Sulla luminosita’ del cielo e sul contenuto di polveri nell’atmosfera

Riassunto Si analizzano andamenti sperimentali della luminosità del cielo nelle zone rossa e bleu dello spettro. Dal confronto con diversi andamenti teorici si ottiene la spiegazione per la diversità di comportamento della luminosità nelle due zone considerate, e si riconosce la possibilità che — sotto certe condizioni — è consentito tener conto della sola diffusione primaria. Considerando anche la diffusione non molecolare si indica un metodo per calcolare, dalle misure di luminosità, il valore di un parametro che rappresenta un indice del contenuto di polveri nell’atmosfera. Si discutono alcuni valori trovati in base a misure eseguite all’Osservatorio Vesuviano.

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Summary Experimental outlines of sky brightness in the red and blue fields of spectrum are analized. From comparison with theoretical predictions one desumes the explanation about the different behaviour of brightness in the two considered fields and possibility — under certain conditions — of taking account only primary scattering. Considering also non-molecular scattering a method is shown to deduce, from the measurements of intensities of sky radiation, the value of a parameter representing the content of dust into atmosphere. Some experimental values found in measurements made at the ? Osservatorio Vesuviano ? are discussed.

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Prof.Lorenzo Casertano, Osservatorio Vesuviano,Resina (Napoli)     

Effects of climate and density-dependent factors on population dynamics of the pine processionary moth in the Southern Alps

Forest pest populations can fluctuate dramatically in relation to climate and density-dependent factors. Although the distributional range of the pine processionary moth Thaumetopoea pityocampa (Lepidoptera Notodontidae) appears to be expanding northward and upslope with climate warming, the relative importance of climate and endogenous, density-dependent factors has not been clearly documented. We analyzed the population dynamics of the moth using long-term data from two provinces in the Southern Alps (Trento: 1990–2009, Bolzano/Bozen: 1975–2011) to evaluate the relative importance of climate and density-dependent factors as regional drivers. Both summer temperatures and rainfall significantly affected population growth rate, with different outcomes depending on the local conditions. Although previous studies indicated that low winter temperatures have negative effects on insect performance, our analyses did not show any negative effect on the population dynamics. A negative density dependent feedback with a 1-year lag emerged as the most important factor driving the population dynamics in both regions. Potential mechanisms explaining the observed negative density feedback include deterioration of host quality, increased mortality caused by pathogens, and increase of prolonged diapause as an adaptive mechanism to escape adverse conditions.     

Building damage assessment after the <Emphasis Type="Italic">Riviera del Brenta</Emphasis> tornado,northeast Italy

A tornado with severe intensity hit the municipalities of Pianiga, Dolo and Mira close to Venice, northeast Italy, causing damages on a wide number of residential and industrial buildings and destroying some historical villas. In this study, the authors show the results of the damage assessment survey performed in the first days after the occurrence of the extreme event. Limited literature deals with damage assessment of European building types due to wind actions, and the available one does not consider building vulnerability as key factor in the structural response of existing structures subject to tornado hazard. In this paper, structural damages surveyed in reinforced concrete frame structures and masonry buildings, representative of common Italian building types, are critically discussed. Additionally, this work provides a database of past tornado events in northeast Italy, evidencing how the analyzed area has been found to be quite prone to tornado hazard.     

Near real-time ocean circulation assimilation and prediction in the Intra-Americas Sea with ROMS

We present the feasibility of a prototype, near real-time assimilation and ensemble prediction system for the Intra-Americas Sea run autonomously aboard a ship of opportunity based on the Regional Ocean Modeling System (ROMS). Predicting an ocean state depends upon numerical models that contain uncertainties in their modeled physics, initial conditions, and model state. An advanced model, four-dimensional variational assimilation, and ensemble forecasting techniques are used to account for each of these uncertainties. Every 3 days, data from the previous 7 days period were assimilated to generate an estimate of the circulation and to create an ensemble of 2 weeks forecasts of the ocean state. This paper presents the methods and results for a multi-resolution assimilation system and ensemble forecasts of surface fields and dominant surface circulation features. When compared to post-processed science quality observations, the state estimates suffer from our reliance on real-time, quick-look satellite observations of the ocean surface. Despite a number of issues, the ensemble forecast estimate is often superior to observational persistence. This proof-of-concept prototype performed well enough to reveal deficiencies, provide useful insights, valuable lessons, and guidance for future improvements in real-time ocean forecasting.