#1Daily mean 03 SAT (DU) R6 smooth R5 R6 smooth Cc1297 EUBREW NET TOTAL OZONE MEASUREMENTS AT ITALIAN BREWER STATIONS (ROME AND AOSTA) Siani A.M.1, Casale G.R.1, Pedone M.¹, Scarlatti F., Diémoz H.2 Sapienza Università di Roma; 2 Arpa Valle d'Aosta INTRODUCTION The availability of long-term records of total ozone content (TOC) and UV data represents a valuable source of information in studies on the assessment of short and long-term changes and their impact on terrestrial ecosystem. In addition, ground-based observations provide the ground-truth for satellite-derived products, mainly in polluted and in mountain areas where large uncertainties in space-borne estimates may be detected. To our knowledge, details about processing software packages applied to Brewer TOC measurements are usually not specified in studies on satellite vs ground-based comparisons and on the long term TOC variability. This study analyzes the differences between TOC data processed by the Brewer Processing Software (BPS, by Dr Fioletov and Ogyu of Environment Canada) and by O3Brewer (by Dr Stanek of Solar and Ozone Observatory of CHMI/International Ozone Service). The comparison of BPS and O3Brewer data with Ozone Monitoring Instrument (OMI). GROUND-BASED DATA (GB) Aosta (Brewer #066, 45.7°N, 7.4°E, 570 m asl): 29/01/2007-31/12/2015 Rome (Brewer #067, 41.9°N, 12.5°E, 75 m asl): 01/01/1992-31/12/2015 SATELLITE DATA (SAT) Aura OMI OMTO3(v8.5, L2 OVP): 01/10/2004-31/12/2015 (source: http://avdc.gsfc.nasa.gov) STATISTICAL METRICS USED IN THE COMPARISON A measure of the agreement is given by the following parameters: Spearman correlation (RHO), Mean Percentage Error (MPE%), Mean Bias (MB) Standard Deviation from MB, Root Mean Square Error (RMSE) and their normalized (%) values with respect to the TOC ground-based means. BREWER DS PROCESSING ALGORITHM Direct Sun TOC calculation DS= (MS(9)-ETC+(XR6-R6))/(Aα mu) MS(9)= double ratio; ETC= extra terrestrial constant; XR6 = value of R6 from the last calibration; R6= R6 ratio for the day; Aa = weighted ozone absorption coefficient, mu air mass. = - DS measurements were processed with the rejection criteria: measurement Max_DS_std = 2.5 DU (std=standard deviation), Max_mu = 4.0 in both software packages. Standard lamp (SL) correction: BPS adjusts the ETC based on the difference between SL test values at the time of the most recent calibration and the present values. It takes the average of SL-test values from 15 consecutive days since that calibration. 03Brewer adjusts the ETC using a smoothing filter (Gaussian, 20-days width) on SL ratios creating the SLsmooth file. R6 LO 4000 Rome Rome 400 4000 good ahomalous 300 calbrations 3000 200 2000 100 1000 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 1/1/1992-31/12/2015 0 -100 8000 -200 6000 good amalo calbrations 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 1/1/1992 31/12/2015 600 2000 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 1/1/1992-31/12/2015 500 3000 2500 2000 1500 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 1/1/1992-31/12/2015 5000 4000 good anomalous 3000 calibrations 2000 1000 2007 8000 400 300 200 03Brewer vs BPS. Rome R5 R6 good R5 R6 anomalous calibrations 03Brewer vs BPS, Rome 80 R5&R6 good calibrations good RS&R603brewer anomalous R5 R603brewer good R5 R6 BPS aromalis RS2R6 BPS 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 1/1/1992-31/12/2015 Aosta 400 300 Aosta 40 R5&R6 good R5&R6 anomalous calibrations 30 200 Diff (DU) 100 20 0 -100 10 2008 2009 2010 2011 2012 2013 2014 2015 2016 1/1/2007-31/12/2015 -200 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 1/1/2007 31/12/2015 Diff/DLIN Diff (DU) good 6000 anomalous calibrations 4000 2000 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 1/1/2007-31/12/2015 03(DU) 600 500 400 -10 good R5 R603brewer anomalous R5 R603brewer good RS&R6 BPS anomalous RS&R6 BPS -20 -30 Diff (DU) -20 -40 -60 -80 60 40 20 0 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016 1/1/1992 31/12/2015 03Brewer vs BPS, Aosta R5&R6 good calibrations 1900 1850 180, 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 1/1/2007-31/12/2015 Fig. 1: Daily R6 and R5 time series and R6 smoothed (from SLsmooth file created by O3Brewer software). SL correction is not applied by 03brewer when there are no SL measurements and when R6 and R5 values are above 400 units and 700 units, respectively in reference to the values of the last calibration. These are indicated as anomalous R5 and R6 values (red dots). Days without both R5 and R6 values are not considered. 