189 research outputs found
Snow precipitation at four ice core sites in East Antarctica: Provenance, seasonality and blocking factors
No full textSnow precipitation is the primary mass input to the Antarctic ice sheet and is one of the most direct climatic indicators, with important implications for paleoclimatic reconstruction from ice cores. Provenance of precipitation and the dynamic conditions that force these precipitation events at four deep ice core sites (Dome C, Law Dome, Talos Dome, and Taylor Dome) in East Antarctica were analysed with air mass back trajectories calculated using the Lagrangian model and the mean composite data for precipitation, geopotential height and wind speed field data from the European Centre for Medium Range Weather Forecast from 1980 to 2001. On an annual basis, back trajectories showed that the Atlantic-Indian and Ross-Pacific Oceans were the main provenances of precipitation in Wilkes Land (80%) and Victoria Land (40%), respectively, whereas the greatest influence of the ice sheet was on the interior near the Vostok site (80%) and in the Southwest Ross Sea (50%), an effect that decreased towards the coast and along the Antarctic slope. Victoria Land received snowfall atypically with respect to other Antarctica areas in terms of pathway (eastern instead of western), seasonality (summer instead of winter) and velocity (old air age). Geopotential height patterns at 500 hPa at low (>10 days) and high (2-6 days) frequencies during snowfall cycles at two core sites showed large positive anomalies at low frequencies developing in the Tasman Sea-Eastern Indian Ocean at higher latitudes (60-70°S) than normal. This could be considered part of an atmospheric blocking event, with transient eddies acting to decelerate westerlies in a split region area and accelerate the flow on the flanks of the low-frequency positive anomalies. © 2010 Springer-Verlag
Climate and Energy Production – A Climate Services Perspective
No full textIn the energy sector climate information can play a strategic role, particularly in hot spot regions such as the Mediterranean region. In order to limit GHG emissions, within the European Union framework there will be opportunities for trading renewable energy quotas among member states and to gain credit for electricity imported from renewable sources in countries outside the European Union. This framework will trigger new strong interaction between climate information providers and energy sector stakeholders. The basic assumption of this perspective, of course, is that a prediction of climate on multi-decadal time scales is attainable. © 2013 Elsevier Inc. All rights reserved
Testing the effects of temporal data resolution on predictions of the effects of climate change on bivalves
No full textThe spatial-temporal scales on which environmental observations are made can significantly affect our perceptions of ecological patterns in nature. Understanding potential mismatches between environmental data used as inputs to predictive models, and the forecasts of ecological responses that these models generate are particularly difficult when predicting responses to climate change since the assumption of model stationarity in time cannot be tested. In the last four decades, increases in computational capacity (by a factor of a million), and the evolution of new modeling tools, have permitted a corresponding increase in model complexity, in the length of the simulations, and in spatial-temporal resolution. Nevertheless, many predictions of responses such as shifts in range boundaries are often based on coarse spatial and temporal data, for example monthly or yearly averages. Here we model the effects of environmental change on the physiological response of an ecologically and commercially important species of mussel, the fitness of which can have a cascading influence on ecosystem levels. Using a Dynamic Energy Budget (DEB) model integrated with climatic data produced from IPCC-A1B scenarios, we investigated the effect of temporal resolution of physical data on predictions of the growth and reproductive output of the mussel Mytilus galloprovincialis. We ran models using five different temporal scales, 6, 4, 3, 2 and 1. h (derived by interpolating between 6. h points), at 5 Italian locations in the Central Mediterranean Sea, for the period ranging from 2006 to 2009. Results from these models were further compared against the results from a DEB model that used hourly environmental data recorded at the five locations as inputs. Model outputs included estimates of life history traits relevant to ecological performance as well as parameters related to Darwinian fitness. Results showed that predictions of maximum theoretical shell length were similar regardless of which source of environmental data was used. However, while the DEB model using 1-h modeled data produced predictions of reproductive output very similar to those obtained using recorded (hourly) environmental data from the same time period, results using coarser resolution modeled data greatly underestimated reproductive output. Thus, the use of modeled weather data can yield predictions similar to those generated from measured data, but only when data are provided at relatively high frequency. Our results suggest that metrics of model skill can diverge significantly when physical outputs of climate models are applied to biological questions, and that the temporal resolution of environmental data can strongly alter predictions of biological responses to environmental change. © 2014 Elsevier B.V
A numerical approach for planning offshore wind farms from regional to local scales over the Mediterranean
No full textRenewable energy resources, such as wind, are available worldwide. Locating areas with high and continual wind sources are crucial in pre-planning of wind farms. Vast offshore areas are characterized by higher and more reliable wind resources in comparison with continental areas. However, offshore wind energy production is in a quite preliminary phase. Elaborating the potential productivity of wind farms over such areas is challenging due to sparse in situ observations. The Mediterranean basin is not an exception. In this study we are proposing numerical simulations of near-surface wind fields from regional climate models (RCMs) in order to obtain and fill the gaps in observations over the Mediterranean basin. Four simulations produced with two regional climate models are examined here. Remote sensing observations (QuikSCAT satellite) are used to assess the skill of the simulated fields. A technique for estimating the potential energy from the wind fields over the region is introduced. The wind energy potential atlas and the map of a wind turbine's functional range are presented, locating the potentially interesting sub-regions for wind farms. The ability of models to reproduce the annual cycle and the probability density function of wind speed anomalies are detailed for specified sub-regions. © 2015 Elsevier Ltd
Short-term predictability of photovoltaic production over Italy
