Statistico‐dynamical downscaling for Mediterranean heavy precipitation

Beaulant, A. L.; Joly, Bruno; Nuissier, Olivier; Somot, Samuel; Ducrocq, Véronique; Joly, Alain; Sevault, Florence; Déqué, Michel; Ricard, Didier

doi:10.1002/qj.796

Cited by 28 publications

(28 citation statements)

References 35 publications

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“…Drobinski et al, 2005;Guénard et al, 2006;Lebeaupin Brossier and Drobinski, 2009), heavy precipitation (e.g. Ducrocq et al, 2008;Lebeaupin et al, 2006;Beaulant et al, 2011;or Vrac and Yiou, 2010) and heat waves and droughts (e.g. Schär et al, 2004;Fischer et al, 2007;Vautard et al, 2009).…”

Section: Vrac Et Al: Statistical and Dynamical Downscaling Of Thementioning

confidence: 99%

Dynamical and statistical downscaling of the French Mediterranean climate: uncertainty assessment

Vrac

Drobinski²,

Merlo³

et al. 2012

Nat. Hazards Earth Syst. Sci.

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153

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Abstract. ERA-40 reanalyses, and simulations from three regional climate models (RCMs) (ALADIN, LMDZ, and WRF) and from one statistical downscaling model (CDFt) are used to evaluate the uncertainty in downscaling of wind, temperature, and rainfall cumulative distribution functions (CDFs) for eight stations in the French Mediterranean basin over 1991-2000. The uncertainty is quantified using the Cramer-von Mises score (CvM) to measure the "distance" between the simulated and observed CDFs. The ability of the three RCMs and CDF-t to simulate the "climate" variability is quantified with the explained variance, variance ratio and extreme occurrence. The study shows that despite their differences, the three RCMs display very similar performance. In terms of global distributions (i.e. CvM), all models perform better than ERA-40 for both seasons and variables. However, looking at variance criteria, RCMs are not always much better than ERA-40 reanalyses, whereas CDF-t produces accurate results when applied to ERA-40. In a second step, a combined statistical/dynamical downscaling approach has been used, consisting in applying CDF-t to the RCM outputs. It shows that CDF-t applied to the RCM outputs does not necessarily produce better results than those from CDF-t directly applied to ERA-40. It also shows that CDF-t applied to RCMs generally improves the downscaled CDFs and that the "additional" added value of CDF-t applied to the RCMs is independent of the performance of the RCMs in terms of CvM, explained variance, variance ratio and extreme occurrence.

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Section: Vrac Et Al: Statistical and Dynamical Downscaling Of Thementioning

confidence: 99%

Dynamical and statistical downscaling of the French Mediterranean climate: uncertainty assessment

Vrac

Drobinski²,

Merlo³

et al. 2012

Nat. Hazards Earth Syst. Sci.

Self Cite

153

156

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“…The 'detection' algorithm outlined above has been applied to a coupled Mediterranean climate scenario evolution to retrieve potential HPE cases. These cases have then been simulated in detail with a convection-permitting model; the results of these studies are presented in a companion paper (Beaulant et al, 2011). …”

Section: Synthesis and Conclusionmentioning

confidence: 99%

“…The second objective of this paper is then to build a detection algorithm based on a discriminating analysis of a few relevant parameters that can be used to 'capture' situations propitious to HPEs, either in climate scenarios or in longrange operational forecasting. A companion paper (Beaulant et al, 2011) describes such an application for a climate scenario.…”

Section: Introductionmentioning

confidence: 99%

A statistical downscaling to identify the large‐scale circulation patterns associated with heavy precipitation events over southern France

Nuissier

Joly

et al. 2011

Quart J Royal Meteoro Soc

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This study assesses the potential for a detection algorithm to identify discriminating analysis-based statistical predictors of a few relevant parameters that can be used to capture heavy precipitation events (HPEs), or, at least, their associated largescale circulation (LSC) patterns in a climate scenario. HPEs are defined from a sample combining 'large-scale' fields from the ECMWF ERA-40 reanalysis with local observations from the Météo-France rain-gauge network. In a first step, LSC patterns considered as significantly favouring HPE over southern France are identified and described with the greatest robustness possible. For that purpose, an objective automatic clustering of the unfiltered 500 hPa geopotential height field is performed. Four clusters are obtained. Among them, the most discriminating for heavy precipitation is characterised by a synoptic-scale deep upper-level low northwest of the area of interest, inducing a southerly flow over the western Mediterranean Sea and southern France. In a second step, other lower-scale parameters are used to refine the characteristics of the clusters. It has been found that the low-level moisture transport is a relevant low-level ingredient to regionally characterise heavy precipitation. Indeed, 'Cévennes' cases are related to more south to southeasterly flows over the Gulf of Lion, whereas 'Languedoc-Roussillon' events occurred preferentially within a more pronounced easterly wind component with two streams of low-level moisture transport. Moreover, in-depth examination of the low-level features reveals that HPEs tend to occur when the wind blows in a specific direction and for the greatest low-level moisture flux over the Gulf of Lion. Finally, the predictive skill of a detection tool for HPEs over southern France, with only synoptic-scale favourable parameters as predictors, is discussed. It is shown that this tool allows selection of HPE situations in more than 70% of cases.

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“…Downscaling techniques can be either statistical or dynamical or both (Wilby and Wigley, 1997;Xu, 1999;Xuan et al, 2009;Beaulant et al, 2011). Several works aim at downscaling the Ensemble Prediction System (EPS) forecast (Molteni et al, 1996) of the ECMWF (European Centre for Mediumrange Weather Forecasts).…”

Section: Introductionmentioning

confidence: 99%

Perturbation of convection-permitting NWP forecasts for flash-flood ensemble forecasting

Vincendon

Ducrocq

Nuissier

et al. 2011

Nat. Hazards Earth Syst. Sci.

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Abstract. Mediterranean intense weather events often lead to devastating flash-floods. Extending the forecasting lead times further than the watershed response times, implies the use of numerical weather prediction (NWP) to drive hydrological models. However, the nature of the precipitating events and the temporal and spatial scales of the watershed response make them difficult to forecast, even using a high-resolution convection-permitting NWP deterministic forecasting. This study proposes a new method to sample the uncertainties of high-resolution NWP precipitation forecasts in order to quantify the predictability of the streamflow forecasts. We have developed a perturbation method based on convection-permitting NWP-model error statistics. It produces short-term precipitation ensemble forecasts from single-value meteorological forecasts. These rainfall ensemble forecasts are then fed into a hydrological model dedicated to flash-flood forecasting to produce ensemble streamflow forecasts. The verification on two flash-flood events shows that this forecasting ensemble performs better than the deterministic forecast. The performance of the precipitation perturbation method has also been found to be broadly as good as that obtained using a state-of-the-art research convectionpermitting NWP ensemble, while requiring less computing time.

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Statistico‐dynamical downscaling for Mediterranean heavy precipitation

Cited by 28 publications

References 35 publications

Dynamical and statistical downscaling of the French Mediterranean climate: uncertainty assessment

Dynamical and statistical downscaling of the French Mediterranean climate: uncertainty assessment

A statistical downscaling to identify the large‐scale circulation patterns associated with heavy precipitation events over southern France

Perturbation of convection-permitting NWP forecasts for flash-flood ensemble forecasting

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