threshold exceedance
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Author(s):  
Brian R. La Cour ◽  
Thomas W. Yudichak

AbstractThe relationship between quantum entanglement and classical impropriety is considered in the context of multi-modal squeezed states of light. Replacing operators with complex Gaussian random variables in the Bogoliubov transformations for squeezed states, we find that the resulting transformed variables are not only correlated but also improper. A simple threshold exceedance model of photon detection is considered and used to demonstrate how the behavior of improper Gaussian random variables can mimic that of entangled photon pairs when coincidence post-selection is performed.


2021 ◽  
Author(s):  
Maryse Charpentier-Noyer ◽  
Olivier Payrastre ◽  
Eric Gaume ◽  
Pierre Nicolle ◽  
François Bouttier ◽  
...  

<p>The Aude river flash floods that occurred on October 15 and 16, 2018 are among the most important in southeastern France in recent years. The triggering rainfall of the event was characterized by a very fast evolution and low predictability. During the night, nearly 243.5mm of rain in 6 hours was recorded near the city of Carcassonne. In addition to significant considerable material damage, 15 people lost their lives during this flood and 99 people were injured. After the event, the CNRM proposed new forecast ensembles, targeting the possibility of short-term nowcasting (0-6h) of this phenomenon. These ensembles are based on the several NWP models of Météo France: the first ensemble corresponds to the operational AROME-PE product (12 members), the second is a combination of the AROME-PE and AROME-PI models (18 members); finally, the last ensemble corresponds to the second one with a spatial perturbation (90 members). In addition to these ensemble forecasts, ANTILOPE J+1 high resolution observed precipitation data are available.  The work presented here aims to evaluate, from a hydrological point of view, these three rainfall ensembles specifically designed to improve short-range rainfall now casting. Based on the CINECAR distributed hydrological model, discharge ensembles are calculated for nearly 1200 sub-watersheds with an elementary drainage area of 5km². These  forecasts  are compared for each sub-basin with the CINECAR simulation obtained with ANTILOPE J+1 rainfall data.This evaluation approach enables to compensate the lack of discharge observations during the event and to enlarge the dataset used for evaluation. The evaluation results presented combine synthetic scores (CRPS and rank diagrams) often used for ensemble forecasts, but also a user-oriented evaluation framework based on threshold exceedance detection and anticipation. Thresholds for each sub-watershed correspond to the 5, 10, 20 and 50 year return period discharges (SHYREG database). ROC curves are at first established independently of the level of anticipation. In a second time, the anticipation delays are analyzed,. This work finally reveals that (1) synthetic ensemble forecast evaluation scores are not always sufficient to evaluate forecasts; (2) the user oriented evaluation shows a clear hierarchy between the three forecast product ensembles in terms of threshold exceedance detection, but not in terms of anticipation levels.</p>


2021 ◽  
Author(s):  
Sanjaya Devkota ◽  
Deepak Kc ◽  
Michel Jaboyedoff ◽  
Govind Acharya

<p>Landslides are common in the mid-hill region of Nepal where the terrain slopes are steep and consist of fragile geo-morphology. In Nepal, the casual and triggering factors of the landslides are respectively the underlying geology, intense rainfall and unplanned construction of rural roads is highly recognized, which is however less known and limited in study. Establishment of rainfall threshold for landslides at the watershed landscape is data driven, which is scared in the context of Nepal. The only available long term daily rainfall and sparsely available historical landslides date has been used to develop the rainfall threshold model for the two watersheds in central and western mid-hill regions respectively the Sindhukhola and Sotkhola in Bagmati and Karnali Provinces of Nepal. The watersheds are located in two distinct hydro-climatic regions in terms of rainfall amount and intensity. Historical daily (monsoonal) rainfall data of over four decades (1970-2016) were analyzed available from the Department of Hydrology and Meteorology (DHM)/Government of Nepal and five days’ antecedent rain was calculated. With the limitedly available temporal landslides data, correlation was examined among the 5-days antecedent rain (mm/5days) and daily rainfall (mm/day) portrayed the rainfall threshold (RT) model (Sindhukhola=180-1.07R<sub>T5adt</sub> and Sotkhola = 110-0.83*R<sub>T5adt</sub>). Utilizing the five days’ antecedent rain fitted into the model, results the threshold rainfall. Deducting the five days’ antecedent rains to the RT described the threshold exceedance (R) for the landslides. The model can be plotted in simple spreadsheet (landslides date in Y-axis and threshold exceedance R in X-axis) to visualize the changes in the threshold exceedance over time, whenever the threshold exceedance progressively and rapidly increased and crossed the threshold line and reached to the positive (> 0) zone, the plots allows for the landslides warning notice. In case of the threshold exceedance is further increased there is likely to have landslides in the watersheds. The model was validated with the 35 dated landslides recorded in monsoon 2015 in Sotkhola watershed. The result indicated that the model preserves 72% coefficient of determination (R<sup>2</sup>) where there were landslides in the watershed during 2015 monsoon. Due to the simplicity and at the data scarce situation, the model was found to be useful to forecast the landslides during the monsoon season in the region. The model; however, can be improved for better performance whenever the higher resolution time-series landslides data and automated weather stations are available in the watersheds. Linking this model to the proper landslide susceptibility map, and the real time rainfall data through mobile communication techniques, landslide early warning system can be established.</p><p><strong>KEYWORDS: </strong>landslide, rainfall threshold, data-scare, antecedent rainfall</p><p><strong>References:</strong></p><p>Aleotti, P. (2004). A warning system for rainfall-induced shallow failures. Engineering Geology, 73(3-4), 247-265.</p><p>Jaiswal, P. and van Westen, C.J., 2009. Estimating temporal probability for landslide initiation along transportation routes based on rainfall thresholds. Geomorphology, 112(1-2): 96-105.</p><p><strong>Acknowledgement:</strong> Comprehensive Disaster Risk Management Programme – UNDP in Nepal for the opportunity to conduct this research.</p>


