Sea surface temperature from AVHRR-2 data

Summary From the measurements in two channels of the 10 to 13 μm window region, the correction for the atmospheric absorption, useful to retrieve the sea surface temperature from satellite data, can be obtained. By using radiative-transfer model simulations, an up-to-date algorithm was developed, to retrieve the sea surface temperature from the AVHRR (advanced very high resolution radiometer) data. This algorithm has been compared with the algorithms found in the literature. A map of surface temperature in the Northern Adriatic Sea has been processed as an example of application of the algorithm developed. Visiting Scientist at the Joint Research Centre, Commission of the European Communities, 21020 ISPRA.     

Weather regimes and low-level temperature fields

Summary In the present paper we discuss weather regimes in the Northern Hemisphere, identified by means of the probability density distribution of an indicator of the planetary scale 850 mb eddy field during winter. We found that inter-regimes differences have behaviour similar to the one shown at the 500 mb geopotential height. We have speculated that at the upper tail of the distribution of the indicator there may be an additional mode representing a double global blocking flow. For this regime we found that significant features are present also in a sector encompassing the Mediterranean basin. Few speculations about the feasibility of limited-area forecast during inter-regime transition are offered.     

Comparison of measured and calculated high-resolution spectra of far-infra-red stratospheric emission

Summary Far-infra-red stratospheric emission spectra obtained from a balloon-borne platform at 38 km altitude with a spectral resolution of 0.0033 cm⁻¹ are compared with calculated spectra obtained with a radiative-transfer model. The overall agreement between the model and the measurements shows that a good understanding of this spectral interval has been obtained. Differences larger than the measurement error are observed in a few cases. The possible causes of these differences and the work that is needed in order to improve the data base of the model are discussed. Paper presented at the 1^o Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 19–22, 1984, Rome.     

Model of mesoscale wind field obtained from SAR marine images

Summary Wind parameters are directly extracted from marine SAR images by deducing wind stress intensity from a model of pixel statistics, and wind vector at 10 m height from spectral analysis of the mesoscale turbulence present in the stress signature.

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Riassunto I parametri del vento frizionale sono estratti direttamente da immagini SAR deducendo la velocità frizionale da un modello che si basa sulla statistica dei pixel. La direzione e la stabilità atmosferica da una analisi della turbolenza a mesoscala ricavata da appropriate sub-immagini.

     

Surface temperature and emissivity from NOAA images

Summary A procedure to determine the surface temperature from images taken by AVHRR (advanced very high resolution radiometer) on board NOAA11 satellite is described in this paper. The importance of the emissivity parameter to estimate the surface temperature and the possibility to compute both temperature and emissivity maps from the two thermal infrared channels of the AVHRR is shown. Due to the relevance of its scientific content, this paper has been given priority by the Journal Direction.     

Spectral characteristics of wind and air pollution data in an industrial area

Summary A comparison is made between the spectral features of sulfur dioxide concentration and zonal and meridional components of wind speed over a highly industrialized area situated on the coast. The paper focuses on the characteristic times of the meso-synoptic scale. Diurnal and longer period oscillations were identified. Variations of ground-level SO₂ concentrations are attributed to local sea-breeze circulation and to the synoptic weather period of wind speed.     

On the fitness of an algebraic distribution curve to experimental diffusion data

Summary The “witch of Agnesi” is proposed as analytical distribution alternative to the Gaussian one in atmospheric-diffusion estimates. The Agnesi distribution can be derived from the “K theory? and leads finally to algebraic formulae without exponentials, so more easily treated either by hand or by a computer than a Gaussian. Comparing both the Agnesi and the Gaussian distribution with the data set from the EPRI diffusion experiment (plains site), both distribution show a poor fit of the experimental data, slightly better for the Agnesi distribution when literature values for σ _y and σ _z are used.

