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| 5. |
- Cao, Ning, 1987-, et al.
(författare)
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The role of internal feedbacks in sustaining multi-centennial variability of the Atlantic Meridional Overturning Circulation revealed by EC-Earth3-LR simulations
- 2023
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Ingår i: Earth and Planetary Science Letters. - 0012-821X .- 1385-013X. ; 621
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Tidskriftsartikel (refereegranskat)abstract
- A significant multi-centennial climate variability with a distinct peak at approximately 200 years is observed in a pre-industrial (PI) control simulation using the EC-Earth3-LR climate model. This oscillation originates predominately from the North Atlantic and displays a strong association with the Atlantic Meridional Overturning Circulation (AMOC). Our study identifies the interplay between salinity advection feedback and vertical mixing in the subpolar North Atlantic as key roles in providing the continues internal energy source to maintain this multi-centennial oscillation. The perturbation flow of mean subtropical-subpolar salinity gradients serves as positive feedback to sustain the AMOC anomaly, while the mean advection of salinity anomalies and the vertical mixing or convection acts as negative feedback, constraining the AMOC anomaly. Notably, this low-frequency variability persists even in a warmer climate with weakened AMOC, emphasizing the robustness of the salinity advection feedback mechanism.
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| 6. |
- Döscher, Ralf, et al.
(författare)
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The EC-Earth3 Earth system model for the Coupled Model Intercomparison Project 6
- 2022
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Ingår i: Geoscientific Model Development. - : Copernicus GmbH. - 1991-959X .- 1991-9603. ; 15:7, s. 2973-3020
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Tidskriftsartikel (refereegranskat)abstract
- The Earth system model EC-Earth3 for contributions to CMIP6 is documented here, with its flexible coupling framework, major model configurations, a methodology for ensuring the simulations are comparable across different high-performance computing (HPC) systems, and with the physical performance of base configurations over the historical period. The variety of possible configurations and sub-models reflects the broad interests in the EC-Earth community. EC-Earth3 key performance metrics demonstrate physical behavior and biases well within the frame known from recent CMIP models. With improved physical and dynamic features, new Earth system model (ESM) components, community tools, and largely improved physical performance compared to the CMIP5 version, EC-Earth3 represents a clear step forward for the only European community ESM. We demonstrate here that EC-Earth3 is suited for a range of tasks in CMIP6 and beyond.
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| 7. |
- Fuentes-Franco, Ramón, et al.
(författare)
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Exploring the influence of the North Pacific Rossby wave sources on the variability of summer atmospheric circulation and precipitation over the Northern Hemisphere
- 2022
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Ingår i: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 59:7-8, s. 2025-2039
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Tidskriftsartikel (refereegranskat)abstract
- The influence of Rossby waves emitted in the northeastern Pacific Ocean on the Northern Hemisphere’s atmosphere during summer is analysed using ERA5 reanalysis and a new large ensemble performed with the EC-Earth3 model. The Rossby Wave Sources (RWS) trigger wave-like patterns arising from the upper troposphere of the north-eastern Pacific region, causing a response around the Northern Hemisphere with alternating regions of positive and negative correlation values between RWS and geopotential height at 500 hPa. Increased RWS intensity during summer is related to negative temperature anomalies over western North America, and positive temperature anomalies over eastern North America, concurrently with increased precipitation over the western subtropical Atlantic and Northern Europe during summer. Colder than normal conditions on the North Pacific Ocean intensify the RWS and its impact on the global atmospheric circulation. Different warm or cold states in the Pacific and Atlantic Oceans modify the atmospheric response to RWS, showing a change in the middle troposphere (500 hPa) towards a more-wavy structure with cold Pacific conditions, and towards a less-wavy structure with a warm Pacific Ocean. Furthermore, the North Atlantic plays a very important role in hindering (in the case of warm water) or permitting (cold water) that Rossby waves generated in the Pacific modulate the atmospheric conditions over Europe.
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| 8. |
- Johansson, Erik, et al.
