Abstract. An ozone climatology based on ozone soundings for the last 15 years has been constructed for model evaluation and comparisons to other observations. Vertical ozone profiles for 41 stations around the globe have been compiled and averaged for the years 1980–1994 and 1995–2009. The climatology provides information about the median and the width of the ozone probability distribution function, as well as interannual variability of ozone between 1995 and 2009, in pressure and tropopause-referenced altitudes. In addition to single stations, regional aggregates are presented, combining stations with similar ozone characteristics. The Hellinger distance is introduced as a new diagnostic to compare the variability of ozone distributions within each region and used for model evaluation purposes. This measure compares not only the mean, but also the shape of distributions. The representativeness of regional aggregates is discussed using independent observations from surface stations and MOZAIC aircraft data. Ozone from all of these data sets show an excellent agreement within the range of the interannual variability, especially if a sufficient number of measurements are available, as is the case for West Europe. Within the climatology, a significant longitudinal variability of ozone in the troposphere and lower stratosphere in the northern mid- and high latitudes is found. The climatology is used to evaluate results from two model intercomparison activities, HTAP for the troposphere and CCMVal2 for the tropopause region and the stratosphere. HTAP ozone is in good agreement with observations in the troposphere within their range of uncertainty, but ozone peaks too early in the Northern Hemisphere spring. The strong gradients of ozone around the tropopause are less well captured by many models. Lower stratospheric ozone is overestimated for all regions by the multi-model mean of CCMVal2 models. Individual models also show major shortcomings in reproducing the shape of ozone probability distribution functions in various regions and different altitudes, which might have significant implications for the radiative budgets in those models.
Within a conceptual framework of stratospheric injection, CO‐CH 4 background tropospheric chemistry, parameterized pollution production in the continental boundary layer and surface deposition, we use an 11 level GCTM to simulate global distributions of present and pre‐industrial tropospheric O 3 . The chemistry is driven by previously simulated present and pre‐industrial NOx fields, while prescribed fields of CO, CH 4 and H 2 O are held constant. An evaluation with measurements from 12 surface sites, 21 ozonesonde sites and 1 aircraft campaign finds agreement within ±25% for 73% of the observations while identifying systematic errors in the wintertime high‐latitude Northern Hemisphere (NH), the Southern Hemisphere (SH) tropics during biomass burning, and the remote SH. We predict that human activity has increased the annual integral of tropospheric ozone by 39% with 3/4's of that increase in the free troposphere, though the boundary layer [BL] annual integral has increased by 66%. The 2 largest components of the global O 3 budget are stratospheric injection at 696 TgO 3 /yr, and loss through dry deposition, which increases from 459 TgO 3 /yr to a present level of 825 TgO 3 /yr. While tropospheric chemistry's net contribution is relatively small, changing from a pre‐industrial destruction of −236 TgO 3 /yr to a present production of +128 TgO 3 /yr, it is a balance between two much larger terms, −558 TgO 3 /yr of destruction in the background troposphere and +686 TgO 3 /yr of production in the polluted boundary layer. Human impact on O 3 predominates in the summertime extratropical NH and in the tropics during their biomass burning seasons [increases of 50%–100% or more]. Conversely, there has been little increase in most of the upper troposphere [<20%], where ozone's influence on tropospheric climate is strongest.
This paper describes the validation of ozone data from the Upper Atmosphere Research Satellite (UARS) Microwave Limb Sounder (MLS). The MLS ozone retrievals are obtained from the calibrated microwave radiances (emission spectra) in two separate bands, at frequencies near 205 and 183 GHz.
