References of "Erpicum, Michel"
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See detailEtude de l'évolution de l'enneigement dans les Hautes Fagnes (Belgique) au cours des cinquante dernières années à l'aide du modèle climatique régional MAR
Wyard, Coraline ULg; Fettweis, Xavier ULg; Erpicum, Michel ULg

in Erpicum, Michel (Ed.) Actes du XXVIIIe colloque annuel de l’Association Internationale de Climatologie : Modélisations et variabilités (2015, July)

The “Modèle Atmosphérique Régionale” MAR is a regional climate model originally developed to study the polar ice sheets. In this study, the MAR model has been adapted to Belgium in order to study the snow ... [more ▼]

The “Modèle Atmosphérique Régionale” MAR is a regional climate model originally developed to study the polar ice sheets. In this study, the MAR model has been adapted to Belgium in order to study the snow cover evolution of the High Fens (east of Belgium), a region covered by snow on average one to two months per year. As validation, we have sucessfully compared MAR based daily snow heights with snowcam-based and/or laser sensor-based observations over the period 2008-2013. Then, the model has been forced by ERA-Interim since 1958 to study the snow cover evolution during the last fifty years at the summit of Belgium. The results show no significant trend despite global warming. [less ▲]

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See detailFuture climate and surface mass balance of Svalbard glaciers in an RCP8.5 climate scenario: a study with the regional climate model MAR forced by MIROC5
Lang, Charlotte ULg; Fettweis, Xavier ULg; Erpicum, Michel ULg

in Cryosphere (The) (2015), 9

We simulated the 21st century Svalbard SMB with the regional model MAR (RCP8.5 scenario). Melt is projected to increase gently up to 2050 and then dramatically increase, with a larger increase in the ... [more ▼]

We simulated the 21st century Svalbard SMB with the regional model MAR (RCP8.5 scenario). Melt is projected to increase gently up to 2050 and then dramatically increase, with a larger increase in the south of the archipelago. This difference is due to larger ice albedo decrease in the south causing larger increase of absorbed solar radiation. The ablation area is projected to disappear over the entire Svalbard by 2085. The SMB decrease compared to present is projected to contribute 7mm to SLR. [less ▲]

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See detailGlobal, diffuse and direct irradiances modelling over northwestern Europe using regional climate model MAR : validation and construction of a 30-year climatology
Beaumet, Julien ULg; Doutreloup, Sébastien ULg; Fettweis, Xavier ULg et al

Poster (2015, April 17)

Incoming solar global irradiances are modelled using MAR regional climate model forced by ERA-Interim reanalysis. Global irradiances are decomposed into direct and diffuse using sigmoid model from Ruiz ... [more ▼]

Incoming solar global irradiances are modelled using MAR regional climate model forced by ERA-Interim reanalysis. Global irradiances are decomposed into direct and diffuse using sigmoid model from Ruiz-Arias et al. (2010). Results are validated using data from the European Solar Radiation Atlas for Uccle and Braunschweig weather stations. A 30-year climatology has been built and trends and variability have been analyzed. [less ▲]

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See detailSnow cover evolution during the last fifty years in the Hautes Fagnes (Belgium) using the regional climate MAR model
Wyard, Coraline ULg; Fettweis, Xavier ULg; Erpicum, Michel ULg

Conference (2015, April 16)

The MAR model is a regional climate model originally developped for the polar regions to study the surface mass balance. In this study, the MAR model has been adapted to Belgium in order to study the snow ... [more ▼]

The MAR model is a regional climate model originally developped for the polar regions to study the surface mass balance. In this study, the MAR model has been adapted to Belgium in order to study the snow cover evolution of the Hautes Fagnes (south-east of Belgium), a region covered by snow one to two months per year. As validation, we have sucessfully compared MAR based daily snow heights with snowcam-based observations. Then, the model has been forced by ERA-Interim since 1958 to study the snow cover evolution during the last fifty years at the summit of Belgium. The results show non-significant trend. [less ▲]

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See detailRecent summer Arctic atmospheric circulation anomalies in a historical perspective
Belleflamme, Alexandre ULg; Fettweis, Xavier ULg; Erpicum, Michel ULg

in Cryosphere (The) (2015), 9

A significant increase in the summertime occurrence of a high pressure area over the Beaufort Sea, the Canadian Arctic Archipelago, and Greenland has been observed since the beginning of the 2000s, and ... [more ▼]

