The North Atlantic Waveguide and Downstream Impact Experiment

The North Atlantic Waveguide and Downstream Impact Experiment (NAWDEX) explored the impact of diabatic processes on disturbances of the jet stream and their influence on downstream high-impact weather through the deployment of four research aircraft, each with a sophisticated set of remote sensing and in situ instruments, and coordinated with a suite of ground-based measurements. A total of 49 research flights were performed, including, for the first time, coordinated flights of the four aircraft: the German High Altitude and Long Range Research Aircraft (HALO), the Deutsches Zentrum für Luft- und Raumfahrt (DLR) Dassault Falcon 20, the French Service des Avions Français Instrumentés pour la Recherche en Environnement (SAFIRE) Falcon 20, and the British Facility for Airborne Atmospheric Measurements (FAAM) BAe 146. The observation period from 17 September to 22 October 2016 with frequently occurring extratropical and tropical cyclones was ideal for investigating midlatitude weather over the North Atlantic. NAWDEX featured three sequences of upstream triggers of waveguide disturbances, as well as their dynamic interaction with the jet stream, subsequent development, and eventual downstream weather impact on Europe. Examples are presented to highlight the wealth of phenomena that were sampled, the comprehensive coverage, and the multifaceted nature of the measurements. This unique dataset forms the basis for future case studies and detailed evaluations of weather and climate predictions to improve our understanding of diabatic influences on Rossby waves and the downstream impacts of weather systems affecting Europe

Water vapour intercomparison effort in the frame of the Convective and Orographically-induced Precipitation Study

International audienceThe main objective of this work is to provide accurate error estimates for the different water vapour profiling sensors based on an intensive inter-comparison effort. The inter-comparison, performed in the framework of COPS--Convective and Orographically-induced Precipitation Study (01 June-31 August 2007), involves airborne and ground-based water vapour lidar systems, radiosondes with different humidity sensors, GPS and Microwave radiometers (MWR). Simultaneous and co-located data from different sensors are used to compute relative bias and root-mean square (RMS) deviations as a function of altitud

Water vapour intercomparison effort in the frame of the Convective and Orographically-induced Precipitation Study

International audienceThe main objective of this work is to provide accurate error estimates for the different water vapour profiling sensors based on an intensive inter-comparison effort. The inter-comparison, performed in the framework of COPS--Convective and Orographically-induced Precipitation Study (01 June-31 August 2007), involves airborne and ground-based water vapour lidar systems, radiosondes with different humidity sensors, GPS and Microwave radiometers (MWR). Simultaneous and co-located data from different sensors are used to compute relative bias and root-mean square (RMS) deviations as a function of altitud

Water vapour intercomparison effort in the frame of the Convective and Orographically-induced Precipitation Study

The main objective of this work is to provide accurate error estimates for the different water vapour profiling sensors based on an intensive inter-comparison effort. The inter-comparison, performed in the framework of COPS - Convective and Orographically-induced Precipitation Study (01 June-31 August 2007), involves airborne and ground-based water vapour lidar systems, radiosondes with different humidity sensors, GPS and Microwave radiometers (MWR). Simultaneous and co-located data from different sensors are used to compute relative bias and root-mean square (RMS) deviations as a function of altitude. Comparisons between airborne CNRS DIAL and ground-based Raman lidar BASIL from three dedicated flights performed in the frame of the H2Olidar EUFAR project indicate a mean relative bias between the two sensors of 3.9% (0.11 g/kg) and a mean RMS deviation of 13.7% (0.97 g/kg) in the altitude region 0-4.5 kin above ground level. A specific inter-comparison between radiosondes with different humidity sensors (Vaisala RS80-A, RS80-H and RS92) was also performed during COPS. Results from the radiosonde inter-comparison indicate that RS80-A and RS80-H are affected by several systematic sources of error (contamination error, time-lag error, etc.), which have been corrected through established algorithms [1, 2, 3]. After correction for these error sources, mean bias between RS80 (A&H) and RS92 is found to be reduced to -4.5%. Based on the 3 comparisons between BASIL vs airborne DLR DIAL, the mean relative bias is about -3.5% in the altitude region 0-3 Km, while the RMS is approx. 13%. There are also ongoing comparisons between BASIL vs GPS, MWR and radiosondes and between the water vapor sensors located at different sites and the airborne DIALs which will be discussed at the symposium. Thus on the present statistics of comparisons between BASIL vs both the airborne DIALs and GPS and putting equal weight on the data reliability of each instrument, it results in the bias values of. BASIL Raman Lidar-0.3%, DLR DIAL 3.2%, CNRS DIAL-3.6% and GPS 0.6%. More ongoing comparisons between water vapor profiling sensors, especially benefiting from the extraordinary performances of the ground-based UHOH DIAL system, will be discussed at the symposium