References of "Erpicum, Michel"
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See detailSmall impact of surrounding oceanic conditions on 2007–2012 Greenland Ice Sheet surface mass balance
Noel, Brice; Fettweis, Xavier ULg; van de Berg, W.J. et al

in Cryosphere Discussions (The) (2014), 8

During recent summers (2007–2012), several surface melt records were broken over the Greenland Ice Sheet (GrIS). The extreme summer melt resulted in part from a persistent negative phase of the North ... [more ▼]

During recent summers (2007–2012), several surface melt records were broken over the Greenland Ice Sheet (GrIS). The extreme summer melt resulted in part from a persistent negative phase of the North-Atlantic Oscillation (NAO), favouring warmer than normal conditions over the GrIS. In addition, it has been suggested that significant anomalies in sea ice cover (SIC) and sea surface temperature (SST) may partially explain recent anomalous GrIS surface melt. To assess the impact of 2007–2012 SIC and SST anomalies on GrIS surface mass balance (SMB), a set of sensitivity experiments was carried out with the regional climate model MAR. These simulations suggest that changes in SST and SIC in the seas surrounding Greenland do not significantly impact GrIS SMB, due to the katabatic winds blocking effect. These winds are strong enough to prevent oceanic near-surface air, influenced by SIC and SST variability, from penetrating far inland. Therefore, the ice sheet SMB response is restricted to coastal regions, where katabatic winds are weaker. However, anomalies in SIC and SST could have indirectly affected the surface melt by changing the general circulation in the North Atlantic region, favouring more frequent warm air advection to the GrIS. [less ▲]

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See detailÉvolutions multiples et intérêts nouveaux en matière de climatologie depuis 1970.
Erpicum, Michel ULg

Scientific conference (2014, February 25)

Evolution of the knowledge of the main variables of the climates of the Earth according to the recent evolution of the principal tools of climatology and instrumental data coming from international or ... [more ▼]

Evolution of the knowledge of the main variables of the climates of the Earth according to the recent evolution of the principal tools of climatology and instrumental data coming from international or national networks or from experimental measurements conducted in Climatological or Meteorological Institutes. [less ▲]

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See detailEstimation of the Greenland ice sheet surface mass balance contribution to future sea level rise using the regional climate model MAR
Fettweis, Xavier ULg; Gallée, H.; van den Broeke, M. et al

Conference (2013, April 10)

With the aim of estimating the sea level rise (SLR) coming from Surface Mass Balance (SMB) changes over the Greenland ice sheet (GrIS), we report future projections obtained with the regional climate ... [more ▼]

With the aim of estimating the sea level rise (SLR) coming from Surface Mass Balance (SMB) changes over the Greenland ice sheet (GrIS), we report future projections obtained with the regional climate model MAR, forced by outputs of three CMIP5 General Circulation Models (GCMs). Our results indicate that in warmer climates, the mass gained due to increased winter snowfall over GrIS does not compensate the mass lost through increased meltwater run-off in summer. All the MAR projections shows similar non-linear melt increases with rising temperatures as a result of the positive surface albedo feedback, because no change is projected in the general atmospheric circulation over Greenland. Nevertheless, MAR exhibits a large range in its future projections. By coarsely estimating the GrIS SMB changes from CMIP5 GCMs outputs, we show that the uncertainty coming from the GCM-based forcing represents about half of projected SMB changes. In 2100, the CMIP5 ensemble mean projects a SLR, resulting from a GrIS SMB decrease, estimated to be 4 2 cm and 9 4 cm for the RCP 4.5 and RCP 8.5 scenarios, respectively. However, these future projections do not consider the positive melt-elevation feedback. Sensitivity MAR experiments using perturbed ice sheet topographies consistent with the projected SMB changes highlight the importance of coupling climate models to an ice sheet model. Such a coupling will allow to consider the future response of both surface processes and ice-dynamic changes, and their mutual feedbacks to rising temperatures. [less ▲]

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See detailLatest results in forecasting and DLR related to Twenties and other projects
Nguyen, Huu-Minh ULg; Doutreloup, Sébastien; Erpicum, Michel ULg et al

Conference (2013, March 05)

The goal of the meeting was to further (see Minutes of the WG3-DLR meeting which took place in Liège, Belgium, November 27th-28th 2012) investigate the “Dynamic Line Rating DLR” potential for the ... [more ▼]

