23

Bulletin of Glaciological Research ,- (,**0) ,-ῌ-,῍Japanese Society of Snow and Ice

Meteorological observation at July +st Glacier in northwest China from ,**, to ,**/
Akiko SAKAI+, Yoshihiro MATSUDA+, Koji FUJITA+, Sumito MATOBA,, Jun UETAKE.,
Kazuhide SATOW/, Keqin DUAN0, Jianchen PU0, Masayoshi NAKAWO1 and Tandong YAO2
+ Graduate School of Environmental Studies, Nagoya University, c/o HyRAC, Chikusa-ku, Nagoya .0.ῌ20*+, Japan, Institute of Low Temperature Science, Hokkaido University, Sapporo *0*ῌ*2+3, Japan. Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo +/,ῌ2//+, Japan/ Nagaoka National College of Technology, 222 Nishi-katakai-machi Nagaoak-city Niigata 3.*ῌ2/-,, Japan
0 Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, ,0* Donggang West
Road, Lanzhou 1-****, China
1 Research Institute for Humanity and Nature, --/ Takashima-cho, Kamigyo-ku, Kyoto 0*,ῌ*212, Japan
2 Institute of Tibet Plateau Research, Chinese Academy of Sciences, +***2/, Beijing, China(Received April ,0, ,**/; Revised manuscript accepted October +, ,**/)

Abstract
Meteorological observations were carried out at July +st Glacier (J+G) in Northwest China. An
automatic weather station was established at the glacier terminus .,3/ m a.s.l. altitude from June ,**,
to August ,**/. Manual meteorological observations and dust particle counting have also been
conducted at the Base Camp during the summers of ,**,, ,**- and ,**.. The catch ratio of the
precipitation was calibrated, separating it into rain and snow depending on the air temperature, which
relation has been observed at Base Camp. The calibrated annual precipitation in ,**, was about -.*mm, which was more than ,*ῌ above the observed value. Inter-annual variations in the meteorological data revealed that there were remarkable wet calm and cloudy periods during the summer ,**,.

+.

Introduction

Precipitation in mountain areas is relatively highin the arid region of northwest of China. In such areas,
glaciers function as reservoirs of precipitation (Fountain and Tangborn, +32/). Water from the mountains
has been an important resource in the downriver basin, oasis cities and desert. Therefore, ﬂuctuation in
the melt-water from glaciers should have some a#ect
on human activity. Evidence of this can be found inancient oasis cities in the desert that have fallen to
ruin. Such environmental change would be caused by
the change of water resources, which was caused by
the reduction of discharge from mountain area.
Liu and Chen (,***) have revealed that the recent
air temperature increase was larger at higher altitudes in the Tibetan Plateaus indicating that climatechanges at high altitudes would be di#erent fromthose in low altitude areas, where there is an abundance of prior meteorological data. Glaciological data
were obtained beginning in the +3/*s at the J+G in the
Qilian Mountains of China. Moreover, glacial surveys
have been carried out at several glaciers in the Qilian
Mountains (Liu et al., +33,). On the other hand, there isso far a dearth of long-term meteorological data suchas covering more than one year at mountains higher
than .*** meters. Therefore, we set up an automaticweather station near the glacier, from which to collectmeteorological data.
Precipitation is signiﬁcant as an input water mass
to the glacier basin area when we consider the discharge from the basin. The aim of this paper is tocalibrate the observed precipitation, and to elucidate
the current meteorological characteristics of the J+G.

,.

Location and features of the glacierJ+G is located in the Qilian Mountains of northwest China (Fig. +), 1* km south of Jiquan which is oneof the oasis cities along the Western Corridor of the
Yellow River. Figure , shows a topographical map of
the J+G, which was produced by Shi (+322) in +312. The
glacier is located on the northern slope of the Qilian
Mountains, and the top and terminal altitudes wereabout /+** m a.s.l. and .-** m a.s.l., respectively.
Sakai et al. (,**.) have indicated that the shrinkage of J+G has become accelerated in recent +1 years.
The glacier is of the polar type (Huang, +33*), and theinstant ice temperature data has been quite low (ῌ0῍

24Bulletin of Glaciological Research

Fig. +. Location of the July +st Glacier (J+G) in the
Qilian mountains, and the Urumqi No. + Glacier(UN+) in the Tian Shan mountains. Solid lines represent the mountain ranges. Thin lines indicate
borderlines.

at 0 m depth in August in the +31*s) (Xie et al., +32/).
Therefore, some portion of the melt-water refreezes inthe snow layer, making it necessary to take into account the refrozen amounts in order to estimate themass balance of a glacier (Fujita et al., +330; Fujita etal., ,***).