300 200 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 1/1/2007-31/12/2015 Fig. 2: Differences (1st and 3rd panel) in daily TOC values between 03Brewer and BPS. The time series of TOC daily means processed with BPS and O3Brewer (2nd and 4th panel). -42007 2008 2009 2010 2011 2012 2013 2014 2015 2016 1/1/2007 31/12/2015 Fig. 3: Differences in TOC daily means between 03Brewer and BPS for good R6 and R5 values. TOC data with daily std>50 DU and without SL measurements, are excluded. Large differences (~10%) still persist between the two processed TOCs. MPE (%) MBE DU (%) RMSE DU (%) Rome 550 Daily SAT vs GB (R5&R6 good) 500 450 400 350 300 Daily mean 03 SAT (DU) 550 500 450 400 350 300 250 Rome + Daily SAT vs GB (R5&R6 good) Daily mean 03 SAT (DU) n RHO 03Brewer vs BPS Rome Rome 550 All data Daily SAT vs GB (R5&R6 good) Data with good R5 &R6 6453 0.919 5994 0.994 1.15 -0.18 3.60 (1.17) -0.56 (-0.17) 21.34 (6.53) 3.64 (1.11) 500 450 Aosta All data 400 Data with good R5 &R6 2315 0.982 2162 0.999 0.20 -0.04 0.47 (0.14) -0.16 (-0.05) 11.09 (3.39) 2.02 (0.62) 350 300 250 Table 1: Summary of the statistics 03Brewer vs BPS (n= number of pairwise measurements). Data with std >50 DU per day and without SL measurements, are excluded. In brackets the normalized values are in percentages (%). 250 Stand.dev. OMI_vs_GB (good R5 & R6) 200 200 200 200 250 300 350 400 450 500 550 200 250 300 350 400 450 500 550 n 200 250 300 350 400 450 500 550 TOC (BPS) (DU) TOC (103Brewer-BPS|<=2.5DU) TOC (03Brewer) (DU) Aosta 550 Daily SAT vs GB (R5&R6 good) 500 Aosta 550 Daily SAT vs GB (R5&R6 good) 500 Aosta 550 Daily SAT vs GB (R5&R6 good) 500 03Brewer BPS 2452 0.964 MPE RHO (%) Rome daily std ≤50 DU -0.76 MBE DU (%) from MBE RMSE DU (%) DU (%) 2449 0.978 -1.14 -2.56 (-0.80) -3.73 (-1.15) 8.49 (2.64) 7.26 (2.25) 8.87(2.75) 8.16 (2.52) daily std ≤2.5 DU 03Brewer BPS 693 0.976 692 0.980 -1.16 -3.62 (-1.17) -1.52 -4.71 (-1.52) 6.65 (2.15) 5.95 (1.92) 7.57 (2.45) 7.58 (2.45) daily std 50 DU 450 450 450 Daily mean 03 SAT (DU) 400 350 Daily mean 03 SAT (DU) 400 350 Daily mean 03 SAT (DU) 03Brewe-BPS ≤ 2.5 DU 1830 0.975 400 03Brewe-BPS ≤2.5 DU 540 0.976 350 -0.93 -3.11 (-0.96) daily std 2.5DU -1.30 -4.07 (-1.31) Aosta 7.64 (2.37) 8.25 (2.55) 6.38 (2.06) 7.56 (2.44) daily std ≤50DU 300 300 300 03Brewer BPS 1816 0.983 1815 -2.37 -7.76 (-2.36) 0.984 -2.41 -7.89 (-2.40) 7.23 (2.20) 6.98 (2.13) 10.60 (3.23) 10.53 (3.21) 250 250 250 daily std ≤2.5DU 200 200 250 300 350 400 450 500 550 200 200 03Brewer BPS 200 250 300 350 400 450 500 550 200 250 300 350 400 450 500 550 TOC(103Brewer-BPSI<=2.5 (DU)) TOC (03Brewer) (DU) TOC (BPS) (DU) 529 0.984 528 0.985 -2.40 -2.39 -7.28 (-2.37) -7.25 (-2.36) 6.08 (1.98) 5.92 (1.93) 9.48 (3.09) 9.36 (3.05) daily std ≤50 DU 03Brewer-BPS ≤ 2.5 DU 1718 0.984 Fig. 3: Scatter plots OMI vs ground-based TOC (03Brewer, on left panel; BPS on the central panel, on the right when |03brewer-BPS| ≤2.5) for R6 & R5 good and std <50 DU. |03Brewer-BPS ≤2.5 DU 527 0.984 -2.44 -7.92 (-2.43) daily std ≤2.5 DU -2.39 -7.27 (-2.37) 6.82 (2.09) 10.45 (3.20) 6.09 (1.98) 9.48 (3.09) Table 2: Summary of the statistics OMI vs ground based TOC (03Brewer and BPS). TOC were selected with std ≤50 DU and std ≤2.5DU per day (good R5 and R6 values). The comparison was also made with |03brewer-BPS| <2.5 DU. In brackets the normalized values in % . CONCLUSIONS This study analyzed the difference between total ozone column processed by two different software packages in Rome and Aosta. When anomalous SL values occurr, the smoothing filter correction in 03Brewer is not applied, producing TOC anomalies. The difference between BPS and O3Brewer can be less than 1% when R5 and R6 differ by about 20% with respect to the values of the last calibration. However, large differences (up to ~10%) can be still observed, probably due to the larger SL correction applied by BPS with respect to the smoothed correction of O3Brewer. In both sites, the comparison between OMI and ground-based data (taking into account data with good R5 and R6 values) shows a a systematic underestimation of satellite TOC, although some differences between the two processing software packges were found (sligthly higher if TOC data are processed with BPS). This result suggests that a standardized processing protocol (COST Action ES1207-EUBREWNET) is necessary to avoid the inconsistency in SL correction application between different Brewer data processing software packages. Alternately, users could use more than one package as a cross validation of own data. CC BY