Vertical layering of photochemical ozone during land-sea breeze transport

Summary Recent theoretical and experimental studies have shown how local wind fields, such as the land-sea breeze circulation in coastal areas, influence the transport of oxidant precursors and the residence time and re-entry of photochemical compounds. Simple models usually do not take into account the vertical layering of pollutants, assuming a uniform concentration distribution within the boundary layer during transport processes. The present study reports the results of a monitoring survey conducted in an industrial coastal area to assess the time evolution of the vertical layering of ozone subject to land-sea breeze circulation in the boundary layer.     

Tropospheric ozone concentrations related to atmospheric conditions at Iza?a BAPMoN weather station, Canary Islands

Summary The 24h average concentrations of tropospheric ozone were measured in the BAPMoN (Background Atmospheric Pollution Monitoring Network) baseline station of Iza?a (Canary Islands, Spain). Concentrations were studied through a methologody based on nonparametric statistics. Three sectors of wind direction were selected and the air mass properties from these were characterized. The ozone concentration data were related to air masses in terms of aerometric elements. Highest values of ozone concentrations were found when the wind direction was from Sector I or Atlantic Sector because fair-weather conditions are associated with air flows from this sector and with long-range transport possibly from North Atlantic and Europe. Furthermore, the dependence of daily ozone concentration on some cloud types was investigated. Higher ozone concentrations were associated with high clouds having a lesser rate of depletion for solar radiation than middle and low clouds.     

Transport of photochemical ozone along the western Adriatic shore near a petrochemical plant

Summary During the warm months, the whole area surrounding Ravenna's petrochemical plant, which is about 5 km inshore of the northern Adriatic coast (Po Valley region), is subject to photochemical reactions producing high values of ozone concentration. The transport offshore of oxidants' precursors by the land breeze, photochemical reactions and subsequent transport inshore of oxidants by the sea breeze, may cause high concentrations of ozone along the coast up until the late evening. Similar phenomena have already been observed in other coastal regions. Classifying the ozone data into days with different circulations, the following can be seen: on days with W or NW circulation, a regular diurnal variation of ozone correlated with solar radiation is found; with winds from E or SE, the ozone variations are irregular and ozone concentrations can maintain high levels ((40÷70) p.p.b.) even during the nightime. This is a report of the results of several field measurements aimed at showing the ozone production and destruction processes, as well as its recirculation mechanisms under breeze conditions. Paper presented at the 1^o Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 19–22, 1984, Rome.     

Atmospheric stability of surface boundary layer in coastal region of the Wol–Ryong site

In order to provide statistically reliable information of a wind energy site, accurate analysis on the atmospheric stability and climate characteristics in a certain area is a prerequisite. Two 2-D ultrasonic anemometers and one cup anemometer, located perpendicular to the prevailing wind direction, were used to measure the atmospheric wind environment at a height of 4.5 m in coastal region of the Wol–Ryong, Jeju, South Korea. The study is aiming to understand the atmospheric stability about a coastal region, and the effect of roughness length. We calculate the Monin–Obukhov length for division of atmospheric stability about unstable regime, neutral regime and stable regime. The distribution of diurnal Monin–Obukhov length is highly sporadic in the coastal region due to the effect of radiant heat from the surface or other environmental effects. In order to calculate the roughness length in coastal region, three different methods are applied in terms of the surface roughness, flow fluctuation and gust wind, which are called logarithmic profile, standard deviation and gust factor methods. In the study, the atmospheric stability was insignificant when applying these three methods. In the results, three different roughness length scales sufficiently showed the effect of obstacle and surface conditions around the measurement position. On the basis of an overall analysis of the short-term data measured in the Wol–Ryong area, Jeju Island, it is concluded that for the development of future wind energy resources, the Wol–Ryong site could be a good candidate for a future wind energy site.     

An investigation of a possible dependence of brewer number 67''s total-ozone measurements on some atmospheric parameters, together with a presentation of a peculiar synoptic ozone case at Rome

Summary Brewer total ozone data (January–December 1992) measured at the Physics Department, Rome University ?La Sapienza? (41.9° North, 12.5° East) are analysed for dependence on Brewer internal temperature and some meteorological parameters. Non-parametric correlation analysis reveals the independence of total ozone from the internal Brewer temperature. Attention is focused on a peculiar case to show, by means of vertical wind velocity profile, the possible effects of lower stratospheric vertical advection on ozone fluctuations.     

