Pronounced climate changes have occurred since the 1970s, including rapid loss of Arctic sea ice 1 , large-scale warming 2 and increased tropical storm activity 3 in the Atlantic. Anthropogenic radiative forcing is likely to have played a major role in these changes 4 , but the relative influence of anthropogenic forcing and natural variability is not well established. The above changes have also occurred during a period in which the North Atlantic Oscillation has shown marked multidecadal variations 5 . Here we investigate the role of the North Atlantic Oscillation in these rapid changes through its influence on the Atlantic meridional overturning circulation and ocean heat transport. We use climate models to show that observed multidecadal variations of the North Atlantic Oscillation can induce multidecadal variations in the Atlantic meridional overturning circulation and poleward ocean heat transport in the Atlantic, extending to the Arctic. Our results suggest that these variations have contributed to the rapid loss of Arctic sea ice, Northern Hemisphere warming, and changing Atlantic tropical storm activity, especially in the late 1990s and early 2000s. These multidecadal variations are superimposed on long-term anthropogenic forcing trends that are the dominant factor in long-term Arctic sea ice loss and hemispheric warming.There has been pronounced multidecadal variability of the North Atlantic Oscillation (NAO) over the past century 6 , with a negative phase of the NAO from the 1960s into the 1970s (Fig. 1a), associated with weakened westerly winds and cold ocean surface temperatures in the subpolar North Atlantic. This was followed by a rapid switch to a positive NAO phase from the 1980s into the early 2000s, along with strengthened westerly winds and rapid warming in the subpolar North Atlantic. These regional variations were coincident with long-term trends and multidecadal variability in Northern Hemisphere (NH) surface air temperature 2 and Arctic sea ice 1 . The relatively cool period of the 1970s was coincident with enhanced Arctic sea ice 7 , although observations before the satellite era are uncertain. This was followed by a rapid warming of the NH and reduction of Arctic sea ice from the late 1970s through the 2000s. There have been substantial multidecadal variations in Atlantic tropical storm activity 3 , with a relatively quiescent period from the late 1960s through the 1980s, followed by enhanced activity after the mid 1990s.Studies have suggested an important role for anthropogenic forcing in driving some of the above changes 4,8 , and yet the relative roles of natural variability and anthropogenic forcing are uncertain. In particular, the degree to which natural climate variability contributes to these past variations is a critical factor in our confidence in projections of future climate.We use simulations with three different climate models to explore the contribution of multidecadal variations of the NAO 9 to the above changes. The novel experimental design (see Methods) adds NAO-relate...

Previous studies have concluded that the increase in vegetation in the arid northwest of China is related to precipitation rather than temperature. However, these studies neglected the effects of climate warming on water availability that arise through changes in the melting characteristics of this snowy and glaciated region. Here, we characterized vegetation changes using the newly improved third-generation Global Inventory Modeling and Mapping Studies Normalized Difference Vegetation Index (GIMMS-3g NDVI) from 1982 to 2011. We analyzed the temperature and precipitation trends based on data from 51 meteorological stations across Northwest China and investigated changes in the glaciers using Gravity Recovery and Climate Experiment (GRACE) data. Our results indicated an increasing trend in vegetation greenness in Northwest China, and this increasing trend was mostly associated with increasing winter precipitation and summer temperature. We found that the mean annual temperature increased at a rate of 0.04˝C per year over the past 30 years, which induced rapid glacial melting. The total water storage measured by GRACE decreased by up to 8 mm yr´1 and primarily corresponded to the disappearance of glaciers. Considering the absence of any observed increase in precipitation in the growing season, the vegetation growth may have benefited from the melting of glaciers in high-elevation mountains (i.e., the Tianshan Mountains). Multiple regression analysis showed that temperature was positively correlated with NDVI and that gravity was negatively correlated with NDVI; together, these variables explained 84% of the NDVI variation. Our findings suggest that both winter precipitation and warming-induced glacial melting increased water availability to the arid vegetation in this region, resulting in enhanced greenness.

This study investigates the initial stage (IS) and return stroke (RS) currents of 50 triggered lightning flashes (TLFs) that were conducted in southern China. The IS of the negative TLFs has a longer duration and larger average current, charge transfer, and action integral than those reported elsewhere, with geometric means (GMs) of 347.9 ms, 132.5 A, 45.1 C, and 10.0 × 103 A2 s, respectively. Two positive TLFs containing no RS have much greater average currents, charge transfers, and action integrals in the IS when compared with the negative TLFs. The RS has a greater peak current (17.2 kA; GM, same to below), charge transfer within 1 ms (1.3 C), and action integral within 1 ms (5.8 × 103 A2 s), and shorter 10% to 90% rise time (0.4 μs) than elsewhere. The peak current is prominently correlated with the rate of rise, charge transfer within 1 ms, and action integral within 1 ms. Furthermore, when the total duration of the RS and any following continuing currents is longer than 40 ms, the peak current, charge transfer within 1 ms, and action integral within 1 ms of the RS are seldom greater than 25 kA, 2.6 C, and 15 × 103 A2 s, respectively. It is indicated that TLFs containing RSs tend to have a longer duration but a smaller charge transfer during the IS than those without RS. The peak current of the RS is weakly correlated with its preceding silence period when there was no channel base current.

