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7. On the contribution of internal climate variability to European future climate trends

Author

Koenigk, Torben, Bärring, L., Matei, D., Nikulin, G., Strandberg, Gustav, Tyrlis, E., Wang, S., Wilcke, R., Koenigk, Torben, Bärring, L., Matei, D., Nikulin, G., Strandberg, Gustav, Tyrlis, E., Wang, S., and Wilcke, R.

Abstract

Large historical and future ensemble simulations from the Max-Planck Institute and the Canadian Earth System Models and from CMIP5 have been analysed to investigate the uncertainty due to internal variability in multi-decadal temperature and precipitation trends over Europe. Internal variability dominates the uncertainties in temperature and precipitation trends in all seasons at 30-year time scales. Locally, seasonal 30-year temperature trends deviate up to +/- 3 degrees C from the ensemble mean trend. Thus, in the entire of Europe, local seasonal temperature changes until year 2050 from below -1 degrees C up to more than 4 degrees C are possible according to the model results. Up to 30% of all ensemble members show negative temperature trends until year 2050 in winter, up to 10% of the members in summer. Uncertainties of 30-year precipitation trends due to internal variability exceed the trends almost everywhere in Europe. Only in few European regions more than 75% of the members agree on the sign of the change until year 2050. In southern Sweden, minimum and maximum winter (summer) temperature trends in the next 30years differ with up to 7 degrees C (5 degrees C) between individual members of the large model ensembles. Large positive temperature trends are linked to positive (negative) precipitation trends in winter (summer) in southern Sweden. This variability is attributed to the variability in large scale atmospheric circulation trends, mainly due to internal atmospheric variability. We find only weak linkages between the variability of temperature trends and the dominant decadal to multi-decadal climate modes. This indicates that there is limited potential to predict the multi-decadal variability in climate trends. The main findings from our study are robust across the large ensembles from the different models used in this study but at the local scale, the results depend also on the choice of the model.

Published
2020
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10. Process-oriented assessment of RCA4 regional climate model projections over the Congo Basin under 1.5. C and 2. C global warming levels: influence of regional moisture fluxes

Author

Tamoffo, AT, Moufouma-Okia, W, Dosio, A, James, R, Pokam, WM, Vondou, DA, Fotso-Nguemo, TC, Guenang, GM, Kamsu-Tamo, PH, Nikulin, G, Longandjo, G-N, Lennard, CJ, Bell, J-P, Takong, RR, Haensler, A, Tchotchou, LAD, and Nouayou, R

Abstract

© 2019, Springer-Verlag GmbH Germany, part of Springer Nature. Understanding the processes responsible for precipitation and its future change is important to develop plausible and sustainable climate change adaptation strategies, especially in regions with few available observed data like Congo Basin (CB). This paper investigates the atmospheric circulation processes associated with climate model biases in CB rainfall, and explores drivers of projected rainfall changes. Here we use an ensemble of simulations from the Swedish Regional Climate Model (RCM) RCA4, driven by eight General Circulation Models (GCMs) from the Coupled Model Intercomparison Project Phase 5 (CMIP5), for the 1.5∘C and 2∘C global warming levels (GWLs), and under the representative concentration pathways (RCPs) 4.5 and 8.5. RCA4 captures reasonably well the observed patterns of CB rainfall seasonality, but shows dry biases independent of seasons and large scale driving atmospheric conditions. While simulations mimic observed peaks in transition seasons (March–May and September–November), the rain-belt is misplaced southward (northward) in December–February (June–August), reducing the latitudinal extent of rainfall. Moreover, ERA-Interim reanalysis driven RCM simulation and RCM–GCM combinations show similar results, indicating the dominance of systematic biases. Modelled dry biases are associated with dry upper-tropospheric layers, resulting from a western outflow stronger than the eastern inflow and related to the northern component of African Easterly Jet. From the analysis of the climate change signal, we found that regional scale responses to anthropogenic forcings vary across GWLs and seasons. Changes of rainfall and moisture divergence are correlated, with values higher in March–May than in September–November, and larger for global warming of 2.0∘C than at 1.5∘C. There is an increase of zonal moisture divergence fluxes in upper atmospheric layers (>700hPa) under RCP8.5 compared to RCP4.5. Moreover, it is found that additional warming of 0.5∘C will change the hydrological cycle and water availability in the CB, with potential to cause challenges to water resource management, agriculture, hydro-power generation, sanitation and ecosystems.

Published
2019

11. Process-oriented assessment of RCA4 regional climate model projections over the Congo Basin under 1.5 °C and 2 °C global warming levels: influence of regional moisture fluxes

Author

Tamoffo, A., Moufouma-Okia, W., Dosio, A., James, R., Pokam, W., Vondou, D., Fotso-Nguemo, T., Guenang, G., Kamsu-Tamo, P., Nikulin, G., Longandjo, G., Lennard, C., Bell, J., Takong, R., Haensler, A., Djiotang Tchotchou, L., and Nouayou, R.

