Projects/Activities

Objectives 1. To develop the measurement technique further, providing more accurate measurements and extend the method to a larger number of trace species 2. To monitor the presence of CFC:s and other longlived anthropogenic tracers in the stratosphere 3. To use long-lived anthropogenic species as tracers of atmospheric motion, in particular for comparison with atmospheric models Reserarchers: Descartes is a joint research programme currently involving N.R.P Harris and J.A. Pyle, Centre for Atmospheric Science at the Department of Chemistry, University of Cambridge, U.K., and Hans Nilsson and Johan Arvelius, Swedish Institute of Space Physics, Kiruna, Sweden

The atmosphere carries a continuous electric current and , even during fair weather, there is a strong electrostatic electric field, up to 200 volts per meter, close to the ground. This electric current is thought to be due to the accumulated effect of thousands of thunderstorms, mostly in the tropical regions of the Earth. These storms feed a current from the ground up to the ionosphere, a highly conducting layer in the atmosphere which lies above about 70 km altitude. The current spreads out around the globe through this layer and returns to Earth through the atmosphere as the 'fair weather current' outside the thunderstorm areas. Objective: Investigation of the part of the Earths global electrical circuit: fair weather current and its interaction with geomagnetic phenomena, such as, for example, a magnetic substorms. We use the data of the air-earth current measured by a long wire antenna installed in Kiruna/Esrange, Sweden. In July 1999 we have installed a new portable antenna at a distance of about 30 km from the old one. This antenna has a length of nearly 50 m, and we are recording the near ground vertical current with a time resolution of 10 seconds. The data from both instruments will be analysed together - for comparison and possible separation of the meteorological effects.

Objective: to determine how solar activity influences temperatures, winds, electric currents and minor constituents and to allow possible anthropogenic influences to be determined. Uses primarily measurements by the ESRAD and EISCAT radars, plus ground-based and balloon-borne measurements of atmospheric electric fields and currents.

Observation of proton aurora on the dayside with use of spectrometer operated simultaneous in Longyearbyen and Ny-Ålesund. Absolute calibration of the instrument located at The Sverdrupstation were performed in the period 9-13 January 2003.

The focus of this project is the improvement of water vapour measurement techniques in the upper troposphere and lower stratosphere. Routine measurements of water vapour with high accuracy in these altitudes are an unsolved problem of meteorological measurements up to now. Water vapor is the dominant greenhouse gas in the earth's atmosphere. Recent model calculations show that observed water vapour increases in the stratosphere contribute significantly both to surface warming and stratospheric cooling. In addition to climate change both the direct chemical and indirect radiative effects of stratospheric water changes in ozone chemistry are important as well. Despite of many activities in the past ten years, accuracies of the available methods for measuring the water vapour vertical profile in the free atmosphere are still not sufficient. Therefore one of the aims of the forthcoming EU COST Action 723 "The Role of the Upper Troposphere and Lower Stratosphere in Global change", is to improve sounding and remote sensing techniques of water vapour (see http://www.sat.uni-bremen.de/cost/). Another example of the planned work focusing on water vapour is proposed GEWEX (Global Energy an Water Cycle Experiment) Water Vapour Project (GVaP). See [SPARC 2000] and the references therein. The idea of LAUTLOS-WAVVAP comparison/validation experiment which brings together lightweight hygrometers developed in different research groups, which could be used as research-type radiosondes in UTLS region. These include the following instruments: Meteolabor Snow White hygrometer, NOAA frostpoint hygrometer, CAO Flash Lyman alpha hygrometer, Lindenberg FN sonde (a modification of Vaisala radiosonde) and the latest version of regular Vaisala radiosonde with humicap-polymer sensor. The experimental plan of LAUTLOS-WAVVAP is based on the regular launches of multi-sensor payloads from the Sodankylä meteorological balloon launch facility in January -February 2004. The aim is to study the effect of atmospheric conditions such as ambient temperature, water vapour or relative humidity, pressure or solar radiation for each participating hygrometer/radiosonde. Both night and daytime launches are planned. Apart from the intercomparison/validation experiment the campaign also have an scientific aim of studying the stratospheric PSC occurrence and their dependence on local temperature and the water vapour content. The campaign will be hosted by FMI Arctic Research Centre Sodankylä assisted by Vaisala Oyj and is a part of planned Finnish contribution to Cost 723 project. The campaign in Sodankylä is partly funded from LAPBIAT Facility, which belong to the EU program: Access to Research Infrastructures (see: http://www.sgo.fi/lapbiat/). References: SPARC Assessment of Upper Tropospheric and Stratospheric Water Vapor/SPARC Report No2/ December 2000

documentation and monitoring of the aerosol content of a mountain valley atmosphere and its diurnal changes

