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Siloxanes have been found widespread usages in our daily lives, but the knowledge on their migration, transformation and toxicity is still limited. Herein we explored the feasibility of using one-sided silica coated paper as filter membrane to capture siloxanes in the outdoor air, followed by direct mass spectrometric analysis. In contrast to mostly utilized fiber membrane, silica coated paper not only exhibited a higher selective sampling efficiency to three siloxanes with structures of H–[Si(CH3)2–O]7-9-NH2 from air, but also possessed a high tolerance to organic solvent during mass spectrometric analysis. Due to the above features, the analysis sensitivity of those siloxanes with silica coated paper has been improved 3.1–134.8 folds in contrast to those with commercial filter membrane. Furthermore, we monitored variation in the levels of those siloxanes for a period of one month, and found that a close association (R2 = 0.7924–0.9559) existed between their contents and climate parameters (e.g., temperature, weather, atmospheric pressure, humidity, wind direction and wind speed) as well as sampling volume. These knowledge provides a facile and effective methodology to both high-efficient sampling siloxanes and environmental assessment of siloxanes according to climate parameters.

This technical note documents the use of paper as electrospray emitters. The porous structure of the paper automatically delivers the liquid by capillary effects without the need of a mechanical pump. The liquid flow rate can be approximately quantified using Washburn equation. Despite the limited durability, paper-based electrospray emitters exhibit unique features such as ease of multiplexing, self-regulated liquid supply without need of pumps, ultra-low cost, and versatility provided through origami.

The obnoxious odors generated from pulp and paper industries have been the cause of nuisance since the instigation of these industries. The objective of the study was to develop a metal oxide sensor based electronic nose for rapid measurement of odorant concentration and associated odor intensity of major reduced sulfur compounds emitted from different sources of these pulp and paper mills. The gas samples collected from the surroundings of major source points of industry were exposed to sensor array of the electronic nose and the change in voltage was measured and taken to PC through data acquisition cards. The same sets of samples were also tested with gas chromatography. The results of electronic nose and GC-FPD were correlated using response surface methodology to know the odorant concentration. The model fed with unknown industrial samples had more than 95% prediction capability. To determine odor intensity by electronic nose firstly a collective index was generated using SVD based 2-norm method (e-nose index) proportional to the sensors response relative to reference gas, methyl mercaptan. Secondly the e-nose index was associated with human expert evaluations. The training of the electronic nose enabled it to predict odorant concentration found at the industrial site and associated odor intensity in methyl mercaptan equivalent. The overall results of the experiments carried out suggest the potential of electronic nose as a device for on or off line measurement of odorant concentration and odor intensity.

Levoglucosan is used as a tracer of biomass burning; however, its determination often requires expensive analytical techniques. Therefore, this study describes the development of an inexpensive and useful method using paper-based analytical devices (PADs) to determine levoglucosan based on colorimetric measurements. The color intensities were correlated with the analytical concentrations and presented linear behavior in the range from 0 to 64.8 μg mL−1. The achieved limits of detection and quantification were 2 and 6 μg mL−1, respectively. The conversion rate of levoglucosan into glucose was 81 ± 8% and the average recovery was 105 ± 9%. Moreover, the method presented selectivity for levoglucosan, showing variation in colorimetric signal intensity lower than 8% in the presence of other saccharides (xylose, glucose, galactose, maltose, mannose, arabinose, and fructose). The accuracy of the method was confirmed by comparison with gas chromatography-mass spectrometry. The proposed method was explored to determine levoglucosan in samples of atmospheric particulate matter collected in Goiania city (Brazil) and the values ranged from 0.08 to 1.10 μg m−3, showing the high impact of the biomass burning to the particulate matter in the region's atmosphere. The method was also used to detect levoglucosan in rainwater samples. Therefore, the use of PADs can simplify fieldwork involving the determination of levoglucosan in atmospheric particulate matter.

In this communication we provide our answers to the comments by Usoskin (2017) on our recent paper (Popova et al, 2017a). We show that Principal Component Analysis (PCA) allows us to derive eigen vectors with eigen values assigned to variance of solar magnetic field waves from full disk solar magnetograms obtained in cycles 21–23 which came in pairs. The current paper (Popova et al, 2017a) adds the second pair of magnetic waves generated by quadruple magnetic sources. This allows us to recover a centennial cycle, in addition to the grand cycle, and to produce a closer fit to the solar and terrestrial activity features in the past millennium.

