Inter-comparisons of the V8 SBUV instruments (Nimbus 7, NOAA 9, 11, and 16): Time, Altitude and Latitude dependency

The weekly zonal mean data sets with ± 2.5 degree interval are used to make time series plots of the ratios of retrieved to a priori layer ozone (in Dobson Units). The figure below is the selected plot with four altitudes (21 km, 30 km, 37 km, and 50 km) at the Equator latitudinal zone. Instruments are distingushed with colors (red: N7, black: N9, Green: N11, and Blue: N16) (Click on the figure below for the full size version). The midpoint pressures of V8 SBUV 20 layers are converted to logarithm-scale standard altitude in km using a scale height of 7 km. The V8 a priori has an annual cycle and annual mean that vary with altitude (approx. 5 km layers) and latitude (10 degree band), but has no inter annual or long-term variability. Therefore, these ratio plots can demonstrate the both V8 algorithm retrieval performance as well as possible instrument problems.

Quasi-Biennial Oscillation (QBO) cycles are found in lower layers in 21 km - 24 km at the Equator. Volcanic effects in 1982 and 1991 are also seen at 30 km at the Equator. In general, most of instruments are matched up well during the overlapped time periods within ± 8 % except for early years of N9 (pre 1993 not on plots, but on DVD) due to the unsolved instrument performance issues. Mismatched alignment among instruments also has latitude and altitude-dependency, particularly in the southern hemisphere.

The APPENDIX contains other latitudes and altitude versus latitude contour plots of instrument offsets in the overlaps.

Profile Quality Checking : the Percent Occurrence of Good Profiles

The figure below shows percentage of profiles with error code of 0 (good retrieval) and 1(solar zenith angle greater than 84 degree) per scan for each day. The significant decrease in N7 is during the non-synch period, decrease in N9 and N11 is due to grating drive problems and all N11 1995 data at high solar zenith angles.

V8 SBUV Profile Total Ozone Comparison with Dobson Stations in the Northern Hemisphere

The profile total ozone is more reliable and less wavelength-dependent errors than conventional TOMS-like total ozone product. The matched-up V8 SBUV profile total ozone data are averaged on a weekly basis and compared with ground-based Dobson total ozone measurements from 40 stations in the northern hemisphere. The smoothed data with 15 points running average are shown as solid lines for each instrument. V8 SBUV profile total ozone is slightly higher up to 2 % (~ 6 D.U) than Dobson total ozone, but has no significant long-term trends. (Click on the figure below for the full size version).

Seasonal Variations of Layer Ozone over Lauder New Zealand (45S, 170E)

The figure below is to show seasonal variations and cycles over Lauder New Zealand (45S,170E) at four altitudes. All available matched-up samples (n=872) for the N11 time period are used to make these plots. Thick red lines are smoothed microwave data with 7 points running average. Blue lines are smoothed V8 SBUV data with 7 points running average. A dynamic transport from ozone rich air in tropics builds up the maximum ozone in late winter and early spring in lower stratosphere at 24 km. A typical annual cycle (maximum in summer and minimum in winter) is shown in middle stratosphere at 34 km. In upper stratosphere above 43 km, a winter (June, July, August) ozone maximum is dominant due to the reduced ozone destruction rate. The V8 SBUV data agree well with the microwave data in terms of both offset and seasonal cycle variation. This result is consistent with SAGE II, lidar, and sonde comparison results by Brinksma et al. [2002]

Time Series of Microwave to V8 SBUV Layer Ozone over Mauna Loa(20N, 156W)

The figure below is the time series analysis of the ratio of microwave to V8 SBUV layer ozone over Mauna Loa (20N, 156W). Three solid lines are the linear regression fits for the time periods of N09 (Jul. 1995 - Jul. 1997), N11(Jul. 1997 - March 2001), and N16 (Oct. 2000 - Nov. 2002), respectively at four altitudes. Mauna Loa is a good site to do intercomparison because it is not only the primary Network for the Detection of Stratospheric Change (NDSC) station for the tropics and subtropics, but also shows a low ozone variability that minimizes the uncertainty caused by the fact that not exactly the same air volume is measured by every instrument [McPeters et al., 1999]. This plot does not show any significant trend for this short-term period (7 and 1/2 years), and also demonstrates a good agreement between SBUV instruments in the overlaps except in N09 time period coincidences at 37 km. Nevertheless, the linear regression fits have no significant slope larger than the standard deviation (numbers not shown here) as Tsou et al. [2000] described.

