Total Ozone Measuring Spectrometers

Syage, J. A., and M. N. Ross, An Assessment of the Total Ozone Mapping Spectrometer for Measuring Ozone Levels in a Solid Rocket Plume, Geophys. Res. Lett., 23, 3227-3230 (1996). Symonds, R. B W. I. Rose, and M. H. Reed, Contribution of Cl-and F-Bearing Gases to the Atmosphere by Volcanoes, Nature, 334, 415-418 (1988). 

Hudson, R.D., J. Kim and A.M. Thompson (1995) On the derivation of tropospheric column ozone from radiance measured by the total ozone mapping spectrometer. Journal of Geophysical Research 100 11138-11145. 

Krueger, A.J., L.S. Walter, P.K. Bhartia, C.C. Schnetzler, N.A. Krotkov, I. Sprod and G.J.S. Bluth (1995) Volcanic sulfur dioxide measurements from the total ozone mapping spectrometer (TOMS) instruments. Journal of Geophysical Research 100 14057-14076. 

Figure 11.5 This diagram comes from NASA s ozone monitoring programme TOMS (Total Ozone Mapping Spectrometer). The ozone hole over the Antarctic (shown in purple and pink on the diagram) is largest in the Antarctic spring. Note Dobson Units are a measure of the total amount of ozone in a vertical column from the ground to the top of the atmosphere.

Measurements of the gaseous sulfur dioxide released were obtained with the Total Ozone Mapping Spectrometer (TOMS Krueger, 1983) and with the Solar Backscatter Ultraviolet Spectrometer (SBUV Heath et d., 1983), both carried on the Nimbus 7 satellite. Three instruments on board the Solar Mesosphere Explorer (SME) also revealed features of the cloud the Infrared Radiometer measured the thermal emission from the aerosols, while the Visible and Near Infrared Spectrometers measured the backscat-tered solar radiation. The three instruments are limbscanning and view the atmosphere along the track of the sunsynchronous polar orbit (Barth et d., 1983 Thomas et d., 1983). Ground based and airborne spectro-photometric measurements of sulfur dioxide have also been carried out (Evans and Kerr, 1983). 

Krueger A. J., Walter L. S., Bhartia P. K., Schnetzler C. C., Krotkov N. A., Sprod I., and Bluth G. J. S. (1995) Volcanic sulfur dioxide measurements from the Total Ozone Mapping Spectrometer (TOMS) instruments. J. Geophys. Res. 100, 14057-14076. 

FIGURE 4-40 The Antarctic ozone hole, October 1991, as measured by the total ozone mapping spectrometer (TOMS) from the Nimbus 7 satellite. The hole covers the Antarctic continent and extends as far north as the tip of South America. (Reprinted with permission from R. Stolarski, R. Bojkov, L. Bishop, C. Zerefos, J. Staehelin, and J. Zawodny, 1992, Measured Trends in Stratospheric Ozone, Science 256 342-349. Copyright 1992, American Association for the Advancement of Science.)... 

Since 1978 spectral measurements of sunlight backscattered from the Earth to the space have been made from satellites, starting with NASA s Nimbus-7 satellite with the TOMS (Total ozone mapping spectrometer) instrument. This spectrometer was designed to measure backscattered UVR at six wavelengths in the UV-B and UV-A and to derive total column ozone amount from these radiance data. This application is well established and the uncertainty is well... 

Fishman, J. and Brackett, V. G. (1997). The climatological distribution of tropospheric ozone derived from a satellite measurements using version 7 Total Ozone Mapping Spectrometer and Stratospheric Aerosol and Gas Experiment data sets./. Geophys. Res. 102, 19275-19278. 

FIGURE 7.3 Antarctic ozone minima. 1979-2003. The ozone minima are given above the data points and the dates of recorded minima are given below the data points. The data, in Dobson units (DU), were measured by the Total Ozone Mapping Spectrometer (TOMS) spacecraft. (Source http // jwocky.gsfc.nasa.gov/multi/ min ozone.gif)... 

Total Ozone Mapping Spectrometers (TOMS) measure solar irradiance and radiance backscattered by the earth s atmosphere at six wavelengths extending from approximately 310 to 380 nm. TOMS measurements can be used to estimate the tropospheric ozone amount by the calculation of the difference of total ozone minus stratospheric ozone amount measmed by another satellite instrument (SAGE Stratospheric Aerosol and Gas Experiment), in particular when stratospheric ozone variations are small, usually over the tropics. However, the residual tropospheric ozone calculation has some limitation in accuracy because the tropospheric ozone amount is calculated as a small difference of two large numbers (total and stratospheric ozone). Measurements of the TOMS instra-ment on Nimbus 7 satellite have been used to estimate tropical tropospheric ozone trends from 1978 to 1992. 

The growth of the Antarctic ozone hole, located mostly over the continent of Antarctica, since 1979. The images were made from data supplied by total ozone-mapping spectrometers (TOMSs), The color scale depicts the total ozone values in Dobson units, with the lowest ozone densities represented by dark blue, (The ozone over a given area is compressed to 0°C and 1 atm pressure, and the thickness of the slab is measured, 1 Dobson unit = 0,01 mm thickness,)... 

For example, analysis of a combined set of data from ground-based measurements using Dobson spectrometers and related approaches as well as ozonesondes and SBUV from 1979 to 1994 indicates that at midlatitudes in the Northern Hemisphere, the trend in total ozone is as much as -7% per decade in the winter and spring compared to - 3% per decade in the summer and fall in the Southern Hemisphere at midlatitudes, there is less seasonal variation but negative trends in total ozone in the range —3 to —6% per decade are observed (Harris et al., 1997). Trends in the tropics were not clearly statistically significant. 

Ground-based measurements of total ozone use the Dobson spectrometer. This instrument measures the column density of ozone in the atmosphere by optical absorption, with the sun or the moon as background source. The data are expressed as an equivalent column height at standard pressure and... 

The CD spectrometer is usually required to work near the limits of sensitivity—e.g., reading AA values of <10 4 at a total absorbance of 1. Thus, particular care needs to be taken with cleanliness and orientation of cells and with settings of scan rate, time constant, and bandwidth. It is also important, especially when recording far-UV spectra, that the lamp is not old and that the mirrors are not clouded from radiation and traces of ozone. Because the spectrometer is a single-beam instrument, it is essential always to watch carefully for evidence of instrumental drift during measurements of sample and baseline. 

Measurements of the total amounts of ozone in a vertical column of the atmosphere can be made with a Dobson spectrometer from the penetration of 300-320 nm ultraviolet radiation to the earth s surface. 

FIGURE 4.1 Total column ozone (60° N to 60° S) from January 1979 to May 1994 measured by the solar backscattered ultraviolet spectrometer (World Meteorological Organization, 1994). The solid line is a least squares fit to the data through May 1991. The dashed line is an extrapolation through May 1994. The annual cycle and the quasi-biennial oscillation (QBO) have been removed. 

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