Blowing snow in eastern Antarctica
In addition to having their axes approximately horizontal, about 10 percent of the crystals in the simulation had Parry orientations and were responsible for the Parry arc and heliac arc. Parry orientations have long been known to be the cause of these two halos, but some writers have wondered whether a simple columnar crystal would fall with two prism faces horizontal. Perhaps some sort of cluster of crystals would be necessary to achieve the horizontal prism faces, or in single crystals perhaps two opposite prism faces would have to be much larger than the others, resulting in tabular crystals. The presence of the Parry arc and the heliac arc in the actual display, together with the absence of clusters or obviously tabular forms in the crystal sample, indicates that simple columnar crystals by themselves can assume Parry orientations. This display illustrates the sort of inferences that can sometimes be drawn from examining crystals during halo displays.
Thorough understanding of the relation between crystal types and halo types would permit halos to be used as indicators of crystal types present in halo producing clouds. Since crystal types are thought to be a function of atmospheric conditions, halo types should in principle be indicators of atmospheric conditions. The computer simulation program is similar to that originally developed by Pattloch and Trankle (1984). This research was supported in part by National Science Foundation grant DPP 84-14178.
Blowing snow in eastern Antarctica
times are possible, giving a more meaningful relation between wind speed and flux (e.g., Tabler 1975). In figure 1, frequency
References Pattloch, F., and E. Trankle. 1984. Monte Carlo simulation and analysis of halo phenomena. Journal of the Optical Society of America A, 1(5),
520-526.
D-47, 1 DEC 1985 30
GERD WENDLER
Geophysical Institute University of Alaska Fairbanks, Alaska 99701
U
Lfl ,
900 800
2
264
125 150 175 200 225 250 mV
U U
A large-scale U.S.-French experiment IAGO (Interaction-Atmosphere-Glace-Ocean) was carried out in Adélie Land, East Antarctica, and was first described by Wendler and Poggi (1980) and Poggi et al. (1982). This experiment included setting up meteorological towers to gather wind, temperature, and radiation data; taking balloon, kite, and airborne measurements through the boundary layer; and taking blowing snow measurements. It is the last of these data, which were collected at D-47 (67°23'S 138°43'E, 1,560 meters altitude), that will be highlighted here. The station is some 100 kilometers from the coastline, the winds are strong (12.6 meters per second mean annual value) and very constant in direction (0.94 wind direction constancy). Apart from their intrinsic value, blowing snow measurements are also of importance to understand the mass balance of Antarctica better, because large amounts of snow are lost to the oceans in areas as windy as Adélie Land. We measured the number and sizes of the snow particles photoelectrically with a device developed by the University of Alaska. We patterned the design after Schmidt (1977), the biggest design change being that not only the frequency, but also the mean size varied linearly with the output voltage. This is important, because the cube of the diameter must be used in the flux calculation, and small errors in the diameter might otherwise result in large errors in the fluxes. Measuring the fluxes photoelectrically has the big advantage that the air flow is not disturbed as with mechanical devices which have been previously used in Antarctica (e.g., Budd 1966; Radok 1970; Kobayashi 1978). Further, short integration
1000
m he9ht
700 600
Lij L
400 6 7 8 9 10 11 12 13 14 15 16 rn/s
350
125 150 175 200 225 250 mV
320 E UI
250
200
U)
150 in 6 7 8 9 10 11 12 13 14 15 16 m/
Figure 1. Number of particles per second (frequency) and mean size of the particles against wind speed for one specific event (1 December 1985) and one specific height (30 centimeters) at D-47, East Antarctica. ANTARCTIC JOURNAL
and size are plotted against wind speed for 4-second intervals. It can be seen that stronger winds not only pick up more particles but also larger ones. The frequency is about 700 particles per square centimeter per second while the size ranges between 150 and 250 nanometers. The values agree with those found by other investigators (e.g., Schmidt 1977). Further, a visual inspection of the sizes was carried out in the field with the help of a fine grid and a magnifying glass: good agreement was found. From size and frequency (figure 1) the fluxes can be calculated, which are presented against wind speed in figure 2. A linear relationship between the logarithm of the flux and the wind speed was found. The flux density decreased strongly with altitude; however, the same slope of the curves were found for different heights. By integrating the fluxes with height, the total flux can be determined for any specific wind speed. In summer, when the snow blowing measurements were carried out, the wind speed was somewhat below the annual mean; nevertheless, drifting snow was observed about half of the time. Drifting snow was observed with winds speeds of about 8 meters per second; with a speed of 14 meters per second well developed blowing snow was observed; and when the wind speed reached 20 meters per second, visibility went down to 20 meters. The automatic weather station at D-47 gives us a very good frequency distribution of the wind speed year round (figure 3). Using these data, the total drifting snow could be calculated. A value of about 6.3 x 10 kilograms per meter per year was found, which is a high but credible value for this windy area. Loewe (1970) suggested values of up to 7 x lO b kilograms per meter per year for windy areas. This work was supported by National Science Foundation grant DPP 81-00161.
