Wind speed, wind direction, and air temperature at Pegasus North
Wind speed, wind direction, and air temperature at Pegasus North during 1990 CHARLES R. STEARNS
1991, a second unit was installed about 300 meters south of the south end of the runway and about 200 meters east of the line of the runway 166.51°E. The second automatic weather station unit is equipped to measure temperatures at depths in the ice of 0, —0.05, —0.10, —0.20, —0.40, —0.80, and - 1.60 meters. The ice is covered with snow that is variable in depth and the ice at the site is not horizontally flat. Figure 1 in Stearns and Weidner (Antarctic Journal, this issue) shows the locations of the two automatic weather station sites near the Pegasus runway. The data from the Pegasus North unit for 1990 will be given here. The automatic weather station unit at Pegasus North measures wind speed, wind direction, air temperature, and relative humidity at a nominal height of 3 meters. Air pressure is measured at the electronics enclosure. The vertical air temperature difference is measured between 3.0 meters and 0.50 meter. Estimates of the sensible and latent heat fluxes to the air can be made using the wind speed, vertical air-temperature difference, and the relative humidity. The results for 1989 are presented by Stearns and Weidner (1990). During 1989 between 22 January and 11 November, there was no evidence of air temperature high enough to melt the snow. During December 1990, the air temperatures were above freezing frequency and accompanied with strong winds. Figure
and GEORGE A. WEIDNER
Department of Meteorology University of Wisconsin Madison, Wisconsin 53706
The blue-ice area south of White and Black islands is being considered as a runway for wheeled aircraft. In 1989 and 1990, one automatic weather station unit was located in the area to monitor the meteorology of the region to find out if the site is satisfactory for wheeled aircraft operations. The first automatic weather station unit was installed on 22 January 1989 about 2 nautical miles south of the downed aircraft named Pegasus. The unit was removed 11 November 1989 for installation on Mount Erebus and another unit was installed on 23 January 1990 at 77.95°S 166.51°E near Malcolm Mellor's Chalet at the north end of the Pegasus runway. On 13 January
Wind Speed & Temperature vs. Time Pegasus North Site December 1990, 3 hourly values 30
30 Wind Speed • -. Temperature a a
-. 20
20
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0
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I I I I . —20 16 18 20 22 24 26 28 30 32 0 2 4 6 8 10- 12 14 Day of the Month
Figure 1. Three-hourly values of air temperature and wind speed at Pegasus North for the month of December 1990. (ms- 1 denotes meters per second.) 1991 REVIEW
251
I is a graph of 3-hourly values of the wind speed and air temperature at the Pegasus North site for December 1990. The air temperature sensor is shielded from the Sun but is not mechanically ventilated so the temperature should be suspect if the wind speed is less than 2 knots or 1 meter per second. Figure 1 shows several occasions when the wind speed is above 1 meter per second and the air temperature is 2 to 4 °C above freezing. Figure 2 presents the mean wind speed in a 10°-wide wind direction interval as a function of the wind direction for the interval. As in 1989 (Stearns and Weidner 1990), the pattern is similar showing the highest mean wind speeds coming from the direction of 195°. Figure 2 also shows the wind direction frequency in percent as a function of the wind direction. The
most frequent wind direction is from 60° or from the direction of Scott Base. The table gives the monthly mean values of air temperature and wind speed, the resultant wind speed and direction, and the maximum wind speed and direction from the monthly climatic summarizes for Pegasus North. The sensible and latent heat fluxes are calculated from the 3-hourly values of air temperature, wind speed, vertical air temperature difference, and relative humidity. The total latent heat flux for the year is equivalent to the sublimation of 94 millimeters of water from the surface. The resultant wind direction is between 73° and 131° while the monthly maximum wind speed are from 150° to 198°. The pattern is similar in 1989. Figure 3 shows the wind speed
Mean Annual Wind Speed for each Wind Direction Category Pegasus North Site 1 January - 31 December 1990
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I I I I 0 30 60 90 120 150 180 210 240 270 300 330 360 Wind Direction Category, deg +/— 5 deg
Wind Direction Frequency vs. Wind Direction Category Pegasus North Site 1 January — 31 December 1990
