bluuebunny/crossref_metadata_2025 huggingface dataset:
Sediment suspension due to waves
Authors: Vittori G.
Published: June 2003

A simulation of the turbulent flow and sediment dynamics in the boundary layer originated close to the seabed by a first‐order Stokes wave is performed. The flow field is obtained by the numerical integration of Navier‐Stokes and continuity equations while sediment trajectories are computed via a simplified model that assumes a one‐way coupling. Hence the results describe situations characterized by low concentrations and small values of the Stokes particle number. The investigation of the interaction of turbulent vortex structures with sediment shows that particles are picked up from the bed and carried into suspension when the low‐speed streaks start to break up and to generate small incoherent vortices that increase mixing effects. The low‐speed streaks are generated close to the seabed at the end of the accelerating phases, when the flow velocity is maximum, and breakdown during the decelerating phases of the cycle. The effects of turbulence structure and sediment characteristics on pickup and deposition rates are investigated and quantified by varying the values of the parameters which control the phenomenon.
Sea‐surface aerodynamic roughness
Authors: Mahrt L. , Vickers Dean , Frederickson Paul , Davidson Ken , Smedman Ann‐Sofi
Published: June 2003

This study surveys and evaluates similarity theory for estimating the sea‐surface drag coefficient with the bulk aerodynamic method. The most commonly used formulations of the aerodynamic roughness length, required by similarity theory, are examined using data sets from four different field programs. These relationships include the Charnock formulation and the wave age modified Charnock relationship. The goal is to assess the overall performance of simple formulations of the roughness length including cases where the Charnock formulation is not expected to apply, and to assess the errors resulting from application of the Charnock formulation to all conditions, as is done in many numerical models where an explicit wave model cannot be accommodated. This examination indicates that spurious self‐correlation explains more variance than actual physical relationships, even after eliminating weak wind cases. Frequent cases of anomalously low stress and very small values of the Charnock coefficient further reduce the usefulness of this formulation for the present data sets. Causes of the frequent very small values of the Charnock coefficient are briefly investigated.
Open boundary conditions for barotropic waves
Authors: Nycander J. , Döös K.
Published: June 2003

Open boundary conditions (OBCs) should give small artificial reflection of outgoing waves. Most OBCs proposed in the literature are designed to cope with the fact that the phase velocity of these waves is in general unknown. However, an even more important problem is the presence of a “slow mode”, i.e., a quasi‐stationary geostrophic flow, at the open boundary. This geostrophic flow should be separated from the superimposed waves when constructing the OBC. It is also important to write the OBC on integrated form, to avoid model drift and make sure that the correct solution is approached asymptotically. New conditions are derived using these ideas. Several OBCs are tested in one‐dimensional and two‐dimensional numerical simulations. The new conditions are found to perform better than the previous ones.
An impact of estimating tropospheric delay gradients on tropospheric delay estimations in the summer using the Japanese nationwide GPS array
Authors: Iwabuchi Tetsuya , Miyazaki Shin'ichi , Heki Kosuke , Naito Isao , Hatanaka Yuki
Published: June 2003

We used various analysis strategies to evaluate zenith tropospheric delays (ZTDs) retrieved from the Japanese nationwide Global Positioning System (GPS) array in the summer of 1996. We compared results from the network solution obtained by daily routine data analyses and two‐point positioning analyses with and without a tropospheric delay gradient model. We investigated two 14‐day periods in summer 1996, when water vapor distributions were highly azimuthally asymmetric. ZTD differences up to 4 mm, dependent on clusters used in the network analysis, were found between the network and the point analyses. We also found that differences in the estimated ZTD between the two‐point positioning analyses were correlated with the north components of the estimated tropospheric delay gradients. This is consistent with our simulation studies based on the north‐south asymmetry in the satellite coverage. The estimated tropospheric delay gradient vectors averaged over the periods pointed southward, which matches with the general meteorological condition in summer over the Japanese Islands. The temporal and spatial variations in the gradient estimates matched well with the moisture field determined by ZTD, in particular, during the passage of a weather front. Thus, tropospheric delay gradients obtained by GPS are expected to contain real horizontally anisotropic distribution of water vapor.
Estimation of land surface temperature from a Geostationary Operational Environmental Satellite (GOES‐8)
Authors: Sun Donglian , Pinker Rachel T.
Published: June 2003