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Riassunto Viene proposta la ?versiera di Agnesi? come distribuzione alternativa alla Gaussiana in calcoli di diffusione atmosferica. La distribuzione di Agnesi può essere derivata dalla ?K theory? e porta in definitiva a formule algebriche senza esponenziali, piú facilmente trattabili sia in calcoli a mano che con il computer. Confrontando le due distribuzioni Agnesi e Gaussiana con i dati della campagna sperimentale EPRI di Kincaid esse dimostrano entrambe una scarsa adattabilità ai dati sperimentali che tuttavia è tendenzialmente migliore per la Agnesi quando la deviazione standard sperimentale è sostituita da valori di letteratura di σ _y e σ _z comunemente impiegati.

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Резюме Предлагается ?локон Анвези? как анаалитическое алвтернативное распределение распределению Гаусса при описании атмосферной диффузии. Распеделение Анвези может бытв получено из ⩉К теории? и приводит к алгебраической формуле без экспонент, что является более удобным при ручых или компвютерных вычисленииях, чем распределение Гаусса. Проводится сравнение распеделения Анвези и распределения Гаусса с системой данных из EPRI диффузионного эксперимента. Оба рапеделения плохо соответствуют эксперименталвным данным, однако рас↪ределение Анвези дает иесколвко лучшее соответствие, ктгда исполвзуются литературные значения для σ _y и σ _z .

     

Three-dimensional single Doppler radar analysis of an occluded front

Summary Single Doppler radar analysis has been applied to an occluded front associated with the last stages of cyclonic activity over the Norrk?ping area in Central Sweden. Validation was conducted of the analysis methods, such as reflectivity contouring and wind calculation from Doppler radial velocity using velocity azimuth display (VAD). The structure of the cloud system was identified as composed of a stratocumulus cloud layer, horizontally divided into two sectors of high reflectivity (>20 dBZ), oriented parallel to the surface occluded front, each extending around 80 km W-E and 50 km S-N. Embedded in these two precipitating areas were local regions of very high reflectivity (up to 50 dBZ), indicating the presence of scattered heavy precipitation and showers. The case study represents a test of the capabilities of single Doppler radar analysis techniques to be introduced in the next future into the operative forecasting environment in Italy.

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Riassunto Tecniche di analisi dei dati da singolo radar Doppler meteorologico vengono applicate allo studio di un fronte occluso associato alla fase terminale di decadimento di un'area ciclonica sulla verticale di Norrk?ping nel Sud della Svezia. Scopo principale dello studio è la validazione dei metodi di analisi dei dati, in particolare la mappatura dei campi di riflettività e il calcolo dei campi di vento dalla velocità radiale Doppler utilizzando il velocity azimuth display (VAD). Il sistema nuvoloso risulta costituito da stratocumuli ed è suddiviso in orizzontale in due settori di elevata riflettività (>20 dBZ), orientati parallelamente al fronte occluso e ciascuno con un'estensione intorno a 80 km in direzione W-E e 50 km in direzione S-N. I volumi ad elevata riflettività (fino a 50 dBZ) rinvenuti all'interno di queste due zone di precipitazione rivelano la presenza di intense precipitazioni isolate e di acquazzoni. Lo studio costituisce un test delle potenzialità delle tecniche di analisi dei dati da singolo radar Doppler, il quale dovrà essere quanto prima introdotto nel sistema di previsioni meteorologiche in Italia.

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Резюме Радарный анализ с использованием эффекта Доплера применяется к поглощенному фронту, связанному с последними стадиями циклонической активности над областью Норкёпинг в центральной Швеции. Оценивается применимость методов анализа, таких как построение контура отражательной способности и вычисление ветров из радиальной скорости Доплера, исполязуя индикатор азимута скорости. Определяется структура системы облаков, которая представляет слой слоистокучевых облаков, разделённый в горизонтальном направлении на два сектора с высокой отражательной способностью (>20 dBZ), ориентированных параллельно поверхности поглощённого фронта, простирающихся на расстояния порядка 80 км W-E и 50 км S-N. Внутри этих областей имеются области с очень высокой отражательной способностью (вплоть до 50 dBZ), что указывает на присутствие рассеивающих тяжёлых осадков и ливней. Исследованный случай представляет проверку возможностей техники радарного анализа с использованием простого эффекта Доплера для применения в будущем для оперативного прогнозирования окружающей среды в йталии.