Abstract

Understanding the processes responsible for precipitation and its future change is important to develop plausible and sustainable climate change adaptation strategies, especially in regions with few available observed data like Congo Basin (CB). This paper investigates the atmospheric circulation processes associated with climate model biases in CB rainfall, and explores drivers of projected rainfall changes. Here we use an ensemble of simulations from the Swedish Regional Climate Model (RCM) RCA4, driven by eight General Circulation Models (GCMs) from the Coupled Model Intercomparison Project Phase 5 (CMIP5), for the 1.5 ∘C and 2 ∘C global warming levels (GWLs), and under the representative concentration pathways (RCPs) 4.5 and 8.5. RCA4 captures reasonably well the observed patterns of CB rainfall seasonality, but shows dry biases independent of seasons and large scale driving atmospheric conditions. While simulations mimic observed peaks in transition seasons (March–May and September–November), the rain-belt is misplaced southward (northward) in December–February (June–August), reducing the latitudinal extent of rainfall. Moreover, ERA-Interim reanalysis driven RCM simulation and RCM–GCM combinations show similar results, indicating the dominance of systematic biases. Modelled dry biases are associated with dry upper-tropospheric layers, resulting from a western outflow stronger than the eastern inflow and related to the northern component of African Easterly Jet. From the analysis of the climate change signal, we found that regional scale responses to anthropogenic forcings vary across GWLs and seasons. Changes of rainfall and moisture divergence are correlated, with values higher in March–May than in September–November, and larger for global warming of 2.0 ∘C than at 1.5 ∘C. There is an increase of zonal moisture divergence fluxes in upper atmospheric layers (>700hPa) under RCP8.5 compared to RCP4.5. Moreover, it is found that additional warming of 0.5 ∘C will change the hydrological cycle and water availability in the CB, with potential to cause challenges to water resource management, agriculture, hydro-power generation, sanitation and ecosystems.

Published
2019

19. Mean climate and representation of jet streams in the CORDEX South Asia simulations by the regional climate model RCA4

Author

Iqbal, Waheed, Syed, F. S., Sajjad, H., Nikulin, G., Kjellström, Erik, Hannachi, Abdel, Iqbal, Waheed, Syed, F. S., Sajjad, H., Nikulin, G., Kjellström, Erik, and Hannachi, Abdel

Abstract

A number of simulations with the fourth release of the Rossby Center Regional Climate Model (RCA4) conducted within the COordinated Regional climate Downscaling EXperiment (CORDEX) framework for South Asia at 50 km horizontal resolution are evaluated for mean winter (December-March) and summer (June-September) climate during 1980-2005. The two driving data sets ERA-Interim reanalysis and the general circulation model EC-Earth have been analyzed besides the RCA4 simulations to address the added value. RCA4 successfully captures the mean climate in both the seasons. The biases in RCA4 appear to come from the driving data sets which are amplified after downscaling. The jet streams influencing the seasonal precipitation variability in both seasons are also analyzed. The spatial and quantitative analysis over CORDEX South Asia generally revealed the ability of RCA4 to capture the mean seasonal climate as well as the position and strength of the jet streams despite weak/strong jet representation in the driving data. The EC-Earth downscaled with RCA4 exhibited cold biases over the domain and a weak Somali jet over the Arabian Sea. Moreover, the moisture transport from the Arabian Sea during summer is pronounced in RCA4 simulations resulting in enhanced monsoon rainfall over northwestern parts of India. Both the Somali jet and the tropical easterly jet become stronger during strong summer monsoon years. However, there is robust impact of wet years in summer over the Somali jet. Wet-minus-dry composites in winter indicate strengthening (weakening) of the subtropical jet in RCA4 run by ERA-Interim (EC-Earth). The driving data have clear reflections on the RCA4 simulations.

Published
2017
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20. Precipitation in the EURO-CORDEX 0.11∘0.11∘ and 0.44∘0.44∘ simulations: high resolution, high benefits?

Author

Prein, A., Gobiet, A., Truhetz, H., Keuler, K., Goergen, K., Teichmann, C., Fox Maule, C., Van Meijgaard, E., Déqué, M., Nikulin, G., Vautard, R., Colette, A., Kjellström, E., Jacob, D., National Center for Atmospheric Research [Boulder] (NCAR), Zentralanstalt für Meteorologie und Geodynamik (ZAMG), Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung (AWI), Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), University of Bonn, Max Planck Institute for Meteorology (MPI-M), Max-Planck-Gesellschaft, Danish Meteorological Institute (DMI), Royal Netherlands Meteorological Institute (KNMI), Groupe d'étude de l'atmosphère météorologique (CNRM-GAME), Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS), Swedish Meteorological and Hydrological Institute (SMHI), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Extrèmes : Statistiques, Impacts et Régionalisation (ESTIMR), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Institut National de l'Environnement Industriel et des Risques (INERIS), Laboratoire Kastler Brossel (LKB (Jussieu)), Université Pierre et Marie Curie - Paris 6 (UPMC)-Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Universität Bonn = University of Bonn, Centre national de recherches météorologiques (CNRM), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2016

26. Daily precipitation statistics in a EURO-CORDEX RCM ensemble: added value of raw and bias-corrected high-resolution simulations

Author

Casanueva, A., primary, Kotlarski, S., additional, Herrera, S., additional, Fernández, J., additional, Gutiérrez, J. M., additional, Boberg, F., additional, Colette, A., additional, Christensen, O. B., additional, Goergen, K., additional, Jacob, D., additional, Keuler, K., additional, Nikulin, G., additional, Teichmann, C., additional, and Vautard, R., additional

Published
2015
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27. Precipitation in the EURO-CORDEX $$0.11^{\circ }$$ 0 . 11 ∘ and $$0.44^{\circ }$$ 0 . 44 ∘ simulations: high resolution, high benefits?