The goal of the meeting was to further (see Minutes of the WG3-DLR meeting which took place in Liège, Belgium, November 27th-28th 2012) investigate the “Dynamic Line Rating DLR” potential for the efficient management of electric grids in view of the increasing share of intermittent renewable energies (wind & solar) and to proceed with the preparation of two posi-tion papers dedicated to 1) DLR forecasting and 2) DLR planning. It was also aimed at finaliz-ing the Terms of Reference for the establishment of a new Working Group within the Cigré B2 Study Committee. [less ▲]

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See detailImportant role of the mid-tropospheric atmospheric circulation in the recent surface melt increase over the Greenland ice sheet
Fettweis, Xavier ULg; Hanna, Edward; Lang, Charlotte ULg et al

in Cryosphere (The) (2013), 7

Since 2007, there has been a series of surface melt records over the Greenland ice sheet (GrIS), continuing the trend towards increased melt observed since the end of the 1990's. The last two decades are ... [more ▼]

Since 2007, there has been a series of surface melt records over the Greenland ice sheet (GrIS), continuing the trend towards increased melt observed since the end of the 1990's. The last two decades are characterized by an increase of negative phases of the North Atlantic Oscillation (NAO) favouring warmer and drier summers than normal over GrIS. In this context, we use a circulation type classification based on daily 500 hPa geopotential height to evaluate the role of atmospheric dynamics in this surface melt acceleration for the last two decades. Due to the lack of direct observations, the interannual melt variability is gauged here by the summer (June–July–August) mean temperature from reanalyses at 700 hPa over Greenland; analogous atmospheric circulations in the past show that ~70% of the 1993–2012 warming at 700 hPa over Greenland has been driven by changes in the atmospheric flow frequencies. Indeed, the occurrence of anticyclones centred over the GrIS at the surface and at 500 hPa has doubled since the end of 1990's, which induces more frequent southerly warm air advection along the western Greenland coast and over the neighbouring Canadian Arctic Archipelago (CAA). These changes in the NAO modes explain also why no significant warming has been observed these last summers over Svalbard, where northerly atmospheric flows are twice as frequent as before. Therefore, the recent warmer summers over GrIS and CAA cannot be considered as a long-term climate warming but are more a consequence of NAO variability affecting atmospheric heat transport. Although no global model from the CMIP5 database projects subsequent significant changes in NAO through this century, we cannot exclude the possibility that the observed NAO changes are due to global warming. [less ▲]

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See detailFuture projections of the Greenland ice sheet energy balance driving the surface melt
Franco, Bruno ULg; Fettweis, Xavier ULg; Erpicum, Michel ULg

in Cryosphere (The) (2013), 7

In this study, simulations at 25 km resolution are performed over the Greenland ice sheet (GrIS) throughout the 20th and 21st centuries, using the regional climate model MAR forced by four RCP scenarios ... [more ▼]

In this study, simulations at 25 km resolution are performed over the Greenland ice sheet (GrIS) throughout the 20th and 21st centuries, using the regional climate model MAR forced by four RCP scenarios from three CMIP5 global circulation models (GCMs), in order to investigate the projected changes of the surface energy balance (SEB) components driving the surface melt. Analysis of 2000–2100 melt anomalies compared to melt results over 1980–1999 reveals an exponential relationship of the GrIS surface melt rate simulated by MAR to the near-surface air temperature (TAS) anomalies, mainly due to the surface albedo positive feedback associated with the extension of bare ice areas in summer. On the GrIS margins, the future melt anomalies are preferentially driven by stronger sensible heat fluxes, induced by enhanced warm air advection over the ice sheet. Over the central dry snow zone, the surface albedo positive feedback induced by the increase in summer melt exceeds the negative feedback of heavier snowfall for TAS anomalies higher than 4 °C. In addition to the incoming longwave flux increase associated with the atmosphere warming, GCM-forced MAR simulations project an increase of the cloud cover decreasing the ratio of the incoming shortwave versus longwave radiation and dampening the albedo feedback. However, it should be noted that this trend in the cloud cover is contrary to that simulated by ERA-Interim–forced MAR for recent climate conditions, where the observed melt increase since the 1990s seems mainly to be a consequence of more anticyclonic atmospheric conditions. Finally, no significant change is projected in the length of the melt season, which highlights the importance of solar radiation absorbed by the ice sheet surface in the melt SEB. [less ▲]

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See detailCurrent and future atmospheric circulation at 500 hPa over Greenland simulated by the CMIP3 and CMIP5 global models
Belleflamme, Alexandre ULg; Fettweis, Xavier ULg; Lang, Charlotte ULg et al

in Climate Dynamics (2013), 41(7-8),

The Greenland ice sheet is projected to be strongly affected by global warming. These projections are either issued from downscaling methods (such as Regional Climate Models) or they come directly from ... [more ▼]