A significant increase in the summertime occurrence of a high pressure area over the Beaufort Sea, the Canadian Arctic Archipelago, and Greenland has been observed since the beginning of the 2000s, and particularly between 2007 and 2012. These circulation anomalies are likely partly responsible for the enhanced Greenland ice sheet melt as well as the Arctic sea ice loss observed since 2007. Therefore, it is interesting to analyse whether similar conditions might have happened since the late 19th century over the Arctic region. We have used an atmospheric circulation type classification based on daily mean sea level pressure and 500 hPa geopotential height data from five reanalysis data sets (ERA-Interim, ERA-40, NCEP/NCAR, ERA-20C, and 20CRv2) to put the recent circulation anomalies in perspective with the atmospheric circulation variability since 1871. We found that circulation conditions similar to 2007–2012 have occurred in the past, despite a higher uncertainty of the reconstructed circulation before 1940. For example, only ERA-20C shows circulation anomalies that could explain the 1920–1930 summertime Greenland warming, in contrast to 20CRv2. While the recent anomalies exceed by a factor of 2 the interannual variability of the atmospheric circulation of the Arctic region, their origin (natural variability or global warming) remains debatable. [less ▲]

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See detailStable climate and surface mass balance in Svalbard over 1979–2013 despite the Arctic warming
Lang, Charlotte ULg; Fettweis, Xavier ULg; Erpicum, Michel ULg

in Cryosphere (The) (2015), 9

With the help of the regional climate model MAR (Modèle Atmosphérique Régional) forced by the ERA-Interim reanalysis (MARERA) and the MIROC5 (Model for Interdisciplinary Research on Climate) global model ... [more ▼]

With the help of the regional climate model MAR (Modèle Atmosphérique Régional) forced by the ERA-Interim reanalysis (MARERA) and the MIROC5 (Model for Interdisciplinary Research on Climate) global model (MARMIROC5) from the CMIP5 (Coupled Model Intercomparison Project) database, we have modelled the climate and surface mass balance of Svalbard at a 10 km resolution over 1979–2013. The integrated total surface mass balance (SMB) over Svalbard modelled by MARERA is negative (−1.6 Gt yr−1) with a large interannual variability (7.1 Gt) but, unlike over Greenland, there has been no acceleration of the surface melt over the past 35 years because of the recent change in atmospheric circulation bringing northwesterly flows in summer over Svalbard, contrasting the recent observed Arctic warming. However, in 2013, the atmospheric circulation changed to a south–southwesterly flow over Svalbard causing record melt, SMB (−20.4 Gt yr−1) and summer temperature. MIROC5 is significantly colder than ERA-Interim over 1980–2005 but MARMIROC5 is able to improve the near-surface MIROC5 results by simulating not significant SMB differences with MARERA over 1980–2005. On the other hand, MIROC5 does not represent the recent atmospheric circulation shift in summer and induces in MARMIROC5 a significant trend of decreasing SMB (−0.6 Gt yr−2) over 1980–2005. [less ▲]

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See detailSensitivity of Greenland Ice Sheet surface mass balance to perturbations in sea surface temperature and sea ice cover: a study with the regional climate model MAR
Noel, Brice; Fettweis, Xavier ULg; van de Berg, W.J. et al

in Cryosphere (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), favoring warmer atmospheric conditions than normal over the GrIS. Simultaneously, large anomalies in sea ice cover (SIC) and sea surface temperature (SST) were observed in the North Atlantic, suggesting a possible connection. To assess the direct 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 forced by ERA-Interim. These simulations suggest that perturbations in SST and SIC in the seas surrounding Greenland do not considerably impact GrIS SMB, as a result of the katabatic wind blocking effect. These offshore-directed winds prevent oceanic near-surface air, influenced by SIC and SST anomalies, from penetrating far inland. Therefore, the ice sheet SMB response is restricted to coastal regions, where katabatic winds cease. A topic for further investigation is how anomalies in SIC and SST might have indirectly affected the surface melt by changing the general circulation in the North Atlantic region, hence favoring more frequent warm air advection towards the GrIS. [less ▲]

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See detailSolar irradiance modelling over Belgium using Regional Climate Models within the frame of a day-ahead photovoltaic production forecasting system
Beaumet, Julien ULg; Doutreloup, Sébastien ULg; Fettweis, Xavier ULg et al

Poster (2014, October 06)

WRF-ARW and MAR climate models performances for the modelling of solar irradiances over Belgium are evaluated using in-situ measurements at Sart-Tilman and Daussoulx. Different WRF-ARW settings are tested ... [more ▼]

WRF-ARW and MAR climate models performances for the modelling of solar irradiances over Belgium are evaluated using in-situ measurements at Sart-Tilman and Daussoulx. Different WRF-ARW settings are tested. Sigmoid model proposed by Ruis-Ariaz etal. (2010) is used to decompose solar irradiance into direct and diffuse fraction. The performance of this model using measured and modelled global irradiances is also evaluated. [less ▲]

