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HyMeX working groups

WG1 WG2 WG3 WG4 WG5 All WGs Members access to WGs

Each Working Group addresses one of the five major themes of HyMeX and HyMeX Science Plan which describes the scientific questions to be tackled and defines the general programme strategy. Scientific activities carried out in the programme are coordinated within the WGs.

WG1: Water Budget of the Mediterranean Sea (see section 3.1 of the WhiteBook)

The Mediterranean Sea is characterised by a negative water budget (excess evaporation over freshwater input) balanced by a two-layer exchange at the Strait of Gibraltar composed of a warm and fresh upper water inflow from the Atlantic superimposed to a cooler and saltier Mediterranean outflow. Light and fresh Atlantic water is transformed into denser waters through interactions with the atmosphere that renew the Mediterranean waters at intermediate and deep levels, and generate the thermohaline circulation. Although the scheme of this thermohaline circulation is reasonably well drawn, little is known about its variability at seasonal and inter-annual scales. The feedback of the Mediterranean sea basin on the atmosphere through the terms of the water budget needs also to be further investigated. Finally, the budget of the Mediterranean Sea has to be examined in the context of global warming, and in particular by assessing the impact of an increase of the ocean heat content on high-impact weather event frequency and intensity.

The Key Scientific Questions in this topic are:

Coordinators :
Dr Ludwig Wolfgang , Perpignan , France
Dr Mariotti Annarita , Rome , Italy
Dr Somot Samuel , Toulouse , France

Topic 1.1 : Estimation/observation, observed trends, climate projection of the different terms of the budget
1.1a- Precipitation over the Sea
1.1b- Evaporation over the Sea
1.1c- River Run-off
1.1d- Water vapour transport
1.1e- Strait exchanges
Topic 1.2: Global budget of the Mediterranean Sea
1.2a- Quantification
1.2b- Influence of the intense events on the global Mediterranean water budget
1.2c- Impact of the climate change on the global water budget

WG2: Hydrological Continental cycle (see section 3.2 of the WhiteBook)

The rainfall climatology of the Mediterranean region is characterised by dry summers frequently associated with very long drought periods, followed by fall and winter precipitation that are mostly very intense. This results in high daily/seasonal variability in aquifer recharge, river discharge, soil water content and vegetation characteristics, the interactions of which with the atmosphere are not well known. This includes for example the impact of the large extension forest fires associated with drought during summer on the evapotranspiration component of the hydrological cycle. The role of the surface states (land use/land cover) and of the soils on rainfall modulation needs also to be better understood. Hydrological and hydrogeological transfer functions are also characteristic of the Mediterranean basin, notably because of the specificities of the peri-mediterranean karstic and sedimentary aquifers. Progress in their understanding is of primary importance for the development of integrated management of the hydrosystems, and its adaptation to anthropogenic pressure and climate change.

The Key Scientific Questions addressed in this topic are:

Coordinators :
Dr Braud Isabelle , Paris , France
Dr. Chanzy André , Avignon , France

Topic 2.1 : Processes studies and small catchment scale modelling of the water and energy balance
2.1a- Understanding and modelling the role of the vegetation
2.1b- Monitoring evapotranspiration over complex terrains
2.1c- Snow processes
2.1d- Understanding and modelling water pathways at the hillslope scale
2.1e- Understanding and modelling aquifers at catchment scales
2.1f- Integrated modelling for catchments of a few km2 to tens of km2
Topic 2.2: The regional scale contribution of the continental surfaces to the water budget
2.2a- Near-surface atmospheric analyses at regional scale
2.2b- Land cover description at regional scale
2.2c- Sub-grid scale parameterizations for SVAT at regional scale
2.2d- Transversal issues: interfaces and database
Topic 2.3: Polluant dynamics in intermittent rivers
Topic 2.4: Climatic and anthropogenetic change
Topic 2.5: Remote sensing observations for processes and modelling

WG3: Heavy rainfall, flash-floods and floods (see section 3.3 of the WhiteBook)

During the fall season, western Mediterranean is prone to heavy precipitation and devastating flash-flooding and floods. Daily precipitation above 200 mm are not rare during this season, reaching in some cases values as exceptional as 700 mm recorded in September 2002 during the Gard (France) catastrophe. Large amounts of precipitation can accumulate over several day-long periods when frontal disturbances are slowed down and strengthened by the relief (e.g. Massif Central and the Alps), but also, huge rainfall totals can be recorded in less than a day when a mesoscale convective system (MCS) stays over the same area for several hours. Whereas the large scale environment propitious to heavy precipitation is relatively well known, progress has to be made on the understanding of the mechanisms that govern the anchoring region of the system as well as of those that occasionally produce uncommon amounts of precipitation. The contrasted topography, the complexity of the continental surfaces in terms of geology and land use, the difficulty to characterise the initial moisture state of the watersheds make the hydrological impact of such extreme rainfall events very difficult to assess and predict.