Physically based, spatially distributed hydrological models have mostly been calibrated manually; a few were calibrated automatically but without full consideration of conflicted multi-objectives. Here, we successfully applied the non-dominated sorting genetic algorithm II (NSGA-II) and its two variants, namely the reference point-based R-NSGA-II and the extension ER-NSGA-II, to multiobjective, automatic calibration of the SHETRAN hydrological model. Moreover, we demonstrated the possibility of speeding up the calibration process by adjusting the recombination and mutation parameters of the optimization algorithms. The simulated binary crossover and polynomial mutation were used with respective probabilities of 0.9 and 0.1, and crossover and mutation distribution indices (η , η ) with values of (0.5, 0.5), (2.0, 0.5) and (20., 20.). The results indicate that the use of smaller (η , η ) speeded up the optimization process of SHETRAN calibration, especially during the initial stage, for all three algorithms; however, the use of the R-NSGA-II and ER-NSGA-II did not provide a more efficient optimization compared to the NSGA-II. The broad search of the algorithms, enabled by the generation of diversified solutions due to the use of small (η , η ), contributed to the improved efficiency. Finally, we successfully validated the optimal solutions for both the basin outlet and the internal gauging stations.

Cs is a common radionuclide present in nuclear wastes and released from nuclear power plant accidents. It is hard to be removed from water with traditional technology. The current study aimed at developing of efficient cost-effective adsorbent for removing Cs with modified MCM-41 with specific functional groups -SH. Mesoporous material MCM-41 was selected due to its large surface area and tunable pore structure. Functional -SH groups were grafted into the pores of MCM-41 to enhance its capability of selective adsorption of Cs from multi-element (Co, Sr) water solution. The adsorption results showed that the maximum adsorption capacity was 29.24 mg/g. Both Langmuir and Freundlich models described the adsorption processes of Cs, indicating co-existence of both monolayer and multilayer adsorption in the surface and inner pores of the materials. TEM, FTIR, and Raman spectroscopy analyses indicated that -SH groups were successfully bounded into the pores of MCM-41. The present study approved the surface functional modified MCM-41 which might be a good alternative candidate for cleaning up of radionuclide Cs from nuclear power plant accidents and relevant nuclear accident events.

Automatic calibration is preferred because it provides an objective and extensive searching in the feasible parameter space. In this study, the Modified Shuffled Complex Evolution (MSCE) optimization algorithm is applied to automatically calibrate the physically-based spatially-distributed hydrological model SHETRAN in the 705-km

A reverse micelle-assisted route was reported to prepare ZnO nanorods from two different precursors, Zn(NH3)42+ and Zn(OH)42−, respectively. The reverse micelles were used as microreactors, which lead into anisotropic growth of ZnO crystals during a simple solvothermal process.

A robust hydrological impact assessment is indispensable for mitigation and adaptation planning. This study presents an integrated modelling methodology for evaluating climate change impacts on water availability, sediment yield and extreme events at the catchment scale. We propose the use of the spatial–temporal Neyman–Scott Rectangular Pulses (STNSRP) model—RainSim V3 and the rainfall conditioned daily weather generator—ICAAM‐WG, as well as the physically based spatially distributed hydrological model—SHETRAN. The change factor approach was applied for obtaining unbiased rainfall and temperature statistics. The ICAAM‐WG was developed based on the modified Climate Research Unit daily Weather Generator (CRU‐WG). The methodology is proposed to generate synthetic series of hourly precipitation, daily temperature and potential evapotranspiration, hourly runoff and hourly sediment discharge. We demonstrated a possible application in a 705‐km2 Mediterranean climate basin in southern Portugal. The case study showed the evaluation of future climate change impacts on annual and monthly water balance components and sediment yield, annual and seasonal flow duration curves, empirical extreme value distributions and the theoretical fits. It did not consider the possible uncertainty due to the limit of computational resources. The methodology can be well justified as follows: (a) the use of synthetic hourly instead of daily precipitation enables SHETRAN to be more capable of reproducing reliable storm runoff processes and the consequent sediment transport processes; (b) the use of SHETRAN makes possible the impact assessment to be accessible for any model grid square within the study basin; (c) the use of a statistical–stochastic downscaling method facilitates the generation of the synthetic series with unlimited length. It makes possible robust hydrological impact assessments if uncertainties related to the global climate model, regional climate model, greenhouse gas emission scenario, downscaling method, hydrological model and observational data are considered.