Author

Prein, A. F., primary, Gobiet, A., additional, Truhetz, H., additional, Keuler, K., additional, Goergen, K., additional, Teichmann, C., additional, Fox Maule, C., additional, van Meijgaard, E., additional, Déqué, M., additional, Nikulin, G., additional, Vautard, R., additional, Colette, A., additional, Kjellström, E., additional, and Jacob, D., additional

Published
2015
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28. Precipitation in complex orography simulated by the regional climate model RCA3

Author

Guttler, I. (author), Stepanov, I. (author), Nikulin, G. (author), Jones, C. (author), Brankovic, C. (author), Guttler, I. (author), Stepanov, I. (author), Nikulin, G. (author), Jones, C. (author), and Brankovic, C. (author)

Abstract

The aim of this study is to evaluate the improvement in simulated precipitation of the third version of the Rossby Centre Climate model (RCA3), when run at horizontal resolutions of 50, 25, 12 and 6 km. The analysis is focused on the countries of Switzerland and Norway, where complex orography can play a dominant role in precipitation formation. Observation data sets used for model validation were for Switzerland, the RhiresD dataset, an approximately 2-km resolution product of the Swiss National Meteorological Service (MeteoSwiss), and over Norway, the KLIMAGRID dataset (Mohr, 2007), a 1-km resolution product of the Norwegian Meteorological Institute (METNO), is used. The range of horizontal resolutions in experiments facilitates a systematic analysis of the impact of increasing the horizontal resolution on precipitation, in two different climate regimes., Geoscience & Remote Sensing, Civil Engineering and Geosciences

Published
2014

29. Managing the effects of multiple stressors on aquatic ecosystems under water scarcity. The GLOBAQUA project

Author

Navarro-Ortega, A., Acuña, V., Bellin, A., Burek, P., Cassiani, G., Choukr-Allah, R., Dolédec, S., Elosegi, A., Ferrari, F., Ginebreda, A., Grathwohl, P., Jones, C., Raultl, P.K., Kok, K., Koundouri, P., Ludwig, R.P., Merz, Ralf, Milacic, R., Muñoz, I., Nikulin, G., Paniconi, C., Paunović, M., Petrovic, M., Sabater, L., Skoulikidis, N.T., Slob, A., Teutsch, Georg, Voulvoulis, N., Barceló, D., Navarro-Ortega, A., Acuña, V., Bellin, A., Burek, P., Cassiani, G., Choukr-Allah, R., Dolédec, S., Elosegi, A., Ferrari, F., Ginebreda, A., Grathwohl, P., Jones, C., Raultl, P.K., Kok, K., Koundouri, P., Ludwig, R.P., Merz, Ralf, Milacic, R., Muñoz, I., Nikulin, G., Paniconi, C., Paunović, M., Petrovic, M., Sabater, L., Skoulikidis, N.T., Slob, A., Teutsch, Georg, Voulvoulis, N., and Barceló, D.

Abstract

Water scarcity is a serious environmental problem in many European regions, and will likely increase in the near future as a consequence of increased abstraction and climate change. Water scarcity exacerbates the effects of multiple stressors, and thus results in decreased water quality. It impacts river ecosystems, threatens the services they provide, and it will force managers and policy-makers to change their current practices. The EU-FP7 project GLOBAQUA aims at identifying the prevalence, interaction and linkages between stressors, and to assess their effects on the chemical and ecological status of freshwater ecosystems in order to improve water management practice and policies. GLOBAQUA assembles a multidisciplinary team of 21 European plus 2 non-European scientific institutions, as well as water authorities and river basin managers. The project includes experts in hydrology, chemistry, biology, geomorphology, modelling, socio-economics, governance science, knowledge brokerage, and policy advocacy. GLOBAQUA studies six river basins (Ebro, Adige, Sava, Evrotas, Anglian and Souss Massa) affected by water scarcity, and aims to answer the following questions: how does water scarcity interact with other existing stressors in the study river basins? How will these interactions change according to the different scenarios of future global change? Which will be the foreseeable consequences for river ecosystems? How will these in turn affect the services the ecosystems provide? How should management and policies be adapted to minimise the ecological, economic and societal consequences? These questions will be approached by combining data-mining, field- and laboratory-based research, and modelling. Here, we outline the general structure of the project and the activities to be conducted within the fourteen work-packages of GLOBAQUA.

Published
2014

30. Regional climate modeling on European scales: a joint standard evaluation of the EURO-CORDEX RCM ensemble

Author

Kotlarski, S., primary, Keuler, K., additional, Christensen, O. B., additional, Colette, A., additional, Déqué, M., additional, Gobiet, A., additional, Goergen, K., additional, Jacob, D., additional, Lüthi, D., additional, van Meijgaard, E., additional, Nikulin, G., additional, Schär, C., additional, Teichmann, C., additional, Vautard, R., additional, Warrach-Sagi, K., additional, and Wulfmeyer, V., additional

Published
2014
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31. Assessment of the performance of CORDEX Regional Climate Models in Simulating Eastern Africa Rainfall

Author

Endris, H., Omondi, P., Jain, S., Lennard, C., Hewitson, B., Chang’a, L., Awange, Joseph, Dosio, A., Ketiem, P., Nikulin, G., Panitz, H., Büchner, M., Stordal, F., Tazalika, L., Endris, H., Omondi, P., Jain, S., Lennard, C., Hewitson, B., Chang’a, L., Awange, Joseph, Dosio, A., Ketiem, P., Nikulin, G., Panitz, H., Büchner, M., Stordal, F., and Tazalika, L.