For the first time in Austria, routine monitoring of the ozone layer as well as routine spectral UV measurements have been performed at Sonnblick. Column ozone, ozone profile, SO2 column, Nox column and spectral UV (from 290 to 325 nm) has been measured with a Brewer spectrometer type MKIV (No 093) since 1994. From 1997 on broad band erythemal UV has been recorded with a Robertson Berger biometer. For registration of the spectral ultraviolet irradiance-particularly the spectral UVB-radiation- a Bentham spectrometer (double monochromator) has been adapted so that it can be used under the extreme climatic conditions on a mountain top. Routine measurements of the spectral irradiance in the spectral range of 280-500 nm are performed in 0.5 nm steps every half hour. Additional information on cloudiness is supplied by a upwards looking CCD camera equipped with a fish eye lense. Sonnblick station is embedded in the EDUCE, GAW and WMO networks.

For a two year period daily samples of selected trace gases (nitric acid, sulfur dioxide and ammonia) and aerosol compounds (sulfate, nitrate, oxalate and ammonium) are determined with filter packs at the Sonnblick Observatory. The measurements will be used to identify the seasonal cycles of the selected trace gases and aerosol compounds at the 3 km level above Central Europe. Especially during the cold season previous measurements showed that samples collected at the Observatory represent free tropospheric air masses. Together with wet deposition measurements carried out at the site scavenging parameters are calculated.

Objective 1: Proof of the possibility to estimate temperatures from meteor decay times using co-located, simultaneous meteor observations on two, well separated frequencies (32.55 MHz/SKiYMET radar and 53.5 MHz/ALWIN MST radar) without the assumption of a predetermined temperature gradient. The second method for determining temperature height profiles uses the direct measurement of the ambipolar diffusion coefficient in conjunction with pressure data to estimate temperatures. Pressure data from empirical models are often too unreliable, therefore pressure data derived from rocket-borne falling spheres measurements could be used for a reliable temperature determination. Objective 2: Proof of the method using co-located meteor radar measurements and falling sphere soundings conducted in 2002 at Andenes (69N) during the MaCWAVE campaign. It should be possible to estimate meteor temperature profiles in a height range between 82 km and about 94 km.

Polar stratospheric clouds play a key-role in polar ozone destruction. Cold temperatures in the vortex allow formation of these clouds. Depending on the PSC-type different formation-temperatures have to be reached. Synoptic temperatures do not always fall to these formation-temperatures, but waves in the atmosphere can lead to additional cooling of several 10 K, which allows PSC-formation. Whereas the wave-activity at the ESRANGE is very high due to hilly surrounding area, the orographic wave-activity at ALOMAR is expected to be rather small. Waves with long wavelengths will be present at both stations simultaneously. Coordinated measurements of temperature and aerosols will show both the large-scale wave-part and also the locally induced wave-part. Such measurements should allow identification of the different wavelngth scales and in addition contribute to a better estimate of the importance of wave-induced clouds for PSC-formation.

During the past years, atmospheric research in high latitudes has been focussed on processes causing ozone loss in the polar winter lower stratosphere1). Recent research efforts also dealt with regions up to the lower mesosphere, and studied the effects of charged particle precipitation on NO and ozone2)-5). However, the measurement techniques and hence the database for studying such processes in this altitude range are very limited. The Airborne SUbmillimeter Radiometer ASUR6),7) of the Institute of Environmental Physics of the University of Bremen has recently been equipped with a high-resolution spectrometer that will enable the retrieval of vertical profiles of ozone up to an altitude of about 65 - 70 km. Its measurement capabilities comprise also several other species of interest, especially NO. This makes the measurement technique particularly suitable for upper stratospheric/lower mesospheric studies. The lidar at ALOMAR is capable of measuring highly resolved vertical profiles of ozone up to an altitude of 60 km, thus giving the rare opportunity for intercomparison and validation studies in an altitude range reaching from the lower stratosphere to the lower mesosphere. Therefore we propose to perform simultaneous ozone measurements of the ASUR instrument with the ALOMAR lidar, supported by launches of ozone sondes.

