SBUV Ozone Profile Data INTRODUCTION These files contain ozone profile data from backscatter ultraviolet instruments on a series of 8 spacecraft. 1 = Nimbus 4 BUV 04/11/1970 - 05/06/1977 2 = Nimbus 7 SBUV 10/31/1978 - 06/21/1990 3 = NOAA 9 SBUV/2 02/02/1985 - 02/19/1998 4 = NOAA 11 SBUV/2 12/01/1988 - 03/27/2001 5 = NOAA 14 SBUV/2 02/05/1995 - 09/28/2006 6 = NOAA 16 SBUV/2 10/03/2000 - 12/31/2010 7 = NOAA 17 SBUV/2 07/11/2002 - 12/31/2010 8 = NOAA 18 SBUV/2 06/05/2005 - 12/31/2010 Data are given as daily files of individual measurements, and as zonal means. All data here are in ASCII format so they can be read on any platform. Data files containing much more detailed information are available from the Goddard DISC in HDF format. These data were the result of new (2011) processing. Radiance data from the different instruments were put on a consistent calibration scale for the version 8.6 reprocessing. THE OZONE MEASUREMENT All the spacecraft were in south-to-north, sun-synchronous polar orbits such that ozone measurements were taken for the entire world every 24 hours. SBUV is a nadir-viewing instrument with approximately a 200 kilometer (depending on orbit altitude) square field of view at the sub-satellite point. One measurement is made every 32 seconds along the orbital track, approximately every 1.8 degrees in latitude, from 80 degrees south to 80 degrees north. The initial orbit was always close to local noon/midnight but the NOAA spacecraft 9 to 16 experienced orbit drift such that they went through the terminator a few years after launch. Data too close to the terminator lose accuracy and are usually not usable for trend analysis. SBUV directly measures the ultraviolet sunlight scattered by the Earth's atmosphere at 12 wavelengths from 255 nm to 340 nm. Total column ozone is inferred using wavelengths longward of 312.5 nm, wavelengths that penetrate to the ground. Total ozone is calculated by taking the ratio of two wavelengths (312 nm and 331 nm, for example), where one wavelength is strongly absorbed by ozone while the other is absorbed only weakly. The ozone vertical profile is inferred from measurements from 255 nm through 306 nm, wavelengths which do not penetrate to the ground. The ozone cross section is higher at the shorter wavelengths and penetrations is less - 288 nm penetrates to about 38 km, while 255 nm penetrates only to 50 km. Thus, a wavelength scan is equivalent to an altitude scan. The profile inversion uses an optical statistical method to obtain ozone profiles from the measured radiances and from a priori information. For details see Bhartia et al. [1996]. The SBUV data in version 8.6 were reprocessed with an updated calibration to correct for instrument errors. The ozone cross sections of Brion, Daumnot, and Malicet were used. A cloud height climatology derived from Aura OMI inversions was used. Bhartia, P.K., R.D. McPeters, C.L. Mateer, L.E. Flynn, and C. Wellemeyer, Algorithm for the estimation of vertical ozone profile from the backscattered ultraviolet (BUV) technique, J. Geophys. Res., 101, 18793-18806, 1996. McPeters, R.D., P.K. Bhartia, A.J. Krueger, J.R. Herman, C.G. Wellemeyer, C.J. Seftor, G. Jaross, O. Torres, L. Moy, G. Labow, W. Byerly, S.L. Taylor, T. Swissler, and R.P. Cebula, Earth Probe Total Ozone Mapping Spectrometer (TOMS) Data Products User's Guide, NASA/TP-1998-206895, November 1998. THE DATA FILES The "zonal_means" directory