A New Snow Sampler for Stratigraphic Observation

Katsuhiro YAMAMOTO, Hiroji FUSHIMI, Tetsuo OHATA, Yoichi TANAKA, Koichi IKEGAMI, and Keiji HIGUCHI*

Abstract

A new core sampler was developed. Its sampler pipes are made of acrylic acid resin to be con-

venient to examine the stratification of a core. A fur of seal is pasted inside the sampler cutter in

order to prevent the loss of sample when the sampler is pulled up. The sampler joint was also deviced

to be suitable for jointing the sampler pipes.

The sampler was used for the measurement of water equibalence of snow covers and for stratigraphic

observations within them. All devices were successful. It was observed that the amount of contraction

of a core depended on snow form and sampling procedure, and the value of the ratio of the snow

depth to the core length varied from 1. 04 to 1. 35. In order to reproduce the stratification within a

snow cover from that in a core, it is suggested that the height of an interface within the snow cover is,

as an approximation, estimated from multiplying that of the corresponding interface by the value of

the ratio of the snow depth to the core length. It is shown that the error of this estimated height is

less than 8. 4% of the snow depth. A method for the improvement on this error is suggested. The

new devices for the sampler are applicable to core samplers used for other deposits as well as snow

cover.

1, Introduction

Stratigraphic observations on snow covers

have been made extensively in order to understand

the relation of metamorphism of snow covers to

meteorological parameters, behaviour of water

within snow covers and physical process of snow

disasters such as avalanches and snowmelt floods

and to forecast their occurrences. Since it has

been necessary for the stratigraphic observations

to dig pits, studies concerned with the variation

of snow cover stratification in space and time

have come across some difficulties, so far. Then,

it would be useful to develop a core sampler to

observe the stratification within snow covers by

examining the core sample.

Snow samplers are one of core samplers.

They are currently used for the measurement of

water equivalence which is a fundamental quan-

tity in hydrology. Their technique and history

are described by Onuma (1955 a, b). Usual

snow samplers have, however, a weak point : a

part of sample frequently drops out of the snow sampler when the sampler is pulled out from the

snow cover. This point is commonly observed in

other core samplers such as one used for soil

deposits and have frequently troubled us so far.

It is considered to be necessary that a means

against dropping of a sample is deviced.

Vickers and Rose (1972) proved that a

short pulse radar technique could be used to

remotely sense the depth, density and water equi-

valence of a snow cover and the horizontal stra-

tification within it. However it is necessary in

that technique to examine the stratifications

within observed snow covers at some reference

points.* Water Research Institute, Nagoya University

33

142 雪 氷39巻 3号 1977 年

The present experiments were carried out to

develop a core sampler which could be used for

stratigraphic observations of snow covers and the

measurement of water equivalence, simultane-

ously. The device against dropping of a sample

was also made. It is considered that this device

is also useful to core samplers used for other

deposits as well as snow cover.

2. Design for the Core Sampler The core sampler developed in the present

experiments is shown in Fig. 1. The pipe of the

sampler was made of acrylic acid resin to observe

the structure of core samples. Acrylic acid resin

was employed because of adequency in trans-

parency, mechanical strength and hardness. Although the resin is brittler than metals, no

trouble has occurred in our snow survey where

the sampler has been extended up to 3 m in

length by jointing the sampler pipes. In order

to obtain the nearly same cross-section area of

the sampler cutter as that of a 69 type snow

sampler developed by Meteorological Agency of

Japan (2, 000 mm2), the pipe of 60 mm in outer diameter, 3 mm in thickness and 1, 000 mm in

length was used.

The construction of the sampler cutter is

shown in Fig. 2. The diameter of the cutter

was determined from the inner diameter of the

sampler pipe. The finished diameter of the

cutter is measured to be 53. 20 mm, then the

cross-section area is 2, 223 mm2. A fur ofseal

was pasted inside the cutter to makesampling

easy. It is expected that the fur will notblock

the passage of a core when the sampler ispushed

into a snow cover. On the other hand, when

the sampler is pulled out, the fur prevents the

taken core from dropping out of the sampler.

