Abstract

Abstract. Heavy precipitation (HP) constitutes a major meteorological threat in the western Mediterranean (WMed). Every year, recurrent events affect the area with fatal consequences for infrastructure and personal losses. Despite this being a well-known issue widely investigated in the past, open questions still remain. Particularly, the understanding of the underlying mechanisms and the modeling representation of the events must be improved. One of the major goals of the Hydrological Cycle in the Mediterranean Experiment (HyMeX; 2010–2020) has been to advance knowledge on this topic. In this article, we present an overview of the most recent lessons learned from HyMeX towards an improved understanding of the mechanisms leading to HP in the WMed. The unique network of instruments deployed as well as the use of finer model resolutions and coupled models provided an unprecedented opportunity to validate numerical model simulations, develop improved parameterizations, and design high-resolution ensemble modeling approaches and sophisticated assimilation techniques across scales. All in all, HyMeX, and particularly the science team heavy precipitation, favored the evidencing of theoretical results, the enrichment of our knowledge on the genesis and evolution of convection in a complex topography environment, and the improvement of precipitation forecasts. Illustratively, the intervention of cyclones and warm conveyor belts in the occurrence of heavy precipitation has been pointed out, and the crucial role of the spatiotemporal distribution of atmospheric water vapor for the understanding and accurate forecast of the timing and location of deep convection has been evidenced, as has the complex interaction among processes across scales. The importance of soil and ocean conditions and the interactions among systems were highlighted, and such systems were specifically developed in the framework of HyMeX to improve the realism of weather forecasts. Furthermore, the benefits of cross-disciplinary efforts within HyMeX have been a key asset in bringing our knowledge about heavy precipitation in the Mediterranean region a step forward.

Highlights

  • Introduction and motivationA 10-year multidisciplinary program on the Mediterranean water cycle, HyMeX (Hydrological Cycle in the Mediterranean Experiment; Drobinski et al, 2014), has come to an end (2010–2020)

  • With heavy orographic precipitation in stable and neutral atmospheric conditions having already been investigated in past experiments (e.g., MAP – the Mesoscale Alpine Programme; Bougeault et al, 2001) and being well understood, the focus of HyMeX was on the development of quasistationary mesoscale convective systems (MCSs), which are well known to be responsible for recent heavy precipitation events (HPEs) and floods in the area (Nuissier et al, 2008; Buzzi et al, 2014; Romero et al, 2014 among others)

  • Derstanding of the mechanisms leading to Heavy precipitation (HP) in the western Mediterranean (WMed) have been accomplished

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Summary

Introduction and motivation

A 10-year multidisciplinary program on the Mediterranean water cycle, HyMeX (Hydrological Cycle in the Mediterranean Experiment; Drobinski et al, 2014), has come to an end (2010–2020). This is mostly in relation to (a) model limitations in terms of predictability of smallscale processes (e.g., convection, turbulence) and feedbacks (e.g., soil, atmosphere, ocean) as well as their nonlinear interaction across scales, (b) lack of knowledge regarding underlying mechanisms, and (c) absence of adequate observations to help us advance our understanding and improve model capabilities This issue is one of the main objectives of the HyMeX international program and of its associated first special observation period (SOP1; Ducrocq et al, 2014; Jansa et al, 2014; Ferreti et al, 2014) from 5 September to 6 November 2012, which was dedicated to heavy precipitation and flash flooding.

Heavy precipitation during the HyMeX SOP1 period
State-of-the-art observational capabilities and modeling activities
HyMeX modeling strategy
Illustrative case
Large-scale dynamics and HPE occurrence
Advances in moist processes understanding
Low-level dynamical processes
Convection-triggering mechanisms
Cold pools
Land conditions and feedback to the atmosphere
Air–sea interactions and coupling
Microphysics
Increasing model resolution simulations
Improvement of parameterization schemes
Data assimilation
Predictability and ensemble forecasts
Findings
Discussion
Full Text
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