Abstract: De afdeling Seismologie van het KNMI heeft een op een aantal meetlocaties infrasound arrays in gebruik. Een array bestaat uit 6 tot 14 infrasound sensoren (microbarometers). In het kader van de bewaking van het het kernstop verdrag is het doel om de calibratie en kwaliteitsborging van deze sensoren in te richten analoog aan de (andere) operationele sensoren van het KNMI. Cruciaal in de borging van de kwaliteit is een geautomatiseerde test voorziening en calibratie procedure waarmee de kwaliteit van de microbarometer kan worden vastgesteld. In een project is een werkende testopstelling onder laboratorium condities geconstrueerd. Dit rapport beschrijft deze experimentele opstelling en laat zien wat de met deze opstelling haalbare kwaliteit is. Een operationele calibrator wordt n.a.v. dit rapport echter NIET gerealiseerd.

Abstract: Doel van het project LDUR was het vaststellen van eindgebruikerseisen (EndUser Requirements) met betrekking tot bliksemdetectie en deze vertalen naar de instrumentele en functionele eisen die het KNMI stelt aan bliksemdetectie voor de periode 2011-2020. In het kader van dit project zijn gebruikerseisen geïnventariseerd en is een marktverkenning uitgevoerd. De resultaten daarvan zijn vertaald in aanbevelingen. De gebruikerseisen zijn vastgesteld door het afnemen van interviews. Deze eisen zijn per toepassing samengevat en waar mogelijk vertaald naar meetbare grootheden.

Abstract: A method for daily monitoring of the differential reflectivity bias for polarimetric weather radars is presented. Sun signals detected in polar volume data produced during operational scanning of the radar are used. This method is an extension of that for monitoring the weather radar antenna pointing at low elevations and the radar receiving chain using the sun. The online sun monitoring can be used to check the agreement between horizontal and vertical polarization lobes of the radar antenna which is a prerequisite for high-quality polarimetric measurements. By performing both the online sun monitoring and rain calibration at vertical incidence, the differential receiver bias and differential transmitter bias can be disentangled. Results from the polarimetric radars in Trappes (France) and Bornholm (Denmark) demonstrating the importance of regular monitoring of the differential reflectivity bias are discussed.

Abstract: A method for operational monitoring of a weather radar receiving chain, including the antenna gain and the receiver, is presented. The ‘‘online’’ method is entirely based on the analysis of sun signals in the polar volume data produced during operational scanning of weather radars. The method is an extension of that for determining the weather radar antenna pointing at low elevations using sun signals, and it is suited for routine application.

Abstract: In 2007 KNMI has successfully upgraded the Dutch radar network. The digital receivers and data processing equipment integrated in our METEOR 360AC radar sensors (SELEX SI) and the product processing, in our central computer facilities, are currently in full operation. In the Poster presentation highlights of this upgrade project will be discussed with a focus on basic radar processing.

Abstract: When operating a network of weather radars for monitoring of (severe) precipitation and (strong) wind, data quality and network homogeneity are of crucial importance. Using sun for offline calibration of the antenna alignment is a well-established method and tools for this are included in the software packages provided by the radar manufacturers. This offline calibration is typically performed during radar maintenance. Solar signals can, however, be detected automatically in polar reflectivity data produced operationally by a weather radar.

Abstract: KNMI operates a SAFIR Lightning Detection System for monitoring (severe) convection and for feeding a climatological database. The localization accuray and detection efficiency of the lightning discharges is crucial for these applications. In this presentation the preliminary results of the validation of SAFIR with weather radar, infrasoundsensors, and LOFAR, the ASTRON new low-frequency digital radio telescope array will be discussed.

Abstract: In the early 90s, a stepwise procedure for the rejection of anomalous propagation) clutter has been developed and implemented in the C-band weather radars of KNMI. This procedure is based on distinguishing between the inherently fluctuating Rayleigh-scattered precipitation signals and the relatively stable ground clutter signals. A Dynamical clutter map is constructed from the "fluctuation" flags using a spatial averaging procedure and a decision-making model. Anomalous propagation clutter over land is removed almost completely, while the system is partly (40 %) effective in removing sea clutter. All in all, the radar operators and customers are quite satisfied with the performance of this statistical clutter rejection method.

Info: In conjunction with the 81st meeting of the American Meteorological Society a radar calibration workshop was organized by Paul Joe (MSC, Canada). This workshop was held on 13 and 14 January 2001 in Albuquerque, New Mexico, and about 35 presentations were given on various topics related to radar calibration.

Abstract: KNMI (Royal Netherlands Meteorological Institute) has upgraded its Lightning Detection System (LDS). This new system is called FLITS (Flash Localisation by Interferometry and Time of arrival System) to distinguish it from the former system called SAFIRK. From 1987 onward KNMI uses automated observing systems to record lightning activity for nowcasting and climatological purposes. The first system was a time of arrival system called LPATS (Lightning Tracking and Positioning System) operated by KEMA, a Dutch energy provider. In 1995 this system was replaced by a Safir system, called SAFIRK, that was acquired in a joint effort by KNMI, The Royal Dutch Air Force, and The Royal Dutch Navy. Soon it became clear that the three detection stations used by this initial system offered too little coverage. Therefore raw data from the Belgium Safir system is used from 1997 onward to enhance reliability and coverage in southern direction. In 2001 a fourth detection station of type Safir 3000, situated in the north east of the Netherlands, came into operation. Within the scope of the project LDUP that upgrades the SAFIRK system to FLITS, the three original detection stations are now upgraded to SAFIR 3000 type stations as weel. In this project also the servers and all vendor software is replaced.

Abstract: Pulse to pulse radar echo fluctuations have been used to distinguish rain from anomalous propagation clutter. For 1 deg. sectors at fixex range 14 echo samples from successive pulses are tested for clutter. This test has a clutter detection rate of only 45 percent, but in each 1 deg. 2 km polar radar pixel 8 range bins can be tested.The 8 tests are shown to be nearly independent and their combined result allows 85 percent of the clutter pixels to be detected.Finally the pattern of suspect pixels in the completed radar picture is analysed on a scale of about 10 km.The total result in an average removal efficiency of about 98 percent.