Indicators of Antarctic ozone depletion

[摘要] An assimilated data base of total column ozone measurements from satelliteshas been used to generate a set of indicators describing attributes of theAntarctic ozone hole for the period 1979 to 2003, including (i) dailymeasures of the area over Antarctica where ozone levels are below 150 DU,below 220 DU, more than 30% below 1979 to 1981 norms, and more than 50%below 1979 to 1981 norms, (ii) the date of disappearance of 150 DU ozonevalues, 220 DU ozone values, values 30% below 1979 to 1981 norms, andvalues 50% below 1979 to 1981 norms, for each year, (iii) daily minimumtotal column ozone values over Antarctica, and (iv) daily values of the ozonemass deficit based on a O₃<220 DU threshold. The assimilated data basecombines satellite-based ozone measurements from 4 Total Ozone MappingSpectrometer (TOMS) instruments, 3 different retrievals from the Global OzoneMonitoring Experiment (GOME), and data from 4 Solar Backscatter Ultra-Violet(SBUV) instruments. Comparisons with the global ground-based Dobsonspectrophotometer network are used to remove offsets and drifts between thedifferent data sets to produce a global homogeneous data set that combinesthe advantages of good spatial coverage of satellite data with good long-termstability of ground-based measurements. One potential use of the derivedindices is detection of the expected recovery of the Antarctic ozone hole.The suitability of the derived indicators to this task is discussed in thecontext of their variability and their susceptibility to saturation effectswhich makes them less responsive to decreasing stratospheric halogen loading.It is also shown that if the corrections required to match recent Earth ProbeTOMS measurements to Dobson measurements are not applied, some of theindictors are affected so as to obscure detection of the recovery of theAntarctic ozone hole.

[学科分类] 大气科学