The Impact of Anthropogenic Forcing and Natural Processes on Past, Present, and Future Rainfall over Victoria, Australia

Cool-season (April to October) rainfall dominates the annual average rainfall over Victoria, Australia, and is important for agriculture and replenishing reservoirs. Rainfall during the cool season has been unusually low since the beginning of the Millennium Drought in 1997 (~12% below the twentieth-century average). In this study, 24 CMIP5 climate models are used to estimate 1) the extent to which this drying is driven by external forcing and 2) future rainfall, taking both external forcing and internal natural climate variability into account. All models have preindustrial, historical, and twenty-first-century (RCP2.6, RCP4.5, and RCP8.5) simulations. It is found that rainfall in the past two decades is below the preindustrial average in two-thirds or more of model simulations. However, the magnitude of the multimodel median externally forced drying is equivalent to only 20% of the observed drying (interquartile range of 40% to −4%), suggesting that the drying is dominated by internally generated rainfall variability. Underestimation of internal variability of rainfall by the models, however, increases the uncertainties in these estimates. According to models the anthropogenically forced drying becomes dominant from 2010 to 2029, when drying is evident in over 90% of the model simulations. For the 2018–37 period, it is found that there is only a ~12% chance that internal rainfall variability could completely offset the anthropogenically forced drying. By the late twenty-first century, the anthropogenically forced drying under RCP8.5 is so large that internal variability appears too small to be able to offset it. Confidence in the projections is lowered because models have difficulty in simulating the magnitude of the observed decline in rainfall.

The Role of Energy Valuation of Agroforestry Biomass on the Circular Economy

The use of biomass has increased significantly in recent years. In this context, the use of not valued high-potential biomass (NVHPB) is emerging as a suitable alternative. This is the case of pruning vine, pruning kiwi, scrub (heather, gorse, broom) and forest pruning. The objective of this research was to study the potential of six selected agroforestry biomasses as biofuels in thermochemical processes. For that purpose, biomass was collected by specific machinery. Proximate and ultimate analyses were carried out as well as the inorganic compounds’ determination. Then, natural and forced drying were conducted. Low heating values (LHV) between 17 and 20 MJ/kg (dry basis) were achieved in all analyzed cases. Granulometric reduction, biomass classification and densification took place. Finally, energy recovery tests through microcogeneration were carried out. Values close to 97% in cogeneration efficiency were reached (9% net electric yield and 88% thermal yield), offering an alternative to obtain clean energy.

Relative Contribution of Anthropogenic Forcing and Natural Processes to Rainfall Variability over Victoria, Australia

<p>Victoria is the second-most populated and most densely populated state in Australia with a population of over 6.5 million. Over two thirds of the population live in greater Melbourne. It is also a major area for agriculture and tourism and is the second largest economy in Australia, accounting for a quarter of Australia's Gross Domestic Product. Any changes in Victoria's climate has huge impacts in these sectors. Rainfall over Victoria during the cool season (e.g. April to October) has been unusually low since the beginning of the Millennium Drought in 1997 (~12% below the 20<sup>th</sup> century average). Cool season rainfall contributes two-third to annual rainfall and is very important for many crops and for replenishing reservoirs across the state. Here we examine the extent to which this reduction in cool season rainfall is driven by external forcing, and the prospects for future multi-decadal rainfall, taking both external forcing and internal natural climate variability into account.</p><p>We analyse simulations from 40 global climate models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) under preindustrial and historical forcing, as well as three scenarios for the 21<sup>st</sup> century: Representative Concentration Pathway (RCP)2.6, RCP4.5 and RCP8.5, which vary markedly in the amount of greenhouse gas emitted over the coming century. While the 1997-2018 average rainfall for cool season is below the preindustrial average in more than two-thirds of models under the three scenarios, the magnitude of the externally-forced drying is very small (median decline is around -2.5% in all three scenarios with an interquartile range around -5% to +1%). The model ensemble results suggest that external forcing contributed only 20% (interquartile range -41% to 4%) to the drying observed in 1997-2018, relative to 1900-1959. These results suggest that the observed drying was dominated by natural, internal rainfall variability. While the multi-model median is below average from 1997-2018 onwards, the externally-forced drying only becomes clear from 2010-2029, when the proportion of models exhibiting drying increases to over 90% under all three scenarios. This agreement reflects the increase in the magnitude of the externally-forced drying. We estimate that there is a 12% chance that internal rainfall variability will completely offset the externally-forced drying averaged over 2018-2037, regardless of scenario. By the late 21<sup>st</sup> century the externally forced change under RCP8.5 is so large that drying – even after taking internally variability into account - appears inevitable. </p><p>Confidence in the modelled projections is lowered because models have difficulty in simulating the magnitude of the observed decline in rainfall. Some of this difficulty appears to arise because most models seem to underestimate multidecadal rainfall variability. Other candidates are: the observed drying may have been primarily due to the occurrence of an extreme, internally-driven event; the models underestimate the magnitude of the externally-forced drying in recent decades; or some combination of the two. If externally-forced drying is underestimated because the response to greenhouse gases is underestimated then the magnitude of projected changes might also be underestimated.</p>

Control of Drying Shrinkage of Magnesium Silicate Hydrate Gel Cements

Cracks were observed when the magnesium silicate hydrate gel cement (prepared by 40% MgO/ 60% silica fume) was dried. This drying cracking is believed to be caused when unbound water evaporates from the binder. The shrinkage upon forced drying to 200 °C of mortars made up from a reactive magnesium oxide, silica fume and sand was measured using dilatometry. The magnitude of the drying shrinkage was found to decrease when more sand or less water was added to the mortars and can be as low as 0.16% for a mortar containing 60 wt% sand and a water to cement ratio of 0.5, which is of a similar order of magnitude as observed in Portland cement based mortars and concretes. A simple geometrical interpretation based on packing of the particles in the mortar can explain the observed drying shrinkages and based on this analysis the drying shrinkage of the hydration products at zero added solid is estimated to be 7.3% after 7 days of curing.

Influence of Relative Humidity on the Moisture Evaporation of Monocomponent Water-Borne Sealer for Wooden Furniture under Forced Drying Condition

The moisture evaporation amount and drying velocity of monocomponent sealer on the maple-veneered panels as base materials, under the drying conditions of constant temperature of 30°C and relative humidity varied from 30% to 70%, were measured in this study. The results indicated that the moisture evaporation amount increased, and drying velocity decreased with drying time under the same relative humidity, while the moisture evaporation amount decreased with the increase of relative humidity. The drying velocities were remarkable different under different relative humidities. During the same period of drying time, the difference degree of moisture evaporation amount within the relative humidity range of 30% to 50% was smaller than that within the relative humidity range of 50% to 70%.