1,720,986 research outputs found
A. Clutter and anomalous propagation identification using doppler-polarimetric measurements and vertical reflectivity profile
No full textClutter and rainfall discrimination by means of doppler-polarimetric measurements and vertical reflectivity profile analysis
No full textA method to remove effects of radar beam interaction with the ground in various propagation conditions. impact on data quality
No full text
Impact of combined beam blocking and anomalous propagation correction algorithms on radar data quality
No full textDebris flows rainfall thresholds in the Apennines of Emilia-Romagna (Italy) derived by the analysis of recent severe rainstorms events and regional meteorological data
Full text linkRecent severe rainstorms events in October 2014 and September 2015 triggered more than a hundred debris-flows in the western part of the Apennines of Emilia-Romagna (Italy). In this work, we tested a novel method to define debris flows rainfall thresholds for the 2014 and 2015 rainstorms (which have been used as reference events) and to extend these results across the Apennines of Emilia-Romagna, making use of long-term rainfall data of the regional raingauges network. Results are compared, for validation, to rainfall rates recoded during other past rainstorm-debris flows events (which have been used as validation events). At first, the method involves a spatial discriminant analysis between the spatial distribution of debris flows and the high frequency weather-radar rainfall data for the 2014 and 2015 reference events. The analysis defines rainfall cutoff values over rainfall durations from 30′ to 6 h, related to verification indices in the ROC curves, which are used as debris flows rainfall thresholds. Exceedance ratios are calculated between the computed rainfall thresholds and the rainfall rates at 10 years return periods at corresponding rainfall durations computed for raingauges located in the areas affected by the 2014 and 2015 events. The ratios are then used as multipliers of the rainfall rates at 10 years return periods over rainfall durations from 30′ to 6 h calculated for all other raingauges in the regional study area. To spatialize thresholds calculation to the regional scale, the computed thresholds are interpolated across the Apennines of Emilia-Romagna. The research resulted in the assessment of two-levels debris flows rainfall thresholds curves which seem to be adequate to discriminate rainfall rates recorded during past debris flows events used for validation. Discussion evidences advantages and limits of our approach, compares results to existing debris flows thresholds and highlights their possible use in a multi-stage warning procedure at regional scale
Spatial characterization and classification of rainfall fields derived from operational c-band weather radar data
No full textSewer Flow Prediction at a Large Urban Scale: Influence of Radar Rainfall Spatial Resolution
No full textThere is a growing interest in using radar rainfall data to evaluate the performance of urban drainage systems in near real time. This paper describes a study based on a large (55 km2) urban catchment in northern Italy. Different spatial resolutions of radar data have been compared and used as input to a numerical hydrological-hydraulic model of the drainage system, constructed by means of Infoworks CS software. The results show that the spatial resolution of weather radar data plays a significant role when modelling the hydrological behaviour of the drainage system and using different resolutions may result in significant differences in peak flows and runoff volumes
DEBRIS FLOWS IN VAL PARMA AND VAL BAGANZA (NORTHERN APENNINES) DURING THE 12-13TH OCTOBER 2014 ALLUVIAL EVENT IN PARMA PROVINCE (ITALY)
No full textDuring the 13 October 2014 rainstorm event that affected the
Val Parma and Val Baganza area, several debris flows affected
the Mt. Cervellino relief (northern Apennines, Italy), causing
severe and widespread damages to check-dams, roads and other
infrastructures. Such event, together with the Piacenza province
event of 2015, has generated the perception of debris flows as
a breaking new potential cause of widespread damages in the
Emilia-Romagna. The meteorological event of October 2014,
reconstructed by means of rain gauges and radar data, reached
intensities as high as 80 mm/hour, which is well above any debris
flow triggering thresholds presented in literature. However, data
show that debris flows have occurred in any location where 30
mm/hour were exceeded. The result was the occurrence of tens
of debris flows, which were triggered in zones of failure of slope
debris coverage along the streams, and that remobilized and
scoured debris along the track and destroyed several check dams
and damaged roads that were overflown by debris. This paper is
aimed to document the distribution and characteristics of the debris
flow events that occurred during such event. By doing so, it also
warns against this potentially destructive events that, in a changing
meteorological framework, might result much more frequent and
widespread than expected also in the northern Apennines
Reflectivity and velocity radar data assimilation for two flash flood events in central Italy: A comparison between 3D and 4D variational methods
Full text linkThe aim of this study is to provide an evaluation of the impact of two largely used data assimilation techniques, namely three- and four-dimensional variational data assimilation systems (3D-Var and 4D-Var), on the forecasting of heavy precipitation events using the Weather Research and Forecasting (WRF) model. For this purpose, two flash flood events in central Italy are analysed. The first occurred on September 14, 2012 during an Intensive Observation Period of the Hydrological cycle in the Mediterranean experiment (HyMeX) campaign, while the other occurred on May 3, 2018. Radial velocity and reflectivity acquired by C-band weather radars at Mt. Midia (central Italy) and San Pietro Capofiume (northern Italy), as well as conventional observations (SYNOP and TEMP), are assimilated into the WRF model to simulate these damaging flash flood events. In order to evaluate the impact of the 3D-Var and 4D-Var assimilation systems on the estimation of short-term quantitative precipitation forecasts, several experiments are carried out using conventional observations with and without radar data. Rainfall evaluation is performed by means of point-by-point and filtering methodologies. The results point to a positive impact of the 4D-Var technique compared to results without assimilation and with 3D-Var experiments. More specifically, the 4D-Var system produces an increase of up to 22% in terms of the Fractions Skill Score compared to 3D-Var for the first flash flood event, while an increase of about 5% is achieved for the second event. The use of a warm start initialization results in a considerable reduction in the spin-up time and a significant improvement in the rainfall forecast, suggesting that the initial precipitation spin-up problem still occurs when using 4D-Var
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