(författare)
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Vertical structure of cloud radiative heating in the tropics : confronting the EC-Earth v3.3.1/3P model with satellite observations
- 2021
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Ingår i: Geoscientific Model Development. - : Copernicus GmbH. - 1991-959X .- 1991-9603. ; 14:6, s. 4087-4101
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the coupling of clouds to large-scale circulation is one of the grand challenges for the global climate research community. In this context, realistically modelling the vertical structure of cloud radiative heating (CRH) and/or cooling in Earth system models is a key premise to understand this coupling. Here, we evaluate CRH in two versions of the European Community Earth System Model (EC-Earth) using retrievals derived from the combined radar and lidar data from the CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellites. One model version is also used with two different horizontal resolutions. Our study evaluates large-scale intraseasonal variability in the vertical structure of CRH and cloud properties and investigates the changes in CRH during different phases of the El Niño–Southern Oscillation (ENSO), a process that dominates the interannual climate variability in the tropics.EC-Earth generally captures both the intraseasonal and meridional pattern of variability in CRH over the convectively active and stratocumulus regions and the CRH during the positive and negative phases of ENSO. However, two key differences between model simulations and satellite retrievals emerge. First, the magnitude of CRH, in the upper troposphere, over the convectively active zones is up to twice as large in the models compared to the satellite data. Further dissection of net CRH into its shortwave and longwave components reveals noticeable differences in their vertical structure. The shortwave component of the radiative heating is overestimated by all model versions in the lowermost troposphere and underestimated in the middle troposphere. These over- and underestimates of shortwave heating are partly compensated by an overestimate of longwave cooling in the lowermost troposphere and heating in the middle troposphere. The biases in CRH can be traced back to disagreement in cloud amount and cloud water content. There is no noticeable improvement of CRH by increasing the horizontal resolution in the model alone. Our findings highlight the importance of evaluating models with satellite observations that resolve the vertical structure of clouds and cloud properties.
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| 9. |
- Johansson, Mattias Erik, 1980, et al.
(författare)
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The Dual-Beam mini-DOAS technique - measurements of volcanic gas emission, plume height and plume speed with a single instrument
- 2009
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Ingår i: Bulletin of Volcanology. - 0258-8900 .- 1432-0819. ; 71, s. 747-751
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Tidskriftsartikel (refereegranskat)abstract
- The largest error in determining volcanic gas fluxes using ground based optical remote sensing instruments is typically the determination of the plume speed, and in the case of fixed scanning instruments also the plume height. We here present a newly developed technique capable of measuring plume height, plume speed and gas flux using one single instrument by simultaneously collecting scattered sunlight in two directions. The angle between the two measurement directions is fixed, removing the need for time consuming in-field calibrations. The plume height and gas flux is measured by traversing the plume and the plume speed by performing a stationary measurement underneath the plume. The instrument was tested in a field campaign in May 2005 at Mt. Etna, Italy, where the measured results are compared to wind fields derived from a meso-scale meteorological model (MM5). The test and comparison show that the instrument is functioning and capable of estimating wind speed at the plume height.
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| 12. |
- Koenigk, Torben, et al.