Acidity is a critical characteristic of aerosol particles that impacts many atmospheric chemical reactions. However, the measurement of aerosol acidity remains challenging because of the high ionic strength of atmospheric aerosol particles. In this study, we developed and evaluated a direct method for measuring the pH of atmospheric aerosol samples using pH testing paper. We first examined the color responses of six pH testing papers under various ionic strengths and selected the best performing paper for further testing at higher ionic strength. This paper was then tested under realistic high-ionic-strength conditions created using hygroscopic equilibrium under high and constant relative humidity (RH). A KNO3 saturated solution was used to maintain an RH of 92% in an airtight box. Under these conditions, the hygroscopic constituents in aerosol particles form droplets of aqueous solutions that possess high ionic strength. On the basis of these results, a method for the direct pH measurement of aerosol particle samples was developed. The pH of the atmospheric aerosol samples was measured using this method under high RH to demonstrate its versatility. Our results indicate that this method requires more than approximately 12 μg per spot of fine (PM0.2–2.0 in this study) particles to form a detectable droplet. Compared with previous methods, our direct pH measurement method is simpler, more convenient, and reliable for wide application without excess dilution in practice, and it may be used to obtain important basic information required to study atmospheric aerosols.

On-site measurement of methanethiol (CH 3 SH) was performed for three years on ships and cars near a pulp and paper plant standing on the shore of Lake Baikal in Siberia, Russia, to investigate the behavior and impact of atmospheric CH 3 SH emitted from a point source. Despite its strong odor, there are few reports on atmospheric CH 3 SH, while many investigations have been carried out on dimethyl sulfide (DMS). In this work, CH 3 SH and DMS were measured every 15 min by a recently developed automated instrument based on single column trapping/separation and chemiluminescence measurement. Hydrogen sulfide, sulfur dioxide and ozone were also measured simultaneously by individual instruments. Of these sulfur compounds, CH 3 SH was dominant and its concentration sometimes reached several tens of ppbv. The concentration of CH 3 SH was high at night, because of the lack of photodecomposition and local winds from the mountain to the lake. Such time variation was marked in the summer. The CH 3 SH level decreased significantly downwind, while decreases in concentrations of other compounds such as DMS and SO 2 were relatively small. From these temporal and spatial variations, the behavior of CH 3 SH is described in this paper. The impact of CH 3 SH near the Siberian big sources is discussed with the presented data.

This paper describes the results of comprehensive empirical studies of the inherent optical properties (IOPs), the remote sensing reflectance R rs (λ) and the contents of the principal optically active components (OAC) i.e. coloured dissolved organic matter (CDOM), suspended particulate matter (SPM) and chlorophyll a , in the waters of 15 lakes in Polish Pomerania in 2007–2010. It presents numerous spectra of the total absorption a (λ) and scattering b (λ) ≈ b p (λ) of light in the visible band (400–700 nm) for surface waters, and separately, spectra of absorption by CDOM a CDOM (λ) and spectra of the mass-specific coefficients of absorption a * (SPM) p (λ) and scattering b * (SPM) p (λ) by SPM. The properties of these lake waters are highly diverse, but all of them can be classified as Case 2 waters (according to the optical classification by Morel & Prieur 1977) and they all have a relatively high OAC content. The lakes were conventionally divided into three types: Type I lakes have the lowest OAC concentrations (chlorophyll concentration C a = (8.76 ± 7.4) mg m −3 and CDOM absorption coefficients a CDOM (440) = (0.57 ± 0.22) m −1 (i.e. mean and standard deviation), and optical properties (including spectra of R rs (λ)) resembling those of Baltic waters. Type II waters have exceptionally high contents of CDOM ( a CDOM (440) = (15.37 ± 1.54) m −1 ), and hence appear brown in daylight and have very low reflectances R rs (λ) (of the order of 0.001 sr −1 ). Type III waters are highly eutrophic and contain large amounts of suspended matter, including phytoplankton ( C SPM = (47.0 ± 39.4) g m −3 , C a = (86.6 ± 61.5) mg m −3 ; a CDOM (440) = (2.77 ± 0.86) m −1 ). Hence the reflectances R rs (λ) of these type of waters are on average one order of magnitude higher than those of the other natural waters, reaching maximum values of 0.03 sr −1 in λ bands 560–580 nm and 690–720 nm (see Ficek et al. 2011). The article provides a number of empirical formulas approximating the relationships between the properties of these lake waters.

