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A fuzzy logic hydrometeor classification algorithm (HCA), allowing discrimination between six microphysical species regardless of the radar wavelength is presented and evaluated. The proposed method is based upon combination sets of dual-polarimetric observables (reflectivity at horizontal polarization ZH, differential reflectivity ZDR, specific differential phase KDP, correlation coefficient ρHV) along with temperature data inferred from a numerical weather prediction model output. The performance of the HCA is evaluated using 20 h of multi-frequency dual-polarimetric radar data collected during the first Special Observation Period (SOP1) of the Hydrological Cycle in the Mediterranean Experiment (HyMeX). A new method based upon intercomparisons of retrieved hydrometeor data deduced from pairs of neighbouring radars (S-band vs. S-band and S-band vs. C-band) over a common sampling area is proposed to evaluate the consistency of hydrometor classification outputs. S-/C-band radar comparisons generally show better consistency than S-/S-band radar comparisons due to issues with the identification of the 0°C isotherm on one of the two S-band radars. Imperfect attenuation correction at C-band may also lead into differences in hydrometeor fields retrieved from the C- and S-band radars in convective situations, but retrieved hydrometeor data are globally very consistent from one radar to another. Comparisons against in situ airborne data also confirm the overall good performance of the HCA. In a second experiment, an original method allowing the production of multi-radar three-dimensional (3D) hydrometeor fields from single-radar 2D hydrometeor data is tested on a bow-echo convective system observed with C- and S-band radars. The resulting 3D hydrometeor fields provide a detailed view of the bow-echo microphysical structure and confirm the good performance of both the HCA and interpolation technique. [ABSTRACT FROM AUTHOR]

The structure of a bow-echo system that crossed southeast France on 24 September 2012 during the first Special Observation Period of the Hydrological cycle in the Mediterranean Experiment (HyMeX) is investigated from a three-dimensional lightning mapping array (LMA), an operational lightning network, and operational polarimetric radar observations. Lightning observations reveal that 97% of flash initiation and 93% of flash propagation occurred within the convective region. Through combining LMA and radar-derived microphysical data it is also shown that lightning initiation events and propagation mostly occurred in regions containing graupel (initiation = 70%, propagation = 58%), ice (initiation = 22%, propagation = 33%), and to a lesser extent hail (initiation = 6%, propagation = 5%). The detailed analysis of the lightning activity during two periods of contrasted electrical activity suggests that wet hail growth processes and/or charge redistribution within the cloud may have had a negative impact on lightning initiation occurrences and propagation. The most active periods in terms of lightning activity occurred in conjunction with a vigorous, terrain driven, updraught that transported graupel particles above a height of 12 km. [ABSTRACT FROM AUTHOR]

The PEACH project (Projet en Electricité Atmosphérique pour la Campagne HyMeX – the Atmospheric Electricity Project of the HyMeX Program) is the atmospheric electricity component of the Hydrology cycle in the Mediterranean Experiment (HyMeX) experiment and is dedicated to the observation of both lightning activity and electrical state of continental and maritime thunderstorms in the area of the Mediterranean Sea. During the HyMeX SOP1 (Special Observation Period) from 5 September to 6 November 2012, four European operational lightning locating systems (ATDnet, EUCLID, LINET, ZEUS) and the HyMeX lightning mapping array network (HyLMA) were used to locate and characterize the lightning activity over the northwestern Mediterranean at flash, storm and regional scales. Additional research instruments like slow antennas, video cameras, microbarometer and microphone arrays were also operated. All these observations in conjunction with operational/research ground-based and airborne radars, rain gauges and in situ microphysical records are aimed at characterizing and understanding electrically active and highly precipitating events over southeastern France that often lead to severe flash floods. Simulations performed with cloud resolving models like Meso-NH and Weather Research and Forecasting are used to interpret the results and to investigate further the links between dynamics, microphysics, electrification and lightning occurrence. Herein we present an overview of the PEACH project and its different instruments. Examples are discussed to illustrate the comprehensive and unique lightning data set, from radio frequency to acoustics, collected during the SOP1 for lightning phenomenology understanding, instrumentation validation, storm characterization and modeling. [ABSTRACT FROM AUTHOR]

The radar network deployed in southern France during the first special observing period (SOP 1) of the Hydrological Cycle in the Mediterranean Experiment (HyMeX) was designed to precisely document the 3D structure of moist upstream flow impinging on complex terrain as a function of time, height, and along-barrier distance, and surface rainfall patterns associated with orographic precipitation events. This deployment represents one of the most ambitious field experiments yet, endeavoring to collect high-quality observations of thunderstorms and precipitation systems developing over and in the vicinity of a major mountain chain. Radar observations collected during HyMeX represent a valuable, and potentially unique, dataset that will be used to improve our knowledge of physical processes at play within coastal orographic heavy precipitating systems and to develop, and evaluate, novel radar-based products for research and operational activities. This article provides a concise description of this radar network and discusses innovative research ideas based upon preliminary analyses of radar observations collected during this field project with emphasis on the synergetic use of dual-polarimetric radar measurements collected at multiple frequencies. [ABSTRACT FROM AUTHOR]

The PEACH (Projet en Electricité Atmosphérique pour la Campagne HyMeX - the Atmospheric Electricity Project of HyMeX Program) project is the Atmospheric Electricity component of the HyMeX (Hydrology cycle in the Mediterranean Experiment) experiment and is dedicated to the observation of both lightning activity and electrical state of continental and maritime thunderstorms in the area of the Mediterranean Sea. During the HyMeX SOP1 (Special Observation Period; 5 September-6 November 2012), four European Operational Lightning Locating Systems (OLLSs) (ATDNET, EUCLID, LINET, ZEUS) and the HyMeX Lightning Mapping Array network (HyLMA) were used to locate and characterize the lightning activity over the Southeastern Mediterranean at flash, storm and regional scales. Additional research instruments like slow antennas, video cameras, micro-barometer and microphone arrays were also operated. All these observations in conjunction with operational/research ground-based and airborne radars, rain gauges and in situ microphysical records aimed at characterizing and understanding electrically active and highly precipitating events over Southeastern France that often lead to severe flash floods. Simulations performed with Cloud Resolving Models like Meso-NH and WRF are used to interpret the results and to investigate further the links between dynamics, microphysics, electrification and lightning occurrence. A description of the different instruments deployed during the field campaign as well as the available datasets is given first. Examples of concurrent observations from radio frequency to acoustic for regular and atypical lightning flashes are then presented showing a rather comprehensive description of lightning flashes available from the SOP1 records. Then examples of storms recorded during HyMeX SOP1 over Southeastern France are briefly described to highlight the unique and rich dataset collected. Finally the next steps of the work required for the delivery of reliable lightning-derived products to the HyMeX community are discussed. [ABSTRACT FROM AUTHOR]