(författare)
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Arctic climate change in 21st century CMIP5 simulations with EC-Earth
- 2012
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Ingår i: Climate Dynamics. - : Springer-Verlag New York. - 0930-7575 .- 1432-0894. ; 40:11-12
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Tidskriftsartikel (refereegranskat)abstract
- The Arctic climate change is analyzed in anensemble of future projection simulations performed withthe global coupled climate model EC-Earth2.3. EC-Earthsimulates the twentieth century Arctic climate relativelywell but the Arctic is about 2 K too cold and the sea icethickness and extent are overestimated. In the twenty-firstcentury, the results show a continuation and strengtheningof the Arctic trends observed over the recent decades,which leads to a dramatically changed Arctic climate,especially in the high emission scenario RCP8.5. Theannually averaged Arctic mean near-surface temperatureincreases by 12 K in RCP8.5, with largest warming in theBarents Sea region. The warming is most pronounced inwinter and autumn and in the lower atmosphere. The Arcticwinter temperature inversion is reduced in all scenarios anddisappears in RCP8.5. The Arctic becomes ice free inSeptember in all RCP8.5 simulations after a rapid reductionevent without recovery around year 2060. Taking intoaccount the overestimation of ice in the twentieth century,our model results indicate a likely ice-free Arctic inSeptember around 2040. Sea ice reductions are most pronouncedin the Barents Sea in all RCPs, which lead to themost dramatic changes in this region. Here, surface heatfluxes are strongly enhanced and the cloudiness is substantiallydecreased. The meridional heat flux into theArctic is reduced in the atmosphere but increases in theocean. This oceanic increase is dominated by an enhancedheat flux into the Barents Sea, which strongly contributes tothe large sea ice reduction and surface-air warming in thisregion. Increased precipitation and river runoff lead to morefreshwater input into the Arctic Ocean. However, most ofthe additional freshwater is stored in the Arctic Ocean whilethe total Arctic freshwater export only slightly increases.
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| 13. |
- Loeb, Norman G., et al.
(författare)
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New Generation of Climate Models Track Recent Unprecedented Changes in Earth's Radiation Budget Observed by CERES
- 2020
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 47:5
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Tidskriftsartikel (refereegranskat)abstract
- We compare top-of-atmosphere (TOA) radiative fluxes observed by the Clouds and the Earth's Radiant Energy System (CERES) and simulated by seven general circulation models forced with observed sea-surface temperature (SST) and sea-ice boundary conditions. In response to increased SSTs along the equator and over the eastern Pacific (EP) following the so-called global warming hiatus of the early 21st century, simulated TOA flux changes are remarkably similar to CERES. Both show outgoing shortwave and longwave TOA flux changes that largely cancel over the west and central tropical Pacific, and large reductions in shortwave flux for EP low-cloud regions. A model's ability to represent changes in the relationship between global mean net TOA flux and surface temperature depends upon how well it represents shortwave flux changes in low-cloud regions, with most showing too little sensitivity to EP SST changes, suggesting a pattern effect that may be too weak compared to observations.
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| 14. |
- Lu, Zhengyao, et al.
(författare)
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Natural decadal variability of global vegetation growth in relation to major decadal climate modes
- 2023
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326 .- 1748-9318. ; 18:1
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Tidskriftsartikel (refereegranskat)abstract
- The ongoing climate change can modulate the behavior of global vegetation and influence the terrestrial biosphere carbon sink. Past observation-based studies have mainly focused on the linear trend or interannual variability of the vegetation greenness, but could not explicitly deal with the effect of natural decadal variability due to the short length of observations. Here we put the variabilities revealed by remote sensing-based global leaf area index (LAI) from 1982 to 2015 into a long-term perspective with the help of ensemble Earth system model simulations of the historical period 1850-2014, with a focus on the low-frequency variability in the global LAI during the growing season. Robust decadal variability in the observed and modelled LAI was revealed across global terrestrial ecosystems, and it became stronger toward higher latitudes, accounting for over 50% of the total variability north of 40 degrees N. The linkage of LAI decadal variability to major natural decadal climate modes, such as the El Nino-Southern Oscillation decadal variability (ENSO-d), the Pacific decadal oscillation (PDO), and the Atlantic multidecadal oscillation (AMO), was analyzed. ENSO-d affects LAI by altering precipitation over large parts of tropical land. The PDO exerts opposite impacts on LAI in the tropics and extra-tropics due to the compensation between the effects of temperature and growing season length. The AMO effects are mainly associated with anomalous precipitation in North America and Europe but are mixed with long-term climate change impacts due to the coincident phase shift of the AMO which also induces North Atlantic basin warming. Our results suggest that the natural decadal variability of LAI can be largely explained by these decadal climate modes (on average 20% of the variance, comparable to linear changes, and over 40% in some ecosystems) which also can be potentially important in inducing the greening of the Earth of the past decades.
