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Brewer Workshop Beijing May 15 Brewer Worshop – Beijin R EGIONAL B REWER C ALIBRATION C ENTER - E UROPE Alberto Redondas Marrero Virgilio Carreño Sergio Afonso Juan José Rodriguez Franco Fernando Almansa Marta Sierra Izaña 2011

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Brewer Workshop Beijing May 15 1.Introduction 2.Ozone algorithm 3.Ozone Filter Correction 4.Methods for Filter issues detection and correction determination AEMET, Agencia Estatal de Meteorología 2 Brewer Workshop Beijing May 15 Attenuation filter issues in brewer ozone calculations

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No linearity of the attenuation filter is a know issue on the brewer ozone calculation (see for example Volodya Savastiouk Phd Thesis 2008) 08/05/201526/01/2008 AEMET, Agencia Estatal de Meteorología 3

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weights w i : –1, +0.5, +2.2, and –1.7 Wavelengths : 310, 313, 317, and 320nm. Fo : extraterrestrial count rates. F : measured count rates P 0,p : standard surface air pressure /average station air pressure SCAi : molecular scattering optical depths for each wavelength I at po. O3i : ozone absorption optical depths for each wavelength i. AMF SCA : direct sun air mass factors for molecular scattering AMF O3 : direct sun air mass factors for ozone absorption respectively. R is the Earth’s radius (6370km) h EFFx is the effective layer height. ( It is set to h EFFSCA =5km and h EFFO3 =22km.

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Brewer Workshop Beijing May 15 In a ideal brewer the ozone do not depend of the attenuation filter. 1.Attenuation Filters are “neutral” 2.Nominal wavelengths and weights verify : If the attenuation is linear with wavelength, do not affect the ozone calculation. AEMET, Agencia Estatal de Meteorología 5 Brewer Workshop Beijing May 15

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Attenuation Filter : Ozone Algorithm Ozone SAG Helsinki -2009

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Brewer Workshop Beijing May 15 Attenuation Filters : In a real instrument a)the filters can not be neutral b)Even if there are linear with wavelengths If the slope is to big you see the effect in the ozone. AEMET, Agencia Estatal de Meteorología 7

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Filter Brewer Calibration Ozone SAG Helsinki -2009

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Brewer Workshop Beijing May 15 AEMET, Agencia Estatal de Meteorología 9

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Brewer Workshop Beijing May 15 The effect can be accounted using a ETC correction for the affected filter. If you know the attenuation of every wavelengths The correction in can be implemented as the ussual Standard Lamp correction. AEMET, Agencia Estatal de Meteorología 10

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Brewer Workshop Beijing May 15 Determination of the ETC correction a)Internal test using Direct Sun b)Filter wavelength dependence a)FI.RTN, FWTEST b)AT.RTN c)Calibration d)Langley AEMET, Agencia Estatal de Meteorología 11

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Brewer Workshop Beijing May 15 Internal Test This procedure check on the data record if one particular brewer is affected by this issue and estimate the correction. We look in to the ozone differences in simultaneous measurement performed with different filter Requires a long record (one year) of ozone measurement without changes on the instrument calibration With for example Martin Stanek’s O3Brewer produce a report with include : Date, time,filter, airmass, ozone, MS9 Select simultaneous measurements (10 min, airmass <0.05), performed with different filter. Look for significant differences on the statistics from f#3 to f#4, ( you have only significance for high air mass) AEMET, Agencia Estatal de Meteorología 12

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Brewer Workshop Beijing May 15 AEMET, Agencia Estatal de Meteorología 13

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Brewer Workshop Beijing May 15 AEMET, Agencia Estatal de Meteorología 14

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Brewer Workshop Beijing May 15 Filter Characterization : FI.RTN % IOS description of the fi test output in fioavg.\#\#\# file % (created by V. Savastiouk) % % date Te AF CY N Slit0 std Slit1 std Slit2 std Slit3 std Slit4 std Slit5 std % % % % % % % % Te - temperature, % AF - FW2 position, % CY-number of cycles for that AF % N - number of repetition (fi does several loops one inside the other and N % is the outer most loop). % Slit0-6 are the values for the attenuations, except for AF=1 Ozone SAG Helsinki -2009

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Brewer Workshop Beijing May 15 Filter Characterization : FI.RTN AEMET, Agencia Estatal de Meteorología 16 filter #1filter #2filter #3filter #4filter #5 slit # slit # slit # slit # slit # slit # mean

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Brewer Workshop Beijing May 15 filter #1filter #2filter #3filter #4filter #5 ETC Filt. Corr. (median) ETC Filt. Corr. (mean) ETC Filt. Corr. (CI) ETC Filt. Corr.(CI) AEMET, Agencia Estatal de Meteorología 17

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Brewer Workshop Beijing May 15 Comparison with other instrument AEMET, Agencia Estatal de Meteorología 18

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Brewer Workshop Beijing May 15 Comparison with other instrument AEMET, Agencia Estatal de Meteorología 19

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Brewer Workshop Beijing May 15 Langley AEMET, Agencia Estatal de Meteorología 20

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Brewer Workshop Beijing May 15 AEMET, Agencia Estatal de Meteorología 21

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Brewer Workshop Beijing May 15 AEMET, Agencia Estatal de Meteorología 22

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Brewer Workshop Beijing May 15 Langley Langley determination of the ETC correction AEMET, Agencia Estatal de Meteorología 23

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Brewer Workshop Beijing May 15 #185 FI results AEMET, Agencia Estatal de Meteorología 24 F1 F2 F3 F4 F5 Median Mean ci ci

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Brewer Workshop Beijing May 15 Attenuation Filter Check Brewer Calibration Ozone SAG Helsinki MethodContras FIRequires a large number of measuremetns ATNeed evaluation Reference Comparison Error in reference Internal comparison Enough data during intercomparison ? ETC calculationFilter & airmass are correlated, sometimes regression fail

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Brewer Workshop Beijing May 15 Filter TODO LIST Explain de difference langley- FI Evaluate the performance of AT routine Evaluate for every instrument Dead Time – Filter dependence Brewer Calibration Ozone SAG Helsinki -2009

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Brewer Workshop Beijing May 15 Recommendations: When produce the summary of your data, don`t forget to store the filter. Introduce the FI routine in your schedule, at the end of the day. AEMET, Agencia Estatal de Meteorología 27

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Brewer Workshop Beijing May 15 Apendix AEMET, Agencia Estatal de Meteorología 28

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Brewer Workshop Beijing May 15 AEMET, Agencia Estatal de Meteorología 29

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