No full textPhotovoltaic (PV) power production increased drastically in Europe throughout the last years. Since about the 6% of electricity in Italy comes from PV, an accurate and reliable forecasting of production would be needed for an efficient management of the power grid. We investigate the possibility to forecast daily PV electricity production up to ten days without using on-site measurements of meteorological variables. Our study uses a PV production dataset of 65 Italian sites and it is divided in two parts: first, an assessment of the predictability of meteorological variables using weather forecasts; second, an analysis of predicting solar power production through data-driven modelling. We calibrate Support Vector Machine (SVM) models using available observations and then we apply the same models on the weather forecasts variables to predict daily PV power production. As expected, cloud cover variability strongly affects solar power production, we observe that while during summer the forecast error is under the 10% (slightly lower in south Italy), during winter it is abundantly above the 20%
Understanding and attributing the Euro-Russian summer blocking signatures
No full textIn this work, we focus on summer blocking events over the Euro-Russian region related with heat waves. An analysis of the main characteristics of summer Euro-Russian blocking events in global Reanalysis as well as in the 20th century CLIVAR atmospheric simulations is carried out to assess whether anthropogenic forcing might have affected the blocking events occurrence and the associated heat waves strength in recent decades. Over the Euro-Russian region, blocking episodes, associated to warm events over Northern and Central Europe, become significantly longer in the second half of the century when the anthropogenic forcing is included in the simulations. © 2014 Royal Meteorological Society
Assessing climate change impacts on European wind energy from ENSEMBLES high-resolution climate projections
No full textClimate change may alter the geographical pattern and intensity of near-surface winds which are the “fuel” for wind turbines. In a context of fast current and planned development of wind power worldwide, investigating the impacts of climate change on wind power generation is necessary. This study aims at assessing future changes in the potential for wind power generation over the whole Europe and in the effective wind power production from national wind farms operating at the end of 2012 and planned by 2020. For this purpose, a simplified wind power generation model is applied to an ensemble of 15 regional climate projections achieved from 10 Regional Climate Models downscaling six Global Climate Models under the SRES A1B emission scenario from the ENSEMBLES project. The use of a relatively large multi-model ensemble allows the identification of robust changes and the estimation of a range of uncertainties associated with projected changes. We show with a high level of confidence that, under the A1B scenario, over most of Europe, changes in wind power potential will remain within ±15 and ±20 % by mid and late century respectively. Overall, we find a tendency toward a decrease of the wind power potential over Mediterranean areas and an increase over Northern Europe. Changes in multi-year power production will not exceed 5 and 15 % in magnitude at the European and national scale respectively for both wind farms in operation at the end of 2012 and planned by 2020. Therefore, climate change should neither undermine nor favor wind energy development in Europe. However, accounting for climate change effects in particular regions may help optimize the wind power development and energy mix plans
Observed and modeled global ocean turbulence regimes as deduced from surface trajectory data
No full textA large-scale tool for systematic analyses of the dispersal and turbulent properties of ocean currents and the subsequent separation of dynamical regimes according to the prevailing trajectories taxonomy in a certain area was proposed by Rupolo. In the present study, this methodology has been extended to the analysis of model trajectories obtained by analytical computations of the particle advection equation using the Lagrangian opensource software package Tracing the WaterMasses of the NorthAtlantic and theMediterranean(TRACMASS), and intercomparisons have been made between the surface velocity fields from three different configurations of the global Nucleus for European Modelling of the Ocean (NEMO) ocean/sea ice general circulation model. Lagrangian time scales of the observed and synthetic trajectory datasets have been calculated by means of inverse Lagrangian stochastic modeling, and the influence of the model field spatial and temporal resolution on the analyses has been investigated. In global-scale ocean modeling, compromises are frequently made in terms of grid resolution and time averaging of the output fields because high-resolution data require considerable amounts of storage space. Here, the implications of such approximations on the modeled velocity fields and, consequently, on the particle dispersion, have been assessed through validation against observed drifter tracks. This study aims, moreover, to shed some light on the relatively unknown turbulent properties of near-surface ocean dynamics and their representation in numerical models globally and in a number of key regions. These results could be of interest for other studies within the field of turbulent eddy diffusion parameterization in ocean models or ocean circulation studies involving long-term coarse-grid model experiments. © 2013 American Meteorological Society
Electricity demand forecasting over Italy: Potential benefits using numerical weather prediction models
No full textElectricity demand forecasting is a critical task for energy management of power grids. Due to the wide use of refrigeration and residential air-conditioning devices, electricity demand in Italy is influenced by weather conditions, especially during summer. This paper performs daily load forecasting for Italy through statistical modeling with the aim of studying the influence of temperature. The actual capability of available weather forecasts to contribute in predicting electricity loads is evaluated by using weather data from numerical weather prediction (NWP) models. Time-series models have been used and compared with a naive predictor on working-days daily load during June and July in years 2003-2009 considering lead-times between one and five days. Results are analyzed both at the national level and at regional scale, using unprecedented historical load data provided by the Italian transmission grid manager. It is shown that the use of weather data provided by NWP models leads to performance improvements, especially for the hottest areas where the use of electricity is more heavily influenced by temperature. Furthermore, by observing the gap between load forecast models using reanalysis and operational forecast weather data we can obtain some clues about the limitations of the weather forecast models we used on specific geographic areas in Italy. © 2013 Elsevier B.V
Southern Hemisphere midlatitude Atmospheric Variability of the NCEP-NCAR and ECMWF Reanalyses
No full text- …