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See detailMICROPHYSIQUE DES NUAGES ET RAYONNEMENT SOLAIRE : COMPARAISON DES MESURES IN SITU AU MONT RIGI EN HAUTE BELGIQUE ET DES DONNÉES CLOUD PHYSICAL PROPERTIES (CPP) OBTENUES À PARTIR DES IMAGES METEOSAT-9
Beaumet, Julien ULg; Clerbaux, Nicolas; Cornet, Yves ULg et al

in Camberlin, Pierre; Richard, Yves (Eds.) Actes du XXVIIe Colloque de l'Association Internationale de Climatologie : CLIMAT : SYSTÈME & INTERACTIONS (2014, July 02)

Le rayonnement solaire global mesuré au mont Rigi a été comparé à l'épaisseur optique des nuages (COT) estimée à l'aide des données SEVIRI. Une relation logarithmique avec un coefficient de détermination ... [more ▼]

Le rayonnement solaire global mesuré au mont Rigi a été comparé à l'épaisseur optique des nuages (COT) estimée à l'aide des données SEVIRI. Une relation logarithmique avec un coefficient de détermination d'environ 0,5 a été trouvée. Ce résultat plutôt faible peut en grande partie s'expliquer par un nombre limité de cas où subsistent des erreurs de positionnement ou par des interactions plus complexes entre nébulosité et rayonnement. De plus, l'incertitude sur l'estimation de l'épaisseur optique des nuages à l'aide des données SEVIRI pour les nuages optiquement plus épais n'est pas négligeable. [less ▲]

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See detailComparaison entre le profil vertical de la vitesse du vent observé dans les basses couches de la troposphère et celui simulé par le modèle WRF en Belgique
Doutreloup, Sébastien ULg; Fettweis, Xavier ULg; Beaumet, Julien ULg et al

in Camberlin, Pierre; Richard, Yves (Eds.) Actes du XXVIIe Colloque de l'Association Internationale de Climatologie : CLIMAT : SYSTÈME & INTERACTIONS (2014, July 02)

In the framework of FLEXIPAC project funded by the "RELIABLE" program of Walloon Region (Belgium), the Laboratory of Climatology Topoclimatology (LCT) of the University of Liège (Belgium) aims to adjust ... [more ▼]

In the framework of FLEXIPAC project funded by the "RELIABLE" program of Walloon Region (Belgium), the Laboratory of Climatology Topoclimatology (LCT) of the University of Liège (Belgium) aims to adjust the WRF regional model (v.3.4.) forced by the ERA-Interim reanalysis for Belgium. Our analysis shows that wind speeds at 100m simulated by WRF are systematically overestimated compared to wind speeds extracted from wind productions of two wind farms. In order to solve this problem, four ways are considered in this contribution. The first way is to compare the WRF model with the reanalysis data. The second way is to test the influence of the spatial resolution by running WRF with a finer resolution. The third way is to smooth WRF outputs, where in order to analyze the variability created by the model. And finally, the fourth way is to compare the WRF model with the MAR (v3.3.) regional model. This last way seems to confirm that the MAR model better simulates wind speeds at 10m and at 100m than the WRF model. [less ▲]

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See detailSolar irradiance modelling over Belgium using WRF-ARW : A sensitivity analysis of Mellor-Yamada-Nakanishi-Niino (BYNN) boundary layer scheme parameters
Beaumet, Julien ULg; Doutreloup, Sébastien ULg; Fettweis, Xavier ULg et al

Conference (2014, June 06)

Global solar irradiances at ground level are modelled over Belgium using latest version of WRF-ARW regional climate model (RCM). The model set-up used has a resolution of 5 kilometres. The boundary layer ... [more ▼]

Global solar irradiances at ground level are modelled over Belgium using latest version of WRF-ARW regional climate model (RCM). The model set-up used has a resolution of 5 kilometres. The boundary layer scheme chosen is the Mellor-Yamada-Nakanishi-Niino (MYNN) 2.5 scheme with the Turbulent Kinetic Energy (TKE) closure proposed by Canuto et al., (2008) and Kitamura (2010). In this scheme, the modification of some parameters allows to change the determinant mixing length (surface layer, planet boundary layer, top of boundary layer/entrainment) which then modifies heat and moistures fluxes produced by turbulent mixing. Such modifications have significant influences on modelled cloudiness and therefore on modelled global solar irradiance incoming at the surface. The present study proposes a sensitivity analysis of the different parameters that influence the mixing length ('alp1' to 'alp5') and the TKE diffusion ('Sqfac') in order to find the most suitable constant values of these parameters for the modelling of cloudiness over Belgium. Results of different simulations are compared with global solar irradiance measurements performed by the Centre Spatial de Liège at Sart-Tilman in 2013 and 2014. Firsts results show that the dry bias frequently found when using WRF-ARW with standard set-ups can be greatly reduced thanks to an increased modelled cloudiness. The quantitative and qualitative effects of these modifications over cloudiness are also analysed by displaying 2D representation of modelled clouds over Sart-Tilman and confronting them with on-site observations. [less ▲]

