UK Stratospheric UV Measurements

Various data checks and processes are applied to the spectral UV monitoring data before they are finalised.

Firstly, providing that the instrument is operating correctly within calibration, results of the 30 minute spectral scans are automatically uploaded to this web site as provisional Solar UV Index results on a daily basis. These are available in a tabular form and as daily UV index graphs clearly flagged as “Provisional” data.

Example of daily UV Index graph (Click to open)

On a daily basis further quality checks are carried out by Manchester University. These involve both manual inspection of the data and use of the SHICRIVM software. The SHICRIVM outputs a set of data flags which are then used to assign a data quality level of “Good”, “Moderate” or “Poor” to the results. The assessment of quality is based on diagnosis a number of criteria in the UV spectra such as light level, spikes and local anomalies. If the reviewed data set and associated quality flags are both available then the data are published on this web site as ratified with appropriate flagging information attached.

A quality flag is assigned to each individual spectral scan, and to the overall daily maximum Solar UV index value, based on the percentage of “good” values in each data set. The quality flags are presented alongside the graphs of daily and annual Solar UV index for the Reading monitoring site.

Example of Annual Solar UV Index graph with Quality Flags. (Click to open)

Only the ratified raw spectral data are made available for download by researchers from this web site. Measurements are carried out by Dr. Ann Webb and her team at the University of Manchester under a Defra funded contract. If the data are downloaded for research purposes then an acknowledgement of the project team and funding source (Defra) would be appreciated.