The dropping of a core from the 69 type sam-

pler have frequently troubled us so far.The assembly of a joint is shown in Fig. 3,

The joint was deviced under the followingcondi-

tions: ( 1 ) joint is strong enough to withstand

bending force, ( 2 ) jointing procedure issimple,

( 3 ) even when joint freezes, it can beunjointedeasily, and ( 4 ) when a taken core is long, it

can be divided into short columns withoutdistu-

rbing the structure of the core. In Fig.3.,flanges

of acrylic acid resin are pasted on every ends of

the sampler pipes, except the end jointed to the

Fig. 1. Core sampler developed in the present

experiment.

図1,　 本 研 究 で開 発 した コア ー ・サ ソプ ラー

Fig. 2. A cross section view of the sampler cutter.

A fur of seal is pasted inside the cutter.

This prevents a core from dropping out

of the sampler.

図2.　 サ ソプ ラー刃 部 の断 面 図.採 取 コ ア ーの脱落

防 止 の た め,ア ザ ラ シの皮 毛 を 内壁 に貼 って

あ る.

34

9月 A New Snow Sampler for Stratigraphic Observation 143

cutter. Two pipes with flanges are jointed by a

coupler of metal. The coupler consists of two

half-cylinders whose cross-section is shown in Fig.

3. Two half-cylinders are jointed by a hinge

and can be fastened by two catches. The catch

consists of a phosphor bronze belt, which is used

for a hasp, and a pin, which is used for a staple.

The pin is soldered on one of the half-cylinder

of the coupler. The belt is soldered at one end

on the other half-cylinder and has, at another

end, a hole to catch that pin. The catch is

buried in a groove on the outside of the coupler.

(We have a plan of changing the type of the catch into such type as one used in a keyholder

and a toolbox for simpler handling). In order

to transmit rotations about the axis of the sam-

pler across the joint, each flange has a groove

parallel to the axis of the sampler pipe and a

pin soldered on the inside of the coupler is put in the grooves of two flanges.

3. Observation

The sampler developed in the present experi-

ments was tested in the snow survey in hilly

countries around the Lake Biwa on 7-11 March,

1977. All our devices were successful.

3.1 Effect of the fur of seal The fur of seal pasted inside the sampler

cutter was so effective that dropping of a taken

core from the sampler was not observed in sam-

plings more than a hundred times. There was a

possibility that a little friction between the fur

and a core during pushing the sampler into a

Table 1. Comparisons in the efficency of sampling between the sampler developed in the present work and a 69 type sampler developed by Meteorological Agency of Japan.

表1　 本研究で開発 した採 雪器 と気象庁69型 採雪器 の採雪率 に関す る量の比較

Fig. 3. Assemblage views of the sampler joint. Two sampler pipes with flanges are jointed by a coupler. The coupler consists of two half-cylinders which are jointed by a hinge and can be fastened by two catches. The pin-grooves of flanges system transmits rotations about the sampler axis across the joint.

図3.　 サ ソ プ ラ ー管 接 続 部 の組 立 図.鍔 を 付 け た2

本 のサ ソ プ ラー管 を連 結 金 具 に よ り接 続 す

る.連 結 金 具 に は,2枚 の半 円 筒 状金 具 の1

辺 を蝶 板 で繋 ぎ,他 端 の 掛 金 で 締 付 け る方式

を採 用 した.鍔 に彫 った 溝 及 び そ こに 差 込 む

ピ ソは,サ ソプ ラー軸 の回 りの 回 転 運 動 を 伝

達 す るた め の も の で あ る.

