Mesoscale energetics and flows induced by sea-land and mountain-valley contrasts

We study the relative importance of sea-land and mountain-valley thermal contrasts in determining the development of thermally forced mesoscale circulations (TFMCs) over a mountainous peninsula. We first analyse the energetics of the problem, and using this theory, we interprete the numerical simulations over Calabria, a mountainous peninsula in southern Italy. The CSU 3-D nonlinear numerical model is utilised to simulate the dynamics and the thermodynamics of the atmospheric fields over Calabria. Results show the importance of orography in determining the pattern of the flow and the local climate in a region as complex as Calabria. Analysis of the results shows that the energetics due to the sea-land interactions are more efficient when the peninsula is flat. The importance of the energy due to the sea-land decreases as the mountain height of the peninsula increases. The energy stored over the mountain gains in importance, untill it is released by the readjustment of the warm mountain air as it prevails over the energy released by the inland penetration of the sea breeze front. For instance, our results show that over a peninsula 100 km wide the energy over the mountain and the energy in the sea-land contrast are of the same order when the height of the mountain is about 700 m, for a 1500 m convective boundary layer (CBL) depth. Over the Calabrian peninsula, the energy released by the hot air in the CBL of the mountain prevails over the energy released by the inland penetration of the sea air. Calabria is about 1500 m high and about 50 km wide, and the CBL is of the order of 1500 m. The energy over the mountain is about four time larger than the energy contained in the sea-land contrast. Furthermore, the energetics increase with the patch width of the peninsula, and when its half width is much less than the Rossby radius, the MAPE of the sea breeze is negligible. When its half width is much larger than the Rossby radius, the breezes from the two opposing coastlines do not interact. Over Calabria peninsula, numerical simulations show that the flow is highly ageostrophic, and that the flow intensity increases from sunrise to reach its maximum in the afternoon but before sunset, which suggests that, in the late part of the day, the conversion of potential energy into kinetic energy is balanced by the dissipation.     

Comparison of CO2 Dynamics and Air–Sea Gas Exchange in Differing Tropical Reef Environments

An array of MAPCO₂ buoys, CRIMP-2, Ala Wai, and Kilo Nalu, deployed in the coastal waters of Hawaii, have produced multi-year high temporal resolution CO₂ records in three different coral reef environments off the island of Oahu, Hawaii. This study, which includes data from June 2008 to December 2011, is part of an integrated effort to understand the factors that influence the dynamics of CO₂–carbonic acid system parameters in waters surrounding Pacific high-island coral reef ecosystems and subject to differing natural and anthropogenic stresses. The MAPCO₂ buoys are located on the Kaneohe Bay backreef, and fringing reef sites on the south shore of Oahu, Hawaii. The buoys measure CO₂ and O₂ in seawater and in the atmosphere at 3-h intervals, as well as other physical and biogeochemical parameters (conductivity, temperature, depth, chlorophyll-a, and turbidity). The buoy records, combined with data from synoptic spatial sampling, have allowed us to examine the interplay between biological cycles of productivity/respiration and calcification/dissolution and biogeochemical and physical forcings on hourly to inter-annual time scales. Air–sea CO₂ gas exchange was also calculated to determine whether the locations were sources or sinks of CO₂ over seasonal, annual, and interannual time periods. Net annualized fluxes for CRIMP-2, Ala Wai, and Kilo Nalu over the entire study period were 1.15, 0.045, and ?0.0056 mol C m^?2 year^?1, respectively, where positive values indicate a source or a CO₂ flux from the water to the atmosphere, and negative values indicate a sink or flux of CO₂ from the atmosphere into the water. These values are of similar magnitude to previous estimates in Kaneohe Bay as well as those reported from other tropical reef environments. Total alkalinity (A_T) was measured in conjunction with pCO₂, and the carbonic acid system was calculated to compare with other reef systems and open ocean values around Hawaii. These findings emphasize the need for high-resolution data of multiple parameters when attempting to characterize the carbonic acid system in locations of highly variable physical, chemical, and biological parameters (e.g., coastal systems and reefs).     