     

Short analysis of rainfall trends in Friuli-Venezia Giulia from 1951 to 1986

Summary Annual and seasonal rainfall data taken in the period 1951–1986 have been spatially averaged over the region Friuli-Venezia Giulia and analysed with the aim of searching for the presence of trends. The results of the two rank tests recommended by the World Meteorological Organization (WMO) support the hypothesis of a decreasing trend in the autumn rainfall and, with less probability, an increasing trend in spring.     

Heat source reconstruction from noisy temperature fields using an optimised derivative Gaussian filter

The aim of this paper is to present a post-processing technique based on a derivative Gaussian filter to reconstruct heat source fields from temperature fields measured by infrared thermography. Heat sources can be deduced from temperature variations thanks to the heat diffusion equation. Filtering and differentiating are key-issues which are closely related here because the temperature fields which are processed are unavoidably noisy. We focus here only on the diffusion term because it is the most difficult term to estimate in the procedure, the reason being that it involves spatial second derivatives (a Laplacian for isotropic materials). This quantity can be reasonably estimated using a convolution of the temperature variation fields with second derivatives of a Gaussian function. The study is first based on synthetic temperature variation fields corrupted by added noise. The filter is optimised in order to reconstruct at best the heat source fields. The influence of both the dimension and the level of a localised heat source is discussed. Obtained results are also compared with another type of processing based on an averaging filter. The second part of this study presents an application to experimental temperature fields measured with an infrared camera on a thin plate in aluminium alloy. Heat sources are generated with an electric heating patch glued on the specimen surface. Heat source fields reconstructed from measured temperature fields are compared with the imposed heat sources. Obtained results illustrate the relevancy of the derivative Gaussian filter to reliably extract heat sources from noisy temperature fields for the experimental thermomechanics of materials.     

Long-term thermal storage: a parametric analysis of the thermal discharge of an embedded large-size storage tank

Summary It has been analysed the influence of some design parameters on the thermal discharge of a large-size thermal storage tank. The results that have been achieved can suggest satisfactory solutions from the economical as well as structural point of view in the plant's design.

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Riassunto è stata analizzata l'influenza di alcuni parametri di progetto sul raffreddamento di un accumulatore di calore di grandi dimensioni. I risultati consentono di indirizzare le scelte progettuali piú adeguate da compiersi sotto il profilo dei costi e della complessità strutturale dell'impianto.

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Nondimensional temperature and wind profiles and their changes under the influence of terrain and stability conditions

Summary The object of this paper is to present some of the results obtained by the analysis of the set of vertical profile measurements of momentum and temperature fluxes, of the mean wind speed and temperature. The conditions of validity of the Monin-Obukhov theory over a complex terrain are discussed. Paper presented at the GNFAO/EURASAP Meeting, Turin, September 1989. To speed up publication, proofs were not sent to the author and were supervised by the Scientific Committee.     

Study of the medium- and long-range transport analysing the data of the Chernobyl accident

Summary In the present work we analyse the meteorological factors that characterized the transport and deposition on the ground of the radionuclides from the Chernobyl nuclear power station over Northern Italy during the accident in April–May 1986. The aim of our study is to test some computational procedures and meteorological analyses specific for a comprehensive study of long-range pollution transport problem. By reconstructing the particle trajectories of the radioactive Chernobyl plume, we determined the most probable starting and arrival date of the plume and the level over the source. Moreover, analysis of the meteorological configuration up-and downwind the Alps permitted us to explain the temporal displacement between different kinds of measured fall-out.

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Riassunto Nel presente lavoro si analizzano i fattori meteorologici che hanno caratterizzato il trasporto e la deposizione sull'Italia Settentrionale del materiale radioattivo fuoriuscito dalla centrale nucleare di Chernobyl durante l'incidente di aprile-maggio 1986. Lo studio ha avuto come scopo quello di verificare e mettere a punto procedure di calcolo e di analisi di dati meteorologici finalizzate ai problemi di trasporto d'inquinanti a lunga distanza. La ricostruzione delle traiettorie percorse dalla nube radioattiva ha permesso di determinare la data di partenza e di arrivo piú probabile della nube e l'altezza di livellamento sopra la sorgente. Inoltre considerazioni sulla situazione meteorologica sopra e sottovento le Alpi hanno permesso di spiegare lo sfasamento temporale tra i diversi tipi di fall-out misurati.

