In last decades, the impact of climate change started to appear in the semi-arid regions of the Mediterranean Basin. The severity and frequency of drought events in Northwestern Algeria have affected ...water resources availability and agriculture. This study aims to evaluate the temporal evolution of drought events characteristics, such as drought duration, frequency and severity, of the Beni Bahdel Dam catchment, Northwestern Algeria. Drought characteristics have been derived from the Standardized precipitation index (SPI) computed for the period from 1941 to 2100 using precipitation data from observations and simulations of the regional climate model RCA4 (Rossby Centre Atmosphere model, version 4). The RCA4 model was forced by the global circulation model MPI-ESM-LR under two
Representative Concentration Pathways (RCPs) scenarios. The ability of the
model simulations was firstly assessed to reproduce the drought
characteristics from observed data (1951–2005). Then, future changes in
drought characteristics over the twenty-first century were investigated
under the two scenarios (RCP4.5 and RCP8.5). Results show an amplification of drought frequencies and durations in the future under the RCP8.5 scenario.
As the focus of climate policy shifts from pledges to implementation, there is a growing need to track progress on climate change mitigation at the country level, particularly for the land-use ...sector. Despite new tools and models providing unprecedented monitoring opportunities, striking differences remain in estimations of anthropogenic land-use CO.sub.2 fluxes between, on the one hand, the national greenhouse gas inventories (NGHGIs) used to assess compliance with national climate targets under the Paris Agreement and, on the other hand, the Global Carbon Budget and Intergovernmental Panel on Climate Change (IPCC) assessment reports, both based on global bookkeeping models (BMs).
In this contribution, we aim at the modelling of the impedance of a differential sensor in eddy-current non-destructive testing. This mode of control is very common in the detection of abrupt ...geometrical and electromagnetic variations, disturbances generated by slow variations of dimensions and temperature being in particular not observed. We develop a direct semi-analytical model of a voltage-excited system. The formulation is based upon the use of coupled electric circuits. It provides a particular form of the differential impedance, which clarifies the role of the electromagnetic and geometric characteristics. This form of impedance will allow the investigation of non-destructive testing by means of differential sensors and will facilitate the development of real-time inversion procedures. The model is validated by results published in the literature. We exploit it in order to study various electric and geometrical parameters of the control system.
In order to model the global solar radiation based on meteorological parameters for the Bejaia site, we established a database of more than 26,000 points obtained by recording every eight minutes of ...illumination and meteorological parameters (sunshine hours, ambient temperature, air pressure, relative humidity and rainfall). empirical models have been developed using several parameters and, recently, prognostic and prediction models based on artificial intelligence techniques such as neural networks. The daily averages were used to test NN models with 5 parameters and the relationship with the coefficient of the highest correlation was chosen. Two thirds were used to establish the model and one third for validation. We compared its performance with four models in the literature (Angstrom-Prescott, Bahel, Newland and Abdalla).
A warming climate is altering land-atmosphere exchanges of carbon, with a potential for increased vegetation productivity as well as the mobilization of permafrost soil carbon stores. Here we ...investigate land-atmosphere carbon dioxide (CO.sub.2) cycling through analysis of net ecosystem productivity (NEP) and its component fluxes of gross primary productivity (GPP) and ecosystem respiration (ER) and soil carbon residence time, simulated by a set of land surface models (LSMs) over a region spanning the drainage basin of Northern Eurasia. The retrospective simulations cover the period 1960-2009 at 0.5° resolution, which is a scale common among many global carbon and climate model simulations. Model performance benchmarks were drawn from comparisons against both observed CO.sub.2 fluxes derived from site-based eddy covariance measurements as well as regional-scale GPP estimates based on satellite remote-sensing data. The site-based comparisons depict a tendency for overestimates in GPP and ER for several of the models, particularly at the two sites to the south. For several models the spatial pattern in GPP explains less than half the variance in the MODIS MOD17 GPP product. Across the models NEP increases by as little as 0.01 to as much as 0.79 g C m.sup.-2 yr.sup.-2, equivalent to 3 to 340 % of the respective model means, over the analysis period. For the multimodel average the increase is 135 % of the mean from the first to last 10 years of record (1960-1969 vs. 2000-2009), with a weakening CO.sub.2 sink over the latter decades. Vegetation net primary productivity increased by 8 to 30 % from the first to last 10 years, contributing to soil carbon storage gains. The range in regional mean NEP among the group is twice the multimodel mean, indicative of the uncertainty in CO.sub.2 sink strength. The models simulate that inputs to the soil carbon pool exceeded losses, resulting in a net soil carbon gain amid a decrease in residence time. Our analysis points to improvements in model elements controlling vegetation productivity and soil respiration as being needed for reducing uncertainty in land-atmosphere CO.sub.2 exchange. These advances will require collection of new field data on vegetation and soil dynamics, the development of benchmarking data sets from measurements and remote-sensing observations, and investments in future model development and intercomparison studies.
This paper presents a mathematical modeling of thin layer drying of tomato (Solanum lycopersicum L.). To this end, two different methods are used to dehydrate tomato slices namely the solar drying ...(in an indirect solar drier), and the forced convective drying (in a convective drier). In the solar drier, the experiments are carried out at a constant air velocity of 1 m s-1 and average temperatures of 37.2°C, 39.9°C and 42.5°C. In the convective drier, the experiments are performed with five different temperatures (30°C, 40°C, 50°C, 60°C and 70°C) at a constant air velocity of 1 m s-1. In order to estimate and select the appropriate drying curve equation, fifteen different thin layer mathematical drying models available in the literature are applied to the experimental data. The models are compared using the correlation coefficient (r) and the standard error (s) and are predicted by a non-linear regression analysis using the Curve Expert software. The Midilli-Kucuk model shows a better fit to the experimental drying data according to (r) and (s) for the two drying methods. The effect of the drying temperature on the parameters of this model is also determined. The experimental drying curves show only a falling drying rate period. On average, tomatoes are dried until the moisture content to 0.15 kg water kg-1 dry matter from 14.36 kg water kg-1 dry matter in the solar drying, and to the moisture content of 0.10 kg water kg-1 dry matter from 12.66 kg water kg-1 dry matter in the convective drying.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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