COST 717 USE OF RADAR OBSERVATIONS IN HYDROLOGICAL AND NWP MODELS The main objective of the Action is the assessment, demonstration and documentation of the contribution that advanced radar information such as radial Doppler winds, vertical wind profiles, rainfall and reflectivity can make to assimilation schemes for Numerical Weather Prediction and hydrological models. WG1 Using radar information in hydrological models WG2 Using radar observations in parameterization and validation of atmospheric models WG3 Using radar information for assimilation in atmospheric models Thanks to the many participants from 21 countries. Andrea Rossa, Chairman, MeteoSwiss (Switzerland), Michael Bruen, WG1 Chairman and Action Vice Chairman, University College Dublin (Ireland), Dieter Frühwald, WG2 Chairman, Deutscher Wetterdienst (Germany), Bruce MacPherson, WG3 Chairman, The Met. Office (United Kingdom), COST 717 web address: 1 Review current use of radar data in hydrological models; 2 identify the error characteristics of different radar measurements at a range of scales (temporal and spatial) and examine how these impact on hydrological models; 3 provide a list of requirements for radar data in differing hydrological models for rural and urban catchments, and for urban drainage models; 4 evaluate the use of radar data and calibration techniques in hydrological models to provide quantitative precipitation forecast (QPF) information for hydrological models, over and above that provided by raingauge networks; 5 investigate how radar measurements of precipitation type can improve precipitation rate estimation for input to hydrological models; 6 examine how radar observations can provide a better means of coupling atmosphere and surface models; 7 establish a requirement for radar developments needed for future distributed hydrological models and urban drainage models. 1 Review current methods for assimilating radar data; 2 identify the error characteristics of various radar measurements at a range of scales (temporal and spatial) and examine how these impact on assimilation schemes; 3 provide a list of requirements for radar data in NWP models, and investigate the need for development of models to process radar data before input to NWP; 4 assess the impact of introducing radar (precipitation or reflectivity) data more directly into models, for example via 4D- variational techniques, rather than through moisture fields or by latent heat nudging schemes; 5 examine the relative merits of using Velocity Azimuth Display and Doppler radial velocities in NWP models and the possible use of spectral width information in conjunction with windprofiler information from COST 76; 6 identify the benefits for assimilation of international exchange of single site radar data over and above those gained from using a National composite. 1 Identify how the advanced radar measurements reviewed under COST 75 can be used to improve parametrizations in NWP and climate models and to validate cloud resolving models; 2 define measurement requirements for use in parametrization of convective and stratiform systems; 3 compare different approaches to verification of NWP precipitation forecasts using radar data and other 'ground truth' data sources, with a view to recommending standardised methods within Europe. Entry into force : 1999 End of Action : 2004 Signatories: Austria, Belgium, Cyprus, Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Ireland, Italy, The Netherlands, Norway, Poland, Portugal, Slovenia, Spain, Sweden, Switzerland, United Kingdom Working Group 1 accomplished seven reports, e.g. RADAR-BASED HAIL DETECTION: IMPACT OF HEIGHT ASSIGNMENT ERRORS ON THE MEASURED VERTICAL PROFILES OF REFLECTIVITY by Laurent Delobbe and Iwan Holleman The working group produced a major review on 'Quality and assimilation of radar for NWP', organised a joint session on radar assimilation with the SRNWP community and contributed papers to both radar and NWP conferences to raise the profile of radar assimilation. Below is a summary of the HIRLAM group's project on radar radial wind assimilation. Among the results of the working group were 18 reports, e.g. Results of numerical experiments with LM DWD - first attempts to verify precipitation forecast by radar-derived rainfall fields (1998 flood event) by Daniela Rezacova and Zbynek Sokol An additional outcome as a concerted work of all three working groups will be an overview over „Weather Radar Data Quality in Europe: Quality Control and Characterization“ by D. Michelson, T. Einfalt, I. Holleman, U. Gjertsen, K. Friedrich, G. Haase, M. Lindskog, J. Szturc This effort across working groups will cover reflectivity data quality control as well as wind data quality control The outcome of this COST 717 Action has substantially profited from results of the European Projects ACTIF, BALTEX, CARPE DIEM, EFFS, ELDAS, EUMETRAD, FLOODRELIEF, MANTISSA, MITCH, MUSIC, NORDRAD, OPERA, SRNWP, VOLTAIRE, WINPROF as well as from the previous COST Actions COST 72, COST 73 and COST 75