Longterm Multi-Sensoral UV Record

Longterm Multi-Sensoral UV Record

Validation of Daily Maximum UV Index

The satellite-retrieved Daily Maximum UV Index over the period July 1983 to June 2007 were compared to ground-based measurements at five European sites. In order to mask out winter days with very low sun we applied a threshold filter 0.5 to the Maximum UV Index, so that only UVI exceeding that value were included in the validation analysis. The results detailed in the table beneath show that the bias in Daily Maximum UV Index varies among the stations. In Jokioinen and Sodankyla mean bias is about +10% while the median bias is small. In Bilthoven mean bias is -7% and median bias is -13%. In Lindenberg mean bias is -15% and median bias is -19%. In Thessaloniki mean bias is +21% and the median bias is +12%.

Table 1. Results of the statistical error analysis. Numbers in table cells are also links to correspoding figures (link opens in new window)
Station
 mean bias
 median bias
 std
 W20
Sodankyla
 11%
 1%
 0.37
 71%
Jokioinen
 10%
 0%
 0.45
 69%
Bilthoven
 -7%
 -13%
 0.36
 54%
Lindenberg
 -15%
 -19%
 0.28
 45%
Thessaloniki
 21%
 12%
 0.47
 61%

In addition to this summarizing table, we include some illustrative figures of the validation results at each station. These figures show, for instance, how some of the daily errors are averaged out when looking at longer periods: the performance for the monthly mean values is clearly better than for daily values, indicating that the method has potential to serve as an information source for time series studies.

Look at the figures for the validation of satellite daily data data against ground based instruments:


Satellite data against ground-based instruments:

SODANKYLA

 UVISodankyla_scatter.png
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JOKIOINEN

 UVIJokioinen_scatter.png
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BILTHOVEN

 UVIBilthoven_scatter.png
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LINDENBERG

 UVILindenberg_scatter.png
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THESSALONIKI

 UVIThessaloniki_scatter.png
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Jussi Kaurola, 31 August 2009