The Greenland ice sheet is projected to be strongly affected by global warming. These projections are either issued from downscaling methods (such as Regional Climate Models) or they come directly from General Circulation Models (GCMs). In this context, it is necessary to evaluate the accuracy of the daily atmospheric circulation simulated by the GCMs, since it is used as forcing for downscaling methods. Thus, we use an automatic circulation type classification based on two indices (Euclidean distance and Spearman rank correlation using the daily 500 hPa geopotential height) to evaluate the ability of the GCMs from both CMIP3 and CMIP5 databases to simulate the main circulation types over Greenland during summer. For each circulation type, the GCMs are compared to three reanalysis datasets on the basis of their frequency and persistence differences. For the current climate (1961–1990), we show that most of the GCMs do not reproduce the expected frequency and the persistence of the circulation types and that they simulate poorly the observed daily variability of the general circulation. Only a few GCMs can be used as reliable forcings for downscaling methods over Greenland. Finally, when applying the same approach to the future projections of the GCMs, no significant change in the atmospheric circulation over Greenland is detected, besides a generalised increase of the geopotential height due to a uniform warming of the atmosphere. [less ▲]

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See detailCurrent net ecosystem exchange of CO2 in a young mixed forest: any heritage from the previous ecosystem?
Violette, Aurélie ULg; Heinesch, Bernard ULg; Erpicum, Michel ULg et al

Poster (2013)

For 15 years, networks of flux towers have been developed to determine accurate carbon balance with the eddy-covariance method and determine if forests are sink or source of carbon. However, for ... [more ▼]

For 15 years, networks of flux towers have been developed to determine accurate carbon balance with the eddy-covariance method and determine if forests are sink or source of carbon. However, for prediction of the evolution of carbon cycle and climate, major uncertainties remain on the ecosystem respiration (Reco, which includes the respiration of above ground part of trees, roots respiration and mineralization of the soil organic matter), the gross primary productivity (GPP) and their difference, the net ecosystem exchange (NEE) of forests. These uncertainties are consequences of spatial and inter-annual variability, driven by previous and current climatic conditions, as well as by the particular history of the site (management, diseases, etc.). In this study we focus on the carbon cycle in two mixed forests in the Belgian Ardennes. The first site, Vielsalm, is a mature stand mostly composed of beeches (Fagus sylvatica) and douglas fir (Pseudotsuga menziesii) from 80 to 100 years old. The second site, La Robinette, was covered before 1995 with spruces. After an important windfall and a clear cutting, the site was replanted, between 1995 and 2000, with spruces (Piceas abies) and deciduous species (mostly Betula pendula, Aulnus glutinosa and Salix aurita). The challenge here is to highlight how initial conditions can influence the current behavior of the carbon cycle in a growing stand compared to a mature one, where initial conditions are supposed to be forgotten. A modeling approach suits particularly well for sensitivity tests and estimation of the temporal lag between an event and the ecosystem response. We use the forest ecosystem model ASPECTS (Rasse et al., Ecological Modelling 141, 35-52, 2001). This model predicts long-term forest growth by calculating, over time, hourly NEE. It was developed and already validated on the Vielsalm forest. Modelling results are confronted to eddy-covariance data on both sites from 2006 to 2011. The main difference between both sites seems to rely on soil respiration, which is probably partly a heritage of the previous ecosystem at the young forest site. [less ▲]

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See detailFuture projections of the Greenland ice sheet surface mass balance simulated by the regional climate model MAR forced by three CMIP5 global models.
Fettweis, Xavier ULg; Franco, Bruno ULg; Lang, Charlotte ULg et al

Conference (2012, September 11)

As part of the ICE2SEA project, the regional climate model MAR was forced by the global models HadCM3 and ECHAM5 for making future projections of the Greenland Ice Sheet (GrIS) Surface Mass Balance (SMB ... [more ▼]

