E. Palmisano

Hydrological control of flooding: Tuscany, October 1992

In the study of flash-flood occurrence in small catchments the lack of flow measurements is often one of the main limiting factors. Prior to estimating the forecasting potentialities and techniques for such events, an accurate reconstruction of past event flood dynamics is first required. This issue is here addressed by analyzing, with the use of a distributed hydrological model, the hydrometeorological conditions in which a severe flash-flood occurred, on October 1992, on a 48 square kilometers catchment in the Arno basin. Such an event was caused by the persistence of intense convective clusters on the background of widespread rain bands of frontal origin. The distributed hydrological model here adopted is devoted to simulate the evolution and the variability of the primary processes involved in the runoff cycle. Together with the hydrological model structure, other particular aspects of the event reconstruction procedure are discussed: the managing and processing of the information coming from different sensors, with different temporal and spatial resolutions; the identification of local precipitation dynamics (frontal or convective) within small areas of integrated radar and rain gauges data fields; the interpolation of rain gauge data on the basis of the radar-estimated spatial correlation. The results of the distributed modeling, concerning the estimate of the flood wave at various sites, are compared with analogous results obtained with simpler lumped models.

Hydrological Response to Radar Rainfall Maps through a Distributed Model

Weather radars in investigating physical characteristics of precipitation are becoming essential instruments in the field of short term meteorological investigation and forecasting. To analyze the radar signal impact in hydrological forecasting, precipitation input fields, generated through a statistical mathematical model, are supplied to a distributed hydrological model. Such a model would allow the control of the basin response to precipitation measurements obtained by a meteorological radar and, in the meanwhile, to evaluate the influence of distributed input. The distributed model describes the basin hydrological behavior, subdividing it into distinct geometrical cells and increasing the physical significance by reproducing the distributed hydrographic basins characteristics, such as infiltration capacity, runoff concentration time, network propagation speed, soil moisture influence. Each basin cell is characterized by its geological, pedological and morphological status, and may be considered a unitary hydrological system, linked to the others by geomorphological and hydraulic relationships. To evaluate the dynamics of the flood event a synthetic representation of the channel network is introduced, where each stream branch is modeled as a linear reservoir. Finally, the discharge in the outlet section is derived, taking into account the hydraulic characteristics of the upstream branches.

Analysis of radar and raingauge measurements for a critical meteorological event in Tuscany

In this paper, some considerations are given to the employment of C-band polarimetric weather radars for rainfall estimates. The most common error sources are discussed, such as ground clutter and propagation attenuation effects, together with decorrelation in the sampling at the ground between radar and raingauge measurements, which can be quite significant in radar systems located in hilly regions, as is the case of the Arno basin in Tuscany. Since the main objective from a hydrological point of view is the estimate of rainfall at ground, integrations and comparisons are needed between radar and raingauge data, which are characterized by different time and space sampling. The paper is then focussed mainly on this problem and a technique is presented in order to improve radar based rainfall estimates through the integration with raingauge data, in order to enhance the correlation between the two types of measurements. Such a method is finally applied to a serious meteorological event which affected the Arno basin on October 1992.

Weather radar calibration by means of the metallic sphere and multiparameter radar measurements

SummaryAbsolute calibration is an important task in order to obtain reliable and accurate measurements of radar observables and derived meteorological parameters. In this paper two procedures are described; the first one is based on measuring the power received from a metallic sphere and the second utilizes the rainfall estimates obtained by the multiparameter radar measurements. The accuracy of the latter method is studied in detail from the simulation of the dual polarization measurables. The theoretical results are compared with radar measurements relative to a rain event.

Rain assessment through integration of radar and rain‐gauge data in severe storms

This paper deals with the application of several techniques for the correction of multiple errors arising in polarimetric meteorological C‐band radars, when used for rainfall estimation in the presence of both severe meteorological events and a complex orography. In particular, techniques based on radar calibration through rain‐gauge measurements are analysed when used to compensate for errors which can be due to multiple phenomena, including propagation attenuation, beam blocking, ground clutter, intrinsic partial decorrelation between the precipitation observed at the ground and that measured above, and space‐time non‐stationarity of the radar reflectivity conversion law. The techniques considered exploit reliability tests for data validation and alternative algorithms for the correction of propagation attenuation effects. Calibration of radar data with rain‐gauge measurements is performed resorting to two alternative techniques: one looking for an optimal law to be used as a unique reference for the co...

Establishing videoconferencing infrastructure in R. Macedonia

In the next decades European Higher Education will face the major challenges and opportunities of globalization with accelerated technological developments with new providers, new learners and new types of learning. New educational requirements stimulated by the innovative telecommunication technologies together with novel educational materials and methodologies pave the way for the introduction of videoconferencing systems that can be used to establish distance learning environments. The three-year Project ViCES (Video Conferencing Educational Services) was launched and financed by the European Commission within the TEMPUS (Trans-European Mobility Scheme for University Studies) Programme. The VICES project will provide Republic of Macedonia with a technological infrastructure and learning environment that eases student and academic mobility as well as support the process of harmonization of different curricula among educational institutions. This paper presents the different characteristics of the ViCES infrastructure.

Robustness and limitation of algorithms for attenuation correction of C-band meteorological radar

Addresses the problem of jointly correcting beam blocking and C-band propagation attenuation effects in weather radars by resorting to incoherent radar observables and to a clutter discrimination technique. The authors propose a strategy for data processing and discuss its effectiveness based on data gathered during a severe storm occurred in October 1992. Data analysis points out that accounting for the effects of clutter contamination and beam screening in the correction procedure greatly helps in mitigating the effects the instability of iterative techniques utilised for C-band attenuation correction. Nevertheless, in the presence of extremely intense rainfall, the correction algorithm may still. Diverge, clearly evidencing that in such cases the problem of an adequate and careful criterion to derive the specific attenuation-reflectivity conversion relationship becomes of primary importance.

Spatial and temporal sampling errors in rainfall fields reconstruction through meteorological radar data

The accuracy in the reconstruction of space-time rainfall fields through radar rainfall estimates depends both on the accuracy of the estimate in the radar sample volume, and on the data updating capability of the radar system. The last aspect becomes of capital importance when the monitored phenomenon exhibits a high variability both in space and in time. This paper analyzes the problem of the optimal choice, depending on monitored event, of parameters of the radar acquisition, to minimize the error in reconstructing a rainfall field through the radar observation.<<ETX>>