Two algorithms are developed and applied to observations from the Geostationary Operational Environmental Satellite (GOES) to enable frequent estimate of Land Surface Temperature (LST) representing the diurnal cycle. The derived LSTs are evaluated against a wide range of ground observations. Both algorithms are based on radiative transfer theory; one is similar to the classical split window approach used for deriving Sea Surface Temperature (SST), while the other is a three‐channel algorithm. The three‐channel LST algorithm aims to improve atmospheric correction by utilizing the characteristics of the middle‐infrared (MIR) band. Effects of both the atmosphere and the surface emissivity are accounted for. The simulations from the proposed algorithms are compared with previously developed generalized split window algorithm, and a split window algorithm with water vapor correction. During daytime, the proposed new split window algorithm gives the best LST retrievals, while during nighttime, the proposed three‐channel algorithm gives the best retrievals, both within a Root Mean Square (RMS) error of less than 1 K and without a significant bias. Evaluations against the Atmospheric Radiation Measurement (ARM) observations of radiometric surface temperatures and Surface Radiation Network (SURFRAD) observations of outgoing long wave (LW) radiation indicate that LST can be determined from the actual GOES‐8 observations within an RMS accuracy of about 1–2 K, standard error of about 1 K, and bias of less than 1 K. When evaluated against the North Carolina Agricultural Research Service (NCARS) soil temperature as observed at depth of 8 in. and against air temperature observations, the amplitude of the retrieved LST is found to be significantly greater than that of the observed soil temperature, lower than the nighttime air temperature, and higher than the daytime air temperature. When the soil observations are “corrected” to account for the depth difference, they are in good agreement with the LST retrieved from the satellite observations. This indicates that observations of soil temperature, which are more readily available than measurements of “skin” temperatures, can be useful in evaluating satellite‐based estimates. The LST retrieved from both of the proposed algorithms and from a NOAA/NESDIS algorithm, are generally very close to the converted skin temperature from the SURFRAD surface outgoing LW radiation. In most cases, the newly proposed algorithm shows better agreement with ground observations.
New particle formation from photooxidation of diiodomethane (CH2I2)
Authors: Jimenez Jose L. , Bahreini Roya , Cocker David R. , Zhuang Hong , Varutbangkul Varuntida , Flagan Richard C. , Seinfeld John H. , O'Dowd Colin D. , Hoffmann Thorsten
Published: June 2003

Photolysis of CH2I2 in the presence of O3 has been proposed as a mechanism leading to intense new particle formation in coastal areas. We report here a comprehensive laboratory chamber study of this system. Rapid homogeneous nucleation was observed over three orders of magnitude in CH2I2 mixing ratio, down to a level of 15 ppt (∼4 × 108 molec. cm−3) comparable to the directly measured total gas‐phase iodine species concentrations in coastal areas. After the nucleation burst, the observed aerosol dynamics in the chamber was dominated by condensation of additional vapors onto existing particles and particle coagulation. Particles formed under dry conditions are fractal agglomerates with mass fractal dimension, Df ∼ 1.8–2.5. Higher relative humidity (65%) does not change the nucleation or growth behavior from that under dry conditions, but results in more compact and dense particles (Df ∼ 2.7). On the basis of the known gas‐phase chemistry, OIO is the most likely gas‐phase species to produce the observed nucleation and aerosol growth; however, the current understanding of this chemistry is very likely incomplete. Chemical analysis of the aerosol using an Aerodyne Aerosol Mass Spectrometer reveals that the particles are composed mainly of iodine oxides but also contain water and/or iodine oxyacids. The system studied here can produce nucleation events as intense as those observed in coastal areas. On the basis of comparison between the particle composition, hygroscopicity, and nucleation and growth rates observed in coastal nucleation and in the experiments reported here, it is likely that photooxidation of CH2I2, probably aided by other organic iodine compounds, is the mechanism leading to the observed new particle formation in the west coast of Ireland.
Laboratory measurement of electrification of wind‐blown sands and simulation of its effect on sand saltation movement
Authors: Zheng Xiao Jing , Huang Ning , Zhou You‐He
Published: June 2003