Outline of marine currents in the bay of naples and some considerations on pollutant transport

Summary Many T, S, O₂, marine currents and meteorological data, observed with modern techniques and instruments, have been collected by the Institute of Meteorology and Oceanography in the Bay of Naples from 1977 on. Even, if the variability was large, some flow patterns were recognized as well as changes in the trend of currents: a periodicity of 3 to 7 days resulted all the year round with an oscillation of about 18 hours superimposed on it in summertime. The flow patterns resulted from current records and water mass analysis. When the open sea currents are flowing to SE the inner waters of the bay are cut off in a slow cyclonic gyre which leaves the coastal waters in a still slower motion making high pollutant concentration possible. The open sea currents flowing toward NW have branches entering into the bay which provide a fair renaewal of waters. The knowledge we have now of the South-Tyrrhenian surface marine currents indicates prevailing NW flow, hence giving one element in favour of a more or less active renewal of the waters in the bay. NE and WSW winds provided two simple models of water moving from the East coast toward the open sea: the former following the stress of the wind and the latter following the piling up of water along the coastal area. Paper presented at the 1° Congresso del Gruppo Nazionale per la Fisica del-l'Atmosfera e dell'Oceano, Roma, June 19–22, 1984.     

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.     

Features of the altitude-time distribution of ozone over Moscow during the strong ozone depletion in spring 2011 and during the statospheric warming in 2010 according to observations at millimeter wavelengths

The new observational data at millimeter wavelengths of the vertical distribution of stratospheric ozone over Moscow during the significant ozone depletion in the Northern Hemisphere in spring 2011 and during the circulation disturbance in the mid-winter sudden stratospheric warming in 2010 are presented. Significant interannual variations in the altitude distribution of ozone concentration are detected. The revealed significant ozone variations due to large-scale atmospheric processes show the importance of the monitoring of ozonosphere by radio physical methods for studying its evolution.     

Prawn biomonitors of nutrient and trace metal pollution along Asia-Pacific coastlines

To assess coastal ecosystem status and pollution baselines, prawns were collected from the commercial catches of eight Asia-Pacific countries (Australia, Bangladesh, Indonesia, Myanmar, Philippines, Pakistan, Sri Lanka and Thailand). Samples collected from 21 sites along regional coastlines were analysed for trace metal and stable isotopic compositions of H, C, N, O and S. A combination of simple averaging and multivariate analyses was used to evaluate the data. Sites could be assigned to easily recognise polluted and unpolluted groups based on the prawn results. Some filter-feeding clams were also collected and analysed together with the benthic-feeding prawns, and the prawns generally had lower trace metal burdens. Climate change effects were not strongly evident at this time, but altered ocean circulation and watershed run-off patterns accompanying future climate change are expected to change chemical patterns recorded by prawns along these and other coastlines. Stable isotopes, especially ¹⁵N, can help to distinguish between relatively polluted and unpolluted sites.     

A hybrid Lagrangian-Eulerian particle model for reacting pollutant dispersion in non-homogeneous non-isotropic turbulence

Lagrangian stochastic models are recognized as being powerful tools for pollutant dispersion at different scales in complex terrain and at different stability conditions. One of the still unresolved problems is the difficulty of including chemical reactions when, for example, NO₂ or O₃ concentrations have to be predicted in the presence of NO_x emissions. In this work, a Lagrangian stochastic (single particle) model is modified in order to account for simple chemical reactions and tested against measured data in a wind tunnel. It is well-known that, in the single particle models the trajectories are considered independent and hence the concentration correlations and fluctuations cannot be calculated. However, these models can be simply modified to account for the segregation throughout a proper parameterisation derived from measurements. Further, in order to avoid the use of the large amount of computational resources, which would be necessary due to the release of an high number of particles filling the whole domain, needed to reproduce the ozone background concentration, we mark the particles with a deficit of ozone instead of its concentration. A numerical experiment is carried out and the results of the comparisons between calculated and measured concentrations of different species are presented and discussed.     

Wind-Direction Estimation from Single X-Band Marine Radar Image Improvement by Utilizing the DWT and Azimuth-Scale Expansion Method

In this study, a method based on the discrete wavelet transform (DWT) and azimuth-scale expansion is presented to retrieve the sea-surface wind direction from a single X-band marine radar image. The algorithm first distinguishes rain-free and rain-contaminated radar images based on the occlusion zero-pixel percentage and then discards the rain-contaminated images. The radar image whose occlusion areas have been removed is decomposed into different low-frequency sub-images by the 2D DWT, and the appropriate low-frequency sub-image is selected. Images collected with a standard marine HH-polarized X-band radar operating at grazing incidence display a single intensity peak in the upwind direction. To overcome the influence of the occlusion area, before determining the wind direction, the data near the ship bow are shifted to expand the azimuth scale of the data. Finally, a harmonic function is least-square-fitted to the range-averaged radar return of the low-frequency sub-image as a function of the antenna look azimuth to determine the wind direction. Different from the wind-direction retrieval algorithms previously presented, this method is more suitable for sailing ships, as it functions well even if the radar data are heavily blocked. The results show that compared with the single-curve fitting algorithm, the algorithm based on DWT and azimuth-scale expansion can improve the wind-direction results in sailing ships, showing a reduction of 7.84° in the root-mean-square error with respect to the reference.     