Abstract Tropospheric water‐vapour and ozone measurements, using calibrated balloon‐borne sensors, are reported from the Central Equatorial Pacific Experiment (CEPEX). the sensors were launched from the Research Vessel Vickers along 2°S latitude between 156°E (west of the international date line) and 155°W (east of the date line). These measurements are combined with those from water‐vapour sondes launched over the western Pacific warm pool, during the Coupled Ocean‐Atmosphere Response Experiment (TOGA‐COARE). Taking the two experiments CEPEX and TOGA‐COARE together, the sensors included frost‐point hygrometers, Humicap‐A Väisälä sondes, Humicap‐H Väisälä sondes and electrochemical ozone‐sondes. Taken together, the CEPEX and TOGA‐COARE data provide over 150 vertical profiles of water vapour within the troposphere in varied conditions of convective activity ranging from disturbed to suppressed. the primary motivation behind the present analyses is to understand the role of tropical deep convection in the vertical distribution of water‐vapour. With this in mind, the profiles have been analysed in relation to occasions of recent deep convection and occasions when convection was suppressed. We employ three different criteria to identify the profiles influenced by deep convection: brightness temperature in the infrared‐window channel of the Japanese Geostationary Meteorological Satellite (GMS); ozone as a quasi‐conservative tracer for deep convection; and using water vapour itself, that is the wettest versus the driest soundings. Irrespective of the criteria used, we report here that the atmosphere, while under the influence of active deep convection, was found to have relative humidities in excess of 75% over most of the troposphere between the surface and about 14 km. the sondes were launched routinely over a period of 45 days (between CEPEX and TOGA‐COARE), without biasing the sample towards convectively disturbed conditions. A feature of the convectively disturbed profile is a distinct minimum in relative humidity at about 700 hPa, where it was as low as 65%. the low relative humidity was accompanied by relatively high ozone mixing ratios, which raises the possibility of long‐range transport of dry sub‐tropical air into the warm, convectively disturbed, regions of the equatorial Pacific Ocean. Inspection of the analysed fields, and the wind fields from the sondes, supports this assertion. It then follows that the omnipresent minimum of moist static energy and minimum relative humidity at 700 hPa in the inner tropics may be the result of long‐range, inclined, transport of dry air from non‐convective regions. This detection suggests a linkage between the large‐scale circulation, deep convection and the thermodynamic structure within the equatorial troposphere. The results presented here demonstrate the applicability of ozone as a quasi‐conservative tracer of transport in the context of deep convection. The ozone‐based criterion is used to diagnose recent deep convection, independent of the GMS satellite observations, and allows one to follow the evolution of relative humidity and of water‐vapour mixing ratio after the dissipation of the cloud anvil to optically thin conditions. We show that the troposphere dries to low humidity soon after anvil dissipation. This observation leads to the hypothesis that moistening of the atmosphere, away from the core of Cb convection, occurs by evaporation of precipitation falling out of the anvils. After anvil dissipation, the ensuing subsidence in clear air causes the relative humidity and the water mixing ratio to decrease.
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.
[1] We report ozonesonde observations from the following four locations across the United States: Trinidad Head, California; Boulder, Colorado; Huntsville, Alabama; and Wallops Island, Virginia. These ozone profiles clearly indicate evidence of stratosphere-troposphere exchange, boundary layer pollution, and strong seasonal variations. Significant variation at the shortest interlaunch frequencies (typically weekly) appears in all seasons, at all stations throughout the troposphere. Activity near the tropopause dominates in the winter and spring, while boundary layer ozone maximizes in the summer. The vertical extent and maximum values of boundary layer ozone are larger at the eastern stations. Comparisons to the TOMS overpasses indicate agreement to within 2% for the total-column ozone at all stations, with station-to-station mean biases less than 2%. The seasonal variation of the total ozone column is essentially identical at Trinidad Head and Wallops Island, while the summertime values at Boulder are significantly smaller by comparison, and the amplitude of the annual cycle at Huntsville is smaller than the amplitude of the other three stations. The longitudinal character of upper tropospheric ozone shows amounts generally increasing westward from Huntsville, and in the lower troposphere, ozone decreases westward from Huntsville in all seasons. Values to the east of Huntsville increase at all altitudes and seasons, with the possible exception of August when Huntsville's boundary layer and free-tropospheric ozone dominate.
