| 1. |
- Lunt, Daniel J., et al.
(författare)
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DeepMIP : model intercomparison of early Eocene climatic optimum (EECO) large-scale climate features and comparison with proxy data
- 2021
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Ingår i: Climate of the Past. - : Copernicus GmbH. - 1814-9324 .- 1814-9332. ; 17:1, s. 203-227
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Tidskriftsartikel (refereegranskat)abstract
- We present results from an ensemble of eight climate models, each of which has carried out simulations of the early Eocene climate optimum (EECO, similar to 50 million years ago). These simulations have been carried out in the framework of the Deep-Time Model Intercomparison Project (DeepMIP; http://www.deepmip.org , last access: 10 January 2021); thus, all models have been configured with the same paleogeographic and vegetation boundary conditions. The results indicate that these non-CO2 boundary conditions contribute between 3 and 5 degrees C to Eocene warmth. Compared with results from previous studies, the DeepMIP simulations generally show a reduced spread of the global mean surface temperature response across the ensemble for a given atmospheric CO2 concentration as well as an increased climate sensitivity on average. An energy balance analysis of the model ensemble indicates that global mean warming in the Eocene compared with the preindustrial period mostly arises from decreases in emissivity due to the elevated CO2 concentration (and associated water vapour and long-wave cloud feedbacks), whereas the reduction in the Eocene in terms of the meridional temperature gradient is primarily due to emissivity and albedo changes owing to the non-CO2 boundary conditions (i.e. the removal of the Antarctic ice sheet and changes in vegetation). Three of the models (the Community Earth System Model, CESM; the Geophysical Fluid Dynamics Laboratory, GFDL, model; and the Norwegian Earth System Model, NorESM) show results that are consistent with the proxies in terms of the global mean temperature, meridional SST gradient, and CO2, without prescribing changes to model parameters. In addition, many of the models agree well with the first-order spatial patterns in the SST proxies. However, at a more regional scale, the models lack skill. In particular, the modelled anomalies are substantially lower than those indicated by the proxies in the southwest Pacific; here, modelled continental surface air temperature anomalies are more consistent with surface air temperature proxies, implying a possible inconsistency between marine and terrestrial temperatures in either the proxies or models in this region. Our aim is that the documentation of the large-scale features and model-data comparison presented herein will pave the way to further studies that explore aspects of the model simulations in more detail, for example the ocean circulation, hydrological cycle, and modes of variability, and encourage sensitivity studies to aspects such as paleogeography, orbital configuration, and aerosols.
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| 2. |
- Beecken, Jörg, 1982, et al.
(författare)
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Emission factors of SO2, NOx and particles from ships in Neva Bay from ground-based and helicopter-borne measurements and AIS-based modeling
- 2015
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 15:9, s. 5229-5241
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Tidskriftsartikel (refereegranskat)abstract
- Emission factors of SO2, NOx and size-distributed particle numbers were measured for approximately 300 different ships in the Gulf of Finland and Neva Bay area during two campaigns in August/September 2011 and June/July 2012. The measurements were carried out from a harbor vessel and from an Mi-8 helicopter downwind of passing ships. Other measurements were carried out from shore sites near the island of Kronstadt and along the Neva River in the urban area of Saint Petersburg. Most ships were running at reduced speed (10 kn), i.e., not at their optimal load. Vessels for domestic and international shipping were monitored. It was seen that the distribution of the SO2 emission factors is bi-modal, with averages of 4.6 and 18.2 gSO(2) kg(fuel)(-1) for the lower and the higher mode, respectively. The emission factors show compliance with the 1% fuel sulfur content Sulfur Emission Control Areas (SECA) limit for 90% of the vessels in 2011 and 97% in 2012. The distribution of the NOx emission factor is mono-modal, with an average of 58 gNO(x) kg(fuel)(-1). The corresponding emission related to the generated power yields an average of 12.1 gNO(x) kWh(-1). The distribution of the emission factors for particulate number shows that nearly 90% of all particles in the 5.6 nm to 10 mu m size range were below 70 nm in diameter. The distribution of the corresponding emission factors for the mass indicates two separated main modes, one for particles between 30 and 300 nm and the other for above 2 mu m. The average particle emission factors were found to be in the range from 0.7 to 2.7 x 10(16) particles kg(fuel)(-1) and 0.2 to 3.4 gPM kg(fuel)(-1), respectively. The NOx and particulate emissions are comparable with other studies. The measured emission factors were compared, for individual ships, to modeled ones using the Ship Traffic Emission Assessment Model (STEAM) of the Finnish Meteorological Institute. A reasonably good agreement for gaseous sulfur and nitrogen emissions can be seen for ships in international traffic, but significant deviations are found for inland vessels. Regarding particulate mass, the values of the modeled data are about 2-3 times higher than the measured results, which probably reflects the assumptions made in the modeled fuel sulfur content. The sulfur contents in the fuel retrieved from the measurements were lower than the previously used assumptions by the City of Saint Petersburg when carrying out atmospheric modeling, and using these measurements it was possible to better assess the impact of shipping on air quality.