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Wind Direction Category, deg +/— 5 deg Figure 2. Mean annual wind speed and wind direction frequency in 100 wind intervals as a function of the wind direction for Pegasus North for January through December 1990. (ms- 1 denotes meters per second.) 252
ANTARCTIC JOURNAL
Wind Speed vs. Time, Pegasus North Site March 1990, 3 hourly values
28 26 24 22 cn 20 E 18 '-' 16 14 12 (1) 10 4 2 0 -2
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32
Day of the Month
Jo') 330 300 270 240 210 o 180 . 150 -a 120 C ji 90 60 30 0
Wind Direction vs. Time, Pegasus North Site March 1990, 3 hourly values
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32
Day of the Month
Figure 3. Three-hourly values of wind speed and wind direction for March 1990 for Pegasus North. (ms- 1 denotes meters per second.) Monthly mean air temperature, wind speed, sensible heat flux, and latent heat flux, resultant wind speed and direction (VV/DD), and maximum wind speed and direction (VV/DD) for Pegasus North during 1990 Maximum Month Temperature Speed' Resultant' wind QC E0C January -5.4 3.1 2.2/73 12.2/182 15.5 24.1 February -12.0 4.0 2.9/91 16.5/184 3.0 15.3 March -19.5 5.2 2.6/119 26.2/198 -13.0 5.8 April -24.2 4.8 2.2/122 26.4/191 -21.4 3.1 May -25.5 4.0 2.7/83 27.7/185 -12.1 2.8 June -30.6 3.9 2.3/106 28.4/187 -25.9 1.0 July -31.1 3.3 2.3/79 26.2/195 -11.5 1.9 August -35.7 3.8 2.0/86 29.7/192 -29.9 0.4 September -33.8 3.3 2.0/77 18.5/187 -9.4 1.5 October -22.6 4.1 3.2/82 16.8/150 -20.8 2.4 November -10.2 3.5 1.4/100 23.1/163 -7.6 15.6 December -2.4 4.8 2.5/131 19.3/170 -24.7 28.2
every 3 hours for the month of March 1991 which had the highest monthly mean wind speed. The two gusts lasted for 2 to 4 days and are typical of the high wind speed events at Pegasus North. The wind direction during the gusts is from the same sector as the maximum wind speeds given above. The automatic weather station program is supported by National Science Foundation grants DPP 88-18171 and DPP 90-15586.
References Stearns, CR., and G.A. Weidner. 1990. Wind speed events and wind direction at Pegasus site during 1989. Antarctic Journal of the U.S., 25(5), 258-262. Stearns, CR., and G.A. Weidner. 1991. Antarctic automatic weather stations: Austral summer 1990-1991. Antarctic Journal of the U.S., 26(5).
a In degrees Celsius. In meters per second. In watts per square meter. 1991 REVIEW
253
1991, a second unit was installed about 300 meters south of the south end of the runway and about 200 meters east of the line of the runway 166.51°E. The second automatic weather station unit is equipped to measure temperatures at depths in the ice of 0, —0.05, —0.10, —0.20, —0.40, —0.80, and - 1.60 meters. The ice is covered with snow that is variable in depth and the ice at the site is not horizontally flat. Figure 1 in Stearns and Weidner (Antarctic Journal, this issue) shows the locations of the two automatic weather station sites near the Pegasus runway. The data from the Pegasus North unit for 1990 will be given here. The automatic weather station unit at Pegasus North measures wind speed, wind direction, air temperature, and relative humidity at a nominal height of 3 meters. Air pressure is measured at the electronics enclosure. The vertical air temperature difference is measured between 3.0 meters and 0.50 meter. Estimates of the sensible and latent heat fluxes to the air can be made using the wind speed, vertical air-temperature difference, and the relative humidity. The results for 1989 are presented by Stearns and Weidner (1990). During 1989 between 22 January and 11 November, there was no evidence of air temperature high enough to melt the snow. During December 1990, the air temperatures were above freezing frequency and accompanied with strong winds. Figure
and GEORGE A. WEIDNER
Department of Meteorology University of Wisconsin Madison, Wisconsin 53706
The blue-ice area south of White and Black islands is being considered as a runway for wheeled aircraft. In 1989 and 1990, one automatic weather station unit was located in the area to monitor the meteorology of the region to find out if the site is satisfactory for wheeled aircraft operations. The first automatic weather station unit was installed on 22 January 1989 about 2 nautical miles south of the downed aircraft named Pegasus. The unit was removed 11 November 1989 for installation on Mount Erebus and another unit was installed on 23 January 1990 at 77.95°S 166.51°E near Malcolm Mellor's Chalet at the north end of the Pegasus runway. On 13 January
Wind Speed & Temperature vs. Time Pegasus North Site December 1990, 3 hourly values 30
30 Wind Speed • -. Temperature a a
-. 20
20
'I
0
U)
10 -o l) ci (I) -o
