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

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