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| 3. |
- Kageyama, Masa, et al.
(författare)
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A multi-model CMIP6-PMIP4 study of Arctic sea ice at 127 ka : sea ice data compilation and model differences
- 2021
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Ingår i: Climate of the Past. - : Copernicus GmbH. - 1814-9324 .- 1814-9332. ; 17:1, s. 37-62
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Tidskriftsartikel (refereegranskat)abstract
- The Last Interglacial period (LIG) is a period with increased summer insolation at high northern latitudes, which results in strong changes in the terrestrial and marine cryosphere. Understanding the mechanisms for this response via climate modelling and comparing the models' representation of climate reconstructions is one of the objectives set up by the Paleoclimate Modelling Intercomparison Project for its contribution to the sixth phase of the Coupled Model Intercomparison Project. Here we analyse the results from 16 climate models in terms of Arctic sea ice. The multi-model mean reduction in minimum sea ice area from the pre industrial period (PI) to the LIG reaches 50 % (multi-model mean LIG area is 3.20×106 km2, compared to 6.46×106 km2 for the PI). On the other hand, there is little change for the maximum sea ice area (which is 15–16×106 km2 for both the PI and the LIG. To evaluate the model results we synthesise LIG sea ice data from marine cores collected in the Arctic Ocean, Nordic Seas and northern North Atlantic. The reconstructions for the northern North Atlantic show year-round ice-free conditions, and most models yield results in agreement with these reconstructions. Model–data disagreement appear for the sites in the Nordic Seas close to Greenland and at the edge of the Arctic Ocean. The northernmost site with good chronology, for which a sea ice concentration larger than 75 % is reconstructed even in summer, discriminates those models which simulate too little sea ice. However, the remaining models appear to simulate too much sea ice over the two sites south of the northernmost one, for which the reconstructed sea ice cover is seasonal. Hence models either underestimate or overestimate sea ice cover for the LIG, and their bias does not appear to be related to their bias for the pre-industrial period. Drivers for the inter-model differences are different phasing of the up and down short-wave anomalies over the Arctic Ocean, which are associated with differences in model albedo; possible cloud property differences, in terms of optical depth; and LIG ocean circulation changes which occur for some, but not all, LIG simulations. Finally, we note that inter-comparisons between the LIG simulations and simulations for future climate with moderate (1 % yr−1) CO2 increase show a relationship between LIG sea ice and sea ice simulated under CO2 increase around the years of doubling CO2. The LIG may therefore yield insight into likely 21st century Arctic sea ice changes using these LIG simulations.
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| 4. |
- Kozhevnikov, V., et al.
(författare)
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Nonlocal effect and dimensions of Cooper pairs measured by low-energy muons and polarized neutrons in type-I superconductors
- 2013
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Ingår i: Physical Review B Condensed Matter. - : American Physical Society. - 0163-1829 .- 1095-3795. ; 87:10, s. 104508-
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Tidskriftsartikel (refereegranskat)abstract
- The Pippard coherence length xi(0) (the size of a Cooper pair) in two extreme type-I superconductors (In and Sn) was determined directly through high-resolution measurement of the nonlocal electrodynamic effect combining low-energy muon spin rotation spectroscopy and polarized neutron reflectometry. The renormalization factor Z = m*(cp)/2m (m*(cp) and m are the mass of the Cooper pair and the electron, respectively) resulting from the electron-phonon interaction, and the temperature-dependent London penetration depth lambda(L)(T) were determined as well. An expression linking xi(0), Z, and lambda(L)(0) is introduced and experimentally verified. This expression allows one to determine experimentally the Pippard coherence length in any superconductor, independent of whether the superconductor is local or nonlocal, conventional or unconventional.
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| 5. |
- Otto-Bliesner, Bette L., et al.
