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Porcu F.,University of Ferrara | Baguis P.,Royal Meteorological Institute of Belgium | Balabanova S.,Bulgarian Academy of Science | Erturk A.,Ondokuz Mayis University | And 38 more authors.
Natural Hazards and Earth System Sciences | Year: 2014

The development phase (DP) of the EUMETSAT Satellite Application Facility for Support to Operational Hydrology and Water Management (H-SAF) led to the design and implementation of several precipitation products, after 5 yr (2005-2010) of activity. Presently, five precipitation estimation algorithms based on data from passive microwave and infrared sensors, on board geostationary and sun-synchronous platforms, function in operational mode at the H-SAF hosting institute to provide near real-time precipitation products at different spatial and temporal resolutions. In order to evaluate the precipitation product accuracy, a validation activity has been established since the beginning of the project. A Precipitation Product Validation Group (PPVG) works in parallel with the development of the estimation algorithms with two aims: to provide the algorithm developers with indications to refine algorithms and products, and to evaluate the error structure to be associated with the operational products. In this paper, the framework of the PPVG is presented: (a) the characteristics of the ground reference data available to H-SAF (i.e. radar and rain gauge networks), (b) the agreed upon validation strategy settled among the eight European countries participating in the PPVG, and (c) the steps of the validation procedures. The quality of the reference data is discussed, and the efforts for its improvement are outlined, with special emphasis on the definition of a ground radar quality map and on the implementation of a suitable rain gauge interpolation algorithm. The work done during the H-SAF development phase has led the PPVG to converge into a common validation procedure among the members, taking advantage of the experience acquired by each one of them in the validation of H-SAF products. The methodology is presented here, indicating the main steps of the validation procedure (ground data quality control, spatial interpolation, up-scaling of radar data vs. satellite grid, statistical score evaluation, case study analysis). Finally, an overview of the results is presented, focusing on the monthly statistical indicators, referred to the satellite product performances over different seasons and areas. © Author(s) 2014.

El Fadli K.I.,Libyan National Meteorological Center | Cerveny R.S.,Arizona State University | Burt C.C.,Weather Underground LLC | Eden P.,Chilterns Observatory Trust | And 11 more authors.
Bulletin of the American Meteorological Society | Year: 2013

The World Meteorological Organization (WMO) has invalidated the 90-year-old record for the world's highest temperature at El Aziza in south-southwest of Tripoli, Libya, due to problems with instrumentation, siting, and observational procedures. Many other reputable sources have also cited the Azizia record as the world's most extreme temperature. One of the major physical rationales for the acceptance of this temperature record has been given by Lamb who suggested that an exceptional föhn wind resulting from a severe thunderstorm far to the south could have created such a remarkable temperature. several researchers have started to evaluate critically the temperature extreme. The maximum temperature readings increase dramatically, while the minimums continue more or less within range. The daily excursions of temperature suddenly increase, with the September 24, 1922 diurnal temperature ranging from 11°to 45°C.

Petkov B.,CNR Institute of Neuroscience | Petkov B.,Abdus Salam International Center For Theoretical Physics | Tomasi C.,CNR Institute of Neuroscience | Vitale V.,CNR Institute of Neuroscience | And 8 more authors.
Atmospheric Research | Year: 2010

The time-patterns of ground-level solar irradiance during the solar eclipse of 29 March, 2006, were observed at three Italian stations (Lampedusa, Mt. Cimone and Bologna) using different radiometric techniques. The global irradiance measured at the sites was found to reach the minimum at times not coinciding with those predicted by radiative transfer model evaluations, with ahead or lag times depending on the optical characteristics of the surface-atmosphere system in the areas surrounding of the stations. This different behaviour has been mainly attributed to the different influence of the environmental conditions on the diffuse radiance component measured at the observation sites. The present results indicate that the incoming diffuse radiance recorded at the three stations was appreciably affected by contributions arising from extended regions of about 30-100 km range from the stations. Such an explanation agrees very well with the theoretical evaluations obtained in earlier studies. The surrounding environmental areas of impact at ultraviolet wavelengths have been found to be wider than those in the visible and near-infrared spectral ranges. © 2009 Elsevier B.V. All rights reserved.

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