Effect of particulate matter in surface s n o w layers on
the albedo of perennial snow patches
K. Higuchi and A. Nagoshi
Abstract.
The albedo of snow surfaces depends on the amount of particulate matter on
them. Therefore simultaneous observations of these two elements of snow surfaces were carried
out on a perennial snow patch at 2700 m a.s.l. at Tsurugizawa in the Tateyama mountain
range in Central Japan. The particulate matter in the surface snow layer was 102 ^g in 1 cm3 of
snow at the beginning of the snowmelt season and increased to 103—104 /xg in 1 cm3 of snow at
the end of it. Corresponding to the variations in the amount of particulate matter in the surface
snow layer, the albedo of the snow surface changed from 60 to 20 per cent during the snowmelt
season.
Effet de la quantité de matière particulaire dans les couches de neige de surface sur l'albedo des
champs de neige permanents
Résumé.
L'albedo des surfaces de neige dépend dé la quantité de matière particulaire qui
les recouvre. On a donc mesuré simultanément ces deux paramètres dans un champ de neige
permanent à Tsurugizawa (altitude 2700 m) dans la chaîne de montagnes Tateyama (Japon
Central). La teneur en poussières était de 10a ftg/cm3 de neige au début de la saison de fonte
et a augmenté jusqu'à 103-104 fig/cm3 de neige à la fin de celle-ci. En fonction de ces variations
de la quantité de matière particulaire dans la couche de neige de surface, l'albedo de la surface
de neige a varié de 60 à 20 pour cent durant la saison de fonte.
INTRODUCTION
The albedo of a snow surface is an important factor controlling the heat
balance in the melting process at the surface of seasonal snow cover, perennial
snow patches and glaciers. This paper describes a study of the dependency of
the albedo on the amount of particulate matter in the surface snow layer.
PROCEDURES
Observations of the amount of particulate matter in the surface snow layer and
the albedo were carried out on a perennial snow patch at 2700 m a.s.l. at
Tsurugizawa in the Tateyama mountain range in Central Japan (latitude
36C36'N, longitude 137°37'E), in the same area where observations on the mass
balance of snow patches are being continued (Higuchi et al., 1970; Higuchi,
1973 and 1975a).
Snow /samples were collected by scraping surface snow layers of
40 cm x 50 cm with a small plastic container of 380 cm3 which was used to
carry snowmelt water to the laboratory. In addition, samples of "snow layers
under the surface were collected by means of core samples of 6 cm in diameter
and 3-4 m in depth. Sampling was carried out in 1972 on 11 June (when the
snowmelt season began), 5 August, and 1 October (when the snowmelt season
ended).
The measurement of the intensity of incident and reflected light was made
with a CSIRO-type net radiometer at the snow surface where the snow samples
were collected. Since the observation range of this radiometer is from 0.3 ^m to
100 |U.m in wavelength, the albedo of a snow surface calculated from the
observational results by this measurement is the value for light not only of
short waves but also part of longer waves.
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96
K. Higuchi and A. Nagoshi
RESULTS
Characteristics of particulate matter
The shape and size of the particulate matter filtered by a millipore filter of
0.22 fj-m pore size was examined under a polarizing microscope, after the filter
was made transparent by oil immersion. The particles were mainly minerals
such as quartz and feldspar. The most frequently occurring diameter of the
particles in the surface snow layer was 4-6 /xm in June and August, and 8-10 ^m
in October; but that in the snow layer under the surface was less than 4 iim in June.
It was found by the observations that the particulate matter was concentrated
in the surface snow layer of 1 cm in depth. Here, the amount of particulate
matter was two orders larger than in the snow layer under the surface. The
amount of particulate matter in the surface snow layer was obtained by weighing
after the snowmelt water it had been filtered by a millipore filter of 1 ^m pore
size. The results are shown in Fig. 1. From this figure it can be seen that at the
beginning of the snowmelt season in June the amount of particulate matter was
of the order of 0.1 mg in 1 cm3 of snow, and at the end of the melt season in
October this had increased to 2-4 mg in 1 cm3 of snow.