'1)
..10
'r
Li]
C
c,
lip
4
0
E
0
—10
—10
—20
I I I I . —20 16 18 20 22 24 26 28 30 32 0 2 4 6 8 10- 12 14 Day of the Month
Figure 1. Three-hourly values of air temperature and wind speed at Pegasus North for the month of December 1990. (ms- 1 denotes meters per second.) 1991 REVIEW
251
I is a graph of 3-hourly values of the wind speed and air temperature at the Pegasus North site for December 1990. The air temperature sensor is shielded from the Sun but is not mechanically ventilated so the temperature should be suspect if the wind speed is less than 2 knots or 1 meter per second. Figure 1 shows several occasions when the wind speed is above 1 meter per second and the air temperature is 2 to 4 °C above freezing. Figure 2 presents the mean wind speed in a 10°-wide wind direction interval as a function of the wind direction for the interval. As in 1989 (Stearns and Weidner 1990), the pattern is similar showing the highest mean wind speeds coming from the direction of 195°. Figure 2 also shows the wind direction frequency in percent as a function of the wind direction. The
most frequent wind direction is from 60° or from the direction of Scott Base. The table gives the monthly mean values of air temperature and wind speed, the resultant wind speed and direction, and the maximum wind speed and direction from the monthly climatic summarizes for Pegasus North. The sensible and latent heat fluxes are calculated from the 3-hourly values of air temperature, wind speed, vertical air temperature difference, and relative humidity. The total latent heat flux for the year is equivalent to the sublimation of 94 millimeters of water from the surface. The resultant wind direction is between 73° and 131° while the monthly maximum wind speed are from 150° to 198°. The pattern is similar in 1989. Figure 3 shows the wind speed
Mean Annual Wind Speed for each Wind Direction Category Pegasus North Site 1 January - 31 December 1990
16 14 12 (I)
E 10 a
.
C')
•.S. 2 C'
• •. •• •.. S
'nj
•
I I I I 0 30 60 90 120 150 180 210 240 270 300 330 360 Wind Direction Category, deg +/— 5 deg
Wind Direction Frequency vs. Wind Direction Category Pegasus North Site 1 January — 31 December 1990
16 14 C
12
S S •
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S S
0
S. S •••S5•
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Wind Direction Category, deg +/— 5 deg Figure 2. Mean annual wind speed and wind direction frequency in 100 wind intervals as a function of the wind direction for Pegasus North for January through December 1990. (ms- 1 denotes meters per second.) 252
ANTARCTIC JOURNAL
Wind Speed vs. Time, Pegasus North Site March 1990, 3 hourly values
28 26 24 22 cn 20 E 18 '-' 16 14 12 (1) 10 4 2 0 -2
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32
Day of the Month
Jo') 330 300 270 240 210 o 180 . 150 -a 120 C ji 90 60 30 0
Wind Direction vs. Time, Pegasus North Site March 1990, 3 hourly values
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32
Day of the Month
Figure 3. Three-hourly values of wind speed and wind direction for March 1990 for Pegasus North. (ms- 1 denotes meters per second.) Monthly mean air temperature, wind speed, sensible heat flux, and latent heat flux, resultant wind speed and direction (VV/DD), and maximum wind speed and direction (VV/DD) for Pegasus North during 1990 Maximum Month Temperature Speed' Resultant' wind QC E0C January -5.4 3.1 2.2/73 12.2/182 15.5 24.1 February -12.0 4.0 2.9/91 16.5/184 3.0 15.3 March -19.5 5.2 2.6/119 26.2/198 -13.0 5.8 April -24.2 4.8 2.2/122 26.4/191 -21.4 3.1 May -25.5 4.0 2.7/83 27.7/185 -12.1 2.8 June -30.6 3.9 2.3/106 28.4/187 -25.9 1.0 July -31.1 3.3 2.3/79 26.2/195 -11.5 1.9 August -35.7 3.8 2.0/86 29.7/192 -29.9 0.4 September -33.8 3.3 2.0/77 18.5/187 -9.4 1.5 October -22.6 4.1 3.2/82 16.8/150 -20.8 2.4 November -10.2 3.5 1.4/100 23.1/163 -7.6 15.6 December -2.4 4.8 2.5/131 19.3/170 -24.7 28.2
every 3 hours for the month of March 1991 which had the highest monthly mean wind speed. The two gusts lasted for 2 to 4 days and are typical of the high wind speed events at Pegasus North. The wind direction during the gusts is from the same sector as the maximum wind speeds given above. The automatic weather station program is supported by National Science Foundation grants DPP 88-18171 and DPP 90-15586.
References Stearns, CR., and G.A. Weidner. 1990. Wind speed events and wind direction at Pegasus site during 1989. Antarctic Journal of the U.S., 25(5), 258-262. Stearns, CR., and G.A. Weidner. 1991. Antarctic automatic weather stations: Austral summer 1990-1991. Antarctic Journal of the U.S., 26(5).
a In degrees Celsius. In meters per second. In watts per square meter. 1991 REVIEW
253
