaki.

Faculty of Agriculture, University of the Ryukyus, Nishihara, Okinawa, 903-0213 Japan (Present Address: ARENA,
University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8572, Japan, E-mail: maki.taichi.fe@u.tsukuba.ac.jp)
2
Faculty of Agriculture Kyushu University, Hakozaki, Higashi, Fukuoka, 812-8581 Japan3
Formerly Faculty of Agriculture, Kyushu University, Hakozaki, Higashi, Fukuoka, 812-8581 Japan

300
ΔT（地点Ⅰー地点Ⅲ）（P1 － P3）

12.0

12Before
干拓前
After
干拓後

（℃） 6.05
Difference of water temperature (℃)

44

4
4.0
2.033

(℃) 22

clear days in winter before and after thereclamation at Yue.

00
-1-1-2-21989

1997

2 00 4 年

Fig. 2. Variations in air temperature on fine or11
1 99 7 年

24時 day
Time of1 98 9 年時時時

212123時

1819時

1517時

15時

1213

911

67時

35時

3時

1

9時

00.0
1時

ΔT（地点Ⅱー地点Ⅲ）（P2 – P3)

6Reclamation

8.08

水 温 差 (℃ )

気温(℃)

10.0
Air temperature(℃)

2004

Fig. 3. Variations in differences of watertemperatures inside and outside theartificial pond.
Tara (983 m) and Kyoga (1076 m), respectively, andface Isahaya Bay. Onojima and Nishisato are locatedin an inland area.
The meteorological data were obtained by the Kyushu Agricultural Administration Agency, MAFF
from 1989 to 2007. Shimabara, Ohmuta, Taimei and Misumi AMeDAS data as representative data of thearea around the Ariake Sea were used for the analyses and were compared to the air temperature at Azuma,
Onojima and Yue. Nishisato data were not used because of the urban effect caused by buildings and roads.
The analytical data were collected from Jan. 1, 1989 to Dec. 31, 2005.
The data from 1990 to 1996 and the data from 1999 to 2005 are the data in the period before and after
the construction of the front main bank, for Figures 2 to 5, respectively. The hourly meteorological data
are wind speed, wind direction, air temperature and precipitation. Annual averaged temperatures of thedaily maximum, mean and minimum air temperatures, and the differences of 3 averaged temperatures wereanalyzed.

3. Observation Results and Their Considerations
3.1. Diurnal variation in air temperature on fine or clear winter days at Yue
Figure 2 shows the variations in air temperature (3000 data) on fine or clear days in winter before andafter the reclamation in 6 years at Yue. Yue is selected as the place that properly effected by northernwinds at night and by southern winds at daytime in winter. The air temperature after the reclamation waslower than that before the reclamation showing in Figure 3. The temperature difference is especially large
from late afternoon to early morning and is slight during the daytime. The difference is a maximum ofabout 1 ˚C. The extension of reclamation most likely affected the temperature at Yue during the winternights because of strong radiation cooling on the naked reclamation land. The low-temperature northernwind blows during the cold winter half year and the land breeze or mountain wind comes from Tara atnight.
On the other hand, the air temperature increased after the reclamation particularly in winter at Azuma
during the period of northern wind. The northeast wind curved by Tara is a sea breeze that blows fairly
frequently compared to the mountain wind from Unzen (Maki et al., 2008). However, it seemed at Azuma
that the effect by reclamation just after the period from 1997 to 2001 was large, but after 2002 the effectwas small. As Onojima is located in a flat area and far from mountains and the pond, it is little affected bymountain winds or sea breezes. And it was not affected greatly by reclamation; the cooling in winter was
not large in this case.
At Yue during the daytime in summer, the water temperature increased because the pond wasenclosed by the front bank, because the air temperature increased in response to the sunshine, and because
high humidity was brought by a sea breeze into the inland area. But at Onojima, a high-temperature, highhumidity air mass does not enter such an inland area and the effect is not found. These phenomena clearlyaffected on air temperature.

0.8
0.6
0.4
0.2
0‑0.2‑0.4
Wind from pondYueOnojima

AzumaWind from land

Yue

Onojima

Azuma

Fig. 4. Variations in difference of daily maximum airtemperature before and after reclamation.

Difference of daily min. air temp. (℃)

Difference of daily max. air temp. (℃)

301

0.8
0.6
0.4
0.2
0
‑0.2
‑0.4
‑0.6
Wind higher 4m/s

Yue

OnojimaAzuma

Wind lower 3m/s

Yue

Onojima

Azuma

Fig. 5. Variation in daily minimum air temperatures at3points on fine or clear days in winter before andafter the reclamation under 3 m/s and over 4 m/s.