2020 ◽  
Vol 261 ◽  
pp. 114211
Author(s):  
Jun Yang ◽  
Chen Zhao ◽  
Junxing Yang ◽  
Jingyun Wang ◽  
Zhitao Li ◽  
...  

2020 ◽  
Vol 20 (2) ◽  
pp. 425-450 ◽  
Author(s):  
Hélène Roux ◽  
Arnau Amengual ◽  
Romu Romero ◽  
Ernest Bladé ◽  
Marcos Sanz-Ramos

Abstract. This study aims at evaluating the performances of flash-flood forecasts issued from deterministic and ensemble meteorological prognostic systems. The hydrometeorological modeling chain includes the Weather Research and Forecasting Model (WRF) forcing the rainfall-runoff model MARINE dedicated to flash floods. Two distinct ensemble prediction systems accounting for (i) perturbed initial and lateral boundary conditions of the meteorological state and (ii) mesoscale model physical parameterizations have been implemented on the Agly catchment of the eastern Pyrenees with three subcatchments exhibiting different rainfall regimes. Different evaluations of the performance of the hydrometeorological strategies have been performed: (i) verification of short-range ensemble prediction systems and corresponding streamflow forecasts, for a better understanding of how forecasts behave; (ii) usual measures derived from a contingency table approach, to test an alert threshold exceedance; and (iii) overall evaluation of the hydrometeorological chain using the continuous rank probability score, for a general quantification of the ensemble performances. Results show that the overall discharge forecast is improved by both ensemble strategies with respect to the deterministic forecast. Threshold exceedance detections for flood warning also benefit from large hydrometeorological ensemble spread. There are no substantial differences between both ensemble strategies on these test cases in terms of both the issuance of flood warnings and the overall performances, suggesting that both sources of external-scale uncertainty are important to take into account.


Author(s):  
Hélène Roux ◽  
Arnau Amengual ◽  
Romu Romero ◽  
Ernest Bladé ◽  
Marcos Sanz-Ramos

Abstract. This study aims at evaluating the performances of flash flood forecasts issued from deterministic and ensemble meteorological prognostic systems. The hydro-meteorological modeling chain includes the Weather Research and Forecasting model (WRF) forcing the rainfall-runoff model MARINE dedicated to flash flood. Two distinct ensemble prediction systems accounting for (i) perturbed initial and lateral boundary conditions of the meteorological state and (ii) mesoscale model physical parameterizations, have been implemented on the Agly catchment of the Eastern Pyrenees with three sub-catchments exhibiting different rainfall regimes. Different evaluations of the performance of the hydrometeorological strategies have been performed: (i) verification of short-range ensemble prediction systems and corresponding stream flow forecasts, for a better understanding of how forecasts behave, (ii) usual measures derived from a contingency table approach, to test an alert threshold exceedance, and (iii) overall evaluation of the hydro-meteorological chain using the Continuous Rank Probability Score, for a general quantification of the ensemble performances. Results show that the overall discharge forecast is improved by both ensemble strategies with respect to the deterministic forecast. Threshold exceedance detections for flood warning also benefit from large hydro-meteorological ensemble spread. There are no substantial differences between both ensemble strategies on these test cases in terms both of the issuance of flood warnings and the overall performances, suggesting that both sources of external-scale uncertainty are important to take into account.


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