The upper troposphere and lower stratosphere are strongly affected by the appearance of gravity waves with different scales. Due to the exponential decrease of the density with the altitude, the upward propagation of these waves is associated with an increase in their amplitudes. Associated with the wave breaking and with deposit of momentum and energy in the background flow, the dynamical and thermal structure at upper stratospheric and mesospheric heights are essentially influenced. However, their sources and the quantitative aspects of these processes are poorly understood at present. Here we are focussing on the investigation of long periodic gravity waves with periods of several hours and horizontal wavelengths of more than hundred kilometres. In contrast to the pure internal gravity waves, these waves are called inertio-gravity waves due to their influence by the rotation of the Earth, described by the Coriolis effect or by the inertial frequency.

Noctilucent clouds (NLC) remain a fascinating phenomenon of the upper atmosphere to study. The questions about the typical particle density and particle size distribution within a NLC are very prominent ones, to which a number of answers have been given, though some of the answers contradict each other. The parameters of particle size distributions can be derived from groundbased lidar measurements of the spectral dependence of the volume backscatter coefficient of an NLC. Such studies have been performed during a number of NLC events by e.g. the ALOMAR Rayleigh/Mie/Raman (RMR) lidar (von Cossart et al., GRL, 26, 1513, 1999). A drawback of these experiments is the wavelength limitation of the RMR lidar, the shortest wavelength of which is 355 nm. At this wavelength, the sensitivity of the lidar to particles with sizes smaller than, say, 25 nm is minimal. Because a considerable part of the entire particle population may have sizes below that threshold, a lingering question remains whether or not this drawback matters for typical NLC distributions. Using the ALOMAR ozone lidar, a measurement of the NLC volume backscatter coefficient at 308 nm becomes possible. Due to the l-4 -dependence of the backscatter coefficients, the latter are almost a factor of 2 larger at this wavelength than at 355 nm. For this reason and in order to gain a fourth wavelength to the spectral distribution, we aim at using the ozone lidar for the outlined project.

Waves play a major role for the momentum and energy transport in the middle atmosphere [Fritts and van Zandt, 1993] by modifying the local temperature field as well as the general circulation when the waves reach the saturation level and break [Holton, 1983; Fritts, 1984]. The MACWAVE rocket campaign is investigating the wave field in polar latitudes during summer and winter. To learn more about the horizontal structure of the wave field, it is important to measure at more than one station. For the monitoring of the vertical transport by the waves, measurements over a large height range are necessary. The combination of lidars, radiosondes and falling spheres will cover the region from the ground up to approximately 105 km. When comparing data, it is important to take into account the different measurement principles and integration times. The rocket will show small scale variations whereas the lidar permits a continuous monitoring of the temperature and wave situation

These investigations confirm the fact that in the stratosphere the ozone is considerably influenced by dynamical processes and it is a good indicator of them. In this context the main objectives of the proposed study are: 1) to investigate the possible relationship between stratospheric ozone perturbations and the temperature enhancement in the upper mesosphere, observed by Shepherd et al. (2001); 2) to examine whether changes in ozone, concomitant with the phenomenon, take place and how and when they would be manifested; and 3) to investigate the stratospheric ozone behaviour during the equinox atmospheric transition in the North Hemisphere, for better understanding of the middle atmosphere dynamics.

The purpose of the CHAOS_A project is to perform measurements under "Antarctic conditions" during the polar vortex period with the new assembled spectrometer in order to perform tasks that cannot be achieved at low latitudes namely OClO detection. Therefore the campaign focus more in technical aspects than scientific ones. The period of observation may be short to achieve results of scientific interest and those will depend on the meteorology of the stratosphere (position of the polar vortex relative to the station, temperatures at the lower stratosphere, etc). The OClO results will be compared with those obtained by the NILU (Andoya) and Heidelberg U.

Study aerosol properties (size and composition) in the infrared spectral region

By launching several hundred ozonesondes at many Arctic and sub-Arctic stations, one of them Ny-Ålesund, the stratospheric chemical ozone loss will be determined. The launches of all stations will be coordinated by analysis of trajectory calculations based on analysis and forecast wind fields. The aim is to get as many ozone sounding pairs as possible, each of them linked by trajectories in space and time. A statistical description of the ozone differences given by the first and the second measurement of individual sonde pairs will yield the chemical ozone loss with spatial and time resolution.