-.

Fig. ,. Map of the J+G produced by Shi (+322) andlocations of the Base Camp in Qilian mountains.
‘AWS’ indicates location of Automatic Meteorological Station.

Observation

The Automatic Weather Station (AWS) started
measurements near the glacier terminus from +* June,**, and continued collecting data until August ,**/.
Matsuda et al. (,**.) reported preliminary meteorological data during the melting season in ,**,. Data
logging was carried out by CR-+*x (Campbell Scientiﬁc, Ltd.). Instrument types, sampling intervals, logging intervals, and measurement heights of each element are summarized in Table +. Unfortunately, thenet radiometer was damaged in July ,**. and new one
has set up in June ,**/. Downward and upward longwave radiations were also measured from September+*, ,**- beside the AWS site using infrared radiometers (MR-.*, Eko, Co., Ltd.) at intervals of +* minutes.
Spectral response of the infrared radiometers was -ῌ/*mm.
Manual meteorological observations have also
been carried out in the Base Camp at the altitude of-002 m a.s.l. Observation periods and measured elements are summarized in Table ,. Air temperature
was measured by an Assman psychrometer, and winddirection and speed have been measured by a aerovan
produced by Nakaasa Co., Ltd. Precipitation was alsomeasured at Base Camp using a tipping bucket with alogger (HoBo-event) whose resolution was *.+ mm.
The vast Gobi Deserts lies to the north and the
Taklamakan Desert to the west of the Qilian Mountains. Dust particles accumulating on the glacier surface blacken the surface and reduce the surface albedo. Therefore, dust particles were also counted at

the Base Camp using a particle counter (KR-+,, RION
Co., Ltd.) and measured number with particles with*.-, *./, *.1, +, , and / mm in diameter using 3*ῌ sideway
light-scattering method. Those observations were carried out +ῌ/ times a day from June to September ,**..

..

Calibration of precipitation

Precipitation, which was a signiﬁcant factor inevaluating the water balance of the glacier, was measured using a tipping-bucket rain gauge at the meteorological station near the terminus of the glacier. The
gauge measurement for precipitation induces three
di#erent types of error, dynamic loss (caused by the
deformation of the air ﬂow ﬁeld above the gauge
oriﬁce), wetting loss (caused by precipitation adheringto the inside wall of the gauge), and evaporation loss
(caused by evaporation of the precipitation received
by the gauge) (Sevruk, +32/). Dynamic loss is the mostsigniﬁcant factor when considering snow measurement. The catch ratio of the precipitation by the tipping bucket rain gauge depends on the phase of the
precipitation (rain or snow) and the wind speed(Yokoyama et al., ,**-). Thus, it is ﬁrst necessary toinvestigate the occurrence of solid precipitation.
Occurrence probability of solid precipitation
The relation between the probability of the solid
precipitation occurrence and air temperature is shownin the Fig. -. Hail was excluded in the same ﬁgure..+.

Sakai et al.

25

Table +. Instrument name, company name, model type, sampling interval, logging interval, record type, measurement
height for each item measured at Automatic Weather Station near the glacier terminus.
Item

Instrument

Manufactured by

Sampling Logging
interval interval
(sec)
(mm)

Type

Recordtype

Measurement
height (cm)

Rermarks

Wind velocity

Anemometer

Young

Model *-**+-+*

Average,32

Threshold:*4/ msῐ+Wind direction

Vane

Young

Model *-+*+-+*

Average,32

Air temperature

Platinum resistancethermometer (Pt +**)

Vaisala

HMP./D+*+*

Average+2.

Relative humidity

Capacitance typehumidity sensor

Vaisala

HMP./D+*+*

Average+2.

