Seasonal predictions of energy-relevant climate variables through Euro-Atlantic Teleconnections

The goal of this analysis is the better understanding of how the large-scale atmospheric patterns affect the renewable resources over Europe and to investigate to what extent the dynamical predictions of the large-scale variability might be used to formulate empirical prediction of local climate conditions (relevant for the energy sector). The increasing integration of renewable energy into the power mix is making the electricity supply more vulnerable to climate variability, therefore increasing the need for skillful weather and climate predictions. Forecasting seasonal variations of energy relevant climate variables can help the transition to renewable energy and the entire energy industry to make better informed decision-making. At seasonal timescale climate variability can be described by recurring and persistent, large-scale patterns of atmospheric pressure and circulation anomalies that interest vast geographical areas. The main patterns of the North Atlantic region (Euro Atlantic Teleconnections, EATCs) drive variations in the surface climate over Europe. We analyze reanalysis dataset ERA5 and the multi-system seasonal forecast service provided by Copernicus Climate Change Service (C3S). We found that the observed EATC indices are strongly correlated with surface variables. However, the observed relationship between EATC patterns and surface impacts is not accurately reproduced by seasonal prediction systems. This opens the door to employ hybrid dynamical-statistical methods. The idea consists in combining the dynamical seasonal predictions of EATC indices with the observed relationship between EATCs and surface variables. We reconstructed the surface anomalies for multiple seasonal prediction systems and benchmarked these hybrid forecasts with the direct variable forecasts from the systems and also with the climatology. The analysis suggests that hybrid methodology can bring several improvements to the predictions of energy relevant Essential Climate Variables.This work was supported by the European Union’s Horizon 2020 research and innovation programme [Grant Numbers. No 776787, H2020 S2S4E] and by the National Italian project PAR 2019–2021 1.8 ‘Energia dal Mare’.Peer ReviewedPostprint (published version

Anterior capsulorhexis opening reduction after cataract surgery with subluxated lenses

Publisher Copyright: © 2017 The Lithuanian University of Health Sciences.Background and objective: This study sought to evaluate anterior capsulorhexis opening (ACO) reductions after surgery for a subluxated lens. Significant reduction of an ACO supports direct zonular involvement (capsular factors excluded by use of capsular tension rings [CTRs] and modern intraocular lens [IOLs]), and these findings question the long-term efficacy of subluxated lens surgery by means of cataract surgery. A small ACO due to lens mobility, non-enlargement of the ACO, and no lens epithelial cell washing due to an additional risk of further zonular damage were left as additional features to evaluate the possible outcomes of this simplified but still complicated surgery. Materials and methods: Data from 30 patients were used in the final analysis of this prospective study. Phacoemulsifications of subluxated lenses were performed in all patients, and iris/capsule hooks and CTRs or Cionni rings were used as stabilisers of the lens. Photography of the anterior parts (performed at 1 day, 1 week, 1 month, 3 months and 6 months after surgery) was used to evaluate the anterior capsulorhexis openings. Results: Small initial anterior capsulorhexis openings (13.54 mm2) were achieved, and the area reduction at 6 months was 16.70% (mean area at month 6: 11.28 mm2, P < 0.001). The reduction of the ACO area in the pseudoexfoliation (PEX) syndrome patients was 20% relative to the initial size (13.49 mm2 vs. 10.92 mm2, P < 0.001). Two patients exhibited marked ACO reductions, and both were referred for anterior laser capsulotomy treatment. Conclusions: A weak or partially absent zonule does not markedly affect the reduction of the anterior capsule opening if appropriate surgical techniques, support materials and IOLs are used, even in the presence of a small initial capsulorhexis opening area. Therefore, a cataract surgery approach on the subluxated lens should be used. Ocular comorbidities, particularly PEX syndrome, play more significant roles in ACO reduction, and appropriate ACO size reducing inhibitors (e.g., anterior laser capsulotomy) or other types of surgery should be used.publishersversionPeer reviewe

