The 1991 WMO ozone sonde intercomparison

The WMO ozone sonde intercomparison was held at Vanscoy, Saskatchewan from May 13 to May 24, 1991. The purpose of the intercomparison is to evaluate the performance of various ozone sonde types used operationally in the Global Ozone Observing System and to ensure that the accuracy and precision of the measurements are sufficient to detect long-term trends in stratospheric ozone. The intercomparison was sponsored by WMO and hosted by the Atmospheric Environment Service (AES) of Canada. It was attended by scientists from six countries: Canada, Finland, Germany, India, Japan and USA. A total of 10 balloon payloads were launched each carrying 7 or 8 sondes for a total of 67 successful ozone sonde flights. The payloads were carried to altitudes between 35 and 40 km where the flights terminated by balloon burst. Results of the profile measurements made during the series of the profile measurements made during the series of flight are used to determine statistically meaningful evaluations of the different sonde types. A description of the payload and the different ozone sondes is given. Preliminary results of the profile measurements and an evaluation of the performance of the sonde types are presented

Observation of a fast ozone loss in the marginal ice zone of the Arctic Ocean

In both polar regions tropospheric ozone regularly decreases during springtime to negligible concentrations in the atmospheric boundary layer. Here we report the observation of a dramatic ozone depletion event in the atmospheric boundary layer in the vicinity of frost flower fields in the marginal ice zone of the Arctic Ocean monitored by instrumentation on board of the icebreaker RV Polarstern. The ozone mixing ratio decreased from approximately 40 to below 1 ppbV in less than 7 hours. The analyses of backward trajectories and the synoptical conditions demonstrate that the observed decrease was not caused by the transport of ozone-free air, but that the ozone depletion occurred locally. Accordingly, bromine oxide, which is formed during the photochemical destruction of ozone in the presence of reactive bromine compounds, was significantly enhanced: bromine oxide concentrations of approximately 1 · 109 molecules cm-3 are retrieved around the same location from satellite observations. The release of bromine on or, as a result of, the presence of frost flowers appears to be the most likely explanation for the activation of reactive bromine compounds and subsequent depletion of ozone. We conclude that areas in the polar regions covered with frost flowers are the sources of the bromine leading to tropospheric ozone depletion episodes and the observed clouds of bromine oxide

Validation of Tropospheric Emission Spectrometer (TES) nadir ozone profiles using ozonesonde measurements

International audienceWe compare Tropospheric Emission Spectrometer (TES) version 2 (V002) nadir ozone profiles with ozonesonde profiles from the Intercontinental Chemical Transport Experiment Ozonesonde Network Study, the World Ozone and Ultraviolet Data Center, the Global Monitoring Division of the Earth System Research Laboratory, and the Southern Hemisphere Additional Ozonesonde archives. Approximately 1600 coincidences spanning 72.5°S-80.3°N from October 2004 to October 2006 are found. The TES averaging kernel and constraint are applied to the ozonesonde data to account for the TES measurement sensitivity and vertical resolution. TES sonde differences are examined in six latitude zones after excluding profiles with thick high clouds. Values for the bias and standard deviation are determined using correlations of mean values of TES ozone and sonde ozone in the upper troposphere (UT) and lower troposphere (LT). The UT biases range from 2.9 to 10.6 ppbv, and the LT biases range from 3.7 to 9.2 ppbv, excluding the Arctic and Antarctic LT where TES sensitivity is low. A similar approach is used to assess seasonal differences in the northern midlatitudes where the density and frequency of sonde measurements are greatest. These results are briefly compared to TES V001 ozone validation work which also used ozonesondes but was carried out prior to improvements in the radiometric calibration and ozone retrieval in V002. Overall, the large number of TES and sonde comparisons indicate a positive bias of approximately 3-10 ppbv for the TES V002 nadir ozone data set and have helped to identify areas of potential improvement for future retrieval versions

Tracer‐based determination of vortex descent in the 1999/2000 Arctic winter

A detailed analysis of available in situ and remotely sensed N2O and CH4 data measured in the 1999/2000 winter Arctic vortex has been performed in order to quantify the temporal evolution of vortex descent. Differences in potential temperature (θ) among balloon and aircraft vertical profiles (an average of 19–23 K on a given N2O or CH4 isopleth) indicated significant vortex inhomogeneity in late fall as compared with late winter profiles. A composite fall vortex profile was constructed for 26 November 1999, whose error bars encompassed the observed variability. High‐latitude extravortex profiles measured in different years and seasons revealed substantial variability in N2O and CH4 on θ surfaces, but all were clearly distinguishable from the first vortex profiles measured in late fall 1999. From these extravortex‐vortex differences we inferred descent prior to 26 November: as much as 397 ± 15 K (1σ) at 30 ppbv N2O and 640 ppbv CH4, and falling to 28 ± 13 K above 200 ppbv N2O and 1280 ppbv CH4. Changes in θ were determined on five N2O and CH4 isopleths from 26 November through 12 March, and descent rates were calculated on each N2O isopleth for several time intervals. The maximum descent rates were seen between 26 November and 27 January: 0.82 ± 0.20 K/day averaged over 50–250 ppbv N2O. By late winter (26 February to 12 March), the average rate had decreased to 0.10 ± 0.25 K/day. Descent rates also decreased with increasing N2O; the winter average (26 November to 5 March) descent rate varied from 0.75 ± 0.10 K/day at 50 ppbv to 0.40 ± 0.11 K/day at 250 ppbv. Comparison of these results with observations and models of descent in prior years showed very good overall agreement. Two models of the 1999/2000 vortex descent, SLIMCAT and REPROBUS, despite θ offsets with respect to observed profiles of up to 20 K on most tracer isopleths, produced descent rates that agreed very favorably with the inferred rates from observation