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| 17. |
- Sterl, Andreas, et al.
(författare)
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A look at the ocean in the EC-Earth climate model
- 2012
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Ingår i: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 39:11, s. 2631-2657
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Tidskriftsartikel (refereegranskat)abstract
- EC-Earth is a newly developed global climate system model. Its core components are the Integrated Forecast System (IFS) of the European Centre for Medium Range Weather Forecasts (ECMWF) as the atmosphere component and the Nucleus for European Modelling of the Ocean (NEMO) developed by Institute Pierre Simon Laplace (IPSL) as the ocean component. Both components are used with a horizontal resolution of roughly one degree. In this paper we describe the performance of NEMO in the coupled system by comparing model output with ocean observations. We concentrate on the surface ocean and mass transports. It appears that in general the model has a cold and fresh bias, but a much too warm Southern Ocean. While sea ice concentration and extent have realistic values, the ice tends to be too thick along the Siberian coast. Transports through important straits have realistic values, but generally are at the lower end of the range of observational estimates. Exceptions are very narrow straits (Gibraltar, Bering) which are too wide due to the limited resolution. Consequently the modelled transports through them are too high. The strength of the Atlantic meridional overturning circulation is also at the lower end of observational estimates. The interannual variability of key variables and correlations between them are realistic in size and pattern. This is especially true for the variability of surface temperature in the tropical Pacific (El Nio). Overall the ocean component of EC-Earth performs well and helps making EC-Earth a reliable climate model.
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| 18. |
- Thomas, Manu Anna, et al.
(författare)
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Snowfall distribution and its response to the Arctic Oscillation : an evaluation of HighResMIP models in the Arctic using CPR/CloudSat observations
- 2019
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Ingår i: Geoscientific Model Development. - : Copernicus GmbH. - 1991-959X .- 1991-9603. ; 12:8, s. 3759-3772
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Tidskriftsartikel (refereegranskat)abstract
- A realistic representation of snowfall in general circulation models (GCMs) of global climate is important to accurately simulate snow cover, surface albedo, high-latitude precipitation and thus the surface radiation budget. Hence, in this study, we evaluate snowfall in a range of climate models run at two different resolutions by comparing to the latest estimates of snowfall from the CloudSat Cloud Profiling Radar over the northern latitudes. We also evaluate whether the finer-resolution versions of the GCMs simulate the accumulated snowfall better than their coarse-resolution counterparts. As the Arctic Oscillation (AO) is the prominent mode of natural variability in the polar latitudes, the snowfall variability associated with the different phases of the AO is examined in both models and in our observational reference. We report that the statistical distributions of snowfall differ considerably between the models and CloudSat observations. While CloudSat shows an exponential distribution of snowfall, the models show a Gaussian distribution that is heavily positively skewed. As a result, the 10th and 50th percentiles, representing the light and median snowfall, are overestimated by up to factors of 3 and 1.5, respectively, in the models investigated here. The overestimations are strongest during the winter months compared to autumn and spring. The extreme snowfall represented by the 90th percentiles, on the other hand, is positively skewed, underestimating the snowfall estimates by up to a factor of 2 in the models in winter compared to the CloudSat estimates. Though some regional improvements can be seen with increased spatial resolution within a particular model, it is not easy to identify a specific pattern that holds across all models. The characteristic snow- fall variability associated with the positive phase of AO over Greenland Sea and central Eurasian Arctic is well captured by the models.
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| 19. |
- Van Noije, Twan, et al.
