ASI6

Atmospheric measurements from local to regional scale: The role of field experiments
Convener: F. Beyrich  | Co-Conveners: F. C. Bosveld , H. de Bruin 
Oral Programme
 / Mon, 12 Sep, 14:00–18:30  / Room Oxford
 / Tue, 13 Sep, 08:30–10:30  / Room Oxford
Poster Programme
 / Attendance Tue, 13 Sep, 18:30–19:30  / Poster Hall (Ground Floor)
Atmospheric measurements are essential to provide information on the actual state of the atmosphere for nowcasting purposes and for assimilation into numerical weather prediction systems. They also contribute to improve our understanding of atmospheric processes and they provide the basis for an assessment of climate conditions. In particular, there is a strong need for comprehensive observations suitable to validate the parameterizations of atmospheric processes in numerical climate and weather prediction models. Land surface heterogeneity poses special challenges to experimental techniques to match scales between measurements and models.

This session is intended to give a forum to discuss recent developments and achievements in local to regional measurement concepts and technology (scales of the order of 1 to 10 km) over land. Special emphasis will be on field experiments which are performed to improve our understanding of complex atmospheric processes, to collect comprehensive data sets including the data from advanced measurement systems not (yet) suited for operational use and to characterize the performance of new measurement techniques. The focus is on field campaigns and observation methods suitable to study the energy and water cycle components, like temperature and humidity profiles (mean values and spatial / temporal statistics), heat and water storage in the soil, radiation and turbulent fluxes of energy, momentum and trace gases, and cloud physics.

Contributions are invited to present results from recently performed field experiments using ground-based and airborne in-situ techniques as well as remote sensing instruments, including the synergetic use of the different types of measurement systems. Reports on instrumental test campaigns as well as on the plans and design of upcoming campaigns are also welcome.
Public information: The symposium was co-organised by F. Beyrich (DWD Lindenberg), F.C. Bosveld (KNMI De Bilt), and H.A.R. de Bruin (Bilthoven). It was intended to give a forum to discuss recent developments and achievements in local to regional-scale measurement concepts and technology (scales of the order of 1 to 10 km) over land. Inspired by the link between the 11th EMS Annual Meeting with the 10th ECAM, special emphasis was set this time on field experiments which are performed to improve our understanding of complex atmospheric processes, to collect comprehensive data sets including the data from advanced measurement systems not (yet) suited for operational use and to characterize the performance of new measurement techniques. The call for abstracts had found a broad resonance, with 36 submissions (3 of which were withdrawn before the conference) the symposium became one of the th larger sessions of the 11 EMS Annual Meeting. 21 papers (out of 22 planned) were presented during three oral sessions. Another 9 presentations (out of 11 planned) were shown as posters.

The oral program was subdivided into three sessions under the headlines (I) major field experiments, (II) field experiments for process studies, and (III) field experiments for sensor tests and characterisation. The sessions took place on Monday afternoon and Tuesday morning. The symposium started with a keynote
presentation by T. Foken (University of Bayreuth) who gave an overview on the history and recent achievements of field experiments in boundary-layer meteorology. The presentation nicely illustrated the huge progress in the design, equipment and scientific content of boundary-layer field studies from local-
scale field campaigns with just an instrumented tower and some balloon ascents towards complex mesoscale field experiments employing ground-based in-situ and remote sensing technology, airborne measurements and regional-scale sensor networks. The author critically noticed a number of weaknesses often associated with field experiments today. These concern, e.g., the missing link between near-surface micrometeorology and boundary-layer process studies in many experiments (particularly in the ecology community), the missing of important experimental components in field experiments due to budget constraints and the partially non-mature, test status of equipment employed. A second keynote presentation in sub-session III was given by B. Calpini (MeteoSwiss Payerne) who reported about recent
field experiments organised by the World Meteorological Organisation (WMO) to test and characterise new sensor systems for operational use by the National Weather Services. These often extremely carefully designed experiments allow for a comprehensive assessment of the recent status and progress in certain
fields of meteorological sensor technology. Examples presented were the intercomparison of rainfall intensity instruments 2007-2008 in Italy, the thermometer screen / humidity sensor intercomparison 2008-2009 in Algeria, and the most resent radiosonde intercomparison performed in China in 2010. Reports on these intercomparison experiments can be found at:
http://www.wmo.int/pages/prog/www/IMOP/intercomparisons.html .

The contributed papers dealt with a wide range of topics under the general headline. Major field experiments presented were the already well-known AMMA (F. Couvreux, MeteoFrance Toulouse, COPS (N. Filipovic, University of Vienna), and VOCALS (P. Zuidema, University of Miami) experiments, but also the more recent urban FluxSAP-2010 campaign (Y. Brunet, INRA), and the LITFASS-2009 (F. Beyrich, DWD Lindenberg) and BLLAST (M. Lothon, University Toulouse) experiments. The latter one was a very recent field campaign (measurements were performed in June and July 2011 at Lannemezan, France) devoted to study the late afternoon / early evening transition of the atmospheric boundary layer. Concerning meteorological sensor characterisation, several papers demonstrated the capabilities of small-scale unmanned aircraft for measurements of boundary-layer parameters and turbulence (e.g., S. Martin Braunschweig University of Technology, A. v. d. Kroonenberg Tübingen University). S. Griesel (DWD Hamburg) reported on a long-term experiment to characterize state-of-the-art humidity sensors. R. Boers et al. (KNMI De Bilt) presented an interesting paper on sensor synergy for reliable fog detection and characterisation. The gap from research towards operational application was bridged by two talks on a micro-radar network in Northern Italy (S. Turso, Politecnico di Torino) and on the combination of fixed and mobile surface observations into a hybrid system for operational road weather monitoring in Finland (P. Saarikivi, Foreca Ltd. Helsinki).

Overall, the symposium covered a broad spectrum of measurement techniques and atmospheric process studies. It has found broad interest among the conference participants well beyond the list of speakers (the number of people in the audience varied between about 30 and 80) and inspired interesting discussions and contacts among the scientists.

F. Beyrich, F.C. Bosveld, and H.A.R. de Bruin