Downward solar
radiation

Pyranometer

Eko Instrementa
Co., Ltd.

MS-0*++*+*

Average,,+

Spectral response*4-ῌ- mm

Upward solar
radiation

Pyranometer

Eko Instruments
Co., Ltd.

MS-0*++*+*

Average,*3

Spectral response*4-ῌ - mm

Scattered shortwave
radiation

Pyranometer

Eko Instruments
Co., Ltd.

MS-.*,+*+*

Average,*1

Net radiation*

Net radiometer

Radiation andenergy Systems

Q1

+*

+*

Average,,.

Spectral response*4,/ῌ0* mm

Longwaveradiation*

Pyranometer

Eko Instruments
Co., Ltd.

MR-.*

+*

+*

Average,**

Spectral response-ῌ/* mm

Ground temperature

Platinum resistancethermometer (Pt +**)

Hakusan Co. Ltd.

ST++*

+*

+*

Average*4/ cmdepth

until July ,**.

Precipitation

Tipping bucket rain
gauge

Texas
Electronics

TE/,/

+*

+*

Summation

2**4+ mm per tip

Air pressure

Barometric pressure
sensorVaisala

PTB,+*+*+*

Averagefrom Aug. ,**-*) Observation period June ,**,ῌJuly ,**.
**) Observation period September ,**- ῌAugust ,**.

Table ,. Period and manual meteorological observation items at Base Camp. Circle indicates observed items.
,**,
Periodfrom 3-Jun
to +-Sep

Weather῕

Visibility῕Snow line altitude (m)῕Wind direction῕Wind speed

,**-

,**.

+2-Aug ,/-Sep+*-Sep +*-Sep
῕

῕

῕

῕

῕

῕

Air temperature

῕

῕

῕

Humidity῕῕῕Surface condition῕

Surface Temperature῕Sky radiation temperature῕

Cloud amount

῕

῕

῕

Cloud altitude (m)῕Particle counter for Dust
measurement

῕Precipitation῕since it was so rarely observed. The relation between
air temperature and the percentage of solid precipitation occurrence is shown in the following equation.
Pῑῐ,*.0T῏+.1.2
Pῑ+**
Pῑ*

῍,.-ῌTῌ1.,῎.
῍Tῒ,.-῎῍Tΐ1.,῎(+)

Where T is air temperature and P is the percentage ofsolid precipitation occurrence. The equation was derived from the data, when there were more than precipitations. The temperature at /*῍ probability ofsolid precipitation occurrence was about ..1῔ which
is seen in Fig. -. Ding and Kang (+32/) reported a linear
relation with the percentage of solid precipitation
occurrence and air temperature at a meteorologicalstation at Yanglonghe in the Qilian Mountains. Temperatures at +**῍, /*῍ and *῍ occurrence of solid
precipitation were about *, -.0, and 1.,῔, respectively.
Those temperatures are relatively lower than those in
Fig. -. Ageta and Higuchi (+32.) have summarized theoccurrence of solid precipitation in Asia. Ueno et al.
(+33.) reported that the air temperature at /*῍ occurrence of solid precipitation (: T/*) was ,.3῔ in the
Tanggla Mountains of the Tibetan Plateau. Matsuo etal. (+32+a, b) indicated that snow ﬂakes tend to fall

26

Bulletin of Glaciological Research
U*.2῏U

 

 

(-)

where U*.2 and U- are wind velocity at a height of *.2
m and - m, respectively, and z*.2 and z- are the respective heights of the rain gauge and anemometer at themeteorological station. Here, z* was assumed to be *.*+,
which was applied to the soil surface (Oke, +321).
Precipitation can then be calibrated from the equationof Ohno et al. (+332),
CR῏

Fig. -. Relation between the occurrence probability ofsolid precipitation and the air temperature (bottom), and number of precipitation events (above) at
every *./ῐ temperature interval. White circles indicate the occurrence probability of solid precipitation which occurred more than - times.