Mean Profile Differences (%) between V8 SBUV and Ground Measurements (Microwave, Lidar and Sonde)

The V8 SBUV profile ozone data are validated using ground-based data (microwave, lidar, and sonde) with independent calibrations and derivation methods at various locations around globe. Microwave and lidar data are available from NDSC . Ozonesonde data are archived in World Ozone and Ultraviolet Radiation Data Center(WOUDC). The first two initials of the names of stations are used as legends on the plots as follows;

Microwave: LA(Lauder), MA(Mauna Loa), TA(Table Mt).
Lidar: OH(OHP), MA(Mauna Loa), TA(Table Mt).
Sonde: HO(Hohenpeissenberg), PA(Payerne), WA(Wallops Island), HI (Hilo).

  • Microwave comparisons with N9, N11, and N16
  • Lidar comparisons with N9, N11, and N16
  • Sonde comparisons with N7, N9, and N11
The mean percentage differences are calculated by averaging all matched-up samples for those time periods: (N07 : Dec 1978 - Dec 1990), (N09 : Jan 1993 - Feb 1998), (N11 : Dec 1988 - Dec 2001), (N16 : Oct 2000 - Sept 2002). The +/- 1 standard error bars shown on the plots are calculated by dividing the standard deviation of percent difference by the square root of the number of coincidences at that altitude minus one. The numbers in the parenthesis indicate the number of coincidences for a station. For the most upper layers or lower layers, these numbers are slightly reduced because of the sparse sampling of coincidences. The comparison results indicate that V8 SBUV ozone profiles generally agree with external data sources in the altitude range 24 to 50 km (30hPa and 1hPa) to within ± 10% (~5% on average). These results are consistent with Microwave, SAGE II, lidar, and sonde comparison results from Brinksma et al., [2002], Leblanc et al., [2000], and Tsou et al., [2000].

References

Brinksma, E. J., J. Ajtic, J. B. Bergwerff, G.E. Bodeker, I. S. Boyd, J. F. de Haan, W. Hogervorst, J. W. Hovenier, and D.P. J. Swart, Five years of observations of ozone profiles over Lauder, New Zealand, J. Geophys. Res., 107(D14), 10.1029/2001 JD000737, 2002.

Leblanc, T., and I. S. McDermid, Stratospheric ozone climatology from lidar measurements at Table Mountain (34.4N, 117.7W) and Mauna Loa (19.5N, 155.6W), J. Geophys. Res., 105, 14,613-14,623, 2000.

McPeters, R. D., D. J. Hoffman, M. Clark, L. Flynn, L. Froidevaux, M. Gross, B. Johnson, G. Koenig, X. Liu, S. McDermid, T. McGee, F. Mucray, M. J. Newchurch, S. Oltmans, A. Parrish, R.Schnell, U. Singh, . J. Tsou, T. Walsh, and J. M. Zawodny, Results from the 1995 stratospheric ozone profile intercomparison at Mauna Loa, J. Geophys. Res., 104, 30,505-30,514, 1999.

Tsou, J. J., B. J. Conner, A. Parrish, R. B. Pierce, I. S. Boyd, G. E. Bodecker, W. P. Chu, J. M. Russell III, D. P. J. Swart, and T. J. McGee, NDSC millimeter wave ozone observations at Lauder, New Zealand, 1992-1998: Improved methodology, validation, and variation study, J. Geophys. Res., 105, 24,263-24,281, 2000.