Trend of Ozone in the free troposphere above Europe

Summary Ozone observations were made one century ago by the Sch?nbein technique at meteorological observatories in the alpine region. Within the intrinsic limitations of the technique, historical readings have been converted to present-time concentrations (p.p.b.v.). The evaluated ozone level in the free troposphere (17 p.p.b.v.) was twice as large as at the surface; comparable values were obtained by chemical and spectroscopic technique in the first half of our century. Furthermore, the reconstructed ozone trend in the free troposphere shows a sharp increase after the ’50s, as already observed at the surface at midlatitudes of the northern hemisphere.     

Experimental investigations and modelling studies of ozone producing corona discharges

The ozone generation by negative corona discharge in coaxial cylindrical system of electrodes have been studied experimentally in Ar+O₂ and N₂+O₂ mixtures. Both in argon and nitrogen mixtures with oxygen the monotonous decrease in ozone concentration [O₃] was observed at decreasing oxygen content in mixtures and the constant input energy density η. The rate coefficients for the ozone generation and ozone decomposition were obtained by fitting experimentally measured data [O₃]=f(η) with Vasiljev-Eremin formula. The calculated rate coefficient for ozone generation in N₂+O₂ mixtures at low content of oxygen (below 20%) was found considerably higher than that in Ar+O₂ mixtures. Increase in the rate coefficients for ozone generation and decomposition was observed with decreasing content of oxygen in both mixtures. The experimental results are in qualitative agreement with the simple model incorporating five main chemical processes in mechanism of ozone generation. The research was partially supported by Slovak Grant Agency under project 1/765920 The UK EPSRC (Grant GM/98944) and NATO Joint Project PST CLG 976544.     

Secondary-ion-mass spectrometry study on near-stoichiometric LiNbO3 strip waveguide fabricated by vapour transport equilibration and Ti co-diffusion

Secondary-ion-mass spectrometry was applied to study Ti-concentration profiles in the depth direction and on the surface of near-stoichiometric (NS) Ti:LiNbO₃ strip waveguides fabricated using vapour transport equilibration (VTE) and co-diffusion of Ti-metal strips. Results show that the profile of Ti concentration along the width direction on the waveguide surface can be well fitted by a sum of two error functions, while, in the depth direction, the Ti concentration follows either a complementary error function or a generalized Gaussian function. Surface Ti concentration, 1/e width and depth, mean diffusivities along the width and depth directions of the guide are, respectively, 1.04?×?10²¹?cm^–3, 8.5?µm, 6.3?µm, 0.18 and 0.1?µm²/h. Two-dimensional refractive index profile in the NS waveguides is indirectly constructed by assuming linearity between Ti-induced index change and Ti concentration. The surface refractive index increments at 1545?nm, Δn_o and Δn_e , are evaluated to be 3.132?×?10^–3 and 1.186?×?10^–2, respectively. All of the above-mentioned diffusion and optical parameters are compared with the corresponding data of the common congruent Ti:LiNbO₃ waveguide or NS waveguide fabricated starting from a NS substrate. The rationality of the assumed linear relationship between the index change and the Ti concentration is discussed. The results show that the assumed linearity remains controversial, and all expressions and data with regard to the refractive index are the approximate results and need to be verified by direct measurement on refractive index.     

Seasonal variation in natural abundance of δ13C and 15N in Salicornia brachiata Roxb. populations from a coastal area of India