3.2. Variation in water temperatures inside and outside of the artificial pond
Figure 3 shows the seasonal variations in differences of water temperatures inside (P1, P2) andoutside (P3) the artificial pond. The temperature difference has increased over 2 ˚C since 1997. Before
shutting of the gate of front bank, the temperature difference between outside and inside was not large andalso the scale of yearly variation was small, but it became large after 1997. The average maximum watertemperature and variation difference are very large, 3 to 4 ˚C. Because the outside sea water does not enter
the artificial pond and the depth and volume of the pond are smaller than the outside sea, the watertemperature is easily increased by sunshine. For period of about one year, in 2003, the difference of watertemperature decreased to 1 to 2 ˚C and returned close to the temperature before the reclamation. Thisoccurred because at the time there was a short-term opening of the front bank for the purposes of
exchanging from fresh water to sea water and investigating the current water, salinity concentration,
ecology and so on. It is interesting that the exchange of water affected the water and air temperatures.
3.3. Variation in daily maximum air temperature in summer when the wind blows from the pond
From June to August, the wind from the artificial pond is from the WNW to NNW at Azuma, N to E
at Onojima and SSE to SW at Yue. The wind from the inland is from the SW to SE at Azuma, WNW toSE at Onojima and NW to NNE at Yue. It was obtained that wind speed on the ground surface decreased alittle because of resistance of the front bank of Isahaya Bay, and wind direction of the prevailing winddirection on the ground surface also changed to clockwise about 20 degrees (Maki, 2007; Maki et al.,2008).
The variations in difference of daily maximum air temperature (3000 data) before and after
reclamation at 3 points are shown in Figure 4. When the wind came from the direction of the pond at
Azuma and Yue during the daytime in summer, the difference of maximum air temperature significantlyincreased, because the surface water temperature of the small artificial pond with its small amount of water
was raised more by the sunshine than was the water temperature of the Ariake Sea. There seems to be
more wind from the pond at Azuma and Yue because of the higher water temperature. This creates an areaof low pressure, that is, the air is sucked from the outside. However the maximum air temperature at
Onojima did not increase, because Onojima is located inland and far from the pond and is not affected withregard to the maximum air temperature.
At Azuma and Onojima, the maximum air temperature increased when there was wind from inland.
However at Yue, it is interesting that the maximum air temperature decreased significantly, and the wind isfrom the NW to NNE. It is probably a downwind from Tara, which is a woodland as air high humidity andlow temperature.

302

Variation in daily minimum air
0.5
temperature of weak wind on fine or clear(1)
0.4
winter days after the reclamation
0.3
The analytical conditions in winter from0.2
December to February are as follows: Before
0.1
reclamation is 1991 to 1996, while after is 1999
0to 2004. The selected data are the days of weak
‑0.1
wind, fine or clear, no clouds and dry air‑0.2
condition, that is, daily mean wind speed is under‑0.3
3 m/s, sunshine duration is over 7 h per day and‑0.4
daily precipitation is 0 mm.
1990‑1994
1999‑2001
2003‑2005
The variation in daily minimum air
YearYue Onojima Azuma Yue Onojima Azuma Yue Onojima Azuma
temperature (1000 data) at 3 points on fine orclear days in winter before and after the0reclamation at the period of weak wind under 3‑0.2
m/s and over 4 m/s is shown in Figure 5. The‑0.4
variation in air temperature coincides withdifferences in wind speed. At Yue and Onojima,‑0.6
the air temperature decreased on a weak wind day‑0.8
based on radiation cooling, but at Azuma the air‑1temperature increased a little. The reason is‑1.2
mainly that the wind at Azuma in winter is a
‑1.4
prevailing northern wind, that is, the sea breeze‑1.6
comes from the sea or the artificial pond, and the(2)‑1.8
air temperature of the sea breeze in winter is
1990‑1994
1999‑2001
2003‑2005
rather higher than that of the land breeze. It isYear
Yue Onojima Azuma Yue Onojima Azuma Yue Onojima Azuma
interesting that the difference is found that thetopography of north and south places at Azuma
0and Yue around Isahaya Bay.
‑0.1
A decrease in air temperature was found on‑0.2
weak wind days, but when wind speed was high,‑0.3
the phenomenon was destroyed and airtemperature increased. The reason seemed to be‑0.4
radiation cooling resulting from the area being‑0.5
surrounded by a bank. On a strong wind day‑0.6
over 4 m/s, the general wind mainly affects the‑0.7
air temperature, i.e., the high and low air pressure(3)
mainly affect the air temperature, but in keeping‑0.8
1990‑1994
1999‑2001
2003‑2005
with the local wind, i.e., the effect of theYear
disturbance is large in winter, so air temperature
Yue Onojima Azuma Yue Onojima Azuma Yue Onojima Azuma
could be increased by a small amount of radiation
Fig. 6. Difference of the air temperature from 4cooling, a phenomenon that occurs in western
point mean air temperature around theJapan in winter. On the other hand, when there
Ariake Sea.
was a strong wind over 4 m/s at Yue, Azuma andOnojima, the difference of minimum airtemperature increased, in particular at Yue and a little at Azuma, for the reasons mentioned above. It
seemed like based on the wind by disturbance. Because Onojima is inland, there is very little increase inair temperature. In this case, the small amount of radiation cooling from strong winds and increase of air
temperature at disturbance are balanced. Then, it is a rare case in the lowlands in Western Japan, but it
was sometimes observed that temperatures could reach -7 ˚C inside a flat field like a basin field surrounded
by a bank on fine or clear calm days in winter based on radiation cooling.
Difference of mean air temp. (℃)