Upper tropospheric ice sensitivity to sulfate geoengineering

Abstract. Aside from the direct surface cooling that sulfate geoengineering (SG) would produce, investigations of the possible side effects of this method are still ongoing, such as the exploration of the effect that SG may have on upper tropospheric cirrus cloudiness. The goal of the present study is to better understand the SG thermodynamical effects on the freezing mechanisms leading to ice particle formation. This is undertaken by comparing SG model simulations against a Representative Concentration Pathway 4.5 (RCP4.5) reference case. In the first case, the aerosol-driven surface cooling is included and coupled to the stratospheric warming resulting from the aerosol absorption of terrestrial and solar near-infrared radiation. In a second SG perturbed case, the surface temperatures are kept unchanged with respect to the reference RCP4.5 case. When combined, surface cooling and lower stratospheric warming tend to stabilize the atmosphere, which decreases the turbulence and updraft velocities (−10 % in our modeling study). The net effect is an induced cirrus thinning, which may then produce a significant indirect negative radiative forcing (RF). This RF would go in the same direction as the direct effect of solar radiation scattering by aerosols, and would consequently influence the amount of sulfur needed to counteract the positive RF due to greenhouse gases. In our study, given an 8 Tg-SO2 yr−1 equatorial injection into the lower stratosphere, an all-sky net tropopause RF of −1.46 W m−2 is calculated, of which −0.3 W m−2 (20 %) is from the indirect effect on cirrus thinning (6 % reduction in ice optical depth). When surface cooling is ignored, the ice optical depth reduction is lowered to 3 %, with an all-sky net tropopause RF of −1.4 W m−2, of which −0.14 W m−2 (10 %) is from cirrus thinning. Relative to the clear-sky net tropopause RF due to SG aerosols (−2.1 W m−2), the cumulative effect of the background clouds and cirrus thinning accounts for +0.6 W m−2, due to the partial compensation of large positive shortwave (+1.6 W m−2) and negative longwave adjustments (−1.0 W m−2). When surface cooling is ignored, the net cloud adjustment becomes +0.8 W m−2, with the shortwave contribution (+1.5 W m−2) almost twice as much as that of the longwave (−0.7 W m−2). This highlights the importance of including all of the dynamical feedbacks of SG aerosols

Stratospheric Aerosols from Major Volcanic Eruptions: A Composition-Climate Model Study of the Aerosol Cloud Dispersal and e-folding Time

Large explosive volcanic eruptions are capable of injecting considerable amounts of particles and sulfur gases above the tropopause, causing large increases in stratospheric aerosols. Five major volcanic eruptions after 1960 (i.e., Agung, St. Helens, El Chichon, Nevado del Ruiz and Pinatubo) have been considered in a numerical study conducted with a composition-climate coupled model including an aerosol microphysics code for aerosol formation and growth. Model results are compared between an ensemble of numerical simulations including volcanic aerosols and their radiative effects (VE) and a reference simulations ensemble (REF) with no radiative impact of the volcanic aerosols. Differences of VE-REF show enhanced diabatic heating rates; increased stratospheric temperatures and mean zonal westerly winds; increased planetary wave amplitude; and tropical upwelling. The impact on stratospheric upwelling is found to be larger when the volcanically perturbed stratospheric aerosol is confined to the tropics, as tends to be the case for eruptions which were followed by several months with easterly shear of the quasi-biennial oscillation (QBO), e.g., the Pinatubo case. Compared to an eruption followed by a period of westerly QBO, such easterly QBO eruptions are quite different, with meridional transport to mid- and high-latitudes occurring later, and at higher altitude, with a consequent decrease in cross-tropopause removal from the stratosphere, and therefore longer decay timescale. Comparing the model-calculated e-folding time of the volcanic aerosol mass during the first year after the eruptions, an increase is found from 8.1 and 10.3 months for El Chichon and Agung (QBO westerly shear), to 14.6 and 30.7 months for Pinatubo and Ruiz (QBO easterly shear). The corresponding e-folding time of the global-mean radiative flux changes goes from 9.1 and 8.0 months for El Chichon and Agung, to 28.7 and 24.5 months for Pinatubo and Ruiz

Impact of Stratospheric Volcanic Aerosols on Age-of-Air and Transport of Long-Lived Species