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See detailComparison between wind speed observed at 100m height and wind speeds simulated by the WRF and MAR models
Doutreloup, Sébastien ULg; Fettweis, Xavier ULg; Erpicum, Michel ULg et al

Poster (2014, June 06)

In the context of FLEXIPAC project funded by "RELIABLE" program of Walloon Region (Belgium), the Laboratory of Climatology and Topoclimatology (LCT) of the University of Liège (Belgium) aims to adjust the ... [more ▼]

In the context of FLEXIPAC project funded by "RELIABLE" program of Walloon Region (Belgium), the Laboratory of Climatology and Topoclimatology (LCT) of the University of Liège (Belgium) aims to adjust the WRF regional model (v.3.4.) forced by ERA-Interim model. Our analysis shows that wind speeds at 100m height simulated by WRF are systematically overestimated compared to wind speeds extracted from wind productions of two wind farms. In order to identify this problem, four comparisons were performed in this contribution. Firstly, we compare WRF model with reanalysis based forcing model. Secondly, we compare two WRF simulations, where one of them has a more precise spatial resolution. Thirdly, we smooth WRF outputs in time (6-hr running mean) in order to study the accuracy of the 30-min variability generated by WRF model. Finally, we comp compare the WRF model with the MAR (v3.3.) regional model using the same forcing at its lateral boundaries. This last one seems to suggest that the MAR model better simulates wind speeds at 10m and at 100m than WRF model and then that wind speed underestimation by WRF is well linked to the WRF physics itself. [less ▲]

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See detailÉtude des changements de circulation au-dessus de l'océan Austral en été
Belleflamme, Alexandre ULg; Fettweis, Xavier ULg; Erpicum, Michel ULg

in Camberlin, Pierre; Richard, Yves (Eds.) Actes du XXVIIème colloque de l'Association de Climatologie - Climat : système & interactions (2014, June)

Over the five last decades, the reanalyses (ERA and NCEP/NCAR) show a strengthening of the pressure gradient between the southern hemisphere subtropical anticyclone belt and the southern circumpolar lows ... [more ▼]

Over the five last decades, the reanalyses (ERA and NCEP/NCAR) show a strengthening of the pressure gradient between the southern hemisphere subtropical anticyclone belt and the southern circumpolar lows during summer. With the help of an automatic circulation type classification, we show that the strengthening of the pressure gradient is generalised to all circulation types and, paradoxically, it does not cause circulation changes. It is probably implied by the strengthening of the temperature gradient between the tropics and the South Pole, without consequences on the general circulation. Our classification also allows a successful comparison between the two reanalyses in a region where the observation data are rare. [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 detailDo global warming-induced circulation pattern changes affect temperature and precipitation over Europe during summer?
Belleflamme, Alexandre ULg; Fettweis, Xavier ULg; Erpicum, Michel ULg

in International Journal of Climatology (2014)

Future climate change projections are not limited to a simple warming, but changes in precipitation and sea level pressure (SLP) are also projected. The SLP changes and the associated atmospheric ... [more ▼]

Future climate change projections are not limited to a simple warming, but changes in precipitation and sea level pressure (SLP) are also projected. The SLP changes and the associated atmospheric circulation changes could directly mitigate or enhance potential projected changes in temperature and precipitation associated with rising temperatures. With the aim of analysing the projected circulation changes and their possible impacts on temperature and precipitation over Europe in summer [June–July–August (JJA)], we apply an automatic circulation type classification method, based on daily SLP, on general circulation model (GCM) outputs from the Coupled Model Intercomparison Project phase 5 (CMIP5) database over the historical period (1951–2005) and for climate under two future scenarios (2006–2100). We focus on summer as it is the season when changes in temperature and precipitation have the highest impact on human health and agriculture. Over the historical observed reference period (1960–1999), our results show that most of the GCMs have significant biases over Europe when compared to reanalysis data sets, both for simulating the observed circulation types and their frequencies, as well as for reproducing the intraclass means of the studied variables. The future projections suggest a decrease of circulation types favouring a low centred over the British Isles for the benefit of more anticyclonic conditions. These circulation changes mitigate the projected precipitation increase over north-western Europe in summer, but they do not significantly affect the projected temperature increase and the precipitation decrease over the Mediterranean region and eastern Europe. However, the circulation changes and the associated precipitation changes are tarnished by a high uncertainty among the GCM projections. [less ▲]

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