Abstract

This study evaluates the ability of 10 regional climate models (RCMs) from the Coordinated Regional Climate Downscaling Experiment (CORDEX) in simulating the characteristics of rainfall patterns over eastern Africa. The seasonal climatology, annual rainfall cycles, and interannual variability of RCM output have been assessed over three homogeneous subregions against a number of observational datasets. The ability of the RCMs in simulating large-scale global climate forcing signals is further assessed by compositing the El Niño–Southern Oscillation (ENSO) and Indian Ocean dipole (IOD) events. It is found that most RCMs reasonably simulate the main features of the rainfall climatology over the three subregions and also reproduce the majority of the documented regional responses to ENSO and IOD forcings. At the same time the analysis shows significant biases in individual models depending on subregion and season; however, the ensemble mean has better agreement with observation than individual models. In general, the analysis herein demonstrates that the multimodel ensemble mean simulates eastern Africa rainfall adequately and can therefore be used for the assessment of future climate projections for the region.

Published
2013

32. Daily precipitation statistics in a EURO-CORDEX RCM ensemble: added value of raw and bias-corrected high-resolution simulations.

Author

Casanueva, A., Kotlarski, S., Herrera, S., Fernández, J., Gutiérrez, J., Boberg, F., Colette, A., Christensen, O., Goergen, K., Jacob, D., Keuler, K., Nikulin, G., Teichmann, C., and Vautard, R.

Subjects
METEOROLOGICAL precipitation, ATMOSPHERIC physics, ATMOSPHERIC models, ALPINE regions, MOUNTAINS
Abstract

Daily precipitation statistics as simulated by the ERA-Interim-driven EURO-CORDEX regional climate model (RCM) ensemble are evaluated over two distinct regions of the European continent, namely the European Alps and Spain. The potential added value of the high-resolution 12 km experiments with respect to their 50 km resolution counterparts is investigated. The statistics considered consist of wet-day intensity and precipitation frequency as a measure of mean precipitation, and three precipitation-derived indicators (90th percentile on wet days-90pWET, contribution of the very wet days to total precipitation-R95pTOT and number of consecutive dry days-CDD). As reference for model evaluation high resolution gridded observational data over continental Spain (Spain011/044) and the Alpine region (EURO4M-APGD) are used. The assessment and comparison of the two resolutions is accomplished not only on their original horizontal grids (approximately 12 and 50 km), but the high-resolution RCMs are additionally regridded onto the coarse 50 km grid by grid cell aggregation for the direct comparison with the low resolution simulations. The direct application of RCMs e.g. in many impact modelling studies is hampered by model biases. Therefore bias correction (BC) techniques are needed at both resolutions to ensure a better agreement between models and observations. In this work, the added value of the high resolution (before and after the bias correction) is assessed and the suitability of these BC methods is also discussed. Three basic BC methods are applied to isolate the effect of biases in mean precipitation, wet-day intensity and wet-day frequency on the derived indicators. Daily precipitation percentiles are strongly affected by biases in the wet-day intensity, whereas the dry spells are better represented when the simulated precipitation frequency is adjusted to the observed one. This confirms that there is no single optimal way to correct for RCM biases, since correcting some distributional features typically leads to an improvement of some aspects but to a deterioration of others. Regarding mean seasonal biases before the BC, we find only limited evidence for an added value of the higher resolution in the precipitation intensity and frequency or in the derived indicators. Thereby, evaluation results considerably depend on the RCM, season and indicator considered. High resolution simulations better reproduce the indicators' spatial patterns, especially in terms of spatial correlation. However, this improvement is not statistically significant after applying specific BC methods. [ABSTRACT FROM AUTHOR]

Published
2016
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33. Precipitation in the EURO-CORDEX $$0.11^{\circ }$$ and $$0.44^{\circ }$$ simulations: high resolution, high benefits?

Author

Prein, A., Gobiet, A., Truhetz, H., Keuler, K., Goergen, K., Teichmann, C., Fox Maule, C., Meijgaard, E., Déqué, M., Nikulin, G., Vautard, R., Colette, A., Kjellström, E., and Jacob, D.

Subjects
METEOROLOGICAL precipitation, COMPUTER simulation, ATMOSPHERIC models, MOUNTAINS, METEOROLOGICAL observations
Abstract

In the framework of the EURO-CORDEX initiative an ensemble of European-wide high-resolution regional climate simulations on a $$0.11^{\circ }\,({\sim}12.5\,\hbox {km})$$ grid has been generated. This study investigates whether the fine-gridded regional climate models are found to add value to the simulated mean and extreme daily and sub-daily precipitation compared to their coarser-gridded $$0.44^{\circ }\,({\sim}50\,\hbox {km})$$ counterparts. Therefore, pairs of fine- and coarse-gridded simulations of eight reanalysis-driven models are compared to fine-gridded observations in the Alps, Germany, Sweden, Norway, France, the Carpathians, and Spain. A clear result is that the $$0.11^{\circ }$$ simulations are found to better reproduce mean and extreme precipitation for almost all regions and seasons, even on the scale of the coarser-gridded simulations (50 km). This is primarily caused by the improved representation of orography in the $$0.11^{\circ }$$ simulations and therefore largest improvements can be found in regions with substantial orographic features. Improvements in reproducing precipitation in the summer season appear also due to the fact that in the fine-gridded simulations the larger scales of convection are captured by the resolved-scale dynamics . The $$0.11^{\circ }$$ simulations reduce biases in large areas of the investigated regions, have an improved representation of spatial precipitation patterns, and precipitation distributions are improved for daily and in particular for 3 hourly precipitation sums in Switzerland. When the evaluation is conducted on the fine (12.5 km) grid, the added value of the $$0.11^{\circ }$$ models becomes even more obvious. [ABSTRACT FROM AUTHOR]

Published
2016
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44. The sudden stratospheric warming of the Arctic winter 2009/2010: comparison to other recent warm winters.