This article presents a measurement of electrification generated by wind‐blown sands in a field wind tunnel and a numerical methodology to simulate the effect of electrification on the sand saltation movement after the mutual couple interaction between the sand movement and the wind flow is taken into account. The measured data of electric charge on the “uniform” sands in the wind‐tunnel tests show that the sign of electric charge, either negative or positive, is mainly dependent on the diameter size of sand particles, i.e., negative charge is gained when the diameter is smaller than 250 μm and positive charge is obtained if the diameter is larger than 500 μm, and that for both “uniform” and mixed sands, the average charge‐to‐mass ratio decreases with increasing the wind velocity, and increases with height from sand bed. Meanwhile, the measurement of electric field in wind‐sand cloud related to the electric charge displays that the magnitude of electric field increases generally as the wind velocity and the height increase, and the direction of the field is always upwardly vertical to the Earth's surface, which is opposite to that of the fair‐weather field. In order to exhibit the effect of electrification on sand saltation movement, a theoretical model by considering the mutual coupling interaction between wind flow and sand movement is proposed after the electric force exerted on the moving sands is considered. Through solving the nonlinear coupling dynamic equations by a proposed program, the effect of electrification on sand saltation motion, e.g., trajectory, is discussed quantitatively. After that, its effect on wind‐sand transport flux, sand ejecta flux, and wind profile is also displayed. The results show that the prediction for the Bagnold's kink is good agreement with the measurement in literature.
Two‐dimensional cloud‐resolving modeling of the atmospheric effects of Arctic leads based upon midwinter conditions at the Surface Heat Budget of the Arctic Ocean ice camp
Authors: Zulauf Michael A. , Krueger Steven K.
Published: June 2003

A two‐dimensional cloud‐resolving model (CRM) is employed to examine the development of the convective plumes that may form in the vicinity of arctic leads and the impacts such plumes have upon the large‐scale surface heat budget. Numerous observations of varying types from the Surface Heat Budget of the Arctic Ocean (SHEBA) project were used to construct an idealized clear‐sky midwinter case. In a simulation containing a 3.2 km lead under the idealized conditions, a convective plume penetrated the extremely stable boundary layer to a depth of approximately 200 m, and a near‐surface ice cloud propagated at least 50 km downwind. It is notable that similar cloud features were also observed at the SHEBA site near the times when active leads were in the vicinity, though it has not been established that they are, in fact, related. Vertical mixing and lead‐induced circulations approximately doubled the simulated near‐surface wind speed over the lead, greatly increasing the turbulent heat fluxes compared with the initial conditions. The lead‐generated plume increased downwelling longwave radiation significantly, substantially modifying the heat budget over the snow/ice surface. Results were compared with the commonly utilized large‐scale “mosaic” parameterization. Owing to the lack of resolved leads and separate over‐lead and over‐snow profiles the mosaic simulation generated a shallower surface‐based plume with fundamental differences in the surface heat budget. Finally, a small number of sensitivity experiments were run to investigate the relative importance of lead width, ice cover on freezing leads, and humidity of the ambient environment. Variations in these parameters had substantial impacts upon the turbulent heat fluxes above the lead and the cloud radiative forcing upon the downwind snow/ice surface. Typically, it was the balance between these two components that determined whether the large‐scale net upward surface heat flux was impacted in a positive or negative sense.
Regional‐scale modeling of soil freeze/thaw over the Arctic drainage basin
Authors: Oelke Christoph , Zhang Tingjun , Serreze Mark C. , Armstrong Richard L.
Published: June 2003