.\ 20 C
20
15 10
w w 0 0 5 10 15 20 25 30
.\ 20
APR
C
14
10 LLJ LLJ
01
0
15. 2-
LA L . . .
0 5 10 15 20 25 30
20
MAY
15
0 5 10 15 20 25 30
L
L
18-i
w 0 I, 0 5 10 15 20 25 30
\• 20
0 0 5 10 15 20 25 30
20
15
15
j
L 10 w
10 5
LU
5
10
0 5 10 15 20 25 30
ISi
JUN
':
w
0
01
20
I
MR
101
5 10 15 20 25 "1 30
.\ 20
151
15 20 25 30
WIND SPEED (rn/sec)
0
0
0 5 10 IS 20 25 30
20
SEP
15 10 S 0
0 5 10 15 20 25 30
NOV
UL
0 5 10 15 20 25 30
OUL...''4 0 5 10 15 20 25 30
WIND SPEED (rn/5ec)
WIND SPEED (rn/sec)
Figure 3. Frequency distribution of the wind speed each month at D-47, East Antarctica. ("m/sec" denotes "meters per second:')
References Budd, W.W. 1966. The drifting of non-uniform snow particles. In M.
DEL I
Rubin (Ed.), Studies in Antarctic meteorology. (Antarctic Research Se-
16
ries, Vol. 9.) Washington, D.C.: American Geophysical Union.
15
0/
/
14
Kobayashi, S. 1978. Snow transport by katabatic winds in Mizuho Camp area, East Antarctica. Journal of the Meteorological Society of Japan, 56(2), 130-139.
13
Loewe, F. 1970. The transport of SflOW on ice sheets by the wind. In
0
12
Studies on drifting snow. (Meteorology Department, University of
UJ w 11
Melbourne.) Poggi, A., D. Delunay, H. Mallot, and G. Wendler. 1982. Interactions
If)
Atmosphere-Glace-Ocean en Antarctique de l'est. Proceedings of the
Z
Argos Users Conference, Paris, 1982. (In French) Radok, U. 1970. Boundary processes of drifting snow. In Studies of drifting snow. (Meteorology Department, University of Melbourne.) Schmidt, R.A. 1977. A system that measures blowing snow. USDA Forest Service Research Paper, RM-194, 80.
-3 -2 -1 0 1 2 3 4 In LU
1
Figure 2. The logarithm of the flux against wind speed for three specific heights (10, 30, and 60 centimeters on 1 December 1985 at D-47, East Antarctica.
1987 REVIEW
Tabler, R.D. 1975. Estimating the transport and evaporation of blowing snow. In Snow manage of the Great Plains Symposium, (Bismarck, North Dakota, July 1975). Proceedings of Great Plains Agricultural Council, Publication 73, 83-104. Wendler, G., and A. Poggi. 1980. Measurement of the katabatic wind in Antarctica. Antarctic Journal of the U.S., 15(5), 193-195.
265
Thorough understanding of the relation between crystal types and halo types would permit halos to be used as indicators of crystal types present in halo producing clouds. Since crystal types are thought to be a function of atmospheric conditions, halo types should in principle be indicators of atmospheric conditions. The computer simulation program is similar to that originally developed by Pattloch and Trankle (1984). This research was supported in part by National Science Foundation grant DPP 84-14178.
Blowing snow in eastern Antarctica
times are possible, giving a more meaningful relation between wind speed and flux (e.g., Tabler 1975). In figure 1, frequency
References Pattloch, F., and E. Trankle. 1984. Monte Carlo simulation and analysis of halo phenomena. Journal of the Optical Society of America A, 1(5),
520-526.