(författare)
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Large-scale features of Last Interglacial climate : results from evaluating the lig127k simulations for the Coupled Model Intercomparison Project (CMIP6)–Paleoclimate Modeling Intercomparison Project (PMIP4)
- 2021
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Ingår i: Climate of the Past. - : Copernicus GmbH. - 1814-9324 .- 1814-9332. ; 17:1, s. 63-94
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Tidskriftsartikel (refereegranskat)abstract
- The modeling of paleoclimate, using physically based tools, is increasingly seen as a strong out-of-sample test of the models that are used for the projection of future climate changes. New to the Coupled Model Intercomparison Project (CMIP6) is the Tier 1 Last Interglacial experiment for 127 000 years ago (lig127k), designed to address the climate responses to stronger orbital forcing than the midHolocene experiment, using the same state-of-the-art models as for the future and following a common experimental protocol. Here we present a first analysis of a multi-model ensemble of 17 climate models, all of which have completed the CMIP6 DECK (Diagnostic, Evaluation and Characterization of Klima) experiments. The equilibrium climate sensitivity (ECS) of these models varies from 1.8 to 5.6 ∘C. The seasonal character of the insolation anomalies results in strong summer warming over the Northern Hemisphere continents in the lig127k ensemble as compared to the CMIP6 piControl and much-reduced minimum sea ice in the Arctic. The multi-model results indicate enhanced summer monsoonal precipitation in the Northern Hemisphere and reductions in the Southern Hemisphere. These responses are greater in the lig127k than the CMIP6 midHolocene simulations as expected from the larger insolation anomalies at 127 than 6 ka.New synthesis for surface temperature and precipitation, targeted for 127 ka, have been developed for comparison to the multi-model ensemble. The lig127k model ensemble and data reconstructions are in good agreement for summer temperature anomalies over Canada, Scandinavia, and the North Atlantic and for precipitation over the Northern Hemisphere continents. The model–data comparisons and mismatches point to further study of the sensitivity of the simulations to uncertainties in the boundary conditions and of the uncertainties and sparse coverage in current proxy reconstructions.The CMIP6–Paleoclimate Modeling Intercomparison Project (PMIP4) lig127k simulations, in combination with the proxy record, improve our confidence in future projections of monsoons, surface temperature, and Arctic sea ice, thus providing a key target for model evaluation and optimization.
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| 6. |
- Tomar, AS, et al.
(författare)
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Retinoblastoma seeds: impact on American Joint Committee on Cancer clinical staging
- 2023
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Ingår i: The British journal of ophthalmology. - : BMJ. - 1468-2079 .- 0007-1161. ; 107:1, s. 127-132
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Tidskriftsartikel (refereegranskat)abstract
- To investigate whether the American Joint Committee on Cancer (AJCC) clinical category cT2b needs to be subclassified by the type and distribution of retinoblastoma (RB) seeding.MethodsMulticentre, international registry-based data were collected from RB centres enrolled between January 2001 and December 2013. 1054 RB eyes with vitreous or subretinal seeds from 18 ophthalmic oncology centres, in 13 countries within six continents were analysed. Local treatment failure was defined as the use of secondary enucleation or external beam radiation therapy (EBRT) and was estimated with the Kaplan-Meier method.ResultsClinical category cT2b included 1054 eyes. Median age at presentation was 16.0 months. Of these, 428 (40.6%) eyes were salvaged, and 430 (40.8%) were treated with primary and 196 (18.6%) with secondary enucleation. Of the 592 eyes that had complete data for globe salvage analysis, the distribution of seeds was focal in 143 (24.2%) and diffuse in 449 (75.8%). The 5-year Kaplan-Meier cumulative globe-salvage (without EBRT) was 78% and 49% for eyes with focal and diffuse RB seeding, respectively. Cox proportional hazards regression analysis confirmed a higher local treatment failure risk with diffuse seeds as compared with focal seeds (hazard rate: 2.8; p<0.001). There was insufficient evidence to prove or disprove an association between vitreous seed type and local treatment failure risk(p=0.06).ConclusionThis international, multicentre, registry-based analysis of RB eyes affirmed that eyes with diffuse intraocular distribution of RB seeds at diagnosis had a higher risk of local treatment failure when compared with focal seeds. Subclassification of AJCC RB category cT2b into focal vs diffuse seeds will improve prognostication for eye salvage.
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| 7. |
- Volodin, A.M., et al.
(författare)
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Direct ESR detection of S=3/2 states for nitrosyl iron complexes in FeZSM-5 zeolites
- 2001
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Ingår i: Chemical Physics Letters. - 0009-2614 .- 1873-4448. ; 333:1-2, s. 41-44
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Tidskriftsartikel (refereegranskat)abstract
- The formation of paramagnetic complexes between Fe2+ ions and NO molecules with total spin S=3/2 has been observed in FeZSM-5 zeolites. These complexes exhibit a typical ESR signal with a component at g=4.0 and are spectroscopically similar to those observed in iron-containing enzymes. Such spin states of Fe ions have not been reported for heterogeneous catalysts. The application of NO as a spin probe for investigation of the state of low-valence Fe ions in zeolite matrices is discussed. © 2001 Elsevier Science B.V.
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