Optical Frequency Comb as a general-purpose and wide-band calibration source for astronomical high resolution infrared spectrographs

A spectrally filtered Optical Frequency Comb (OFC) laser is proposed as a versatile calibration source for astronomical spectrometers in the 1?C2 ??m spectral range. Such a source overcomes the limitations of current calibration lamps providing a uniform spectrum of equally spaced lines with similar intensity and extremely high long-term frequency stability. We present preliminary studies and results of a system which filters the OFC from a 100 MHz comb spacing to 16 GHz one, an adequate spacing for spectrometers with resolving power ????/???>30000. The first approach employs two Fabry-Perot cavities in series, made of dielectric coated mirrors, followed by a non-linear optical broadening system. The limitations of such a filtering process are discussed. These can be overcome by the second approach, based on filtering cavities with metallic coated mirrors.     

Uncovering the Directional Heterogeneity of an Aggregated Mobile Phone Network

The aggregated mobile phone network (AMPN) (i.e. the calling time or numbers are aggregated at every vertex), which records the call volume between different places over time, has been studied extensively to reveal the mobility patterns of residents, etc. Nevertheless, most previous works were implemented based on the non‐directionality of the network model. This simplification may overlook some important characteristics of AMPN. To explore the AMPN as a directional network model, we introduce the concept of directional heterogeneity in the study of AMPN data. The heterogeneity is twofold: (1) the imbalance of vertex (difference between outgoing and incoming calls of the vertex); and (2) the reciprocity of each edge (difference between the directed weights of the same edge). Taking the data of Singapore as an example, we systematically analyze the directional heterogeneity of AMPN. Our findings include three aspects. First, the AMPN shows as more unbalanced in the night‐time than in the daytime, and its imbalance decreases as vertex granularity increases. Second, the directional heterogeneity varied with locations. Specifically, the residential area is dominated by deficits and others by surpluses. Third, the trajectories of incoming and outgoing calls follow a similar geographical pattern (i.e. southeast‐north‐south‐north‐southeast), indicating the calling behavior and routine mobility of users over time and space.     

Analysis of Summer Ozone Observations at a High Mountain Site in Central Italy (Campo Imperatore, 2388 m a.s.l.)

Tropospheric ozone (O₃) is an important atmospheric pollutant and climate forcer. The Mediterranean basin is a hot-spot region in terms of short-term O₃ distribution, with frequent episodes of high tropospheric O₃, especially during summer. To improve the characterisation of summer O₃ variability in the Mediterranean area, during the period 6–27 August 2009 an experimental campaign was conducted at Campo Imperatore, Mt Portella (CMP), a high mountain site (2,388 m a.s.l.) located in the central Italian Apennines. As deduced from analysis of atmospheric circulation, the measurement site was significantly affected by air masses originating over the Mediterranean basin, which affected the measurement site for 32 % of the time. Analysis of average values and diurnal and day-to-day variability revealed that CMP O₃ observations (average value 60.0 ± 5.1 ppbv) were comparable with measurements at other European mountain stations, indicating a prevalent effect of meteorological conditions and atmospheric transport on the synoptic scale. In fact, only a small “reverse” diurnal variation typically characterises diurnal O₃ variability because of local thermal wind circulation, which sporadically favours transport of air masses rich in O₃ from the foothill regions. Statistical analysis of five-day back-trajectory ensembles indicates that synoptic-scale air-mass transport from the Mediterranean Sea usually results in decreasing O₃ concentrations at CMP, whereas the highest hourly O₃ values are mostly associated with air masses from central continental Europe, eastern Europe, and northern Italy. High O₃ concentrations are also related to downward air-mass transport from higher altitudes. Comparison of in-situ O₃ variability with tropospheric O₃ satellite-based measurements reveals similar features of the two data sets. Together with the results from back-trajectory analysis, this indicates that CMP measurements might usefully improve characterisation of broad-scale O₃ variability over the central Mediterranean basin.     