As part of the ICE2SEA project, the regional climate model MAR was forced by the global models HadCM3 and ECHAM5 for making future projections of the Greenland Ice Sheet (GrIS) Surface Mass Balance (SMB) over 1980-2099 at a resolution of 25km. However, the comparison with MAR forced by the ERA-40 reanalysis over 1980-1999 shows that MAR forced by these GCMs is not able to represent reliably the current SMB due to biases in the general circulation and in the free atmosphere summer temperature modelled by these GCMs around the GrIS. That is why, we present here first results of MAR forced by the next generation of GCMs from the CMIP5 data base (CanESM2, NorESM1 and MIROC5 here). The comparison with the ERA-INTERIM forced MAR simulations over current climate is a lot of better, which increases the reliability and the interest of these new MAR projections. In addition, the new scenarios (RCP 2.6, 4.5, 6.0 and 8.5) of the next IPCC Assessment Report (AR5) are used here. These new simulations show notably that the response of SMB to rising temperature is not a linear function of the temperature anomalies due to the positive albedo feedback which enhances the surface melt. For 2100, in case of extreme rising temperature (RCP 8.5 scenario), MAR simulates a surface GrIS mass loss corresponding to a cumulated sea level rise (SLR) of about 15 cm since 2000! Mainly the changes in SMB and in surface energy balance will be discussed here and estimations of the GrIS surface melt contribution to the SLR using all the CMIP5 outputs will be given. [less ▲]

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See detailRECOURS À UNE CAMPAGNE DE MESURES TOPOCLIMATIQUES APPLIQUÉE POUR UNE ÉTUDE COMPARATIVE DE VARIABLES MÉTÉOROLOGIQUES CONCOMITANTES PROVENANT DES STATIONS MÉTÉOROLOGIQUES DE BRUGGE ET DU MONT RIGI EN BELGIQUE
Pirard, Xavier ULg; Jorion, Nicolas ULg; Doutreloup, Sébastien ULg et al

Poster (2012, September 07)

Une station météorologique automatique munie d’un mât de 10 mètres a été installée à l’Ouest de l’agglomération urbaine de Brugge (Belgique) par le Laboratoire de Climatologie et Topoclimatologie de l’ULg ... [more ▼]

Une station météorologique automatique munie d’un mât de 10 mètres a été installée à l’Ouest de l’agglomération urbaine de Brugge (Belgique) par le Laboratoire de Climatologie et Topoclimatologie de l’ULg. Elle a été équipée afin de confirmer la bonne qualité des prévisions météorologiques du modèle WRF établies dans le cadre du projet européen TWENTIES. Les données récoltées de minute en minute par cette station météorologique offrent également l’opportunité de mettre en évidence le détail de situations météorologiques bien particulières comme celles correspondant aux passages de fronts. [less ▲]

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See detailPower line dynamic rating: forecasting potential period of low wind speed is crucial
Nguyen, Huu-Minh ULg; Doutreloup, Sébastien; Erpicum, Michel ULg et al

Conference (2012, September)

The replacement and building of new electrical power lines (50 000 km in Europe) can’t cope with the growth of RES development in EU for the ten upcoming years. New solutions have to be found to manage ... [more ▼]

The replacement and building of new electrical power lines (50 000 km in Europe) can’t cope with the growth of RES development in EU for the ten upcoming years. New solutions have to be found to manage such power transmission needs. Dynamic Line Rating (DLR) systems are part of the global solution. They allow to increase the power line capacity by an average 20% over the static rating (which is defined as the maximum current-carrying capacity as designed). The ampacity or thermal rating, is calculated thanks to (i) sensors installed directly on the power line conductors, like Ampacimon, (ii) weather data, and (iii) standard thermal models (IEEE, CIGRE). However, in order to be fully effective and to allow an efficient use of assets, ampacity calculation in real-time is not enough; it has to be forecasted as well. Beyond 6h-forecast, weather forecasts are necessary to compute the line ampacity up to two days ahead, as needed by network operation. As wind convection has a major impact on conductor cooling, even low wind speeds (2m/s up to 5m/s) allow a huge ampacity increase (the actual rating can be doubled). Therefore, low wind speed forecast up to 2-days ahead finds a major application in dynamic rating of overhead transmission and distribution lines. [less ▲]

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See detailEvaluation des modèles climatiques régionaux MAR et WRF sur le Svalbard
Lang, Charlotte ULg; Fettweis, Xavier ULg; Erpicum, Michel ULg

Poster (2012, September)

: Il est bien connu que les zones de hautes latitudes sont très sensibles aux changements climatiques. A cause du réchauffement global, la fonte des calottes a augmenté, ce qui à son tour a une influence ... [more ▼]