D-47, 1 DEC 1985 30
GERD WENDLER
Geophysical Institute University of Alaska Fairbanks, Alaska 99701
U
Lfl ,
900 800
2
264
125 150 175 200 225 250 mV
U U
A large-scale U.S.-French experiment IAGO (Interaction-Atmosphere-Glace-Ocean) was carried out in Adélie Land, East Antarctica, and was first described by Wendler and Poggi (1980) and Poggi et al. (1982). This experiment included setting up meteorological towers to gather wind, temperature, and radiation data; taking balloon, kite, and airborne measurements through the boundary layer; and taking blowing snow measurements. It is the last of these data, which were collected at D-47 (67°23'S 138°43'E, 1,560 meters altitude), that will be highlighted here. The station is some 100 kilometers from the coastline, the winds are strong (12.6 meters per second mean annual value) and very constant in direction (0.94 wind direction constancy). Apart from their intrinsic value, blowing snow measurements are also of importance to understand the mass balance of Antarctica better, because large amounts of snow are lost to the oceans in areas as windy as Adélie Land. We measured the number and sizes of the snow particles photoelectrically with a device developed by the University of Alaska. We patterned the design after Schmidt (1977), the biggest design change being that not only the frequency, but also the mean size varied linearly with the output voltage. This is important, because the cube of the diameter must be used in the flux calculation, and small errors in the diameter might otherwise result in large errors in the fluxes. Measuring the fluxes photoelectrically has the big advantage that the air flow is not disturbed as with mechanical devices which have been previously used in Antarctica (e.g., Budd 1966; Radok 1970; Kobayashi 1978). Further, short integration
1000
m he9ht
700 600
Lij L
400 6 7 8 9 10 11 12 13 14 15 16 rn/s
350
125 150 175 200 225 250 mV
320 E UI
250
200
U)
150 in 6 7 8 9 10 11 12 13 14 15 16 m/
Figure 1. Number of particles per second (frequency) and mean size of the particles against wind speed for one specific event (1 December 1985) and one specific height (30 centimeters) at D-47, East Antarctica. ANTARCTIC JOURNAL
and size are plotted against wind speed for 4-second intervals. It can be seen that stronger winds not only pick up more particles but also larger ones. The frequency is about 700 particles per square centimeter per second while the size ranges between 150 and 250 nanometers. The values agree with those found by other investigators (e.g., Schmidt 1977). Further, a visual inspection of the sizes was carried out in the field with the help of a fine grid and a magnifying glass: good agreement was found. From size and frequency (figure 1) the fluxes can be calculated, which are presented against wind speed in figure 2. A linear relationship between the logarithm of the flux and the wind speed was found. The flux density decreased strongly with altitude; however, the same slope of the curves were found for different heights. By integrating the fluxes with height, the total flux can be determined for any specific wind speed. In summer, when the snow blowing measurements were carried out, the wind speed was somewhat below the annual mean; nevertheless, drifting snow was observed about half of the time. Drifting snow was observed with winds speeds of about 8 meters per second; with a speed of 14 meters per second well developed blowing snow was observed; and when the wind speed reached 20 meters per second, visibility went down to 20 meters. The automatic weather station at D-47 gives us a very good frequency distribution of the wind speed year round (figure 3). Using these data, the total drifting snow could be calculated. A value of about 6.3 x 10 kilograms per meter per year was found, which is a high but credible value for this windy area. Loewe (1970) suggested values of up to 7 x lO b kilograms per meter per year for windy areas. This work was supported by National Science Foundation grant DPP 81-00161.
.\ 20 C
20
15 10
w w 0 0 5 10 15 20 25 30
.\ 20
APR
C
14
10 LLJ LLJ
01
0
15. 2-
LA L . . .
0 5 10 15 20 25 30
20
MAY
15
0 5 10 15 20 25 30
L
L
18-i
w 0 I, 0 5 10 15 20 25 30
\• 20
0 0 5 10 15 20 25 30
20
15
15
j
L 10 w
10 5
LU
5
10
0 5 10 15 20 25 30
ISi
JUN
':
w
0
01
20
I
MR
101
5 10 15 20 25 "1 30
.\ 20
151
15 20 25 30
WIND SPEED (rn/sec)
0
0
0 5 10 IS 20 25 30
20
SEP
15 10 S 0
0 5 10 15 20 25 30
NOV
UL
0 5 10 15 20 25 30
OUL...''4 0 5 10 15 20 25 30
WIND SPEED (rn/5ec)
WIND SPEED (rn/sec)
Figure 3. Frequency distribution of the wind speed each month at D-47, East Antarctica. ("m/sec" denotes "meters per second:')
References Budd, W.W. 1966. The drifting of non-uniform snow particles. In M.
DEL I
Rubin (Ed.), Studies in Antarctic meteorology. (Antarctic Research Se-
16
ries, Vol. 9.) Washington, D.C.: American Geophysical Union.
15
0/
/
14
Kobayashi, S. 1978. Snow transport by katabatic winds in Mizuho Camp area, East Antarctica. Journal of the Meteorological Society of Japan, 56(2), 130-139.
13
Loewe, F. 1970. The transport of SflOW on ice sheets by the wind. In
0
12
Studies on drifting snow. (Meteorology Department, University of
UJ w 11
Melbourne.) Poggi, A., D. Delunay, H. Mallot, and G. Wendler. 1982. Interactions
If)
Atmosphere-Glace-Ocean en Antarctique de l'est. Proceedings of the
Z
Argos Users Conference, Paris, 1982. (In French) Radok, U. 1970. Boundary processes of drifting snow. In Studies of drifting snow. (Meteorology Department, University of Melbourne.) Schmidt, R.A. 1977. A system that measures blowing snow. USDA Forest Service Research Paper, RM-194, 80.
-3 -2 -1 0 1 2 3 4 In LU
1
Figure 2. The logarithm of the flux against wind speed for three specific heights (10, 30, and 60 centimeters on 1 December 1985 at D-47, East Antarctica.
1987 REVIEW
Tabler, R.D. 1975. Estimating the transport and evaporation of blowing snow. In Snow manage of the Great Plains Symposium, (Bismarck, North Dakota, July 1975). Proceedings of Great Plains Agricultural Council, Publication 73, 83-104. Wendler, G., and A. Poggi. 1980. Measurement of the katabatic wind in Antarctica. Antarctic Journal of the U.S., 15(5), 193-195.
265