35

144 雪 氷39巻 3号 1977 年

snow cover caused the effective diameter of the

cutter to decrease, because of the same reason

discussed by Onuma (1955 b) on the relation

between the effective diameter of a cutter and

snow depth. Therefore, we compared the values

of water equivalence and average density measured

using our sampler with those measured using the

69type snow sampler (Table 1). It was concluded

from Table 1 that the effect of the friction on

the effective diameter of the cutter can be negle-

cted, although the accurate effective diameter

must be calibrated on the basis of the statistical

treatment of results measured in homogeneous

snow covers over observation fields. It is reason-

able to consider that the friction between the fur

and a core also causes the contraction of the

core to increase. However, the amount of the

contraction due to the friction was not examined.

3. 2 Contraction of core

The amount of contraction of a core depends

upon form of snow and procedure of sampling.

In the case of new snow, the faster the sampler

is pushed into a snow cover, the less its amount

is. In the case of granular snow, the slower the

sampler is pushed, the less it is. When the

sampler is shaken up-and-down during sampling,

it become large in any form of snow. Length (L)

of all core whose structure has been examined in

the present snow survey are plotted against snow

depth (D) in Fig. 4. Throughout our snow

survey, the value of the ratio of snow depth to

core length varied from 1. 04, for a snow cover

almost consisting of tightly settled snow, to 1.35,

for a coarse, wet granular snow cover.

3. 3 Tests for Stratigraphic observation

In order to know the reliability of core same

pie for stratigraphic observation, we compared the stratification at the wall of pit with that of

core, at Kunizakai, Shiga Prefecture.

3. 3. 1 Observation procedures and some res-ults

Firstly, the stratification of a core taken

from point 1 was examined (column C-1 in Fig.

5), in order to obtain the data without precon.

Fig. 4. Plots of the core length versus the snow cover depth.

図4.　 積 雪深 とコ ア ー 長 の 関係

36

9月 A New Snow Sampler for Stratigraphic Observation 145

ceptions on the stratification within the snow

cover. Secondly, the stratification was examined

by digging a pit at point 2 (column P-2 in Fig.

5) . The pit was dug approximately 10 m apart

from point 1, since the snow surface around point

1 had been distrurbed during sampling at point

1. Further, we pushed the sampler into the

snow cover at point 3 near the pit, and widened

the pit to point 4 close to point 3. The heights

of ice layers which showed the clear correspon-

dence between the core at point 3 and the snow

cover at point 4 were measured (columns C-3

and P-4 in Fig. 5), in order to study vertical

deformation of the core due to sampling. In the

case of core observation, it is generally difficult

to find a thin soaked layer and a thin ice layer

within coarse granular snow. However, in the

case of the core at point 3, it was easy, since

we knew the stratification of the snow cover at

point 4. But details of the stratifications of the core at point 3 and the snow cover at point 4

were not recorded.

The grain size of granular snow was classfied

into three classes : fine (f, smaller than 0. 3 mm

in diameter), medium (m, between 0. 3 and O. 8

mm) and coarse (c, larger than 0. 8 mm). Since

the size measured in the snow cover were mostly

smaller than 1. 0 mm, the classification recom-

mended by INTERNATIONAL UNION OF GEOD

ESY AND GEOPHYSICS (IUGG) was not appro-

priate. Results of the observations are shown in

Figs. 5 and 6. In the column in Fig. 5, thin

lines, thick lines and dark bands indicate interfaces

without ice layer, thin ice layer ( < 3 mm) and

thick ice layer (> 3 mm), respectively. Soaked

layers and dirty layers are marked by simple

hatchings and cross hatchings, respectively. Some

correlations between the columns are expressed

by thin lines. It has to be noted that details of

stratifications of the columns, C-3 and P-4 are

not shown as described above. The profile of

Fig. 5. Columns to show the stratification within the snow cover of Kunizakai, Shiga Prefecture, on 9 March, 1977. C-1 and C-3 show the stratifications of cores taken from the points 1 and 3. P-2 P-4 and show the stratifications observed at the points 2 and 4 by digging a pit. In C-3 and P-4, only thick ice layers and a dirty layer are shown. Symbols in column: thin solid line; interface without ice layer, thick solid line; thin ice layer (< 3 mm), dark band; thick ice layer (> 3 mm), simple hatching; soaked layer, cross hatching; dirty layer. Abbreviations: s2; settled snow, f; fine granular (<0. 3 mm in diameter), m; medium granular (0. 3- 0. 8), c; coarse granular (> 0. 8 mm), SS ; snow surface, c.s. ; core surface.