Author

Kuttippurath, J. and Nikulin, G.

Abstract

The Arctic winter 2009/10 was moderately cold in December. A minor warming occurred around mid-December due to a wave 2 amplification split the lower stratospheric vortex into two lobes. The vortices merged again and formed a relatively large vortex in a few days. The temperatures began to rise by mid-January and triggered a major sudden stratospheric warming (SSW) by the reversal of westerlies in late (24-26) January, driven by a planetary wave 1 with a peak amplitude of about 100m² s-2 at 60° N/10 hPa. The momentum flux associated with this warming showed the largest value in the recent winters, about 450 m² s-2 at 60° N/10 hPa. The associated vortex split confined to altitudes below 10 hPa and hence, the major warming (MW) was a vortex displacement event. Large amounts of Eliassen-Palm (EP) and wave 2 EP fluxes (3.9 x 105 kg s-2 ) are found shortly before the MW event at 100 hPa over 45-75° N, suggesting a tropospheric preconditioning of the MW event. We observe an increase in SSWs in the Arctic in recent years, as there were 6MWs in 6 out of the 7 winters of 2003/04-2009/10, which confirms the conclusions of previous studies on the SSWs in winters prior to 2003/04. Each MW event was unique as far as its evolution and related polar processes were concerned. As compared to the MWs in the recent Arctic winters, the strongest MW was observed in 2008/09 and was initiated by a wave 2 event. A detailed diagnosis of ozone loss during the past fifteen years shows that the loss is inversely proportional to the intensity and timing of SSWs in each winter, where early MWs lead to minimal loss. The ozone loss shows a good correlation with the zonal mean amplitude of zonal winds in January over 60-90° N, suggesting a proxy for MWs in the Arctic winters. [ABSTRACT FROM AUTHOR]

Published
2012
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46. Accuracy of pan‐European coastal flood mapping.

Author

Paprotny, D., Morales‐Nápoles, O., Vousdoukas, M. I., Jonkman, S. N., and Nikulin, G.

Subjects
COASTAL mapping, STORM surges, FLOOD control, DIGITAL elevation models, FLOOD risk, SEA level
Abstract

Coastal flood maps covering the whole European continent have become available in recent years. However, their ability to complement or replace high‐resolution local flood maps was not investigated so far. In this paper we compare pan‐European estimates of extreme sea levels and coastal flood extents at given return periods with observations and high‐resolution reference maps. The analysis is done for two pan‐European assessments and one global study. We find that whereas the models have good accuracy in estimating storm surge heights, large disparities exist between the large‐scale flood maps and four local maps of flood extents from England, the Netherlands, Poland, and France. Moreover, the accuracy of the underlying digital elevation model and assumptions about flood protection existing in a given area influence significantly the results. In addition, the first pan‐European projection of temporal trends in the size of flood zones is presented, with and without assuming flood protection levels. [ABSTRACT FROM AUTHOR]

Published
2019
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47. Regional climate downscaling over Europe: perspectives from the EURO-CORDEX community