The radiative perturbation associated to stratospheric aerosols from major explosive volcanic eruptions may induce significant changes in stratospheric dynamics. The aerosol heating rates warm up the lower stratosphere and cause a westerly wind anomaly, with additional tropical upwelling. Large scale transport of stratospheric trace species may be perturbed as a consequence of this intensified Brewer–Dobson circulation. The radiatively forced changes of the stratospheric circulation during the first two years after the eruption of Mt. Pinatubo (June 1991) may help explain the observed trend decline of long-lived greenhouse gases at surface stations (approximately −8 and −0.4 ppbv/year for CH4 and N2O, respectively). This decline is partly driven by the increased mid- to high-latitude downward flux at the tropopause and also by an increased isolation of the tropical pipe in the vertical layer near the tropopause, with reduced horizontal eddy mixing. Results from a climate-chemistry coupled model are shown for both long-lived trace species and the stratospheric age-of-air. The latter results to be younger by approximately 0.5 year at 30 hPa for 3–4 years after the June 1991 Pinatubo eruption, as a result of the volcanic aerosols radiative perturbation and is consistent with independent estimates based on long time series of in situ profile measurements of SF6 and CO2. Younger age of air is also calculated after Agung, El Chichon and Ruiz eruptions, as well as negative anomalies of the N2O growth rate at the extratropical tropopause layer. This type of analysis is made comparing the results of two ensembles of model simulations (1960–2005), one including stratospheric volcanic aerosols and their radiative interactions and a reference case where the volcanic aerosols do not interact with solar and planetary radiation

Sulfate Aerosols from Non-Explosive Volcanoes: Chemical-Radiative Effects in the Troposphere and Lower Stratosphere

SO2 and H2S are the two most important gas-phase sulfur species emitted by volcanoes, with a global amount from non-explosive emissions of the order 10 Tg-S/yr. These gases are readily oxidized forming SO42− aerosols, which effectively scatter the incoming solar radiation and cool the surface. They also perturb atmospheric chemistry by enhancing the NOx to HNO3 heterogeneous conversion via hydrolysis on the aerosol surface of N2O5 and Br-Cl nitrates. This reduces formation of tropospheric O3 and the OH to HO2 ratio, thus limiting the oxidation of CH4 and increasing its lifetime. In addition to this tropospheric chemistry perturbation, there is also an impact on the NOx heterogeneous chemistry in the lower stratosphere, due to vertical transport of volcanic SO2 up to the tropical tropopause layer. Furthermore, the stratospheric O3 formation and loss, as well as the NOx budget, may be slightly affected by the additional amount of upward diffused solar radiation and consequent increase of photolysis rates. Two multi-decadal time-slice runs of a climate-chemistry-aerosol model have been designed for studying these chemical-radiative effects. A tropopause mean global net radiative flux change (RF) of −0.23 W·m−2 is calculated (including direct and indirect aerosol effects) with a 14% increase of the global mean sulfate aerosol optical depth. A 5–15 ppt NOx decrease is found in the mid-troposphere subtropics and mid-latitudes and also from pole to pole in the lower stratosphere. The tropospheric NOx perturbation triggers a column O3 decrease of 0.5–1.5 DU and a 1.1% increase of the CH4 lifetime. The surface cooling induced by solar radiation scattering by the volcanic aerosols induces a tropospheric stabilization with reduced updraft velocities that produce ice supersaturation conditions in the upper troposphere. A global mean 0.9% decrease of the cirrus ice optical depth is calculated with an indirect RF of −0.08 W·m−2

Effects of Selected Wood Species and Moisture Content on PMDI Resin Application and Panel Properties

This study investigated the effect of selected species and moisture conditions on resin distribution and composite panel properties. Flakeboard composites were made from aspen, pine, or poplar flakes that were equilibrated to 4, 8, or 12% moisture content (MC). Resin droplet size (resin "footprint") was measured, as was the percentage of the flake surface that was covered by resin. Aspen flakes showed higher resin coverage and also larger resin droplet sizes. Conversely, pine and poplar flakes had smaller resin droplets and lower resin coverage per flake surface, suggesting greater pMDI penetration. Internal bond (IB) testing revealed optimal performance for aspen flakes at 12% precure MC, and poplar and pine flakes at 8% precure MC. Modulus of rupture and modulus of elasticity results correlated with IB results. Aspen panels bonded at 8 and 12% MC had minimal thickness swell

Effects of Isomer Ratio on Pmdi Resin Reactivity and Oriented Strandboard Properties

The effect of varying 2,4'-MDI to 4,4'-MDI isomer ratio in diphenylmethane diisocyanate (pMDI) adhesives was investigated. In addition to probing resin cure kinetics, oriented strandboard panels were produced to investigate the effect of isomer ratio on panel properties. With one exception, differential scanning calorimetry results showed a trend of increasing activation energy with increasing 4,4'-MDI content—the opposite of what was predicted. Results of internal bond testing indicate that increasing 4,4'-MDI content gave higher internal bond strength, but no correlation was evident between resin and panel density, MOR, MOE, or 24-h thickness swell. It is important to note that isomer ratio was not the only variable within the resin series; oligomer content and hence viscosity increased as 4,4'-MDI content increased, which complicated the analysis