ABSTRACT Quantitative precipitation estimation is a crucial issue especially for predicting flash... more ABSTRACT Quantitative precipitation estimation is a crucial issue especially for predicting flash floods in the small catchments typical of the Mediterranean area. In Italy, Civil Protection has the duty of managing and generating reliable QPE products useful for warning and monitoring purposes in case of severe events over the Italian territory. To this end a dense network of raingauges (about 2000 stations with hourly timestep) is available together with a precipitation field obtained from the National Radar Composite. This work aims at considering and comparing different techniques available for operationally merge rainfall estimation from different sensors . In particular will be presented a comparison of the Modified Conditional Merging algorithm (presented at this conference by Pignone et al.) with a Bayesian procedure that exploits the radar quality maps available for two test sites of the Italian Radar Composite (Mt. Settepani and Il Monte). The aim of this work is twofold, from one side is to test the Bayesian algorithm, its robustness and applicability in an operational context, and, on the other side, to define the best procedure for comparing and evaluating different data merging algorithms potentially useful for Civil Protection applications.
ABSTRACT The city of Genoa, which nestles between the Tyrrhenian sea and the Apennine mountains (... more ABSTRACT The city of Genoa, which nestles between the Tyrrhenian sea and the Apennine mountains (Liguria, Italy) was rocked by severe flash floods on 4th November 2011. About 500 millimeters of rain - a third of the average annual rainfall - fell in six hours. Six people were killed. The raging waters uprooted trees, swept cars, shattered shops and flooded the town center. The synoptic-scale meteorological system, which was responsible for the Genoa flash flood, raged from West Virginia to Maine from 29th until 30th October and was blamed for at least 13 deaths. It moved across the Atlantic Ocean, generated floods that killed 5 people in Southern France, and finally it arrived over the Liguria sea and produced the severe rainfall, which we present here. Cloud-permitting simulations (1 km) of the finger-like convective system responsible for this torrential event over Genoa have been performed using Advanced Research Weather and Forecasting Model (ARW-WRF, version 3.2.1). Two different microphysics (WSM6 and Thompson) as well as three different convection closures (explicit, Kain-Fritsch, and Betts-Miller-Janjic) have been combined to gain a deeper understanding of the physical processes underlying the observed torrential event. Comparison between modeling findings and observed fields provided by raingauge data, satellite data, and radar data have undertaken. The paper presents the results and gathers conclusions.
ABSTRACT The estimation of rainfall fields, especially its spatial distribution and position is a... more ABSTRACT The estimation of rainfall fields, especially its spatial distribution and position is a crucial task both for rainfall nowcasting and for modeling catchment response to rainfall. Some studies of literature about multisensor datafusion prove that combining data from raingauges and radar represents the best way to obtain an enhanced ad more reliable estimation of QPE and of the associated river discharge. Sinclair and Peagram (2004) have proposed the Conditional Merging (CM) technique, a merging algorithm which extract the information content from the observed data and use it within an interpolation method to obtain the rainfall maps. The raingauges provide a punctual measure of the ground-observed rainfall while the remote sensors (radar network or satellite constellation) supply rainfall estimation maps which give an idea of the correlation and structure of covariance of the observed field. In this work is presented an algorithm called Modified Conditional Merging that is based on CM and which is used for real-time estimation of the optimal rainfall maps. The area of interest is Italy, where are both available a dense network of raingauge measurements (about 2000 stations) and a QPE estimated by the Italian Radar composite. The main innovation respect to classical CM is to estimate the structure of covariance and the length of spatial correlation λ, for every raingauge, directly from the cumulated radar rainfall fields. An application to several test cases together with the evaluation of algorithm performances are presented and discussed.
ABSTRACT Quantitative precipitation estimation is a crucial issue especially for predicting flash... more ABSTRACT Quantitative precipitation estimation is a crucial issue especially for predicting flash floods in the small catchments typical of the Mediterranean area. In Italy, Civil Protection has the duty of managing and generating reliable QPE products useful for warning and monitoring purposes in case of severe events over the Italian territory. To this end a dense network of raingauges (about 2000 stations with hourly timestep) is available together with a precipitation field obtained from the National Radar Composite. This work aims at considering and comparing different techniques available for operationally merge rainfall estimation from different sensors . In particular will be presented a comparison of the Modified Conditional Merging algorithm (presented at this conference by Pignone et al.) with a Bayesian procedure that exploits the radar quality maps available for two test sites of the Italian Radar Composite (Mt. Settepani and Il Monte). The aim of this work is twofold, from one side is to test the Bayesian algorithm, its robustness and applicability in an operational context, and, on the other side, to define the best procedure for comparing and evaluating different data merging algorithms potentially useful for Civil Protection applications.
ABSTRACT The city of Genoa, which nestles between the Tyrrhenian sea and the Apennine mountains (... more ABSTRACT The city of Genoa, which nestles between the Tyrrhenian sea and the Apennine mountains (Liguria, Italy) was rocked by severe flash floods on 4th November 2011. About 500 millimeters of rain - a third of the average annual rainfall - fell in six hours. Six people were killed. The raging waters uprooted trees, swept cars, shattered shops and flooded the town center. The synoptic-scale meteorological system, which was responsible for the Genoa flash flood, raged from West Virginia to Maine from 29th until 30th October and was blamed for at least 13 deaths. It moved across the Atlantic Ocean, generated floods that killed 5 people in Southern France, and finally it arrived over the Liguria sea and produced the severe rainfall, which we present here. Cloud-permitting simulations (1 km) of the finger-like convective system responsible for this torrential event over Genoa have been performed using Advanced Research Weather and Forecasting Model (ARW-WRF, version 3.2.1). Two different microphysics (WSM6 and Thompson) as well as three different convection closures (explicit, Kain-Fritsch, and Betts-Miller-Janjic) have been combined to gain a deeper understanding of the physical processes underlying the observed torrential event. Comparison between modeling findings and observed fields provided by raingauge data, satellite data, and radar data have undertaken. The paper presents the results and gathers conclusions.
ABSTRACT The estimation of rainfall fields, especially its spatial distribution and position is a... more ABSTRACT The estimation of rainfall fields, especially its spatial distribution and position is a crucial task both for rainfall nowcasting and for modeling catchment response to rainfall. Some studies of literature about multisensor datafusion prove that combining data from raingauges and radar represents the best way to obtain an enhanced ad more reliable estimation of QPE and of the associated river discharge. Sinclair and Peagram (2004) have proposed the Conditional Merging (CM) technique, a merging algorithm which extract the information content from the observed data and use it within an interpolation method to obtain the rainfall maps. The raingauges provide a punctual measure of the ground-observed rainfall while the remote sensors (radar network or satellite constellation) supply rainfall estimation maps which give an idea of the correlation and structure of covariance of the observed field. In this work is presented an algorithm called Modified Conditional Merging that is based on CM and which is used for real-time estimation of the optimal rainfall maps. The area of interest is Italy, where are both available a dense network of raingauge measurements (about 2000 stations) and a QPE estimated by the Italian Radar composite. The main innovation respect to classical CM is to estimate the structure of covariance and the length of spatial correlation λ, for every raingauge, directly from the cumulated radar rainfall fields. An application to several test cases together with the evaluation of algorithm performances are presented and discussed.
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Papers by F. Pignone