Author

Jacob, Daniela, Teichmann, Claas, Sobolowski, Stefan, Katragkou, Eleni, Anders, Ivonne, Belda, Michal, Benestad, Rasmus, Boberg, Fredrik, Buonomo, Erasmo, Cardoso, Rita M., Casanueva, Ana, Christensen, Ole B., Christensen, Jens Hesselbjerg, Coppola, Erika, De Cruz, Lesley, Davin, Edouard L., Dobler, Andreas, Domínguez, Marta, Fealy, Rowan, Fernandez, Jesus, Gaertner, Miguel Angel, García-Díez, Markel, Giorgi, Filippo, Gobiet, Andreas, Goergen, Klaus, Gómez-Navarro, Juan José, Alemán, Juan Jesús González, Gutiérrez, Claudia, Gutiérrez, José M., Güttler, Ivan, Haensler, Andreas, Halenka, Tomáš, Jerez, Sonia, Jiménez-Guerrero, Pedro, Jones, Richard G., Keuler, Klaus, Kjellström, Erik, Knist, Sebastian, Kotlarski, Sven, Maraun, Douglas, van Meijgaard, Erik, Mercogliano, Paola, Montávez, Juan Pedro, Navarra, Antonio, Nikulin, Grigory, de Noblet-Ducoudré, Nathalie, Panitz, Hans-Juergen, Pfeifer, Susanne, Piazza, Marie, Pichelli, Emanuela, Pietikäinen, Joni-Pekka, Prein, Andreas F., Preuschmann, Swantje, Rechid, Diana, Rockel, Burkhardt, Romera, Raquel, Sánchez, Enrique, Sieck, Kevin, Soares, Pedro M. M., Somot, Samuel, Srnec, Lidija, Sørland, Silje Lund, Termonia, Piet, Truhetz, Heimo, Vautard, Robert, Warrach-Sagi, Kirsten, Wulfmeyer, Volker, Climate Service Center Germany (GERICS), Helmholtz-Zentrum Geesthacht, Hamburg, Germany, NORCE Norwegian Research Centre, The Bjerknes Centre for Climate Research, Bergen, Norway, Department of Meteorology and Climatology, School of Geology, Aristotle University of Thessaloniki, Thessaloniki, Greece, Central Institute for Meteorology and Geodynamics (ZAMG), Vienna, Austria, Department of Atmospheric Physics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic, The Norwegian Meteorological Institute, Oslo, Norway, Danish Meteorological Institute (DMI), Copenhagen, Denmark, School of Geography and the Environment, University of Oxford, Oxford, UK, Instituto Dom Luiz (IDL), Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal, Meteorology Group, Department of Applied Mathematics and Computer Science, Universidad de Cantabria, Santander, Spain, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark, International Centre for Theoretical Physics (ICTP), Trieste, Italy, Royal Meteorological Institute of Belgium (RMIB), Brussels, Belgium, Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland, Agencia Estatal de Meteorología, Madrid, Spain, ICARUS, Department of Geography, Maynooth University, Maynooth, Ireland, University of Castilla-La Mancha, Toledo, Spain, Centre for High-Performance Scientific Computing in Terrestrial Systems, Geoverbund ABC/J, Jülich, Germany, Regional Atmospheric Modeling Group, Department of Physics, University of Murcia, Murcia, Spain, Meteorology Group, Instituto de Física de Cantabria (CSIC-Universidad de Cantabria), Santander, Spain, Croatian Meteorological and Hydrological Service, Zagreb, Croatia, Met Office Hadley Centre, Exeter, UK, Chair of Atmospheric Processes, Brandenburg University of Technology Cottbus - Senftenberg, Cottbus, Germany, Swedish Meteorological and Hydrological Institute, Norrköping, Sweden, Meteorological Institute, University of Bonn, Bonn, Germany, Federal Office of Meteorology and Climatology MeteoSwiss, Zurich-Airport, Switzerland, Wegener Center for Climate and Global Change, University of Graz, Graz, Austria, Royal Netherlands Meteorological Institute (KNMI), De Bilt, The Netherlands, C.I.R.A., Capua, Italy, Centro Euro-Mediterraneo sui Cambiamenti Climatici (CMCC), Lecce, Italy, Laboratoire des Sciences du Climat et de l’Environnement, IPSL, Unité Mixte CEA-CNRS-UVSQ, Université Paris-Saclay, Gif-sur-Yvette cédex, France, Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology, Karlsruhe, Germany, Finnish Meteorological Institute (FMI), Helsinki, Finland, National Center for Atmospheric Research, Boulder, USA, Helmholtz-Zentrum Geesthacht, Geesthacht, Germany, CNRM, Université de Toulouse, Météo-France, CNRS, Toulouse, France, Department of Physics and Astronomy, Ghent University, Ghent, Belgium, Institute of Physics and Meteorology, University of Hohenheim, Stuttgart, Germany, Jacob D., Teichmann C., Sobolowski S., Katragkou E., Anders I., Belda M., Benestad R., Boberg F., Buonomo E., Cardoso R.M., Casanueva A., Christensen O.B., Christensen J.H., Coppola E., De Cruz L., Davin E.L., Dobler A., Dominguez M., Fealy R., Fernandez J., Gaertner M.A., Garcia-Diez M., Giorgi F., Gobiet A., Goergen K., Gomez-Navarro J.J., Aleman J.J.G., Gutierrez C., Gutierrez J.M., Guttler I., Haensler A., Halenka T., Jerez S., Jimenez-Guerrero P., Jones R.G., Keuler K., Kjellstrom E., Knist S., Kotlarski S., Maraun D., van Meijgaard E., Mercogliano P., Montavez J.P., Navarra A., Nikulin G., de Noblet-Ducoudre N., Panitz H.-J., Pfeifer S., Piazza M., Pichelli E., Pietikainen J.-P., Prein A.F., Preuschmann S., Rechid D., Rockel B., Romera R., Sanchez E., Sieck K., Soares P.M.M., Somot S., Srnec L., Sorland S.L., Termonia P., Truhetz H., Vautard R., Warrach-Sagi K., Wulfmeyer V., Electronics and Informatics, Physics, Universidad de Cantabria, Ministerio de Economía y Competitividad (España), CSIC-UC - Instituto de Física de Cantabria (IFCA), Ministerio de Ciencia, Innovación y Universidades (España), Agencia Estatal de Investigación (España), and European Commission

Subjects
IMPACTS, Climate Research, 010504 meteorology & atmospheric sciences, 0208 environmental biotechnology, Climate change, ENSEMBLE, 02 engineering and technology, Land cover, 01 natural sciences, Klimatforskning, COVER CHANGES, 11. Sustainability, ddc:330, Regional science, Adaptation (computer science), Temporal scales, TEMPERATURE, 0105 earth and related environmental sciences, MODEL DESCRIPTION, Global and Planetary Change, regional climate models, EURO-CORDEX, Land use, LAND-USE, FUTURE CHANGES, 15. Life on land, SIMULATIONS, 020801 environmental engineering, Earth system science, CORDEX, Geography, ddc:551.6, 13. Climate action, Earth and Environmental Sciences, MED-CORDEX, EURO-CORDEX, DAILY PRECIPITATION STATISTICS, Downscaling, Regional climate modelling, Regional climate models
Abstract