図5.　 積 雪 内 部 の 層構 造 を 表 す 柱 状 図.1977年3月

9日 滋 賀 県 国境.C4及 びC-3は,地 点1

及 び3よ り採 取 した コ アー の構 造 を示 す. P-

2及 びP-4は,地 点2及 び4で の ピ ッ ト に

よる観 察 結 果.C-3及 びP-4に は,厚 い氷 板

と汚 れ 層 の みが 示 され て い る。

柱 状 図 中 の記 号:細 線;氷 板 の無 い層 境 界,

太 線;薄 い氷 板(＜3mm),黒 い帯;厚 い氷

板(≧3mm),斜 線;水 滲 層,交 叉 斜 線;汚

れ 層.略 号:s3;し ま り雪,f;細 粒 ザ ラ メ

雪(粒 径 く0.3mm),m;中 粒 ザ ラ メ雪(0。3

～0.8mm),6;粗 粒 ザ ラ メ雪(＞0 。8mm),

SS;雪 面, CS;コ ア ーの 上 面 .

37

146 雪 氷39巻 3号 1977 年

wet density at point 2 is also shown in Fig. 5 for

a reference to the snow form.

3. 3. 2 Reproduction of snow cover stratifica-

tion from core stratification

In order to reproduce stratification within a

snow cover from that of a core, positions of

interfaces within the snow cover have to be

estimated from those in the core. Plots of the

height of an ice layer within the snow cover at

point 4 versus that of the corresponding interface

in the core taken from point 3 are shown in Fig.

6. In this figure, plot of the snow depth versus

the core length is also shown. Fig. 6 shows that

heights of interfaces within a snow cover are

approximated by multiplying those in a core

taken from it by the value of the ratio of the

snow depth to the core length. In the case of

R-1 P-2

Fig. 6, it is shown that the errors due to this

approximation are less than 6 cm which is 3

percent of the snow depth. The column R-1 in

Fig. 7 is reproduced from the column C-1 in

Fig. 5 using this approximation. The stratification

of the snow cover at point 2 is also shown in

the column P-2 in Fig. 7 to examine the correla-

Fig. 6. Plots of height of an ice layer within the snow cover (column P-4 in Fig. 5) versus that of the corresponding ice layer in the core (column C-3). The height of the snow surface versus that of the core surface is also plotted.

図6.　 コア ー 中 の 高 さ と積 雪 中 の そ れ との 関係.コ

ア ー の上 面 の高 さ に対 す る雪 面 の高 さ も プ ロ

ッ トして あ る。

Fig. 7. Columns to show the stratifications within

snow cover. R-1 is reproduced from the

column C-1 in Fig. 5 which shows the

stratification of the core. P-2 is the same

as the column P-2 in Fig. 5 and is shown

in order to compare the stratification at

point 1 with that at point 2. Symbols and abbreviations are the same as those in

Fig. 5.

図7.　 積 雪 内部 の層 構 造 を表 す 柱 状 図.R4は 図5,

C-1よ り復 元 した も の。P-2は 図5,P-2と

同一 で あ り,地 点1と2の 層 理 の比 較 の ため

示 す.記 号 及 び 略 号 は 図5と 同 じ。

38

9月 A New Snow Sampler for Stratigraphic Observation 147

tion between both stratifications.

4. Results and Discussions

4. 1 Correlation

The stratifications of columns R-1 and P-2

in Fig. 7 show substantially good correspondences

although some differences are seen between them.

