NSF UV SPECTRORADIOMETER NETWORK 2002-2003 OPERATIONS REPORT
7.3. Amundsen Scott South Pole Station
The Antarctic “ozone hole” in the austral fall of 2002 was one of the smallest since 1988. The maximum
total area in late September was about 19 million km2, which is considerably less than the area of 26.5
million km2 observed in 2001. The ozone hole was virtually gone by late-October, one of its earliest
disappearances since more than a decade. The small size and early disappearance can be attributed to the
occurrence of a comparatively large number of “planetary waves”, which lead to a warming of the lower
stratosphere. Warmer stratospheric temperatures lead in turn to a lower frequency of Polar Stratospheric
Clouds, which help to transform inactive forms of chorine to ozone-destroying active forms. It should be
pointed out that the small hole in 2002 is not an indication that the ozone layer is recovering. The small
size is rather caused by an unusual global weather pattern in 2002.
The ozone hole was centered at the South Pole between 10/12/02 and 10/22/02. This is the only period in
2002 when ozone levels were close to average (Figure 7.3.1). October 25th was the last day in 2002 with
ozone levels below 220 Dobson Units.
UV levels at the South Pole were the lowest on record for almost the entire season. This can be seen at all
wavelength intervals affected by ozone, including the 298.51 - 303.03 nm integral (Figure 7.3.2), erythemal
irradiance (Figure 7.3.3), DNA-weighted daily dose (Figure 7.3.4), and erythemal daily dose
(Figure 7.3.5). The only period with close-to-average UV levels is the period between 10/15/02 and
10/24/02. This is the time when the center of the ozone hole was located over the South Pole.
Radiation in the visible is only marginally affected by total ozone. As the influence of clouds is small at
the South Pole, daily doses measured in the visible during the Volume 12 period should be similar to
historic observations. Yet Figure 7.3.6 suggest that measurements from 2002 are somewhat lower than
typical. This is caused by the upgrade of the radiometer’s collector in January 2000 (see Volume 10
Operations Report). Before the modification, the instrument’s angular response exhibited an azimuth
asymmetry, which was substantially reduced by the upgrade. Daily doses in the visible from the years
2000, 2001, and 2002 agree to within few percent (see Section 5.3), and the main bias seen in Figure 7.3.6
is between data sampled before and after the collector modification. The effect of this modification on
solar data is described in more detail in the introduction to Section 5. We are planning to reprocess our
entire data set to remove the step change. See Bernhard et al. (2003) for details.
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BIOSPHERICAL INSTRUMENTS INC.
CHAPTER 7: EXAMPLES OF NETWORK DATA
500
South Pole: Total Column Ozone
450
Total Column Ozone (DU)
400
350
300
250
200
150
1991-2001
100
Average 1991-2001
50
0
1-Sep
2002
21-Sep
11-Oct
31-Oct
20-Nov
10-Dec
30-Dec
Date
Integrated Spectral Irradiance (µW/cm²)
Figure 7.3.1. Total column ozone at South Pole. TOMS/Earth Probe measurements from 2002 are
contrasted with ozone data from the years 1991-2001 recorded by TOMS /Nimbus-7(1991-1993),TOMS/
Meteor-3 (1993-1994), NOAA/TOVS (1995-1996), and TOMS/Earth Probe (1997-2001) satellites.
September data are from NOAA/TOVS measured in 1995 and 1996.
2
South Pole: 298.507 - 303.03 nm Integrated Spectral Irradiance
1991-2001
Average 1991-2001
1.5
2002
1
0.5
0
1-Sep
21-Sep
11-Oct
31-Oct
20-Nov
10-Dec
30-Dec
Date
Figure 7.3.2. Noontime integrated spectral UV irradiance (298.51 - 303.03 nm) at South Pole.
Measurements from 2002 (squares) are contrasted with individual data points and the average of
measurements taken between 1991 and 2001.
BIOSPHERICAL INSTRUMENTS INC.
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NSF UV SPECTRORADIOMETER NETWORK 2002-2003 OPERATIONS REPORT
10
South Pole: Erythemally (CIE) Weighted Irradiance
Erythemal Irradiance (µW/cm²)
9
1991-2001
8
Average 1991- 2001
7
2002
6
5
4
3
2
1
0
1-Sep
21-Sep
11-Oct
31-Oct
20-Nov
10-Dec
30-Dec
Date
Figure 7.3.3. Erythemally (CIE) weighted irradiance at South Pole. Measurements from 2002 (squares)
are contrasted with individual data points and the average of measurements taken between 1991 and 2001.
DNA-Weighted Daily Dose (kJ/m²)
0.14
0.12
0.1
South Pole: DNA-Weighted Daily Dose
1991-2001
Average 1991-2001
2002
2003
0.08
0.06
0.04
0.02
0
1-Jan
20-Feb
10-Apr
30-May
19-Jul
7-Sep
27-Oct
16-Dec
Date
Figure 7.3.4. Daily DNA-weighted dose at South Pole. Volume 12 measurements from 2002 and 2003 are
contrasted with individual data points and the average of measurements taken between 1991 and 2001.
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BIOSPHERICAL INSTRUMENTS INC.
CHAPTER 7: EXAMPLES OF NETWORK DATA
8
South Pole: Erythemally (CIE) Weighted Daily Dose
Erythemal Daily Dose (kJ/m²)
7
1991-2001
Average 1991-2001
2002
2003
6
5
4
3
2
1
0
1-Jan
20-Feb
10-Apr
30-May
19-Jul
7-Sep
27-Oct
16-Dec
Date
Figure 7.3.5. Daily erythemal dose at South Pole. Volume 12 measurements from 2002 and 2003 are
contrasted with individual data points and the average of measurements taken between 1991 and 2001.
Daily 400-600 nm Integrated Irradiation
(kJ/m²)
14000
South Pole: 400 - 600 nm Integrated Irradiation
12000
10000
1991-2001
8000
Average 1991-2001
2002
6000
2003
4000
2000
0
1-Jan
20-Feb
10-Apr
30-May
19-Jul
7-Sep
27-Oct
16-Dec
Date
Figure 7.3.6. Daily irradiation of the 400-600 nm band at South Pole. Measurements from 2002 - 2003
are contrasted with individual data points and the average of measurements taken between 1991 and 2001.
BIOSPHERICAL INSTRUMENTS INC.
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