The European CORDEX (EURO-CORDEX) initiative is a large voluntary effort that seeks to advance regional climate and Earth system science in Europe. As part of the World Climate Research Programme (WCRP) - Coordinated Regional Downscaling Experiment (CORDEX), it shares the broader goals of providing a model evaluation and climate projection framework and improving communication with both the General Circulation Model (GCM) and climate data user communities. EURO-CORDEX oversees the design and coordination of ongoing ensembles of regional climate projections of unprecedented size and resolution (0.11° EUR-11 and 0.44° EUR-44 domains). Additionally, the inclusion of empirical-statistical downscaling allows investigation of much larger multi-model ensembles. These complementary approaches provide a foundation for scientific studies within the climate research community and others. The value of the EURO-CORDEX ensemble is shown via numerous peer-reviewed studies and its use in the development of climate services. Evaluations of the EUR-44 and EUR-11 ensembles also show the benefits of higher resolution. However, significant challenges remain. To further advance scientific understanding, two flagship pilot studies (FPS) were initiated. The first investigates local-regional phenomena at convection-permitting scales over central Europe and the Mediterranean in collaboration with the Med-CORDEX community. The second investigates the impacts of land cover changes on European climate across spatial and temporal scales. Over the coming years, the EURO-CORDEX community looks forward to closer collaboration with other communities, new advances, supporting international initiatives such as the IPCC reports, and continuing to provide the basis for research on regional climate impacts and adaptation in Europe., S.S. acknowledges the support of NOTUR/NORSTORE projects NN9280K/NS9001K and the Research Council of Norway and its basic institute support of the strategic project on Climate Services. E.K. acknowledges the support of the Greek Research & Technology Network (GRNET) for provision of technical support and facilities (HPC-ARIS). L.S. and I.G. acknowledge the support of Croatian Science Foundation project CARE (2831) and Ministry of Environment and Energy project TF/HR/P3-M1-O1-0101 (www.prilagodba-klimi.hr). J. F. acknowledges support from the Spanish R+D Programme through grant INSIGNIA (CGL2016-79210-R), co-funded by ERDF/FEDER, and the Altamira Supercomputer at Instituto de Física de Cantabria (IFCA-CSIC), member of the Spanish Supercomputing Network. P.T. acknowledges support from the Belgian Science Policy (BELSPO) within the CORDEX.be (BR/143/A2) project, and the VSC (Flemish Supercomputer Center), funded by the Research Foundation - Flanders (FWO) and the Flemish Government – department EWI.M.A.G. acknowledges support from the Spanish R+D Programme through grants CGL2013-47261-R and CGL2017-89583-R, co-funded by the European Regional Development Fund. RF acknowledges support provided by ICHEC (Irish Centre for High End Computing) and the Irish Environmental Protection Agency. K.G. and S.K. gratefully acknowledge the computing time granted through JARA-HPC on the supercomputers JUROPA and JURECA at Forschungszentrum Jülich. M.B. and T.H. acknowledge support by The Ministry of Education, Youth and Sports from the Large Infrastructures for Research, Experimental Development and Innovations project “IT4Innovations National Supercomputing Center – LM2015070” and the INTER-EXCELLENCE program LTT17007, and support by Charles University from the PROGRES Q16 program. We acknowledge the approval and support of the two Flagship Pilot Studies (the FPS on Convective phenomena at high resolution over Europe and the Mediterranean and the FPS on Land Use and Climate Across Scales) by WRCP CORDEX. We thank Merja Tölle for providing simulation CCLM5-0-9-JLU as contribution to the CORDEX-FPS “Convective phenomena at high resolution over Europe and the Mediterranean”. D. M., M.P., and H.T. gratefully acknowledge the support received via the projects HighEnd:Extremes, SPIRIT, and reclip:convex, funded by the Austrian Climate Research Programme (ACRP) of the Klima- und Energiefonds (nos. B368608, B960272, and B769999, respectively), as well as the Jülich Supercomputing Centre (JSC) for compute time on JURECA through the grant JJSC39 and the Vienna Scientific Cluster (VSC) through the grants 70992 and 71193.

Published
2020

48. Testing the Hydrological Coherence of High‐Resolution Gridded Precipitation and Temperature Data Sets

Author

Sebastiano Piccolroaz, Grigory Nikulin, Lavinia Laiti, Stefano Mallucci, Aldo Fiori, Dino Zardi, Alberto Bellin, Bruno Majone, Laiti, L., Mallucci, S., Piccolroaz, S., Bellin, A., Zardi, D., Fiori, A., Nikulin, G., and Majone, B.