Difference of minimum air temp. (℃)

Difference of maximum air temp. (℃)

3.4.

303

3.5. Difference of the air temperature from 4-point mean air temperature around the Ariake Sea
The periods of meteorological data were divided into 3 patterns, i.e., 1990-1994; before thereclamation, 1999-2001; after the reclamation without vegetation and 2003-2005; after recoveredvegetation. The effect of reclamation was found in 1999-2001, in that there was no vegetation under thedry, high salinity conditions compared to the condition before the reclamation in 1990-1994. Thevegetation almost recovered on the reclamation area from 2003-2005. The effects of reclamation to the airtemperatures were almost negated by the recovering of vegetation.
The difference of the air temperature from 4-point mean air temperature around the Ariake Sea isshown in Figures 6(1)-(3).
The differences of the maximum air temperature (Fig. 6(1)) increased significantly due to the increaseof the inland grade with the effects of the naked land and artificial pond from 1999-2001 at Azuma andOnojima compared to the original condition of no reclamation. After the vegetation recovered, thedifference of maximum values at Azuma and Onojima returned back pretty well, but Yue was also foundthe effect of reclamation land in 1999-2001. The difference value decreased significantly after thevegetation recovered, the effect of vegetation became to be larger than that before at Azuma and Onojima
because of a fairly recovering.
The differences of the minimum air temperature (Fig. 6(2)) at 3 locations Azuma, Onojima and Yue
decreased by radiation cooling based on the increment of inland grade, but the recovering grade atOnojima and Yue is pretty large in 2003-2005. The mean air temperature increased at Azuma based on theincrease of the maximum air temperature that the recovering reason of air temperature at Azuma andOnojima with the periods from 1999-2001 to 2003-2005, because of mainly recovering of vegetation, but
not for Yue on maximum air temperature because of the vegetation of the Oe reclamation area.
The differences of mean air temperature (Fig. 6(3)) were not significantly changed by the maximum
and minimum air temperatures, except in 1999-2001 at Azuma.
The differences of the maximum air temperature increased significantly by the increase ofreclamation land in Azuma, Onojima and Yue that was heated during the day by sun. As the vegetation
recovered in 2003-2005, the values at Azuma and Onojima almost recovered. The difference of theminimum air temperature decreased by the radiation cooling of Azuma, Onojima and Yue in 1999-2001,
but the values at Onojima and Yue recovered in 2003-2005.
4. Concluding Remarks
The results were obtained by the meteorological data from Azuma, Onojima and Yue near the area:(1) Wind speed on the ground surface decreased a little because of resistance of the front bank of Isahaya
Bay, and wind direction of the prevailing wind direction on the ground surface also changed toclockwise about 20 degrees.
(2) The water temperature of the artificial pond was increased by the heat of solar radiation during thedaytime in summer in the area isolated when Isahaya Bay was closed off by a bank, and the maximum
air temperature at Yue and Azuma was increased when the wind was blowing toward them from thepond. But at Onojima, the change of air temperature was very small because Onojima was more inland,
the distance from the pond was large and the effect of a local pond was small.
(3) The minimum air temperatures on winter nights on clear or fine days under 3 m/s at Yue and Onojima
decreased after completion of the reclamation at Isahaya Bay because of radiation cooling of the flat
surface land.
(4) The differences of the maximum air temperature increased significantly by the increase of reclamation
land of Azuma, Onojima and Yue by the daytime heating in 1999-2001. As the vegetation recoveredin 2003-2005, the values at Azuma and Onojima almost recovered. The difference of the minimum airtemperature decreased by the radiation cooling of Azuma, Onojima and Yue in 1999-2001, but thevalues at Onojima and Yue were recovered in 2003-2005.
References
Maki T. (2007): Merit and demerit of Isahaya reclaimed land and front bank. Global Environ. Read by Winds, Kokonshoin, 101-116.
Maki T., Urayama K., Wakimizu K. (2008): Variations of meteorological environment at Isahaya Bay reclamation area of Nagasaki
in Japan. Proc. of CIGR, Brazil, CD 1-6.