The paper describes the hydrodynamic part of the coupled ice-ocean model that also includes the ecosystem predictive model. The Baltic Sea model is based on the Community Earth System Model (CESM from NCAR – National Centre for Atmospheric Research). CESM was adopted for the Baltic Sea as a coupled sea-ice model. It consists of the Community Ice CodE (CICE, model version 4.0) and the Parallel Ocean Program (POP, version 2.1). The models are linked through a coupler (CPL7), which is based on the Model Coupling Toolkit (MCT) library. The current horizontal resolution is about 2 km (1/48 degrees). The ocean model has 21 vertical levels and is forced by atmospheric fields from the European Centre for Medium Weather Forecast (ECMWF). A preliminary validation of the hydrodynamic module with in situ measurements and reanalysis from My Ocean ( http://www.myocean.eu ) has also been done. In the operational mode, 48-hour atmospheric forecasts provided by the UM model from the Interdisciplinary Centre for Mathematical and Computational Modelling of Warsaw University (ICM) are used. The variables presented on the website in real time for a 48-hour forecast are temperature, salinity, currents, sea surface height, ice thickness and ice coverage ( http://deep.iopan.gda.pl/CEMBaltic/newlay/index.php ). The embedded model of the marine ecosystem, like ice, is not taken into account in this paper.

Cooling tower emissions are harmful for several reasons such as air polluting, wetting, icing and solid particle deposition, but mainly due to human health hazards (i.e. Legionella). There are several methods for measuring drift drops. This paper is focussed on the sensitive paper technique, which is suitable in low drift scenarios and real conditions. The lack of an automatic classification method motivated the development of a digital image process algorithm for the Sensitive Paper method. This paper presents a detailed description of this method, in which, drop-like elements are identified by means of the Canny edge detector combined with some morphological operations. Afterwards, the application of a J48 decision tree is proposed as one of the most relevant contributions. This classification method allows us to discern between stains whose origin is a drop and stains whose origin is not a drop. The method is applied to a real case and results are presented in terms of drift and PM10 emissions. This involves the calculation of the main features of the droplet distribution at the cooling tower exit surface in terms of drop size distribution data, cumulative mass distribution curve and characteristic drop diameters. The Log-normal and the Rosin–Rammler distribution functions have been fitted to the experimental data collected in the tests and it can been concluded that the first one is the most suitable for experimental data among the functions tested (whereas the second one is less suitable). Realistic PM10 calculations include the measurement of drift emissions and Total Dissolved Solids as well as the size and number of drops. Results are compared to the method proposed by the U.S. Environmental Protection Agency assessing its overestimation. Drift emissions have found to be 0.0517% of the recirculating water, which is over the Spanish standards limit (0.05%).

The concentration of polycyclic aromatic hydrocarbons (PAHs) in the ambient air from a massive open burning of joss paper was simultaneously measured at an open-burning site (OS) and a downwind site (DS) from 6 to 8 August 2006. A total of 16 major PAHs (particle-bound and gas-phase) concentrations were extracted by the Soxhlet analytical method and analyzed by gas chromatography. The dominant PAHs of the total mass of the organic compound at both the sampling sites were low-molecular-weight species. Further, the results showed that the start burning/end burning-dominant PAH concentration ratios at the OS and DS were 10 and 6.2, respectively. Diagnostic ratios were also used in this study to characterize and identify the PAH emission sources. The results suggest that the characterization of air pollutants emitted from open-burning joss paper lies between furnace-burning joss paper and wood combustion.