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Резюме В этой работе мы анализируем метереологические факторы, которые характеризуют транспорт и оседание на землю радионуклидов в Севертоной Италии после аварии на Чернобыльской АЭС в апреля-мае 1986 г. Цель этой работы проверить некоторые вычислительные приемы и метереологический анализ, предлагаемые для исследования проблем транспорта загрязнений на большие расстояния. Реконструируя траектории частиц радиоактивного выброса в Чернобыле, мы определяем наиболее вероятные данные для выброса и уровня над источником. Более того, анаяиз метереологической ситуации в Альпах позволил объяснить временные смещение мезду различными типами измеренных радиоактивных выпадений.

     

Transport of Volcano Etna emissions towards the alpine region using ECMWF data

Summary ECMWF data have been utilised to study the Volcano Etna contribution to the sulphur deposition in the alpine region. Air mass trajectories starting from Etna during the whole 1989 have been computed. Firstly a cluster analysis was applied in order to objectively classify them. Then the total deposition (wet and dry) over Northern Italy of sulphur coming from Volcano Etna was estimated. Paper presented at the IX Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 8–10, 1992, Rome.     

Correlation effects obtained from optical spectra of Fe-pnictides using an extended Drude-Lorentz model analysis

We introduce an analysis model, an extended Drude–Lorentz model, and apply it to Fe-pnictide systems to extract their electron–boson spectral density functions (or correlation spectra). The extended Drude–Lorentz model consists of an extended Drude mode for describing correlated charge carriers and Lorentz modes for interband transitions. The extended Drude mode can be obtained by a reverse process starting from the electron–boson spectral density function and extending to the optical self-energy and, eventually, to the optical conductivity. Using the extended Drude–Lorentz model, we obtained the electron–boson spectral density functions of K-doped BaFe₂As₂ (Ba-122) at four different doping levels. We discuss the doping-dependent properties of the electron–boson spectral density function of K-doped Ba-122. We also can include pseudogap effects in the model using this approach. Therefore, this approach is very helpful for understanding and analyzing measured optical spectra of strongly correlated electron systems, including high-temperature superconductors (cuprates and Fe-pnictides).     

Physical and mathematical analysis of a wind model

Summary We have carried out a mathematical and physical analysis of the instabilities present in a one-layer wind model. The single terms of the basic equation have been discussed, pointing out their influence on the accuracy of the solution and their relationship to the possible instabilities. Possible improvements of the model in different directions are indicated in the final discussion.

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Riassunto Si effettua un’analisi matematica e fisica delle instabilità presenti nel modello del vento ad uno strato. Si discutono i singoli termini dell’equazione di base, sottolineando la loro influenza sulla accuratezza della soluzione e la loro relazione con le instabilità possibili. Nella discussione finale si indicano possibili miglioramenti del modello in diverse direzioni.

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Резюме Проводится математический и физический анализ неустойчивостей, возникающих в одно-слойной модели ветра. Обсуждаются отдельные члены базисного уравнения. Отмечается влияние этих членов на точность решения и их связь с возможными неустойчивостями. Указываются возможные улучцения обсуждаемой модели в различных напавлениях.

     

Low-cost and high-reliability control and data acquisition system for the operation of a solar plant with a long-term thermal storage capability

Summary A solar plant with a long-term thermal storage capability has been built up at the University of Calabria. In this paper it is described the control and data acquisition system for the operation of the plant. Some considerations on the control's schedule of the plant are developed.

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Riassunto Si descrive un sistema di controllo e acquisizione dati a basso costo ed elevata affidabilità per la gestione di un impianto solare dotato di accumulo di calore a lungo termine.