Analysis of Multitemporal NDVI Data for Crop Yield Forecasting in the Sahel

Abstract

Recent investigations demonstrated that inter‐year NOAA‐AVHRR NDVI variations at the middle of the rainy season can provide information on annual crop yields in Sahelian countries. This line of research is presently extended to the consideration of multitemporal NDVI data for several years (1986-1991) pre‐processed by a proven methodology. The investigation was conducted using NDVI and crop yield data from the sahelian sub‐districts of Niger. The results confirm that geographically standardized NDVI data are efficient for crop yield forecasting, but notable differences exist in this prediction capability depending on the beginning of the season. Late beginnings of the growing (rainy) season (after the end of June) allow optimum forecasting only after mid‐August, while early beginnings lead to anticipate the forecasting capability but also to decrease its accuracy. The importance of these findings in the context of an early warning system is finally discussed.     

Modelling the spatial allocation of second-generation feedstock (lignocellulosic crops) in Europe

This paper presents a modelling approach for the spatial allocation of second-generation feedstock (lignocellulosic crops) under a reference policy scenario in European Union of 28 Member State (EU-28). The land-use modelling platform (LUMP) was used in order to simulate the land-use changes from 2010 to 2050. Within the LUMP, the land demand for these lignocellulosic energy crops was derived from the Common Agricultural Policy Regionalised Impact analysis model. Suitability maps were generated for two main energy crop groups: herbaceous and woody lignocellulosic crops, using multicriteria analysis techniques. Biophysical factors (climate, soil properties and topographical aspects), natural and artificial constraints and location-specific land categories were defined as relevant components within the platform. A sensitivity analysis determined the most influential factors to be temperature, precipitation, length of growing period and number of frost-free days. The results of the modelling exercise in the LUMP reflect the significant renewable energy contribution from energy crops in EU-28, which was estimated to be between 2.3 EJ/year (in 2020) and 6.3 EJ/year (in 2050), accounting for 2.3% and 9.6% of total energy consumption in the EU-28. The results of the allocation were aggregated at regional level to analyse trends. Regions with considerably high demand were identified in Germany, the United Kingdom and Poland.     

LITHOPHILE ELEMENTS IN INDIVIDUAL CHONDRULES OF THE H-4 MAFRA CHONDRITE

Bulk and trace lithophilic elements (Al, Ca, Fe, Mn, Ti, Cr, Sr, V and Zn) have been determined in individual chondrules and in other constituents of the H-4 Mafra chondrite by means of flameless A.A. microanalysis. Twenty-four large sized (> 1 mg) chondrules, composite samples of minor-sized (0.1 and 0.2 mg) chondrules and fine-grained “interchondrular” material have been examined. Data on the large-sized chondrules exhibit large compositional variations among cosmochemically coherent groups of elements. A weak anti-correlation was found between the geochemically coherent refractory V and volatile Zn. A possible mass-composition relationship is suggested by the apparent concentration of lithophile high-temperature condensing elements (Ca, Al, Ti) in the minor-sized chondrules. Compositional features tend to support the hypothesis that chondrules originate from a large number of precursor components constituting a distinct grain population in the solar nebula. Melting through a sudden heating of random mixtures of these precursor grains was possibly followed by further condensation of volatiles and accretion.     

Stochastic energy analysis of seismic isolated bridges

In this paper, a parametric stochastic analysis of isolated bridge is proposed with the aim to assess isolation performance and to investigate effects of energetic influence on protection efficiency. The analysis has been carried out in terms of two stochastic parameters of pear-deck maximum displacement and hysteretic energy response, of which a qualitative trend has been observed.Isolated bridge is described by a simple two degree of freedom (TDoF) Bouc–Wen hysteretic model, which has been introduced for its intrinsic ability in reproducing a wide range of real devices behavior. With the aim of taking into consideration intrinsic stochastic nature of seismic events, the ground motion and the structural response have been described by random vibration approach. Results obtained show that protection achieved by shifting structural natural period and reducing input energy by devices dissipation have counteracting effects if related to deck lateral displacement.