without melting in a low humidity atmosphere due tothe relatively large evaporation of the snow ﬂake. The
T/* ranges were lower than that at the J+G, since thehumidity was relatively high in those observed areas.
Calibration of precipitation for wind
Rain and snow were observed visually. Air temperature was also measured by the Assman psychrometer at a height of about +,* cm at the BaseCamp (-002 m a.s.l.) during the precipitation period in
August and September, ,**- and from June to August,,**..
The catch ratio of the precipitation by the tipping
bucket rain gauge depends on the precipitation type(rain or snow) and wind speed (Yokoyama et al., ,**-).
Wind speed was measured at a height of - m (Matsuda
et al., ,**.) at the meteorological station, while theheight of the edge of the rain gauge was about *.2 m.
Wind velocity at the height zi can be expressed asfollows by the logarithmic law (Oke, +321):
..,

Ui῏

u* ῌ zi ῎ῌlnk ῍z*῏(,)

where Ui (m sec῎+) is wind velocity at height zi (m), k is
the Karman constant (῏*..), u* is friction velocity (msec῎+), and z* is roughness length. Since friction velocity is constant, the wind speed at the height of the rain
gauge (height z*.2) can be estimated by the following
equation:+ῌ+῍mU*.2(.)

where CR is the catch ratio of the rain gauge from * to+, m῏*.,+- when the precipitation is snow, and m῏*.*./. when the precipitation is rain according to
Yokoyama et al. (,**-). Yokoyama et al. (,**-) established an equation to calibrate the observed precipitation data using a rain gauge *., m in diameter, while
we measured precipitation using a rain gauge *.,. m
in diameter. Actual precipitation at J+G, therefore,
would be a slightly less than the calibrated precipitation since the catch ratio of the rain gauge with alarger diameter would be larger. Occurrence of solid
precipitation was estimated from Eq. (-). Each calculation was carried out at intervals of +* minutes. The
measured data and calibrated value of precipitation,
both snow and rain, are summarized in Table -. Calibrated precipitation reached as much as ,*ῐ morethan the amount of measured precipitation.
Figure .(a) shows a +*-day summation of eachsnow and rain amount derived from the Eq. (-) from
June ,**, to August ,**/. The liquid precipitation(rain) appeared from July to early September. The
total snow and rain amounts in each year from +/June to ,/ August, which corresponds to the summer
season, are presented in Fig. .(b), revealing that theratio of rain amounts to total precipitation were relatively high during the summer of ,**,, and the snow
amount during the summer of ,**/ was largest during
the observed four years.
Unfortunately, no wind and air temperature data
were measured automatically at the Base Camp. Precipitation observed at the Base Camp was calibratedusing the wind speed measured at AWS. The temperature lapse rate used was ῎*.01ῐ per +** m height,
which induced a temperature di#erence at AWS (measured by the AWS logger) and Base Camp (measured
by Assman) from +* Aug to +* September, ,**..
Precipitation increases with altitude (Collins, +323;
Sevruk, +33.). The increasing rate is di#erent at eachsite and season. Therefore, in order to evaluate thedi#erence in precipitation at various altitudes, weobserved the precipitation at Base Camp to be -002 ma.s.l. altitude from May ,0 to July ,/, ,**., and com-

Sakai et al.

27

Table -. Measured data and calibrated values of precipitation (PR), snow (SN) and rain (RA) were summarized in,**,, ,**-, ,**. and ,**/. Precipitation has increased about ,*ῌ by calibration.
PeriodObserved data

from

to

PR
mm (ῌ)++-Jun-*,+-Jan-*+-Jan-*.
+-Jan-*/-+-Dec-*,-+-Dec-*-+-Dec-*.
,/-Aug-*/,2. ῍+**῎,12 ῍+**῎-** ῍+**῎-21 ῍+**῎

Calibrated value

SN
mm (ῌ)

RA
mm (ῌ)

PR
mm (ῌ)

SN
mm (ῌ)

RA
mm (ῌ)

Increase bycalibrationPRῌ+3+ ῍01῎,.3 ῍3*῎,/2 ῍2/῎--, ῍20῎

3- ῍--῎,3 ῍+*῎., ῍+/῎/0 ῍+.῎--0 ῍+**῎-./ ῍+**῎-0. ῍+**῎.1+ ῍+**῎,-2 ῍1+῎-+. ῍3+῎-+3 ῍20῎.+, ῍20῎

33 ῍,3῎-+ ῍ 3῎./ ῍+.῎/3 ῍+-῎

+3
,.
,+
,,

Fig. /. Daily precipitation measured at Automatic
Weather Station at .,3/ m a.s.l. (above) and at theBase Camp at -2-/ m a.s.l. (bottom).