This paper is the second part of the description of the first stage of the SatBaltyk project’s implementation. Part 1 (Woźniak et al. 2011, in this issue) presents the assumptions and objectives of SatBaltyk and describes the most important stages in the history of our research, which is the foundation of this project. It also discusses the operation and general structure of the SatBaltyk system. Part 2 addresses various aspects of the practical applicability of the SatBaltyk Operational System to Baltic ecosystem monitoring. Examples are given of the Baltic’s characteristics estimated using the preliminary versions of the algorithms in this Operational System. At the current stage of research, these algorithms apply mainly to the characteristics of the solar energy influx and the distribution of this energy among the various processes taking place in the atmosphere-sea system, and also to the radiation balance of the sea surface, the irradiance conditions for photosynthesis and the condition of plant communities in the water, sea surface temperature distributions and some other marine phenomena correlated with this temperature. Monitoring results obtained with these preliminary algorithms are exemplified in the form of distribution maps of selected abiotic parameters of the Baltic, as well as structural and functional characteristics of this ecosystem governed by these parameters in the Baltic’s many basins. The maps cover practically the whole area of the Baltic Sea. Also given are results of preliminary inspections of the accuracy of the magnitudes shown on the maps. In actual fact, the errors of these estimates are relatively small. The further practical application of this set of algorithms (to be gradually made more specific) is therefore entirely justified as the basis of the SatBaltyk system for the effective operational monitoring of the state and functioning of Baltic ecosystems. This article also outlines the plans for extending SatBaltyk to include the recording of the effects and hazards caused by current and expected storm events in the Polish coastal zone.

Levin et al. (2010 ; hereafter LHA) (Levin, Z., Halfon, N., Alpert, P., 2010. Reassessment of rain experiments and operations in Israel including synoptic considerations. Atmos. Res. 97, 513–525. DOI:10.1016/j.atmosres.2010.06.011.), reanalyzed the results of the operational seeding in northern Israel between 1975 and 2007 and the preceding Israel 2 cloud seeding experiment (1969–1975) and concluded that there is no net increase in precipitation over the target areas. Our analysis revealed that a synoptic bias during Israel 2 is one of the reasons for the apparent positive effect of seeding in the northern target area and the negative effect in the southern area both of which disappeared in the following experiment in the south (Israel 3; 1975–1995) and the operational seeding in the north. Ben-Zvi et al. (2010 ;hereafter BRG) criticized our paper primarily on the ground that we did not consider the positive results of Israel 1 experiment (1960–1967). It should be noted that in Israel 1 different seeding lines were used from those in both Israel 2 and the operational period. In addition, its raw data is not accessible anymore for reanalysis. Furthermore, Israel 2 had been designed as a confirmatory cross-over experiment to Israel 1 and failed to reproduce its promising results with double ratio (DR) of ~ 1.00, namely, zero rainfall enhancements. The same DR values were also found in Israel 3 and in the operational seeding. Therefore, because of the differences in the two experiments, the lack of access to the raw data and the disappointing results of the confirmatory experiment, we decided to concentrate our analysis on the more recent seeding activities. The attempt by BRG to explain the reduction of the DR to ~ 1.00 in the operational seeding period by the suppression due to pollution have been disproved by Alpert et al. (2008, 2009) and also fail to explain the sharp decline of the target/control ratio right at the beginning of the operational seeding period when the lucky draw in this area came to its end (see LHA).

In 2001–2007 aerosols were measured in the coastal zone (11 campaigns) and over the open waters of the Gdansk Basin (southern Baltic) (5 campaigns). The marine aerosols contained nitrogen and sulphur compounds, which increased their acidity. This situation intensified during the cool months of the year, when fossil fuel emissions were higher, proportionate to energy and heat requirements. Irrespective of the season, these acidic aerosols were neutralized in the reaction with sea salt. The likelihood of sodium nitrate being formed increased at air humidities > 80% and nitrate concentrations > 30 nmol m− 3. Sodium sulphate was present in aerosols mostly in autumn and winter, with northerly advection, and at the highest wind speeds. The excess of free ammonia resulted in the formation of ammonium sulphate and ammonium nitrate in aerosols over the southern Baltic.