contains files for each instrument of monthly average ozone for 5 degree latitude zones from 80 degrees south to 80 degrees north. The ozone is given in two forms. The format in each case is self explanatory. For example: MZM_lyr_N04.txt ozone in layers + total column ozone MZM_vmr_N04.txt ozone volume mixing ratios INDIVIDUAL MEASUREMENTS The very detailed level 2 data records available from the Goddard DISC have been "compressed" to give only the retrieved ozone profile as layer amounts in 12 levels from the ground to 0.4 hPa. The profiles are also given as mixing ratio at 15 standard pressure levels. (The data are not actually compressed - they just don't give all the ancillary information.) Each day all the individual measurements are given in a single file, 3 lines per measurement, ASCII format. The format is explained in the header in each file. example: pub/sbuv/Nimbus04/Y1970/sbuv_n04_19710102.txt Version 8.6 n04 SBUV data for day 002 1971 (1971/01/02) 746 :Number of records 1) year day sec-gmt Lat Lon SZA Total_Ozone Reflectivity Aerosol_Index Quality_residue Error_Flag 2) ozone (DU) in 13 layers -- pressure level at the bottom of each layer(atm): 1.000 0.0631 0.0400 0.0251 0.0158 0.0100 0.0063 0.0040 0.00251 0.00158 0.0010 0.00063 0.00040 3) ozone (PPMV) at 15 pressure levels(hPa): 0.5 0.7 1.0 1.5 2.0 3.0 4.0 5.0 7.0 10.0 15.0 20.0 30.0 40.0 50.0 1971 2 69 4.39 175.56 27.77 251.0 0.309 2.6 0.117 0 35.78 17.58 37.06 48.699 47.070 31.751 16.831 8.930 4.312 1.771 0.7077 0.2950 0.2295 1.507 2.023 2.847 4.294 5.624 7.292 8.094 8.787 10.203 10.987 9.118 6.729 3.628 1.914 0.972 1971 2 101 6.17 175.11 29.57 257.0 0.247 2.1 0.072 0 41.87 20.46 40.73 48.574 43.114 29.035 16.834 9.247 4.259 1.700 0.6851 0.2909 0.2303 1.488 1.972 2.737 4.128 5.523 7.521 8.425 8.885 9.549 9.863 8.528 6.696 3.957 2.188 1.134 1971 2 197 11.50 173.76 34.98 249.5 0.142 3.7 0.046 2 46.67 22.53 40.63 43.446 36.925 26.753 16.807 8.925 3.905 1.619 0.7056 0.3145 0.2510 1.615 2.082 2.736 3.848 5.040 7.149 8.383 8.936 9.151 8.663 7.281 5.958 3.893 2.312 1.256 1971 2 293 16.82 172.38 40.39 244.0 0.129 3.2 0.053 0 ERROR FLAGS Word 11 of each daily measurement is an error code. The profile ozone error flag: 0 = good retrieval 1 = SolarZenithAngle > 84 degrees 2 = absolute value of (TotalO3 - ProfileTotalO3) > 25 DU 3 = average absolute value of NValueResidualsFinal > 0.20 N-value 4 = absolute value of NValueResidualsFinal at any wavelength > (3 * InstrumentError * 43.4294) 5 = absolute value of (ProfileO3Retrieved/ProfileO3APrioriLayer - 1) in any layer > (3 * APrioriError) 6 = non-convergent solution 7 = upper level profile anomaly 8 = NValueResidualsInitial at any wavelength greater than 18.0 N-value units 9 = total ozone algorithm failure (first guess not available) The value of this flag is increased by 10 for descending orbit data. The value of this flag is increased by 100 (or 200) during broad periods of lesser quality data such as after a major volcanic eruption. OVERPASS DATA SBUV data for selected individual ground sites is included in the overpaas directory for each satellite. Since the SBUV orbit spacing is 26 degrees in longitude, the overpass ozone given is a distance weighted average. Again the ozone is given in two forms, layer amounts and ozone mixing ratio. example: pub/sbuv/Nimbus04/overpass/o3du_n04/nimbus04_sbuv2_l2ovp_o3du_v8.6_arosa_035.txt Arosa, Switzerland OVPID: 035 Latitude: 46.780 