P῍h῎ῐ῍+῏c῍.,3/῏h῎῎Paws ῍-002ῑhῑ.,3/῎ῌ (/)
Fig. .. (a): Fluctuation in +* day-precipitation (rainand snow) from June ,**, to August ,**/. (b):Total rain and snow from +/ June to ,/ August in,**,, ,**-, ,**., and ,**/ respectively. Each
number indicates the ratio of snow or rain to annual precipitation inῌ.

whereP῍h῎ῐPrecipitation at the altitude h m a.s.l. (mm),cῐgradient of the precipitation to the altitudeῐ*.***,,*- (constant number),andpared it with the precipitation measured at AWS near
the glacier terminus.
The calibrated precipitations at AWS and BC
from ,2 May to ,. July, ,**. are shown in Fig. /. The
observed daily precipitation value at the Base Camp
was often larger than that at AWS. This was becausesnow (solid precipitation) often fell at the AWS site(.,3/ m a.s.l.) when rain was falling at the Base Camp(-002 m a.s.l.). The tipping bucket rain gauge can measure instant falling liquid precipitation, while snow
accumulating on the tipping bucket would be measured only after it had melted. This was why precipitation at the AWS was often observed after precipitation occurred.
Total precipitation at each station was +/, mm
and +-+ mm at AWS and Base Camp, respectively.
Therefore, precipitation between the altitudes of -002
and .,3/ can be estimated from the meteorologicalstation by assuming it increases proportionately withthe altitude as shown by Ohta et al. (+33.):

PawsῐPrecipitation at AWS (mm).
Ohta et al. (+33.) reported that the gradient of the
precipitation to the altitude, c, was *.**++1 in the Tanggula Mountains, which was much larger than that at J
+G. It is necessary to observe meso-scale meteorological conditions when considering di#erences in the
precipitation proﬁle with altitude.

/.

Result of observations

Meteorological data
Meteorological data in monthly averages, including the calibrated precipitation data, are summarizedin Table ..
Figure 0 the shows +/-day running mean of windspeed, air temperature, relative humidity, and downward solar radiation in each year (,**,, ,**-, ,**., and,**/). Monthly precipitation is also shown in Fig. 0. It
is worth noting that there were remarkable time cy/.+

28

Bulletin of Glaciological Research

Table .. Meteorological elements summarized as monthly averages. WS: Wind speed;
TA: Air temperature; RH: Relative humidity; PR: Precipitation; TS: Soil surface temperature; AP: Air pressure; SD: Downward solar radiation; SU: Upward solar
radiation; RN: Net radiation. ‘AVE/SUM’ shows the average values in ,**- for each
item. Precipitation was summed. ‘῍’ indicates no data.
Year

Month

WS
m sec῍+

TA
῎

,**,

Jun*
Jul
Aug
Sep
Oct
Nov
Dec

,4+43
,4+41
,43
-4,
-4+

-41
/4*
.4.
῍*41
῍04῍++41
῍+.4+

,**-

Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

,43
-4*
-4+
-4.
,4/
,4+
,4,4,
,4,42
-40
-4+

AVE/SUM

PR
mm

TS
῎

AP
hPa

/2
1+
/2
0.
..
--0

014.
++*4++140
-14.
-40
*4*
*4,

24.
+*4,
34,
.4+
῍-41
῍++41
῍+/4.