X
X
X
> < " " - ^
1
0
1
2
1
3
4
FIGURE 1.
Amount of particulate matter in the surface snow layer and the albedo.
O, values in June; x , values in August; # , values in October.
The average amount of particulate matter in the snow layer from 30 to
300 cm in depth was 5 /xg in 1 cm3 of snow after measurement of the total weight
of matter obtained by filtering the meltwater of core samples in June.
Since the thickness of snow layers melted from June to October was about
10 m, the total amount of particulate matter contained in the melted snow was
5 mg, which is in agreement with the amount of particulate matter in the surface
snow layer in October. Therefore, it can be said that the particulate matter
initially contained in the snow layer was concentrated in the surface snow layer
after melting.
Dependency of the albedo of snow patches on the amount of particulate matter in
the surface snow layer
The results of simultaneous observations of the amount of particulate matter
Effect of particulate matter on albedo
97
in the surface snow layer and the albedo are shown in Fig. 1. The albedo of the
snow surface decreased from a high value at the beginning of the snowmelt
season to a lower value at the end of it, except in one case where a high value
of albedo was observed in October, since the observation was made at an area
covered by new snow. The results obtained here on the dependency of the
albedo on the amount of particulate matter are similar to those obtained by
Onuma et al, (1967) in their experiments on promoting the melting by dispersion
of particles on a snow surface.
CONCLUSION
The albedo of a snow patch decreases exponentially with the increase of the
amount of particulate matter in the surface snow layer, which is a result of the
concentration of particulate matter in the snow layer after melting. Such
particulate matter in the snow layer is supplied during the winter season by
deposition of particles in the atmosphere through washout and fallout. It can
be said, therefore, that the melting process of snow in a mountainous area may
be modified by the change of albedo of the snow surface if the number of
particles in the atmosphere increases by man's activities. Such a problem was
discussed in a separate paper (Higuchi, 1975b).
REFERENCES
Higuchi, K. et al. (1970) Tsurugizawa ni okeru tanensei-sekkei no Kenkyû (I). [Studies on the
perennial snow patches in Tsurugizawa (I)]. Seppyo 32, no. 6, 129-146.
Higuchi, K. (1973) On the possibility of artificial control of the mass balance of a perennial
snow patch. In Hydrology of Glaciers (Proceedings of the Symposium held at Cambridge,
September 1969), pp. 207-212: IAHS Publ. no. 95.
Higuchi, K. (1975a) On the relation between mass balance of perennial snow patches and
climatic variation in Central Japan. In Snow and Ice (Proceedings of the Symposium held
at Moscow, August 1971), pp. 141-143: IAHS Publ. no. 104.
Higuchi, K. (1975b) Change of snow melt and runoff by increase of surface deposition of solid
materials. In Hydrological Characteristics of River Basins and the Effects on these
Characteristics of Better Water Management (Proceedings of the Symposium held at Tokyo,
December 1975), pp._543-548: IAHS Publ. no. 117.
Onuma et al. (1967) Nôkochi ni okeru Yûsetsu-sokushin-hô ni kansuru Kenkyû (I). (The
studies on the methods of promoting the melting of snow on a farm). Seppyo 29, no. 1,
10-25.
DISCUSSION
de Quervain:
Have you done any experiments with artificial contamination of snow surfaces?
What amount of contamination is needed so that the melt rate is decreasing
again ?
Higuchi:
At the end of July 1972 on the snow patch used for this study, we did some
experiments to change the rate of melting by covering the snow surface by a
layer of sand. Thicknesses of the sand layers were 0.1, 0.2, 0.3, 0.5, 1, 2 and
5 cm. The effect of this covering promoted the melting of the snow when the
sand layer was less than 2 cm thick, the maximum effect was observed with a
layer 0.5 cm thick. On the other hand, layers of more than 2 cm thick had the
effect of reducing the melting of the snow.