Column R-1 lacks the thin ice layers correspon-

ding to those of 0. 47, O. 53 and 0. 92 m in depth

in column P-2. They are marked by small

arrows in the figure. They exist between relati-

vely coarse granular layers. The following three

explanations can be conceivable to account for

lack of them in column R-1 : (1) the thin ice

layers under the consideration did not exist at

point 1, ( 2 ) although these layers had existed at point 1, they were broken during sampling

and were not distinguished from coarse granular

snow, and ( 3 ) although these layers had been

taken in the core without break, they were too

thin to be detected under the condition that the

core provided a very narrower observation area

than a pit. The same three explanations can

also be conceivable to account for lack of some

soaked layers in column R-1. The explanations,

( 2 ) and ( 3 ), show that observations with core

are not suitable for examining the fine structure

within a snow cover.

There are some structual differences between

columns R-1 and P-2 below the ice layer which

is seen at the depth 1. 62 m in column R-1 and

at 1. 47 m in column P-2. It is marked by

large arrows. It is possible to consider that this

is caused by the undulation of the ground under

the snow cover. Fig. 7 shows that the bottom

soaked layer is thicker at point 1 than at point

2 and the water level of this layer is lower at

point 1 than point 2. These evidences indicate that point 1 is located near a depression. The

amount of supplied water and the duration of

the supply in lower layers, in and after the

periods of snow melting and raining are then larger and longer at point 1 than at point 2,

according to the theory of water percolation

through a sloped snow cover (Colbeck, 1975).

This causes the degree of metamorphism at point

1 to be different from that at point 2.

The dirty layer shown by cross hatching in

Figs. 5 and 7 was observed in yellowish brown.

It is considered to have been contaminated by

the yellow sand which has fallen on 22•`24

February, 1977. Namely, it is good dating within

the snow cover. Some thick ice layers will be

also dated if the relation between the formation

of an ice layer and meteorological parameters

will be established.

4. 2 Error in the estimated height of an inte-

rface

It is described in section 3. 3. 2 how to esti-

mate the height of an interface within a snow

cover from that in a core. In the present section,

the error of this estimated height is evaluated.

We consider a snow cover and a core taken from

it. The depth of the snow cover and the length

of the core are D and L. We suppose the snow

cover to consist of the two layers : I (the lower

layer) and II (the upper). The length of verti-

cals within the layers I and II are d1 and d2.

The lengths of the parts of the core corresponding

to the layers I and II are 11 and 12. Then,

( 1 )and

( 2 )

It is noted that d1 also expressed the height of

the interface between the layers I and II from

the bottom and 11 also expressed that of the

corresponding interface in the core, too. In order

to evaluate the error of the estimated height of

the interface, the following parameters are intro-

duced:

( 3 )

(4 a)and

(4 b)

al and a2 are the inverses of the contraction ratios

39

148 雪 氷39巻 3号 1977 年

of the layers I and II, respectively. Using these

parameters d1 is expresses by

( 5 )On the other hand, the estimated height, d1', is

( 6 )

where

( 7 )and A is the inverse of the contraction ratio of

the core. Then, the error, E, of the estimated

height is expressed relatively to the snow depth

by

(8 a)

(8 b)on the condition that

( 9 )It is possible to suppose from our observa-

tional evidences on contraction of cores (section

3.2 and Fig. 4) that

(10 a)and

(10 b)unless the sampler is hardly shaken up-and-down

during sampling.

Eqs. (8 b) and ( 9 ) and ineqs. (10 a and

b) yield (see Appendix)

( 11 )Thus the error in the estimated height, d11, of a

interface is less than •}8. 4 percent of the snow

depth.

4. 3 Method for improvement on the error

in the estimated height

When it is necessary to know the more

accurate height of an interface than the value

estimated with the method described in section

3. 3. 2, a complementary measurement is required.

It is possible to measure the depth, consequently

the height, of ice layer using such sounding rod

as is used for measurement of snow depth, since

we can detect the ice layer by the reaction of

the rod in the course of pushing the rod into a

snow cover. The snow cover is considered to

be divided into sublayers bounded by each ice

layer whose height has been measured. Then

the some accurate height of the other interface

within the snow cover can be known by applying

the estimation to each sublayer.