The Key Scientific Questions addressed in this topic are:

Coordinators :
Dr Romero Romualdo , Palma de Mallorca , Spain
Dr Delrieu Guy , Grenoble , France
Dr. Richard Evelyne , Toulouse , France
Dr Montanari Alberto , Bologna , Italy

Topic 3.1 : Heavy precipitation systems
3.1a- Heavy precipitation systems climatology
3.1b- Factors leading to heavy precipitation systems (large scale, mesoscale and microphysical processes)
3.1c- Moisture monitoring and origin
3.1d- Impact of Mediterranean Sea on heavy precipitation events
3.1e- Role of aerosols
3.1f- Modelling and predictability issues
Topic 3.2: Floods and Flash-floods
3.2a- Quantitative precipitation estimation
3.2b- Hydrologic responses to heavy precipitation events
3.2c- Hydraulic responses to heavy precipitation events
3.2d- Modelling and predictability issues
Topic 3.3: Impact of climate change on heavy precipitation and flash-floods

WG4: Intense sea-atmosphere interactions (see section 3.4 of the WhiteBook)

The Mediterranean Sea is characterised by several key-spots of intense air-sea exchanges associated with very strong winds which are caused by the orographic response to large scale forcing (e.g. Mistral, Bora, Sirocco, Tramontana, etc), deep cyclogenesis (e.g. Genoa cyclogenesis, etc), and high/low pressure patterns. These successive intense air-sea exchange events and the associated sea surface cooling affect considerably the heat and water budget of the Mediterranean Sea with formation of dense water and deep ocean convection during winter and early spring. The functioning of the ecosystems is strongly related to this complex dynamics which needs to be better understood. To this purpose, the hydrological and dynamical characteristics as well as the inter-annual variability of the dense water and deep ocean convection formation have to be better documented in order to stress the respective roles of atmospheric forcing and oceanic processes. In return, how such modifications of the ocean mixed layer influence the atmospheric boundary layer should be approached.

The Key Scientific Questions that HyMeX will address in this topic are:

Coordinators :
Dr Lagouvardos Kostas , Athens , Greece
Dr Ivancan-Picek Branka , Zagreb , Croatia
Dr Beranger Karine , Palaiseau , France
Mrs Estournel Claude , Toulouse , France
Dr Josey Simon , Southampton , UK

Topic 4.1 : Strong winds over the Mediterranean Sea
4.1a- Local severe winds
4.1b- Mediterranean cyclogeneses
Topic 4.2: Mediterranean Sea response to strong wind forcing
4.2a- Fast response of the Mediterranean Sea
4.2b- The slow branch of the Mediterranean water cycle
Topic 4.3: Air-sea feedbacks
4.3a- Atmospheric and oceanic circulations
4.3b- Role of marine aerosols on air-sea fluxes
4.3c- Modelling air-sea interactions

WG5: Societal and economical impacts (see section 4 of the WhiteBook)

The Mediterranean region is characterised by an increasing demography, leading to urban sprawl especially on coastal areas. In a context of climate change, the population is confronted with challenging environmental changes, such as short-time extreme events (heavy precipitation, flash-flood, heat wave,...) and long-term modifications (change in access to water resources, droughts,…). HyMeX aims at monitoring vulnerability factors and adaptation strategies developed by different Mediterranean societies to accommodate themselves to the impacts of climate change and intense events.

The Key Scientific Questions that will be addressed in this topic are:

Coordinators :
Dr Llasat Maria-Carmen , Barcelona , Spain
Mrs Lutoff Céline , Grenoble , France
Dr Gruntfest Eve , Colorado Springs , USA

Topic 5.1 : for long-term scenarios definition
Topic 5.2: Impacts of environmental events