ῌ
ῌ
ῌ
ῌ
ῌ
ῌ
ῌ

,/2
+33
,*1
+00
+.1
+*,
1,

./
,2
-.
,.
,3
+0
+/

+.+
++.
+*2+
-2
1
῍2

῍+/42
῍+-43
῍++40
῍04,
῍,41
+4/
-4.
-41
*4+
῍/42
῍+*43
῍+/41

-,
.,
.,
/,
/1
0,
00
0,
/,
.+
-2
-,

*4,
+4,
,43
+*40
-341
2341
++-4.
.24-,4,
04*
*42
*4*

῍+14.
῍+-42
῍243
῍,4,41
14*
24*
24.40
῍-41
῍+*41
῍+14*

ῌ
ῌ
ῌ
ῌ
ῌ
ῌ
ῌ
ῌ
0*1
0*/
0**
/32

22
++2
+2*
,,+
,..
,-,,0
,**
,*2
+0,
32+

+1
-1
./
/3
/+
-0
-,
,2
-.
.,
,+2

῍+1
0,
3+,/
+-,
+-/
++,
30
-3
/
῍1

,42

῍04+

.2

-..43

῍-40

ῌ

+1+

-/

01

Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

-4+
-4.4.
,42
,4.
,4.
,4,4,
,40
,4-4,
-4.

῍+14῍+/43
῍+*42
῍.4῍-4+4*
.4+
-41
῍+4+
῍041
῍+-4*
῍+.4,

-3
-1
.-1
/0
/3
0+
0/
/./
-3
-2

*4.
*4/
.41
+,4/
0,41
004/
314*
2-40
,+4+-41
+4*
*4/

῍+24+
῍+.43
῍242
+41
+4.
041
34*
24*
-4*
῍-4,
῍+,43
῍+/4-

/3.
/30
/32
0*,
0*.
0*/
0*0
0*0
0*1
0*/
0*,
/31

21
+,3
+12
,0/
,02
,.0
,,2
,+,
+3,
+//
33
1.

,,/
..1
3,
.--+
,.3
,./
,01
+,+

+
-,
02
+,2
+*1
+-2
+-,
ῌ
ῌ
ῌ
ῌ
ῌ

AVE/SUM

,43

῍04/

.2

-0.

῍-40

0*,

+12

+*,

ῌ

-4-41
,43
-4,
,41
,40
+42
+43

῍+/40
῍+.42
῍++4.
῍14+
῍,4+42
.4.4*

-.
-,
/,
.+
//
/3
103

*4.
*4*
04+
140
3,4*
2,4.
+0041
++/40

῍+04+
῍+-40
῍24+
῍,4*
,4.
040
140
141

/3.
/3/33
0*,
0*,
0*/
0*1
0*0

21
+-+
+3*
,/1
,11
,1*
,*2
,*2

+-*
+12
-00
.*/
2*+
-//
--+

ῌ
ῌ
ῌ
ῌ
ῌ
ῌ
++1
+++

,**.

,**/

Jan
Feb
Mar
Apr
May
Jun
Jul
Aug**

RH
ῌ

SD
SU
RN
W m῍, W m῍, W m῍,*: Period from ++ to -* Jun., ,**,**: Period from + to ,/ Aug., ,**/

cles of a few weeks of wind speed, humidity, and solar
radiation, and some wet weather and dry weather
would also have been repeated at intervals of about ,or - weeks from July to September in ,**,.
Calibrated annual precipitation reached morethan -** mm, which corresponds to the results ofYang et al. (+33,) and Zhu and Wang (+330). However,
we could not calibrate the precipitation, which accumulated over the tipping bucket and was blown away
by strong wind before ﬂowing into the bucket. It willthus be necessary to calibrate it using a snow-depth
sensor during winter rather than in the melting sea-

Sakai et al.

29

Fig. 0. +/-day running means of wind velocity, air temperature, relative humidity,
and solar radiation in each year. Lowest box depicts monthly precipitation overthree years.

AWS was homogeneous. e can then be evaluated fromthe observed upward longwave radiation as follows:son.
Longwave radiation
Figure 1(a) shows the observed daily mean downward and upward longwave radiations. The latterradiation (LU) can be calculated as follows using the
ground surface temperature (Ts (K)) measured at the
AWS site:/.,

LUῑesTs. ῌ(0)where s is the Stefan-Boltzmann constant (ῑ/.01ῐ+*῏2 W m῏,ῌK῏.) and e is the emissivity of the groundsurface, which depends on the surface conditions,such as snow or debris. During the summer (no snow
cover), the longwave radiation induced from the ground temperature measured by thermometer at AWS(Table +) should be equal to the upward longwave
radiation measured using the infrared radiometer(LU) by assuming that the ground surface around theeῑLUῌsTs. ῍(1)