Acknowledgement

We are heartly grateful to Mr. G. Takamatsu

of Nagoya University for the manufacture of the

sampler. This work was partly supported by a

grant from the Ministry of Education, Japan, for scientific research.

Appendix

Eqs. (8 b) and ( 9 ) yield

(A 1)and

(A 2)a1 and a2 is bounded. The greatest lower

bound is 1. 0. One of the upper is denoted a0.

Then

(A 3)

and

(A 4)

Eqs. (A 1) and (A 2) and ineqs. (A 3) and

(A 4) yield the range of E. The range is expressed by two forms according to the region

of A and each is also expressed by three forms

according to the region of x:

( I ) In the region,

(I-i) when

(A 5)

(I-ii) when

(A 6)and

(I-iii) when

(A 7)

( II ) In the region,

(II-i) when

(A 8)

(II-ii) when

(A 9)

40

9月 A New Snow Sampler for Stratigraphic Observation 149

and

(II-iii) when

(A 10)

For an arbitaly fixed value of A, the greatest

lower bound of E has a minimum value,

(A 11)

at

(A 12)

Similarly, the least upper bound of E has a

maximum value,

(A 13)

at

(A 14)

Eu and EL have a maximum value,

(A 15)

when

(A 16)

It is supposed in the text that a0= 1. 4. Then,

EM = 0.084, Namely,

(A 17)

for any value of A between 1 and 1. 4 and any

value of x between 0 and 1.

References

Colbeck, S.C., 1975: A theory for water flow through a layered snow pack. Water Resou-rces Research, 11, 261-266.

Onuma, M., 1955 a: Measurement of water equi-valent of deposited snow by snow sampler. in Shidei, T. ed., Researches on Snow and Ice No. 2, Japanese Society of snow and Ice, Tokyo, 149-155 (in Japanese).

Onuma, M., 1955 b: Snow surveying by various snow samplers. in Shidei, T. ed., Researches on Snow and Ice No. 2, Japanese Society of Snow and Ice, Tokyo, 185-194 (in Japanese).

Vickers, R.S. and G.C. Rose, 1972: High resolu- tion measurements of snowpack stratigraphy using a short pulse RADER. in Proceedings of the Eight International Symposium on Remote Sensing of Environment Vol. 1, University of Michigan, 261-277.

層 理 観 察 用 採 雪 器 の 開 発

山 本 勝 弘 ・伏 見 碩 二 ・大 畑 哲 夫

田 中 洋 一 ・池 上 宏 一 ・樋 口 敬 二

1度 の試料採取に より,採 取コ アの層理観察及び コア重量の測定が可能な,コ ア ・サ ンプ ラーを設計 ・作

成した.こ のサ ンプラーの構造上 の特徴は次の3点 であ る.(1)採 取 コアの層理 をそのまま観 察す るため,

サンプラー管をア ク リル樹脂 で作製 した.(2)試 料採取中,サ ンプラーを引 き上げる時に,採 取コ アがサ

ンプラーか ら脱落す るのを防 ぐため,サ ン プ ラ ー刃内壁に アザ ラシの毛皮(ス キ ー用 シール)を 貼 った。

(3)樹 脂製サ ンプラー管 同士 の接続に適 した継手を考案 した.

このサ ンプラーを積雪 の層理観察及び水 当量測定に使用 し,設 計意図通 りの成果を得た.試 料採 取の際,

コアが縮むが,こ の縮 み量 は雪質及 び試料採取方法に依存 し,積 雪深 とコア長 との比の値 は1.04～1.35の 間

であった.積 雪の層理を復元す る際 に見込 まれ る誤差は,積 雪深の8.4%未 満であ る.こ れ よりも精度 の高

い値を得 るための補 助的測定 法を提案 した.な お,こ のサ ンプラー各部の構造は,積 雪 以外 の堆積物用サ ン

プラーに も適用可能である.

41