4,079 research outputs found

    Probabilistic assessments of climate change impacts on durum wheat in the Mediterranean region

    Get PDF
    Recently, the availability of multi-model ensemble prediction methods has permitted a shift from a scenario-based approach to a risk-based approach in assessing the effects of climate change. This provides more useful information to decision-makers who need probability estimates to assess the seriousness of the projected impacts. <br><br> In this study, a probabilistic framework for evaluating the risk of durum wheat yield shortfall over the Mediterranean Basin has been exploited. An artificial neural network, trained to emulate the outputs of a process-based crop growth model, has been adopted to create yield response surfaces which are then overlaid with probabilistic projections of future temperature and precipitation changes in order to estimate probabilistic projections of future yields. The risk is calculated as the relative frequency of projected yields below a selected threshold. <br><br> In contrast to previous studies, which suggest that the beneficial effects of elevated atmospheric CO<sub>2</sub> concentration over the next few decades would outweigh the detrimental effects of the early stages of climatic warming and drying, the results of this study are of greater concern

    Modelling climate change impacts on crop production for food security

    Get PDF

    Deblurring of frequency-wavenumber images from small-scale seismic arrays

    Get PDF
    Temporary arrays installed in urban areas for investigating the upper-most geological structure typically comprised of a limited number of stations and are arranged in geometries constrained by environmental boundaries. Therefore, it is expected that the frequency–wavenumber images are significantly blurred by the array transfer function and are corrupted by noise. In this paper, the effect of theRichardson–Lucy regularization method applied to the problem of deblurring frequency–wavenumber images is investigated. The images are computed by analysing data from two small-aperture 2-D arrays, installed with different configurations in a test-site within the town of Potenza (Southern Italy) for near-surface investigations. We show that removing the effects of the array response from the frequency–wavenumber images improve the phase-velocity estimation, reducing the relevant level of uncertainty. Furthermore, the Richardson–Lucy regularization method is effective in reducing the level of noise related to spatial aliasing by eliminating spurious peaks, allowing the maxima related to different seismic sources to be better discriminated

    Seismic input motion determined from a surface-downhole pair of sensors: a constrained deconvolution approach.

    Get PDF
    We apply a deconvolution approach to the problem of determining the input motion at the base of an instrumented borehole using only a pair of recordings, one at the borehole surface and the other at its bottom. To stabilize the bottom-tosurface spectral ratio, we apply an iterative regularization algorithm that allows us to constrain the solution to be positively defined and to have a finite time duration. Through the analysis of synthetic data, we show that the method is capable of retrieving reliable input motion, suppressing the effect of the negative interference generated by the downgoing waves. Results obtained by applying the methodology to weak earthquakes recorded at the Ataköy (Istanbul) vertical array are also presented and show that removing the effect of the downgoing waves is remarkable, even considering the recording at a depth of 140 m

    A model-based assessment of adaptation options for Chianti wine production in Tuscany (Italy) underclimate change

    Get PDF
    This paper covers a comprehensive economic analysis of climate change adaptation options for a specific wine producing region, namely Tuscany. As temperature increases under climate change, rainfall patterns will be different, and Chianti wine production in Tuscany therefore needs to adapt in the near future. We address the adaptation challenges and identify grape yield and quality loss as the main impact of climate change on wine production. Relocation of vineyards uphill and introducing drought-resistant varieties are considered as adaptation measures. We appraise these adaptation measures using an optimization framework, where regional wine producers maximize income subject to economic constraints including the climate change impacts on wine productivity and quality. Our simulation shows quantitatively to what extent a higher degree of climate change impact demands a higher degree of adaptation. We find that a combination of the two measures provides a better strategy because it leads to higher economic efficiency. However, uncertainty regarding the efficiency of the new variety discourages the use of this new drought-resistant variety, whereas a higher efficiency would make this choice more favourable. Sensitivity analysis for time horizon and discount rate confirms the theory of investment under uncertainty, showing a shorter time horizon (or more frequent investment) provides the possibility to postpone the decision to implement adaptation measures due to the value of flexibility, while a higher discount rate leads to a later adaptation decision, because uncertainty creates a value of waiting for new information

    The Mw 6.3, 2009 L’Aquila earthquake: source, path and site effects from spectral analysis of strong motion data

    Get PDF
    The strong motion data of 2009 April 6 L’Aquila (Central Italy) earthquake (Mw = 6.3) and of 12 aftershocks (4.1 ≤ Mw ≤ 5.6) recorded by 56 stations of the Italian strong motion network are spectrally analysed to estimate the source parameters, the seismic attenuation, and the site amplification effects. The obtained source spectra for S wave have stress drop values ranging from 2.4 to 16.8 MPa, being the stress drop of the main shock equal to 9.2 MPa. The spectral curves describing the attenuation with distance show the presence of shoulders and bumps, mainly around 50 and 150 km, as consequence of significant reflected and refracted arrivals from crustal interfaces. The attenuation in the first 50 km is well described by a quality factor equal to Q( f ) = 59 f 0.56 obtained by fixing the geometrical spreading exponent to 1. Finally, the horizontal-to-vertical spectral ratio provides unreliable estimates of local site effects for those stations showing large amplifications over the vertical component of motion