(författare)
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EC-Earth3-AerChem : A global climate model with interactive aerosols and atmospheric chemistry participating in CMIP6
- 2021
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Ingår i: Geoscientific Model Development. - : Copernicus GmbH. - 1991-959X .- 1991-9603. ; 14:9, s. 5637-5668
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Tidskriftsartikel (refereegranskat)abstract
- This paper documents the global climate model EC-Earth3-AerChem, one of the members of the EC-Earth3 family of models participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6). EC-Earth3-AerChem has interactive aerosols and atmospheric chemistry and contributes to the Aerosols and Chemistry Model Intercomparison Project (AerChemMIP). In this paper, we give an overview of the model, describe in detail how it differs from the other EC-Earth3 configurations, and outline the new features compared with the previously documented version of the model (EC-Earth 2.4). We explain how the model was tuned and spun up under preindustrial conditions and characterize the model's general performance on the basis of a selection of coupled simulations conducted for CMIP6. The net energy imbalance at the top of the atmosphere in the preindustrial control simulation is on average -0.09 W m-2 with a standard deviation due to interannual variability of 0.25 W m-2, showing no significant drift. The global surface air temperature in the simulation is on average 14.08 ∼ C with an interannual standard deviation of 0.17 ∼ C, exhibiting a small drift of 0.015 ± 0.005 ∼ C per century. The model's effective equilibrium climate sensitivity is estimated at 3.9 ∼ C, and its transient climate response is estimated at 2.1 ∼ C. The CMIP6 historical simulation displays spurious interdecadal variability in Northern Hemisphere temperatures, resulting in a large spread across ensemble members and a tendency to underestimate observed annual surface temperature anomalies from the early 20th century onwards. The observed warming of the Southern Hemisphere is well reproduced by the model. Compared with the ECMWF (European Centre for Medium-Range Weather Forecasts) Reanalysis version 5 (ERA5), the surface air temperature climatology for 1995-2014 has an average bias of -0.86 ± 0.05 ∼ C with a standard deviation across ensemble members of 0.35 ∼ C in the Northern Hemisphere and 1.29 ± 0.02 ∼ C with a corresponding standard deviation of 0.05 ∼ C in the Southern Hemisphere. The Southern Hemisphere warm bias is largely caused by errors in shortwave cloud radiative effects over the Southern Ocean, a deficiency of many climate models. Changes in the emissions of near-term climate forcers (NTCFs) have significant effects on the global climate from the second half of the 20th century onwards. For the SSP3-7.0 Shared Socioeconomic Pathway, the model gives a global warming at the end of the 21st century (2091-2100) of 4.9 ∼ C above the preindustrial mean. A 0.5 ∼ C stronger warming is obtained for the AerChemMIP scenario with reduced emissions of NTCFs. With concurrent reductions of future methane concentrations, the warming is projected to be reduced by 0.5 ∼ C.
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| 22. |
- Wyser, Klaus, et al.
(författare)
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The SMHI Large Ensemble (SMHI-LENS) with EC-Earth3.3.1
- 2021
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Ingår i: Geoscientific Model Development. - : Copernicus GmbH. - 1991-959X .- 1991-9603. ; 14:7, s. 5781-5796
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Tidskriftsartikel (refereegranskat)abstract
- The Swedish Meteorological and Hydrological Institute used the global climate model EC-Earth3 to perform a large ensemble of simulations (SMHI-LENS). It consists of 50 members, covers the period 1970 to 2100, and comprises the SSP1-1.9, SSP3-3.4, SSP5-3.4-OS, and SSP5-8.5 scenarios. Thus, it is currently the only large ensemble that allows for analyzing the effect of delayed mitigation actions versus no mitigation efforts and versus earlier efforts leading to similar radiative forcing at the year 2100. We describe the set-up of the SMHI-LENS in detail and provide first examples of its application. The ensemble mean future changes in key variables in the atmosphere and ocean are analyzed and compared against the variability across the ensemble members. In agreement with other large-ensemble simulations, we find that the future changes in the near-surface temperature are more robust than those for precipitation or sea level pressure. As an example of a possible application of the SMHI-LENS, we analyze the probability of exceeding specific global surface warming levels in the different scenarios. None of the scenarios is able to keep global warming in the 21st century below 1.5 degrees C. In SSP1-1.9 there is a probability of approximately 70% to stay below 2 degrees C warming, while all other SSPs exceed this target in every single member of SMHI-LENS during the course of the century. We also investigate the point in time when the SSP5-8.5 and SSP5-3.4 ensembles separate, i.e., when their differences become significant, and likewise when the SSP5-3.4-OS and SSP4-3.4 ensembles become similar. Last, we show that the time of emergence of a separation between different scenarios can vary by several decades when reducing the ensemble size to 10 members.