     

Spectral analysis and trend of total ozone observations at Vigna di Valle

Summary Time series analyses of measurements of total ozone make possible an in-depth climatological study of this important stratospheric gas. The Italian Air Force's Vigna di Valle Observatory (42°N, 12°E, 262 m a.s.l.) provided a time series of monthly averages (January 1958–December 1988) of total ozone. Spectral analysis and running averages were combined to detect medium-(QBOs of estimated (4÷5) DU amplitudes) and long-term fluctuations (possible correlation to 11-year solar cycle) and to filter them, leaving any overlapping trends unaltered. Total ozone trend estimates produced by the present study were +0.1% per decade for the 1959–1987 period and a decrease of −0.4% per decade for the more recent 1970–1987 span, over which a pronounced ozone depletion caused mainly by CFCs is assumed. This study has supported by the CNR-ENEL Project ?Interaction of energy system with human health and environment?.     

Evaluations of particulate mass loading from visibility observations and atmospheric turbidity measurements

Summary Three extinction models for urban aerosol particles, having Junge-type size distribution curves, were determined by using a very accurate computer programme based on Mie extinction theory for spherical particles. For each model, the volume extinction coefficients were calculated at seven visible and near-infra-red wave-lengths, for twenty-seven values of Junge parameter ranging from 1.8 to 4.4, and for five values of relative humidity from 0% to 85%. Moreover, the volume extinction coefficients produced by five monomodal models, based on log-normal size distribution curves for urban particles (composed of water-soluble substances, dustlike aerosol, and carbonaceous substances), were calculated at the seven wave-lengths and for five values of relative humidity from 0% to 90%. These monomodal models can be used to define bimodal and trimodal extinction models consisting of variable number fractions of small and large particles. Evaluations of the vertical particulate mass loading from sun photometer measurements and of particulate mass loading at ground level from visibility observations can be obtained by following the procedures suggested herein for both Junge-type and multimodal extinction models. Atmospheric turbidity and visibility measurements taken at various urban stations in the Po Valley were examined by means of the above procedures. The results show that in the cases in which ?ngstr?m's spectral exponent is relatively high (>1.3), Junge-type models give, reliable evaluations of the atmospheric particulate mass loading. In the other cases, the Junge-type extinction model and the bimodal models including the large urban particle mode can be used to determine the lower and the upper limits of particulate mass loading.

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Riassunto Tre modelli di estinzione per particelle atmosferiche di origine urbana, aventi curve di distribuzione dimensionale del tipo di Junge, sono stati definiti usando un programma di calcolo molto accurato per l'estinzione di Mie da parte di particelle sferiche. I coefficienti di estinzione di ogni modello sono stati determinati a sette lunghezze d'onda nel visibile e vicino infrarosso, per ventisette valori del parametro di Junge da 1.8 a 4.4 e per cinque valori dell'umidità relativa dallo 0% all'85%. Inoltre, i coefficienti di estinzione prodotti da cinque modelli monomodali, basati su curve log-normali della distribuzione dimensionale per particelle di tipo urbano (composte di sostanze solubili in acqua, polveri e sostanze carboniose), sono stati calcolati alle sette lunghezze d'onda e per cinque valori dell'umidità relativa dallo 0% al 90%. Questi modelli monomodali possono essere usati per definire modelli di estinzione bimodali e trimodali, composti da particelle di piccole e grandi dimensioni, in percentuali numeriche variabili. Seguendo i procedimenti da noi proposti sia per i modelli del tipo di Junge che per quelli multimodali, valutazioni realistiche del contenuto verticale della massa di particelle possono essere ricavate da misure di fotometria solare, mentre si possono ottenere buone stime del contenuto di massa per volume unitario al livello del suolo da osservazioni di visibilità. Diverse misure di torbidità atmosferica e visibilità eseguite in differenti località urbane della pianura padana sono state esaminate usando questi procedimenti. I risultati mostrano che nei casi in cui l'esponente spettrale di ?ngstr?m è relativamente alto (>1.3), i modelli del tipo di Junge forniscono stime affidabili del contenuto atmosferico di massa delle particelle. Negli altri casi, i modelli di estinzione del tipo di Junge e i modelli bimodali che contengono il modello monomodale di grandi particelle urbane possono essere usati per effettuare una stima di minima ed una di massima del contenuto atmosferico di massa delle particelle.