During five campaigns at sea and 11 on land in 2001–2007, aerosols were measured in the coastal zone and over the open sea in the Gdansk Basin (southern Baltic). Sea salt concentrations were high both over Gdynia (2.0–12.2 μ g m − 3 ) and at sea (1.3–14.5 μ g m − 3 ). The intensity of the generation and transport of marine aerosols increased exponentially with wind speeds > 5 m s − 1 over land and > 3 m s − 1 over the Gulf of Gdansk, this being most noticeable with Baltic and oceanic advection. Sea breezes were conducive to the transport of marine aerosols over land areas. The sea was also the origin of both sea salt and non-sea salt sulphate aerosols. An interesting increase in the proportion of non-sea salt-related sulphates (86.7%) was observed in spring, when the biological processes in the sea were more intense.

The emissions of polycyclic aromatic hydrocarbons (PAHs) were quantified for two joss paper furnaces burning two kinds of joss papers (recycled paper made and virgin bamboo made). A cyclone and a wet scrubber were installed in series on one of the two furnaces. Particulate and gaseous PAHs were collected with a sampling system meeting the criteria of U.S. EPA Modified Method 5. Twenty-one species of PAH were analyzed by GC/MS. Individual PAH emission factors vary from less than 1 mg kg −1 fuel to several tens of mg kg −1 fuel. The total (sum of 21 compounds) and the carcinogenic PAH (benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indeno[1,2,3,-cd]pyrene, dibenz[a,h]anthracene) emission factors were not statistically different for the two furnaces and averaged 71.0 and 3.2 mg kg −1 , respectively. The PAH profiles showed a predominance of naphthalene (58.1%), phenanthrene (11.7%) and fluorene (7.5%). Of the two joss papers examined, bamboo-made joss paper showed less emission in both particulate and gaseous PAHs. For particulate and gaseous PAHs, the removal efficiencies of total PAHs by the air pollution control devices were 42.5% and 11.7%, respectively. PAH emission factors in high airflow conditions were generally lower than those in low airflow condition.

The influence of the near-water wind field on the radiance of a marine shallow was studied on the basis of daily SeaWiFS ocean colour scanner data and QuickScat scatterometer wind data collected from 1999 to 2004 in the southern Caspian Sea, where the deep basin borders a vast shallow west of the shore of meridional extent. It was found that radiance distributions, clustered by wind rhumbs, exhibited different long-term mean patterns for winds of opposing directions: within the shallow’s boundaries, the radiances were about twice as high for winds having an offshore component with reference to the onshore wind conditions. The zonal profile of radiance across the shallow resembled a closed loop whose upper and lower branches corresponded to the offshore and onshore winds respectively. The loop was the most pronounced at sites with 10–15 m of water for any wavelength of light, including the red region. On the basis of specific features of the study area, we attributed this pattern to sunlight backscattered from bottom sediments resuspended by bottom compensation currents induced by the offshore winds.

A primary production model for the Barents Sea shows a hot spot of organic carbon settlement to the sea bed over 100 km long, a shallow pile of highly permeable sediments (mainly large Balanus , Mya and Pecten shell fragments over 1 cm in size) of glacial origin. Hydrodynamic flow models suggest an intensive, deep flow of near-bottom waters into the sediment. Depending on wave height, water in shallow (30 m depth) places may percolate more than 5 m into the sediment. During 10 days of stormy weather as much as 4 to 8 kg wet weight pelagic biomass can be processed per square metre through this extremely permeable sediment. Analogous processes known in coastal waters lead to intense biocatalytic phenomena and metabolism of organic carbon within the seabed, estimated here as more intense than surface consumption. Spitsbergenbanken may be acting as a huge sink for organic carbon and an important source of nutrients in one of the most productive areas of the North Atlantic.