High and fluctuating salinity is characteristic for coastal salt marshes, which strongly affect the physiology of halophytes consequently resulting in changes in stable isotope distribution. The natural abundance of stable isotopes (δ¹³C and δ¹⁵N) of the halophyte plant Salicornia brachiata and physico-chemical characteristics of soils were analysed in order to investigate the relationship of stable isotope distribution in different populations in a growing period in the coastal area of Gujarat, India. Aboveground and belowground biomass of S. brachiata was collected from six different populations at five times (September 2014, November 2014, January 2015, March 2015 and May 2015). The δ¹³C values in aboveground (?30.8 to ?23.6?‰, average: ?26.6?±?0.4?‰) and belowground biomass (?30.0 to ?23.1?‰, average: ?26.3?±?0.4?‰) were similar. The δ¹³C values were positively correlated with soil salinity and Na concentration, and negatively correlated with soil mineral nitrogen. The δ¹⁵N values of aboveground (6.7–16.1?‰, average: 9.6?±?0.4?‰) were comparatively higher than belowground biomass (5.4–13.2?‰, average: 7.8?±?0.3?‰). The δ¹⁵N values were negatively correlated with soil available P. We conclude that the variation in δ¹³C values of S. brachiata was possibly caused by soil salinity (associated Na content) and N limitation which demonstrates the potential of δ¹³C as an indicator of stress in plants.     

Elements for a comparison between the Tyrrhenian and Ligurian coastal currents during spring

Summary Hydrological and current measurements effected along the western Italian coasts permit to compare the main dynamical peculiarities of the coastal circulation of the Ligurian and Tyrrhenian basins, evidencing in particular their different response to atmospheric fluctuations. While the Ligurian currents show a great energy that depends essentially on the large-scale circulation, the Tyrrhenian shelf dynamics is characterized by a low thermohaline driven velocity, largely influenced by the local wind. Paper presented at the 1° Congresso del Gruppo Nazionale per la Fisica dell' Atmosfera e dell'Oceano, Rome, June 19–22, 1984.     

Wind field modifications due to an anemometer tower

Summary Variations in wind velocity and direction due to the mounting structure are studied using Gill anemometers mounted on 1.8 m long arms of a 232 m high tower. The tower ?shadowing? effect for the observed range, from 0 to 20 m/s, is in linear correlation with the velocity. The polar diagrams of the variations in wind speed and direction are presented as a function of the wind's direction. The horizontal component decreases by 15% when the anemometer is on the windward side of the tower, and by a maximum of 80% on the lee side. In the latter case the decrease is highly sensitive to wind direction. Variations in direction do not exceed 15 degrees. Paper presented at the IV Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 22–24, 1987, Rome.     

Elimination of zero-order diffraction in digital off-axis holography

A simple experimental method of eliminating zero-order diffraction in the reconstructed image of off-axis digital holography is presented. Holographic diffraction grating acting as a beam splitter, an off-axis holography system is formed. The holograms of object with different recording parameters are obtained by adjusting the reflecting mirror in the recording optical system to vary the incidence orientation of the object beam in CCD to introduce a phase shift. The zero-order image can be eliminated by numerically processing the holograms of object with different recording parameters. The theoretical analyses have been done in detail and the experimental results are also given. The zero-order image eliminated, the area of reconstructed image increases remarkably, the image quality can then be significantly improved and the better resolution obtained. The experimental results show that the method presented in this paper is feasible, simple in optical system and easy in operation and data processing.     

Elemental characterization of airborne particles in Khartoum,Sudan

The aim of this study was to investigate the elemental composition of airborne particles in the Khartoum area, particularly small inhalable particles of diameter ≤10 µm. Aerosol particles were collected during the period April–May 2001. The sampling was done using a dichotomous virtual impactor capable of separating airborne particles <2.5 µm in a fine mode and 2.5–10 µm particles in a coarse mode. Energy‐dispersive x‐ray fluorescence analysis was used to determine the elemental concentrations of 14 elements in the samples. Concentrations of black carbon were also measured on the two size fractions. The results obtained were compared with previous data from Khartoum and other African locations. Si, K, Ca, Ti, Mn, Fe, Zn and Sr were found to be dominant in the collected particulates. Day period collections were found to have higher elemental concentrations than those of night periods. This is attributed to higher traffic levels and wind speeds. The results show that dust aerosol transport and resuspension are the main sources that affect the quality of ambient air in the Khartoum area. The elemental concentrations from anthropogenic sources are generally low. Copyright © 2004 John Wiley & Sons, Ltd.     

船舶运动状态下风速风向测量补偿与数字仿真

为了研究船舶运动状态下的风速风向精确测量,设计了一种船舶风速风向动态测量及误差补偿的数字仿真系统。通过对船舶航行状态下的风速风向测量原理进行分析,建立了船舶平面运动的相对风速风向和真风风速风向的解算模型,并根据船舶空间运动的风速风向测量及其误差补偿算法,对船舶横摇、纵摇状态下的风速风向的动态测量和误差补偿进行了数字仿真。数字仿真结果表明,该方法能够消除船舶航行时的运动姿态对风速风向测量带来的影响,为船舶的操纵控制和航行安全提供了精确和可靠的风速风向数据信息。