deg. Longitude: 9.680 deg. Altitude: 1840 m Value 1 (year) : Year Value 2 (mon) : Month Value 3 (day) : Day Value 4 (doy) : Day of Year Value 5 (time) : Weighted time of overpass (seconds UT) Value 6 (dist) : Weighted distance to station (km) Value 7 (#pts) : Number of points used in overpass Value 8 (sza) : Average satellite solar zenith angle Value 9 (ptoz) : Profile total ozone (Dobson Units) Value 10-30 : Layer ozone amount (DU) for 21 layers Layer Bottom Pressure (hPa) 1013.25 639.3 403.4 254.5 160.6 101.3 63.9 40.3 25.5 16.1 10.1 6.39 4.03 2.55 1.61 1.01 0.639 0.403 0.254 0.161 0.101 year mon day doy time dist #pts sza ptoz L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 L13 L14 L15 L16 L17 L18 L19 L20 L21 1970 04 11 101 39129 440.2 8 39.6 438.7 16.72 12.34 15.22 32.64 47.57 53.83 66.36 61.75 44.92 32.69 23.63 15.70 8.53 3.79 1.62 0.727 0.331 0.150 0.067 0.030 0.024 1970 04 12 102 36367 462.9 8 38.7 447.2 15.76 12.91 16.15 34.99 50.62 56.20 67.75 61.48 44.46 33.01 23.98 15.29 7.95 3.59 1.62 0.759 0.352 0.159 0.071 0.032 0.025 1970 04 13 103 37762 927.4 16 37.3 419.1 15.83 11.93 14.66 31.24 44.89 50.34 62.53 59.08 43.83 32.36 23.31 14.93 7.78 3.49 1.55 0.720 0.334 0.152 0.069 0.031 0.025 1970 04 15 105 37766 1020.2 16 37.1 402.6 14.73 11.91 14.59 30.72 43.56 47.98 58.19 54.28 41.25 32.22 24.05 15.13 7.72 3.47 1.53 0.703 0.324 0.148 0.067 0.030 0.025 1970 04 16 106 38218 169.6 8 37.7 386.9 13.53 10.89 12.94 26.70 37.77 42.85 55.36 55.38 43.59 33.46 24.32 15.45 8.08 3.64 1.60 0.730 0.336 0.152 0.069 0.031 0.025 1970 04 17 107 37760 941.7 16 34.6 377.2 14.62 10.52 12.41 25.40 35.84 40.76 53.03 53.83 43.21 33.50 23.97 15.05 8.26 3.89 1.65 0.711 0.316 0.142 0.064 0.029 0.025 1970 04 18 108 39123 437.4 8 36.0 351.8 13.32 10.05 11.67 23.50 32.82 37.17 48.34 49.01 39.25 31.18 24.22 16.34 8.42 3.60 1.57 0.734 0.343 0.157 0.071 0.032 0.026 1970 04 19 109 36361 456.4 8 35.1 352.0 11.66 9.20 10.44 20.71 29.34 35.12 49.40 54.03 44.82 33.73 23.07 14.86 8.57 4.03 1.69 0.726 0.322 0.144 0.065 0.030 0.025 1970 04 20 110 37763 931.5 16 35.5 441.6 19.76 15.27 18.77 38.68 52.05 52.74 59.25 54.14 42.51 33.56 24.01 15.14 8.58 4.10 1.73 0.736 0.323 0.144 0.065 0.030 0.025 PROBLEMS WITH THE DATA Coverage: Because the instruments are nadir viewing and the satellites are in an inclined orbit, data are only taken from 80 degrees south to 80 degrees north. The orbits are spaced 26 degrees apart in longiude. Polar Night: Because SBUV measures ozone using scattered sunlight, it is not possible to measure ozone when there is no sun (in the polar regions in winter). Consequently there will always be areas of missing data at high latitudes due to polar night. INTERNET SERVICES NASA/Goddard Space Flight Center's Laboratory for Atmospheres has a Web Site devoted to Atmospheric Science. This site titled: Space Based Measurements of Ozone and Air Quality in the Ultraviolet and Visible contains information on ozone and other parameters including reflectivity, aerosol index, SO2 and NO2. The URL address of this site is: http://ozoneaq.gsfc.nasa.gov Direct access to SBUV data is available via an anonymous FTP account: ftp toms.gsfc.nasa.gov. logon: anonymous password: your e-mail address cd pub/sbuv (This is the best way to quickly download a large number of files.) CONTACT Dr. Richard McPeters (science) NASA Goddard Space Flight Center, Code 614 Greenbelt, Maryland 20771 USA richard.d.mcpeters@nasa.gov