The remote sensing reflectance R rs , concentrations of chlorophyll a and other pigments C i , suspended particulate matter concentrations C SPM and coloured dissolved organic matter absorption coefficient a CDOM (λ) were measured in the euphotic zones of 15 Pomeranian lakes in 2007–2010. On the basis of 235 sets of data points obtained from simultaneous estimates of these quantities, we classified the lake waters into three types. The first one, with the lowest a CDOM (440 nm) (usually between 0.1 and 1.3 m −1 and chlorophyll a concentrations 1.3 C a −3 ), displays a broad peak on the reflectance spectrum at 560–580 nm and resembles the shape of the remote sensing reflectance spectra usually observed in the Baltic Proper. A set of R rs spectra from the Baltic Proper is given for comparison. The second lake water type has a very high CDOM absorption coefficient (usually a CDOM (440 nm) > 10 m −1 , up to 17.4 m −1 in Lake Pyszne; it has a relatively low reflectance ( R rs −1 ) over the entire spectral range, and two visible reflectance spectra peaks at ca 650 and 690–710 nm. The third type of lake water represents waters with a lower CDOM absorption coefficient (usually a CDOM (440 nm) −1 ) and a high chlorophyll a concentration (usually C a > 4 mg m −3 , up to 336 mg m −3 in Lake Gardno). The remote sensing reflectance spectra in these waters always exhibit three peaks ( R rs > 0.005 sr −1 ): a broad one at 560–580 nm, a smaller one at ca 650 nm and a well-pronounced one at 690–720 nm. These R rs (λ) peaks correspond to the relatively low absorption of light by the various optically active components of the lake water and the considerable scattering (over the entire spectral range investigated) due to the high SPM concentrations there. The remote sensing maximum at λ ≈ 690–720 nm is higher still as a result of the natural fluorescence of chlorophyll a . Empirical relationships between the spectral reflectance band ratios at selected wavelengths and the various optically active components for these lake waters are also established: for example, the chlorophyll a concentration in surface water layer C a = 6.432 e 4.556 X , where X = [max R rs (695 ≤ λ ≤ 720) – R rs (λ = 670)]/max R rs (695 ≤ λ ≤ 720), and the coefficient of determination R 2 = 0.95.

By analyzing COSMIC data, Sharma et al. (2010) found more than 50% reduction in electron density during a solar eclipse at the F2-layer and above, with the peak of similar to 70% at 370 km. So great eclipse effect on topside ionosphere was very abnormal and much different from previous studies. However, by comparing the cosmic data with IRI results, we find that the abnormal reduction comes mainly from the significant local time variation at sunrise, not from the eclipse effect. Furthermore, we simulated the eclipse effect by using a theoretical model to confirm our analysis. (C) 2011 Elsevier Ltd. All rights reserved.

A lifecycle assessment to estimate greenhouse gas emissions in Australia from the paper cycle is summarised. The greenhouse gas emissions from paper in Australia in 1999/2000 were estimated to be 12.1 million tonnes (Mt) of CO2 equivalent. Nearly half of this amount consisted of CH4 emissions from landfilled waste paper. Various waste management options were modelled to investigate the greenhouse impact of a tonne of paper over its whole lifecycle. Options that keep paper out of landfills significantly reduce greenhouse emissions, waste-to-energy recovery being most effective. Recycling is also beneficial, and is of particular interest from a management perspective because it can be controlled by the pulp and paper industry. These findings can be extended to other wood-based and organic wastes.

Ash formation during industrial-scale bubbling fluidized bed (BFB) and circulating fluidized-bed (CFB) combustion of bark, waste wood and paper mill sludges has been studied. The principal ash formation mechanism was the sintering of 0.2–4 μ m paper filler mineral particles into larger, porous ash agglomerates from 10 to 200 μ m in size which dominated the fly ash total mass and specific surface area. Fly ash total mass concentration at the electrostatic precipitator inlet conditions varied from 4.5 g N -1 m -3 at BFB to 8.3 g N -1 m -3 at CFB while the respective total surface area concentrations as determined with nitrogen absorption were 32 and 83 m 2 N -1 m -3 . During bark combustion in the BFB, we observed an ultrafine mode at 0.05 μ m consisting of spherical particles and their chain-type agglomerates. Ultrafine mode mass and surface area concentrations were 3 and 0.1 m 2 N -1 m -3 , respectively, as determined with the electrical low-pressure impactor and with the differential mobility analyzer. Ultrafine particles were formed via nucleation of volatilized ash species followed by particle growth via collision and coalescence and via vapor condensation. During waste wood combustion in the CFB, ultrafine particle concentration was significantly lower than during bark combustion in BFB, indicating reduced ash volatilization during CFB combustion. When co-firing sludge with bark in the BFB and with waste wood in the CFB ultrafine particle concentration was further reduced. Results from continuous aerosol measurements by the electrical low-pressure impactor (ELPI), by the scanning differential mobility analyzer (SMPS) and by the tapered element oscillating microbalance (TEOM) as the function of BFB process conditions suggest that co-combustion of sludge reduces significantly the ultrafine particle formation rate. No significant enrichment of alkali and trace metals in the ultrafine particles was observed.