Subjects
Alpine region, 010504 meteorology & atmospheric sciences, 0208 environmental biotechnology, gridded climate data, High resolution, 02 engineering and technology, Coherence (statistics), observational uncertainty, 01 natural sciences, hydrological modeling, Physics::Geophysics, 020801 environmental engineering, 13. Climate action, Adige river basin, hydrological coherence, Water Science and Technology, Precipitation, Computer Science::Distributed, Parallel, and Cluster Computing, Physics::Atmospheric and Oceanic Physics, Geology, 0105 earth and related environmental sciences, Remote sensing
Abstract

Assessing the accuracy of gridded climate data sets is highly relevant to climate change impact studies, since evaluation, bias correction, and statistical downscaling of climate models commonly use these products as reference. Among all impact studies those addressing hydrological fluxes are the most affected by errors and biases plaguing these data. This paper introduces a framework, coined Hydrological Coherence Test (HyCoT), for assessing the hydrological coherence of gridded data sets with hydrological observations. HyCoT provides a framework for excluding meteorological forcing data sets not complying with observations, as function of the particular goal at hand. The proposed methodology allows falsifying the hypothesis that a given data set is coherent with hydrological observations on the basis of the performance of hydrological modeling measured by a metric selected by the modeler. HyCoT is demonstrated in the Adige catchment (southeastern Alps, Italy) for streamflow analysis, using a distributed hydrological model. The comparison covers the period 1989–2008 and includes five gridded daily meteorological data sets: E-OBS, MSWEP, MESAN, APGD, and ADIGE. The analysis highlights that APGD and ADIGE, the data sets with highest effective resolution, display similar spatiotemporal precipitation patterns and produce the largest hydrological efficiency indices. Lower performances are observed for E-OBS, MESAN, and MSWEP, especially in small catchments. HyCoT reveals deficiencies in the representation of spatiotemporal patterns of gridded climate data sets, which cannot be corrected by simply rescaling the meteorological forcing fields, as often done in bias correction of climate model outputs. We recommend this framework to assess the hydrological coherence of gridded data sets to be used in large-scale hydroclimatic studies.

Published
2018

49. Investigating the potential impact of 1.5, 2 and 3 °C global warming levels on crop suitability and planting season over West Africa.

Author

Egbebiyi TS, Crespo O, Lennard C, Zaroug M, Nikulin G, Harris I, Price J, Forstenhäusler N, and Warren R

Abstract

West African rainfed agriculture is highly vulnerable to climate variability and change. Global warming is projected to result in higher regional warming and have a strong impact on agriculture. This study specifically examines the impact of global warming levels (GWLs) of 1.5°, 2° and 3 °C relative to 1971-2000 on crop suitability over West Africa. We used 10 Coupled Model Intercomparison Project Phase5 Global Climate Models (CMIP5 GCMs) downscaled by Coordinated Regional Downscaling Experiment (CORDEX) Rossby Centre's regional Atmospheric model version 4, RCA4, to drive Ecocrop, a crop suitability model, for pearl millet, cassava, groundnut, cowpea, maize and plantain. The results show Ecocrop simulated crop suitability spatial representation with higher suitability, observed to the south of latitude 14°N and lower suitability to its north for 1971-2000 for all crops except for plantain (12°N). The model also simulates the best three planting months within the growing season from September-August over the past climate. Projected changes in crop suitability under the three GWLs 1.5-3.0 °C suggest a spatial suitability expansion for legume and cereal crops, notably in the central southern Sahel zone; root and tuber and plantain in the central Guinea-Savanna zone. In contrast, projected decreases in the crop suitability index value are predicted to the south of 14°N for cereals, root and tuber crops; nevertheless, the areas remain suitable for the crops. A delay of between 1-3 months is projected over the region during the planting month under the three GWLs for legumes, pearl millet and plantain. A two month delay in planting is projected in the south, notably over the Guinea and central Savanna zone with earlier planting of about three months in the Savanna-Sahel zones. The effect of GWL2.0 and GWL3.0 warming in comparison to GWL1.5 °C are more dramatic on cereals and root and tuber crops, especially cassava. All the projected changes in simulated crop suitability in response to climatic variables are statistically significant at 99% confidence level. There is also an increasing trend in the projected crop suitability change across the three warming except for cowpea. This study has implications for improving the resilience of crop production to climate changes, and more broadly, to food security in West Africa., Competing Interests: Jeff Price is an Academic Editor for PeerJ. The authors declare there are no competing interests., (©2020 Egbebiyi et al.)

Published
2020
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50. Using an ensemble of regional climate models to assess climate change impacts on water scarcity in European river basins.

Author

Gampe D, Nikulin G, and Ludwig R

Abstract

Climate change will likely increase pressure on the water balances of Mediterranean basins due to decreasing precipitation and rising temperatures. To overcome the issue of data scarcity the hydrological relevant variables total runoff, surface evaporation, precipitation and air temperature are taken from climate model simulations. The ensemble applied in this study consists of 22 simulations, derived from different combinations of four General Circulation Models (GCMs) forcing different Regional Climate Models (RCMs) and two Representative Concentration Pathways (RCPs) at ~12km horizontal resolution provided through the EURO-CORDEX initiative. Four river basins (Adige, Ebro, Evrotas and Sava) are selected and climate change signals for the future period 2035-2065 as compared to the reference period 1981-2010 are investigated. Decreased runoff and evaporation indicate increased water scarcity over the Ebro and the Evrotas, as well as the southern parts of the Adige and the Sava, resulting from a temperature increase of 1-3° and precipitation decrease of up to 30%. Most severe changes are projected for the summer months indicating further pressure on the river basins already at least partly characterized by flow intermittency. The widely used Falkenmark indicator is presented and confirms this tendency and shows the necessity for spatially distributed analysis and high resolution projections. Related uncertainties are addressed by the means of a variance decomposition and model agreement to determine the robustness of the projections. The study highlights the importance of high resolution climate projections and represents a feasible approach to assess climate impacts on water scarcity also in regions that suffer from data scarcity., (Copyright © 2016. Published by Elsevier B.V.)

Published
2016
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