Previous UV Bulletin

Bulletin 6/2003, issued 11/26/03
Reporting period: 11/10/03 - 11/24/03

Synopsis:
The 2003 ozone hole had almost disappeared by 11/17/03, but ozone values below 200 DU were again observed in Antarctica during the last few days. UV levels at McMurdo and Palmer were generally below the long-term means as the three sites were outside the area of the ozone hole during most of the period. UV levels at the South Pole and Ushuaia fluctuated around the mean. A solar eclipse could be observed at McMurdo, South Pole, and Palmer. Radiation levels during the period of maximum eclipse dropped by over 90%.

As of 11/24/03, areas with total ozone below 220 DU still exist. TOMS satellite images indicate that the ozone hole's remnants are close to Palmer Station. We expect the UV Index to exceed 9 during the next days should this region of ozone depleted air move over Palmer Station.

McMurdo Station, Antarctica:
UV levels measured at McMurdo were below the long-term mean during most of the reporting period. An exception is the period 11/21/03 - 11/23/03, when the ozone hole passed over the station. During these three days, the maximum daily UV Index reached 5.0, while it was below 3.7 for the rest of the period. The long-term average is 3.6, and the highest UV Index historically observed during this period is 7.1, measured on 11/24/99.

On 11/23/03, a partial solar eclipse was visible at McMurdo. The moon started to block the sun at 22:09 UT. The time of maximum eclipse was 23:07, when approximately 77% of the sun's disk was blocked. Radiation levels during this time were 20% of the levels observed before the eclipse's start. Some of the reduction can also be associated with changes in cloud cover.

Palmer Station, Antarctica:
Palmer was outside the area of the ozone hole during the entire reporting period. UV levels were consequently below the long-term mean. The maximum daily UV Index ranged between 2.4 and 6.1. The long-term average and highest UV Index historically observed during this period are 5.3 and 12.9, respectively.

The partial solar eclipse could also be observed at Palmer. The peak coverage occurred on 11/24/03 shortly after 00:00 UT when approximately 64% of the sun's disk was blocked. Reduction in UV occurred at low radiation levels as the eclipse took place shortly before sunset.

South Pole, Antarctica:
UV levels measured at the South Pole fluctuated around the long-term mean. The UV Index ranged between 1.4 and 2.3. Long-term average and maximum UV Index for the reporting period are 2.0 and 3.3, respectively.

On 11/23/03, radiation levels were reduced by a partial solar eclipse. The moon started to block the sun at 22:24 UT. The time of maximum eclipse was 23:18, when approximately 88% of the sun was blocked. The end of the eclipse was on 11/24/03 00:12. Radiation levels during this time were 8-9% of the levels observed immediately before the eclipse's start. There was little influence by clouds during the entire period.

The plot below shows the UV Index measured by GUV-541 and SUV-100 during the time of the eclipse.

Ushuaia, Argentina:
Ushuaia was located outside the area of the ozone hole during the entire period. UV levels fluctuated around the long-term mean, with maximum daily UV Index values ranging between 2.6 and 7.3. The long-term average and maximum UV Index for the reporting period are 5.8 and 10.5, respectively.

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