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| 23. |
- Wyser, Klaus, et al.
(författare)
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Warmer climate projections in EC-Earth3-Veg : the role of changes in the greenhouse gas concentrations from CMIP5 to CMIP6
- 2020
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 15:5
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Tidskriftsartikel (refereegranskat)abstract
- Climate projections for the 21st century for CMIP6 are warmer than those for CMIP5 despite nominally identical instantaneous radiative forcing. Many climate modeling groups attribute the stronger warming in the CMIP6 projections to the higher climate sensitivity of the new generation of climate models, but here we demonstrate that also changes in the forcing datasets can play an important role, in particular the prescribed concentrations of greenhouse gases (GHG) that are used to force the models. In the EC-Earth3-Veg model the effective radiative forcing (ERF) is reduced by 1.4 W m(-2) when the GHG concentrations from SSP5-8.5 (used in CMIP6) are replaced by the GHG concentrations from RCP8.5 (used in CMIP5), and similar yet smaller reductions are seen for the SSP2-4.5/RCP4.5 and SSP1-2.6/RCP2.6 scenario pairs. From the reduced ERF we can estimate the temperature at the end of the century in a full climate simulation with the CMIP6 version of the EC-Earth model but using CMIP5 GHG concentrations instead. For the new SSP5-8.5 and SSP2-4.5 scenarios we find that 50% or more of the temperature increase from CMIP5 to CMIP6 at the end of the century is due to changes in the prescribed GHG concentrations. The implication is that CMIP5 and CMIP6 projections for the 21st century are difficult to compare with each other not only as models differ but also as the forcing conditions are not equal. Therefore, the communication of CMIP6 results to the impact, mitigation and adaptation communities has to be carefully formulated, taking into account the role of the updated GHG concentrations when interpreting the warmer climate projections for the 21st century.
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| 24. |
- Zhang, Qiong, et al.
(författare)
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Simulating the mid-Holocene, last interglacial and mid-Pliocene climate with EC-Earth3-LR
- 2021
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Ingår i: Geoscientific Model Development. - : Copernicus GmbH. - 1991-959X .- 1991-9603. ; 14:2, s. 1147-1169
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Tidskriftsartikel (refereegranskat)abstract
- As global warming is proceeding due to rising greenhouse gas concentrations, the Earth system moves towards climate states that challenge adaptation. Past Earth system states are offering possible modelling systems for the global warming of the coming decades. These include the climate of the mid-Pliocene (similar to 3 Ma), the last interglacial (similar to 129-116 ka) and the mid-Holocene (similar to 6 ka). The simulations for these past warm periods are the key experiments in the Paleoclimate Model Intercomparison Project (PMIP) phase 4, contributing to phase 6 of the Coupled Model Intercomparison Project (CMIP6). Paleoclimate modelling has long been regarded as a robust out-of-sample test bed of the climate models used to project future climate changes. Here, we document the model setup for PMIP4 experiments with EC-Earth3-LR and present the large-scale features from the simulations for the mid-Holocene, the last interglacial and the mid-Pliocene. Using the pre-industrial climate as a reference state, we show global temperature changes, large-scale Hadley circulation and Walker circulation, polar warming, global monsoons and the climate variability modes - El Nino-Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO). EC-Earth3-LR simulates reasonable climate responses during past warm periods, as shown in the other PMIP4-CMIP6 model ensemble. The systematic comparison of these climate changes in past three warm periods in an individual model demonstrates the model's ability to capture the climate response under different climate forcings, providing potential implications for confidence in future projections with the EC-Earth model.
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