Volodya Savastiouk 13 th Brewer User Workshop. Beijing, China September 12-16, 2011 Brewer calibrations: what do they accomplish? Volodya Savastiouk International Ozone Services Inc. Full Spectrum Science Inc.

Volodya Savastiouk 13 th Brewer User Workshop. Beijing, China September 12-16, 2011 Why do Brewers need calibrations? What is done during calibrations? Recommended calibration frequency. Presentation outline:

Volodya Savastiouk 13 th Brewer User Workshop. Beijing, China September 12-16, The most important aspect of Brewer calibrations: maintaining the same ozone reference for all Brewers a)The world’s reference for Brewers is the triad of Brewers in Toronto b)Traveling reference Brewers with the triad either directly in Toronto or using traveling references #017 and #145 2.Keeping the Brewers in working condition and fixing what’s broken 3.Measuring Brewer characterization parameters a)Dead time, dispersion, UV response, ND filters b)Optimal high voltage, SL power 4.Training and educating local personnel Why do Brewers need calibrations?

Volodya Savastiouk 13 th Brewer User Workshop. Beijing, China September 12-16, 2011 Extra Terrestrial Coefficients (ETC): Only a few Brewers are in locations that allow reliable absolute calibrations using the Langley extrapolation technique (Mauna Loa, Izana); the majority of instruments require comparisons with calibrated Brewers for establishing the ETC. Why do Brewers need calibrations? Remember how ozone is calculated in the Brewer software? X=(R6-ETC)/(a*mu) Measured CalEstablished CalEstablished Calculated Ozone absorption coefficient (a): established using the results of the dispersion test and the laboratory-measured ozone cross-sections.

Volodya Savastiouk 13 th Brewer User Workshop. Beijing, China September 12-16, 2011 What is done during calibrations? 1.Initial comparison with the traveling standard (if the Brewer is working) Analysing available historical data Collecting solar/sky data side-by-side with the standard Applying the necessary corrections to the ozone calculations 2. Brewer inspection/maintenance Tracker plate, micrometers, push rod, etc. The extent of this is based on the history of the Brewer 3.Characterization tests Dispersion, UV response, ND filters, dead time 4.Final comparison with the standard Adjusting the ETC if needed

Volodya Savastiouk 13 th Brewer User Workshop. Beijing, China September 12-16, 2011 Data evolution Calibration ETCSL ratio R6cal Run/Stop Dead Time Steps per revolution High voltage Data collection: 1.Observations 2.Tests 3.Notes (log-file)

Volodya Savastiouk 13 th Brewer User Workshop. Beijing, China September 12-16, 2011 Red marks indicate that the Run/Stop test was not ideal Any individual test result does not necessarily describe the state of the instrument. Looking at the historical record is a much more reliable way to diagnose a Brewer. Overall, this instrument is working fine.

Volodya Savastiouk 13 th Brewer User Workshop. Beijing, China September 12-16, 2011 A calibration visit and maintenance improved the RS results

Volodya Savastiouk 13 th Brewer User Workshop. Beijing, China September 12-16, 2011 o3 DEADTIME TEST AT 03:46:45, sep 08, 07 Deadtime (ns) for filter position 0 (high intensity) E-08 (at 03:47:05) E-08 (at 03:47:26) E-08 (at 03:47:46) E-08 (at 03:48:06) E-08 (at 03:48:26) Mean = Std Dev =.7 Deadtime (ns) for filter position 1 (low intensity) E-08 (at 03:49:07) E-08 (at 03:49:27) E-08 (at 03:49:47) E-08 (at 03:50:07) E-08 (at 03:50:27) E-08 (at 03:50:47) E-08 (at 03:51:07) E-08 (at 03:51:27) E-08 (at 03:51:47) E-08 (at 03:52:07) Mean = Std Dev = 1.8

Volodya Savastiouk 13 th Brewer User Workshop. Beijing, China September 12-16, 2011 Dead time slowly changed from 34 ns to 32 ns

Volodya Savastiouk 13 th Brewer User Workshop. Beijing, China September 12-16, 2011 Look for sudden changes in the SL test results

Volodya Savastiouk 13 th Brewer User Workshop. Beijing, China September 12-16, 2011 A/D Values for sep 09/07 at 00:24:56 for instrument number ### Channel# Name Value Value (Lamps off) (Lamps on) 0 Brewer temp 1 (deg C) Brewer temp 2 (deg C) Brewer temp 3 (deg C) H.T. voltage (V) V power supply (V) V power supply (V) V power supply (V) V power supply (V) Rate meter (kc/s) Not used (bits) Not used (bits) Not used (bits) V ss (V) V ss (V) Std lmp current (A) Std lmp voltage (V)

Volodya Savastiouk 13 th Brewer User Workshop. Beijing, China September 12-16, 2011 Sun scan test – final wavelength setting for the Brewer Cal.step

Volodya Savastiouk 13 th Brewer User Workshop. Beijing, China September 12-16, 2011 Data evolution CalibrationDS ozone observations SL tests ETC Real-time ozone values SL-corrected ozone values SL ratio R6cal ETC*=ETC+(R6-R6cal) Calibration ETCSL ratio R6cal

Volodya Savastiouk 13 th Brewer User Workshop. Beijing, China September 12-16, 2011 Data evolution Calibration Observation Calibration Observation When to do maintenance to preserve calibration history? Calibration

Volodya Savastiouk 13 th Brewer User Workshop. Beijing, China September 12-16, 2011 Recommended calibration frequency This is a difficult one. From our experience, a calibration every two years is enough for most Brewers. However, we definitely see the most stability with Brewers that are visited every year. Historical data are often a good indicator on whether the Brewer may benefit from annual calibrations. Of course, all of this is based on the assumption that regular normal maintenance is done to the Brewer between the calibration visits, but that’ll be the topic of another talk.

Volodya Savastiouk 13 th Brewer User Workshop. Beijing, China September 12-16, 2011 In order to maintain (and improve) the quality of the Brewer ozone data regular calibration and maintenance visits are required. It is extremely important to keep the Brewer network traceable the the main Brewer reference, the triad. Conclusions:

Volodya Savastiouk 13 th Brewer User Workshop. Beijing, China September 12-16, 2011 Thank you! Eureka, Canada, February 2011