This short note is a reply to the comments by Le et al. (accepted for publication) on the paper by Sharma et al. (2010) that is concerned with the eclipse time observation of ionospheric TEC and electron density.

Massman in his paper derives an analytical formula for eddy covariance flux corrections, based on equivalent first-order co-spectral transfer functions both at low and high frequencies. At low frequencies flux attenuation due to digital recursive filtering, frequently applied in eddy covariance systems for trend removal, and spectral cut off due to finite averaging time were considered. This comment discusses the form of the transfer function of high-pass digital recursive filter and consequences of block averaging on flux estimate.

In this paper several statements of Kandlikar and Ramachandran concerning the one-to-one correspondence between the spectrometric channels and aerosol size classes, overlaps of the kernels of integral equation, errors of the algebraic systems’ solutions and some inversion algorithms are discussed. It is shown that expression A −1 e ( A -linear algebraic system matrix, e -vector of the experimental errors) cannot be interpreted as the standard deviation of random errors and its adequate interpretation is given. The expressions for standard deviation of the system's solution are derived using the error propagation formula. It is indicated that known inequality for the errors of linear systems’ solutions including condition number of matrix cond is not applicable to the random errors, and the new inequality is given. The approach of smooth continuous size distribution function concept is shown to meet with difficulties since its actual realization is discrete, stochastic and has only two values: 0 and 1.

High ozone levels are regularly reached during summer period in South-European urban areas, calling for careful design of primary pollutants emission reduction strategies. In this perspective the CALGRID modelling system has been applied to Milan metropolitan area, located in the Po Valley, the most industrialised and populated area in Italy. For the first modelling exercise, a simulation domain of 100×100 km2 has been considered and a summer period, characterised by high photochemical activity, has been selected. Hourly emissions have been derived by spatially and temporally disaggregating national inventories data, while standard upper-air and ground-based meteorological data have been used as input to the CALMET pre-processor. A careful analysis of simulation results versus local network monitoring data has revealed some critical points, related to both modelling assumptions and practical data availability. A satisfactory reproduction of daytime ozone behaviour has been, in fact, accomplished, both in urban and suburban sites, while nighttime primary pollutants accumulations and consequent ozone consumption simulated by the model have not found correspondence in the measurements. Nitrogen dioxide has been also successfully modelled, mostly in city surroundings, whereas higher discrepancies have been found in some urban stations. Possible explanations of these facts are discussed in the paper, giving an insight for further work.

We examine the analysis by Lee (1998) of the scalar conservation budget in advective flows. Lee treated the budget in a one-dimensional framework, neglected horizontal derivatives of turbulent quantities and proposed that mean flow advection, simplified to its vertical component, can be used to improve budget closure, when data from only a single tower are available. We conclude: • that the appropriate analysis framework for constructing such budgets is unavoidably two- or three-dimensional because 2D and 3D mean velocity fields always induce streamwise variation in the eddy fluxes of scalars. • that in such flow fields it is generally incorrect to assume that the vertical component of advection w ∂ c /∂z is everywhere much larger than the horizontal component u ∂ c /∂x The vertical component can only provide a good measure of total advective flux divergence in the special circumstance where the tower is located beneath the vertical stagnation streamline of a recirculating flow. By referring to a linear model of scalar transport over a hill we show that the relationship between u ∂ c /∂x and w ∂ c /∂z is entirely dependent on particular flow conditions and that, in general, w ∂ c /∂z cannot even be used to provide a bound on the magnitude of total advection. • that for measurements at heights small compared to the horizontal scale of the advective flow, the horizontal gradient of turbulent flux ∂ u’c’ /∂x can probably be neglected relative to its vertical equivalent ∂ w’c’ /∂z and, • by using simple hydrodynamic models of 2D flows it can be shown that the vertical gradient of mean vertical velocity is approximately constant over tower heights small compared to the horizontal scale of the advective flow. We also comment on the proper choice of coordinate frame for analysis.