: Il est bien connu que les zones de hautes latitudes sont très sensibles aux changements climatiques. A cause du réchauffement global, la fonte des calottes a augmenté, ce qui à son tour a une influence sur le climat via des modifications de la circulation thermohaline, la rétroaction de l’albédo de la glace, l’augmentation du niveau des mers… Nous avons comparé le climat du Svalbard modélisé par deux modèles régionaux (MAR et WRF) à une résolution de 10 km sur la période 2000-2010 à des mesures provenant de plusieurs stations météorologiques localisées dans différentes régions de l’archipel afin d'évaluer lequel de ces modèles pouvait représenter au mieux le climat du Svalbard. [less ▲]

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See detailÉVOLUTION DU COMPORTEMENT DU VENT ET DE SON POTENTIEL POUR LA PRODUCTION D'ÉNERGIE ÉOLIENNE DURANT LES 30 DERNIÈRES ANNÉES : LE CAS DE LA BELGIQUE
Doutreloup, Sébastien ULg; Fettweis, Xavier ULg; Erpicum, Michel ULg

in Bigot, Sylvain; Rome, Sandra (Eds.) Les climats régionaux : observation et modélisation. (Actes du colloque organisé à Grenoble du mercredi 5 au samedi 8 septembre 2012) (2012, September)

Chaque année, le nombre d'éoliennes dans le monde augmente de façon significative suite notamment aux politiques encourageant les productions d'énergie verte afin d’atténuer le réchauffement climatique ... [more ▼]

Chaque année, le nombre d'éoliennes dans le monde augmente de façon significative suite notamment aux politiques encourageant les productions d'énergie verte afin d’atténuer le réchauffement climatique. Toutefois, ce type d'énergie est tributaire de la météo. Cela implique que la production d'énergie éolienne est irrégulière à courte échelle de temps. Cependant, la disponibilité d’électricité de courtes périodes de temps est très importante à connaitre pour les producteurs d'énergie ainsi que pour les gestionnaires de réseaux. Pour ces raisons, il nous parait primordial d’analyser l’évolution de l’intermittence de la vitesse du vent sur les 30 dernières années (1979-2009). Pour ce faire nous utilisons le modèle WRF forcé par les réanalyses ERA-Interim, les réanalyses NCEP2 et certains modèles du GIEC (base de données CMIP5). [less ▲]

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See detailLes modèles globaux projettent-ils plus de blocages anticycloniques en Europe pour le futur ?
Belleflamme, Alexandre ULg; Fettweis, Xavier ULg; Erpicum, Michel ULg

in Bigot, Sylvain; Rome, Sandra (Eds.) XXVème colloque de l'Association Internationale de Climatologie - Les climats régionaux : observation et modélisation (2012, September)

The IPCC projects more frequent and longer heat waves and droughts during summer for future over Western Europe. These extreme events occur during anticyclonic blocking events. We use atmospheric ... [more ▼]

The IPCC projects more frequent and longer heat waves and droughts during summer for future over Western Europe. These extreme events occur during anticyclonic blocking events. We use atmospheric circulation type classifications to determine if the models project an increase of the number and the persistence of these anticyclonic blockings. For recent climate, the number of blocking events depends on the ability of the models to reproduce the observed general circulation. The future projections do not show any systematic evolution of the number of anticyclonic blockings over Western Europe. Nevertheless, other changes like an increase of the temperature will lead to more frequent heat waves and droughts. [less ▲]

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See detailImpact of spatial resolution on the modelling of the Greenland ice sheet surface mass balance between 1990–2010, using the regional climate model MAR
Franco, Bruno ULg; Fettweis, Xavier ULg; Lang, Charlotte et al

in Cryosphere (The) (2012), 6

With the aim to force an ice dynamical model, the Greenland ice sheet (GrIS) surface mass balance (SMB) was modelled at different spatial resolutions (15-50 km) for the period 1990-2010, using the ... [more ▼]

With the aim to force an ice dynamical model, the Greenland ice sheet (GrIS) surface mass balance (SMB) was modelled at different spatial resolutions (15-50 km) for the period 1990-2010, using the regional climate model MAR (Modèle Atmosphérique Régional) forced by the ERA-INTERIM reanalysis. This comparison revealed that (i) the inter-annual variability of the SMB components is consistent within the different spatial resolutions investigated, (ii) the MAR model simulates heavier precipitation on average over the GrIS with diminishing spatial resolution, and (iii) the SMB components (except precipitation) can be derived from a simulation at lower resolution with an intelligent interpolation. This interpolation can also be used to approximate the SMB components over another topography/ice sheet mask of the GrIS. These results are important for the forcing of an ice dynamical model, needed to enable future projections of the GrIS contribution to sea level rise over the coming centuries. [less ▲]

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