CMDL Annual Report 24: 1.5.2 South Pole Climatology

1.5.2 South Pole Climatology

The distribution of the surface wind direction in 1996 and 1997 (Figure 1.8) shows a percentage of clean air sector (grid north-northwest through east-southeast) winds of 94.1% in 1996 and 94.2% in 1997 similar to the 19-year average (93.9%) (Figure 1.9). The percentage of winds in the 10 ms^-1 or greater class was 4.1% in 1996 and 3.5% in 1997 compared to the 19-year average of 3.9%. The annual average wind speeds for 1996 and 1997 were both close to normal.

Wind roses of surface winds for SPO for 1996 (left) and 1997 (right)

Fig. 1.8. Wind roses of surface winds for SPO for 1996 (left) and 1997 (right). The distribution of resultant wind direction and speed are given in units of percent occurrence. Wind speed is displayed as a function of direction in three speed classes.

Fig. 1.9. Wind rose of surface winds for SPO for 1977 through 1995. The distribution of resultant wind direction and speed are given in units of percent occurrence for the 19-year period. Wind speed is displayed as a function of direction in three wind classes.

The average temperature for 1996 (-48.3°C) (Table 1.12) was 0.7°C warmer than the 19-year average of -49.0°C while the average temperature for 1997 (-50.1°C) was 1.1°C below normal. July 1997 tied a record high temperature and January 1997 tied a record low temperature. The minimum temperature in 1996 of -74°C occurred in July while the minimum in 1997 of -79°C occurred in September. The annual average barometric pressure for 1996 (682.1 hPa) was 3.2 hPa higher than the 19-year average while the barometric pressure for 1997 was 0.2 hPa below the long-term average. August 1996, November 1996, and June 1997 set high-pressure records. A pressure of 718.1 hPa in August 1996 was the highest ever recorded in the 21-year history of the station.

TABLE 1.12. SPO 1996 and 1997 Monthly Climate Summary

		Jan.	Feb.		March	April	May	June	July	Aug.	Sept.	Oct.	Nov.	Dec.	Year
									1996
Prevailing wind	NNE			NNE	ENE	NNW	ENE	ENE	N	N	NNE	N	N	N	ENE
direction
Average wind	3.8		4.8		5.6	4.8	5.2	5.7	7.0	6.5	5.7	5.9	5.6	5.4	5.5
speed (m s^-1)
Maximum wind	11		11		11	11	12	12	14	13	11	16	13	11	16
speed* (m s^-1)
Direction of max.	296		36		345	356	316	12	6	24	12	350	6	27	350
wind* (deg.)
Average station	688.6		688.7		678.9	681.2	677.3	677.4	675.3	686.8	681.3	672.4	687.7	690.3	682.1
pressure (hPa)
Maximum pressure*	706		704		690	703	692	688	687	718	695	685	708	699	718
(hPa)
Minimum pressure*	679		675		670	665	667	662	661	668	663	655	674	681	655
(hPa)
Average air	-29.1		-37.1		-56.3	-54.8	-60.3	-59.7	-55.7	-53.1	-59.6	-53.1	-35.4	-25.8	-48.3
temperature (°C)
Maximum temperature*	-19		-23		-36	-37	-42	-44	-36	-36	-48	-31	-23	-19	-19
(°C)
Minimum temperature*	-35		-50		-68	-69	-72	-71	-74	-70	-70	-66	-49	-34	-74
(°C)
Average dewpoint	-32.9		-40.0		-56.9	-55.4	-61.0	-63.2	-59.8	-56.8	-63.1	-56.1	-39.0	-29.5	-50.1
temperature (°C)
Maximum dewpoint	-23		-25		-38	-40	-46	-48	-39	-39	-51	-34	-26	-22	-22
temperature (°C)
Minimum dewpoint	-40		-53		-64	-68	-73	-73	-77	-76	-74	-68	-53	-38	-77
Temperature (°C)
Precipitation (mm)	0		0		0	0	0	0	0	0	0	0	0	0	0
									1997
Prevailing wind	N			ENE	ENE	N	NNE	ENE	E	N	NNE	ENE	N	ENE	NNE
Direction
Average wind	4.2		4.8		5.8	6.4	6.2	5.4	5.0	6.7	5.8	4.5	6.6	4.1	5.5
Speed (m s^-1)
Maximum wind	10		9		12	13	13	14	10	14	14	10	13	9	14
Speed* (m s^-1)
Direction of max.	7		14		32	356	355	12	1	6	19	30	7	11	12
Wind* (deg.)
Average station	688.2		682.3		674.0	678.7	672.8	679.0	668.7	673.0	675.7	676.8	692.3	687.7	678.9
Pressure (hPa)
Maximum pressure*	694		695		684	701	684	707	681	693	696	689	703	696	707
(hPa)
Minimum pressure*	678		671		665	666	660	662	650	657	655	661	663	678	650
(hPa)
Average air	-28.6		-43.4		-54.8	-55.9	-57.8	-57.0	-65.1	-59.6	-59.9	-54.7	-34.0	-27.4	-50.1
Temperature (°C)
Maximum temperature*	-21		-32		-42	-37	-45	-32	-34	-42	-36	-39	-25	-22	-21
(°C)
Minimum temperature*	-38		-54		-68	-71	-72	-72	-76	-75	-79	-61	-53	-32	-79
(°C)
Average dewpoint	-32.3		-46.9		-58.5	-59.6	-61.8	-60.9	-67.7	-62.2	-63.7	-58.0	-37.4	-30.5	-53.1
temperature (°C)
Maximum dewpoint	-24		-35		-45	-41	-48	-35	-37	-45	-38	-41	-28	-25	-24
temperature (°C)
Minimum dewpoint	-43		-58		-72	-76	-78	-77	-79	-74	-83	-65	-57	-35	-83
temperature (°C)
Precipitation (mm)	0		0		0	0	0	0	0	0	0	0	0	0	0

Instrument heights: wind, 10.0 m; pressure, 2841 m (MSL); air temperature, 2.0 m; dewpoint temperature, 2.0 m. Wind and temperature instruments are on a tower 91.4-m grid north-northwest of the Atmospheric Research Observatory.

*Maximum and minimum values are hourly averages.

Acknowledgment. We wish to thank Mark Bieniulis who was responsible for developing software for daily data transfers and automatic data analysis, his work in setting up networks at BRW and SMO, and his dedication to the CMDL meteorology program.

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