Relationship between latex yield of natural rubber trees (Hevea brasiliensis) and climatic variables have been derived. Under humid tropical rainfed conditions, observed latex yields of rubber trees (clone RRII 105) are highly variable from 19.8 to 90.5 g per tree per tap. Maximum temperature experienced during 1 day, 7 days and 30 days prior to the tapping explains about 32%, 42% and 64%, respectively, of the day-to-day variability in latex yields. The multiple regression models to estimate latex yield on a tapping day, with different antecedent weather conditions are developed. The weekly weather conditions associated with optimum yields were maximum temperature of 30.4°C, minimum temperature of 22.8°C, 5.9 h sunshine and 72 mm of rainfall. Any deviation from these meteorological conditions up to 6 months duration may significantly influence latex production. In general, maximum temperature, sunshine duration, vapour pressure deficit and pan evaporation showed significant negative correlation with yield, irrespective of the time period considered. Whereas, significant positive association was observed between rainfall beyond a month period and the latex yield of rubber trees.

Gardner (1996, henceforth G96), examines a number of theories that seek to account for the vertical-wavenumber (m) spectrum of horizontal wind perturbations (u′) induced by gravity waves in the middle atmosphere. He notes that all the theories predict much the same spectra, and so he seeks to “identify the experimental data required to test the fundamental physics upon which these theories are based …” While I applaud Gardner's goal and will at a later stage contribute to it, I must first comment adversely on some aspects of his preliminary summaries and of his observational inferences. My remarks are limited almost exclusively to his discussion of the linear instability theory of Dewan and Good (1986, henceforth DG86) and Smith et al. (1987, henceforth SFV87), called by him the LIT, the diffusive filtering theory (DFT) of Gardner (1994, henceforth G94), and the Doppler spread theory (DST) initiated by Hines (1991b). In all of the theories under discussion, the u′ power spectral density (PSD) is taken in G96 to exhibit an increase with m at m values less than some characteristic value m∗ and a decrease, more-or-less proportional to m−3, in a ‘tail’ region at greater m values up to some upper limit mM, whereafter turbulence is said to set in. The transition at m∗ may be thought of, for convenience of discussion, as being abrupt, though each theory in fact either assumes or derives a smooth transition. The various theories differ from one another in the physical processes that are assumed to establish the tail portion of the spectrum, the tail's range in m, and the intensity of the PSD of the tail. That intensity has been said observationally to be invariant under changes of circumstance and height, a characteristic that is widely attributed to a ‘saturation’ of the spectrum or of the corresponding waves. The tail portion of the spectrum is therefore said by many to be saturated, though the theory of G94 purports to disagree with this concept and in fact provides possible alternatives to the m−3 form (as, indeed, does DG86). The LIT, DFT and DST will be discussed below in sequence.

Some additional data are given for the development of solar-terrestrial physics during the 19th and 20th centuries.

Original editorial can be found at: http://www.sciencedirect.com/ Copyright Elsevier [Full text of this paper is not available in the UHRA]

The similarity between the diurnal patterns of monthly mean dew-point temperatures for April in Nlamey, West Africa and Patancheru, India is striking The small diurnal varlatxon in vapour pressure relative to the vapour pressure defictt is similar in both locations. Although the error m estimating dally mean vapour pressure deficit from two spot readings of humidity is small xn the example given by Culf et al (1994), in India this is not always so for lndlvmal days (as opposed to monthly means) To illustrate this I have compared dally mean vapour pressures from the automatic weather statxon at the ICRISAT Center (readmgs every 5 mln) with means from spot readings at 07 15 and 14 15 h The difference between the two, expressed as a percentage of the mean dally vapour pressure deficit, was computed between May 1981 and October 1985 for each day in the analysis of Butler (1992) This gave the distribution of the error in calculating mean dally vapour pressure deficit from two spot readings of humidity (Fig 1) Overall, the mean error for the whole period was close to zero, but on individual days the error commonly exceeded 10% ...