Global total column ozone trends were calculated by applying a least squares regression models to five homogenized satellite data sets from November 1978 to December 1998. Drifts and offsets in the ...satellite data were removed through comparisons of coincident satellite overpass and ground-based Dobson spectrophotometer measurements and through intersatellite comparisons. The satellite data were remapped into a potential vorticity coordinate (equivalent latitude) before zonal means were calculated. This remapping preserves steep meridional gradients in ozone and ozone trends across the winter polar vortex boundary and thereby reveals statistically significant negative trends just poleward of the Antarctic vortex boundary ( similar to 70 degree S equivalent latitude) during May (-0.51 plus or minus 0.42%yr super(-1) (2 sigma )), June (-0.65 plus or minus 0.44% yr super(-1)) and July (-0.85 plus or minus 0.44% yr super(-1)). This feature is indistinct in trends derived as a function of geographic latitude most likely as a result of the smoothing by zonal averaging across steep ozone gradients. Comparison with similar earlier analysis (November 1978 to May 1991) indicates that Antarctic ozone trends have weakened (from -3.71 plus or minus 1.80% yr super(-1) to -2.95 plus or minus 0.40% yr super(-1)), most likely as a result of saturation, while Arctic ozone trends are now much larger (from -1.05 plus or minus 0.96% yr super(-1) to -1.93 plus or minus 0.40% yr super(-1)) following severe wintertime Arctic ozone depletion in recent years. Midlatitude negative trends calculated over the longer time period are also slightly reduced.
Validation of POAM III NO 2 measurements Randall, C. E.; Lumpe, J. D.; Bevilacqua, R. M. ...
Journal of Geophysical Research: Atmospheres,
10/2002, Volume:
107, Issue:
D20
Journal Article
Peer reviewed
We describe the Polar Ozone and Aerosol Measurement (POAM) III NO
2
measurements and associated errors and compare the POAM III data to correlative measurements obtained from satellite‐, balloon‐, ...and ground‐based instruments. POAM III NO
2
densities are retrieved from 20 to 45 km, with a vertical resolution of about 1.5–2.5 km at altitudes below 40 km and increasing to more than 7 km at an altitude of 45 km. Predicted random errors are on the order of 5% in this altitude range. Sunspots and high aerosol extinction can cause errors in the NO
2
retrievals but generally affect only about 10% of the data or less, depending on the altitude. The agreement between POAM III NO
2
data and correlative observations is excellent, demonstrating that the POAM III measurements are reasonable in terms of their magnitude, profile structure, and temporal variations. The largest number of comparisons was made with the Halogen Occultation Experiment (HALOE) on the Upper Atmosphere Research Satellite. On average, POAM and HALOE agree to within about 0.2 ppbv from 20 to 33 km or within about 6% at most of these altitudes, with no systematic bias. Differences increase to about 0.7 ppbv (17%, POAM higher than HALOE) by 40 km. This difference decreases to about 12% after accounting for a recently discovered error in the HALOE retrievals. Differences decrease above 40 km and are slightly negative (0.1–0.2 ppbv on average) at 45 km, the top edge of the valid POAM III NO
2
altitude range. We conclude that the POAM III NO
2
profiles from 20 to 45 km are appropriate for scientific analysis and for the validation of NO
2
measurements from other instruments.
Validation of POAM III NO sub(2) measurements Randall, CE; Lumpe, J D; Bevilacqua, R M ...
Journal of Geophysical Research. D. Atmospheres,
10/2002, Volume:
107, Issue:
D20
Journal Article
Peer reviewed
We describe the Polar Ozone and Aerosol Measurement (POAM) III NO sub(2) measurements and associated errors and compare the POAM III data to correlative measurements obtained from satellite-, ...balloon-, and ground-based instruments. POAM III NO sub(2) densities are retrieved from 20 to 45 km, with a vertical resolution of about 1.5-2.5 km at altitudes below 40 km and increasing to more than 7 km at an altitude of 45 km. Predicted random errors are on the order of 5% in this altitude range. Sunspots and high aerosol extinction can cause errors in the NO sub(2) retrievals but generally affect only about 10% of the data or less, depending on the altitude. The agreement between POAM III NO sub(2) data and correlative observations is excellent, demonstrating that the POAM III measurements are reasonable in terms of their magnitude, profile structure, and temporal variations. The largest number of comparisons was made with the Halogen Occultation Experiment (HALOE) on the Upper Atmosphere Research Satellite. On average, POAM and HALOE agree to within about 0.2 ppbv from 20 to 33 km or within about 6% at most of these altitudes, with no systematic bias. Differences increase to about 0.7 ppbv (17%, POAM higher than HALOE) by 40 km. This difference decreases to about 12% after accounting for a recently discovered error in the HALOE retrievals. Differences decrease above 40 km and are slightly negative (0.1-0.2 ppbv on average) at 45 km, the top edge of the valid POAM III NO sub(2) altitude range. We conclude that the POAM III NO sub(2) profiles from 20 to 45 km are appropriate for scientific analysis and for the validation of NO sub(2) measurements from other instruments.
For several years NO sub(2) and OClO, two species important to understanding ozone destruction in the Antarctic stratosphere, have been measured at Arrival Heights, Antarctica by two groups: New ...Zealand's National Institute of Water and Atmospheric Research (NIWA) and the NOAA Aeronomy Laboratory in Boulder, Colorado. Using data independently collected by these two groups during the Austral spring of 1996, it is shown that the two data sets are in extremely close agreement. Besides offering validation of the instrumentation and analysis techniques of both groups, this result provides confidence in the more complete history of these species gained by combining the two data sets.
Ozone depletion above Kiruna (67.9 degrees N, 21.1 degrees E), Sweden, was investigated using daily ozone and temperature measurements by ozonesondes between 1 February and 25 March 1997. Using UKMO ...Ertel's potential vorticity (EPV) and wind fields, three dynamically distinct regions were defined on a grid of isentropic surfaces viz.: the polar vortex boundary region characterized by steep EPV gradients, the area poleward of the boundary region (inside the polar vortex), and the area equatorward of the boundary region (outside the polar vortex). Due to dynamically induced displacements of the vortex, measurements were made in all three regions. By calculating the isentropic EPV at each measurement point and comparing it with the values defining the equatorward and poleward edges of the vortex boundary region, all ozone and temperature measurements could be binned according to their position relative to the vortex edge. Since the data outside the polar vortex were highly variable, mean ozone profiles and their standard deviations were calculated and compared only for the two other regions. To investigate whether differences between these mean profiles were indicative of ozone loss, the temporal evolution of ozone mixing ratios measured along several isentropic surfaces was examined, taking into account the diabatic descent of airmasses. Finally, ozone loss rates were calculated for six potential temperature surfaces and loss rates of up to 0.63ppm /month were found inside the Arctic vortex at surfaces descending from approximately 475 K (1 February) to 460 K (25 March).
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