The average upward longwave radiation observed at
the AWS and the surface temperature were -0+.0 W
m῏, and ,2,./ K (3..ῒ), respectively, from June toAugust, ,**.. Therefore, the average e was +.** with astandard deviation of *.*- (at +*-minute intervals) suggesting that the ground surface at the site where
upward longwave radiation was measured can be regarded as a black body.
Net radiation (RN) can be calculated from themeasured upward (SU) and downward (SD) shortwave
radiations and upward (LU) and downward (LD) longwave radiations as follows:
RNῑSD῏SU῎LD῏LU῍(2)The observed net radiation using a net radiometer at

30

Bulletin of Glaciological Research

Fig. 1. (a): Observed daily mean downward (solidlines) and upward (dotted lines) longwave radiation. (b): Daily averages observed (dotted lines)
and calculated (solid lines) net radiation.
Fig. 3. Photographs showing time series of dust smog
taken from .2** m altitude facing north at the J+G.
Photographs (a), (b) and (c) were shot at +,:*0, +-:/*and +.:+/, respectively, on ,* July ,**..

Fig. 2. Variations in number of dust particles , mm (upper) and / mm(lower) in diameter measured by a particle counter, +ῌ/ times aday.

AWS (RNa) was compared with the net radiation thatwas observed to induce observed downward and upward shortwave radiations and downward and upward longwave radiations using Eq. (2) (RNc) in daily
average (Fig. 1(b)). The average di#erence between

RNa and RNc was ../ W mῌ,, with the standard deviation of ,/./ W mῌ,. The discrepancy between RNa and
RNc would be due to the measurement errors, thedi#erence of spectral response of radiometers, and theinhomogeneity of the ground surface around theSakai et al.

AWS.
Dust particles
Fluctuations of the dust particle numbers , and /mm in diameter observed at Base Camp from June toAugust in ,**. were shown in Fig. 2. During the observation period there were several dust peaks indicatingthat dust storms had occurred. A large dust smog
event occurred on ,* July ,**.. Dust smog pictures
were taken from the upper part of the glacier (at thealtitude of .2** m) facing north on ,* July (Fig. 3).
First, the visibility was high, mountains could be seen
well (Fig. 3a), the dust smog gradually increased andﬁnally the visibility became less than +** m (Fig. 3b, c).
Dust smog then continued until the inception ofheavy rain on +/:** ,, July. Dust particles were completely washed away by the heavy rains.

31changes), promoted by the Research Institute for Humanity and Nature (RIHN).

/.-

0.

Concluding remarks

Precipitation is the most important factor whento considering the water balance at a basin. The catch
ratio of the precipitation measured by a tipping bucket has been calibrated to the wind e#ect so as todistinguishing from solid and liquid phases determined from air temperature data. Calibrated annual
precipitation in ,**- was about -.* mm, which waslarger than about ,*ῌ of the measured precipitation.
Climatic features during the summer of ,**, weredi#erent from those of ,**-, ,**. and ,**/. In ,**,,
precipitation was relatively high, and the rain ratio in
the precipitation was also high because of the relatively high air temperature. There were also several
periods when it was relatively wet and calm with low
solar radiation due to cloud cover. On the other hand,relatively dry, windy, ﬁne (without cloud cover) days
predominated in ,**- and ,**.. It might be interesting
to compare the meteorological data observed at the J+G with those at cities near the observation site. Furthermore, the heat-balance elements for melting glacier ice during the summer ,**, might have di#ered
from those in ,**-, ,**. and ,**/.

Acknowledgments
We would like to express our thanks to Prof.
Yutaka Ageta of the Institute for HydrosphericAtmospheric Sciences, Nagoya University, for his valuable suggestions on these analyses. We also wish to
thank all members of the Project for their valuable
support in the ﬁeld. The ﬁeld research and data analyses were funded by a Grant-in-Aid for Scientiﬁc Research (Project No. +.,*3*,*) from the Ministry of
Education, Culture, Sports, Science and Technology ofJapan, and The Sumitomo foundation. This paper is acontribution to the Oasis Project (Historical evolutionof adaptability in an oasis region to water resource

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