Combined Characterisation of GOME and TOMS Total Ozone Using Ground-Based Observations from the NDSC

Several years of total ozone measured from space by the ERS-2 GOME, the Earth Probe Total Ozone Mapping Spectrometer (TOMS), and the ADEOS TOMS, are compared with high-quality ground-based observations associated with the Network for the Detection of Stratospheric Change (NDSC), over an extended latitude range and a variety of geophysical conditions. The comparisons with each spaceborne sensor are combined altogether for investigating their respective solar zenith angle (SZA) dependence, dispersion, and difference of sensitivity. The space- and ground-based data are found to agree within a few percent on average. However, the analysis highlights for both Global Ozone Monitoring Experiment (GOME) and TOMS several sources of discrepancies, including a dependence on the SZA at high latitudes and internal inconsistencies

LAPBIAT Upper Troposphere Lower Stratosphere Water Vapour Validation Project: LAUTLOS - WAVVAP

LAPBIAT* Upper Troposphere Lower Stratosphere Water VapourValidation Project: LAUTLOS WAVVAPEsko Kyrö, Arctic Research Centre (FMI/ARC), Sodankylä, Finland ([email protected])Ulrich Leiterer, Meteorological Observatory Lindenberg, GermanyVladimir Yushkov, Central Aerological Observatory Moscow, RussiaRoland Neuber, Alfred Wegener Institute for Polar and Marine Research, Potsdam, GermanyPaul Ruppert, Meteolabor AG, Wetzikon, SwitzerlandAri Paukkunen, Vaisala Oyj, Helsinki, FinlandHolger Vömel, University of Colorado, Boulder, USAThe focus of this project is the improvement of water vapour measurement techniques in the Upper Troposphere and LowerStratosphere (UT/LS). Routine measurements of water vapour with high accuracy at these altitudes are an unsolved problem up tonow despite many activities in the past ten years. Water vapour is a dominant greenhouse gas in the earths atmosphere. Recentmodel calculations show that observed water vapour increases in the stratosphere contribute significantly both to surface warmingand stratospheric cooling. In addition to climate change, both direct chemical and indirect radiative effects of stratospheric waterchanges on ozone chemistry are important as well. Therefore one of the aims of the forthcoming EU COST Action 723 The Roleof the Upper Troposphere and Lower Stratosphere in Global change is to improve balloon sounding and remote sensingtechniques of water vapour measurements (see http://www.sat.uni-bremen.de/cost/). Another example of the work focusing onwater vapour is proposed by the GEWEX Water Vapour Project (GVaP) (see SPARC Report No. 2, December 2000 and thereferences therein).The idea of LAUTLOS-WAVVAP is a comparison/validation experiment, which brings together lightweight hygrometersdeveloped in different research groups, which could be used as research-type radiosondes in the UTLS region. These include:Meteolabor Snow White hygrometer, NOAA frostpoint hygrometer, CAO Flash Lyman alpha hygrometer, Lindenberg FN sonde(a modification of the Vaisala radiosonde) and the latest version of the regular Vaisala radiosonde with the humicap-polymersensor. The experimental plan is based on regular launches of multi-sensor payloads at Sodankylä in January February 2004. Theaim is to study the effect of atmospheric parameters such as ambient temperature, water vapour content or relative humidity, airpressure and solar radiation on each participating hygrometer/radiosonde records. Both night and daytime launches are planned.The campaign also aims at studying PSC occurrence and their dependence on local temperature and water vapour content. It willbe hosted by the FMI Arctic Research Centre Sodankylä assisted by Vaisala Oyj and is part of the planned Finnish contribution toCost 723 project. The campaign is partly funded from the LAPBIAT Facility, which belongs to the EU program: Access toResearch Infrastructures (see: http://www.sgo.fi/lapbiat/).* Lapland Atmosphere-Biosphere Facility Improving the Human Research Potential and the Socio-Economic knowledge Bas

Mountain wave induced record low stratospheric temperatures above Northern Scandinavia

On 22 January 1997 1200 UT, the routine radiosonde from Sodankylae, Finland, measured a record low temperature of -94.5 C at 26 km. Mesoscale numerical simulations indicate strong mountain wave activity on this day. Two stratospheric temperature minima are simulated: one directly above the Scandinavian mountain ridge and another minimum in its lee about 500 km to the east. Both minima are not resolved in the global analyses. The radiosonde profile as well as the mesoscale model indicate that the eastern mesoscale temperature anomaly is caused by orographic inertia-gravity waves, i.e. hydrostatic mountain waves influenced by Coriolis force. Stratospheric ice clouds were observed visually and by ground based lidar at Kiruna, Sweden and Sodankylae, Finland on this day. The formation of these ice clouds required the cooling in the mountain waves as the temperature according to global analyses were about 3 K above the frost point. The occurrence of additional polar stratospheric ice clouds due to mountain wave cooling increases the efficiency of chlorine activation and has implications for the resulting Arctic ozone depletion. The extraordinary event under consideration occured during a cold air outbreak with a cold front passing over the Scandinavian orography. This front was associated with strong winds in the lower troposphere. At the same time northern Scandinavia was located below the inner edge of the polar vortex, where low synoptic-scale stratospheric temperatures and a strong polar night jet are found. (orig.)30 refs.Available from TIB Hannover: RR 6341(115) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Ozone Profiles in the High-latitude Stratosphere and Lower Mesosphere Measured by the Improved Limb Atmospheric Spectrometer (ILAS)-II: Comparison with other Satellite Sensors and Ozonesondes

A solar occultation sensor, the Improved Limb Atmospheric Spectrometer (ILAS)-II, measured 5890 vertical profiles of ozone concentrations in the stratosphere and lower mesosphere and of other species from January to October 2003. The measurement latitude coverage was 54-71degN and 64-88degS, which is similar to the coverage of ILAS (November 1996 to June 1997). One purpose of the ILAS-II measurements was to continue such high-latitude measurements of ozone and its related chemical species in order to help accurately determine their trends. The present paper assesses the quality of ozone data in the version 1.4 retrieval algorithm, through comparisons with results obtained from comprehensive ozonesonde measurements and four satellite-borne solar occultation sensors. In the Northern Hemisphere (NH), the ILAS-II ozone data agree with the other data within +/-10% (in terms of the absolute difference divided by its mean value) at altitudes between 11 and 40 km, with the median coincident ILAS-II profiles being systematically up to 10% higher below 20 km and up to 10% lower between 21 and 40 km after screening possible suspicious retrievals. Above 41 km, the negative bias between the NH ILAS-II ozone data and the other data increases with increasing altitude and reaches 30% at 61-65 km. In the Southern Hemisphere, the ILAS-II ozone data agree with the other data within 10% in the altitude range of 11-60 km, with the median coincident profiles being on average up to 10% higher below 20 km and up to 10% lower above 20 km