High resolution numerical study of the Algiers 2001 flash flood: sensitivity to the upper-level potential vorticity anomaly

From 9 to 11 November 2001, intense cyclogenesis affected the northern coasts of Africa and more particularly the densely populated city of Algiers. During the morning of 10 November, more than 130 mm of precipitation was recorded at Bouzareah and resulted in mudslides which devastated the Bab-el-Oued district. This disaster caused more than 700 casualties and catastrophic damage. Like many other heavy rainstorms in the western Mediterranean, this event was associated with the presence of an upper-level trough materialized by a deep stratospheric intrusion and characterized by high potential vorticity values. In this study, the impact of this synoptic structure on the localization and intensity of the precipitation which affected Algiers is investigated using a potential vorticity (PV) inversion method coupled for the first time with the French non-hydrostatic MESO-NH model. A set of perturbed synoptic environments was designed by slightly modifying the extent and the intensity of the coherent potential vorticity structures in the operational ARPEGE analysis. It is shown that such modifications may have a strong impact on the fine-scale precipitation forecast in the Algiers region, thereby demonstrating the fundamental role played by the potential vorticity anomaly during this exceptional meteorological event

Forecast verification of cloud cover with satellite observation over West Africa.

13-18 avril 200

Verification of cloud cover forecast with satellite observation over West Africa.

26-30 November

Cycle diurne des poussières désertiques et des cirrus en Afrique de l'ouest par le satellite Météosat Seconde Génération et le modèle Méso-NH.

4 page

Application of local potential vorticity modifications to improve the numerical prediction of an intense Mediterranean cyclone.

13-18 april 200

Impact of initial condition uncertainties on the predictability of heavy rainfall in the Mediterranean : a case study.

10-13 septembre 200

Objective evaluation of mesoscale simulations of the Algiers 2001 flash flood by the model-to-satellite approach

International audienceAn objective evaluation of mesoscale simulations by the model-to-satellite approach is performed. The model-to-satellite approach consists in calculating brightness temperatures (BT) from model variables with a radiative transfer code. It allows to compare directly and quantitatively simulations and observations by calculating statistical scores. This method is detailed and used herein to objectively evaluate an ensemble of Meso-NH simulations of the Algiers 2001 flash flood. In particular, the improvement due to the grid-nesting is shown

Application of local potential vorticity modifications to improve the numerical prediction of an intense Mediterranean cyclone.

2-4 june 200

A combined use of satellite imagery and potential vorticity inversion to improve the numerical simulation of the Algiers 2001 superstorm.

(décembre 2006

Comparison of two methods to forecast a low predictable heavy rainfall case.

9-11 janvier 2007