The freezing and thawing of the active layer of soil in the Arctic terrestrial drainage basin is simulated using a one‐dimensional heat conduction model. Main forcing data are surface air temperature and snow thickness. Emphasis is placed on producing a topography‐improved temperature data set from National Centers for Environmental Prediction (NCEP) reanalysis data, and a snow height data set compiled from SSM/I satellite data and observed climatological snow density. Soil bulk density, soil type and its relative composition are derived from the SoilData System of the IGBP‐DIS. The model is run with 25 km × 25 km resolution and daily time steps for the period September 1998 through December 2000. We compare modeled thaw depths and active layer depths with those measured at Circumpolar Active Layer Monitoring (CALM) field sites. This study shows for the first time the highly variable daily thaw depth over permafrost and seasonally frozen ground depth in nonpermafrost areas, as well as freezing and thawing periods for the whole pan‐Arctic landmass.
Mixing‐height differences between land use types: Dependence on wind speed
Authors: Banta Robert M. , White Allen B.
Published: June 2003

Mixing height and its spatial variation are important for a variety of issues and applications. In a previous study in the region around Nashville, Tennessee, we found a significant difference in the daytime mixed‐layer inversion height zi between the area to the north and west of the city and the area to the south and east. These observations were from 3 days of very light daytime winds. The subregion to the north and west is deciduous forest, and that to the south and east is agricultural and mixed forest land. The differences in zi, which we are referring to as Δ zi, were attributed to differences in surface heat flux characteristics arising from the land use variation. In the present study we investigate the effects of increasing wind speed on Δ zi between the subregions, using a sample of 15 dry days from Southern Oxidants Study 1995. As convective boundary layer (CBL) wind speeds increased from ≲1 to 6 m s−1, Δ zi decreased from 600 m to negligible. We found that an increase in shear‐generated turbulence in the CBL was a probable factor in this decline. Two light‐wind days that followed days with widespread rainfall were also noted. The Δ zi on these days were small. Thus either strong winds or widespread surface moisture availability were able to nullify the effects of the land use/surface heat flux differences on Δ zi between the two subregions.
Tropospheric aerosols in the Mediterranean: 2. Radiative effects through model simulations and measurements
Authors: Meloni D. , di Sarra A. , DeLuisi J. , Di Iorio T. , Fiocco G. , Junkermann W. , Pace G.
Published: June 2003

The radiative effects of tropospheric aerosols at the island of Lampedusa, in the Mediterranean, have been investigated by comparing measurements and results from a radiative transfer model. The model was used to reproduce the measured ultraviolet irradiance spectra (286.5–363 nm) in three cases of cloud‐free conditions in May 1999, allowing the estimation of the aerosol properties and of the direct radiative forcing. Observations show very different aerosol loading and distribution, connected to the different origins of the air masses: low aerosol optical depths are associated with air masses from North Atlantic/Europe (25 and 27 May), and larger particles up to 7 km altitude and larger optical depths are observed for mineral dust coming from the Saharan region (18 May). The detailed description of the atmospheric structure and composition was used to initialize the radiative transfer model. The estimated single‐scattering albedo and asymmetry parameter at 500 nm for the desert dust are in the range 0.73–0.84 and in the range 0.75–0.79, respectively. Radiative transfer calculations show that differences of the surface ultraviolet irradiance larger than 10% may arise from the lack of a detailed knowledge of the aerosol size distribution. Aerosol may also increase or reduce the absorption effectiveness of tropospheric ozone, depending on the characteristics of the particles. Estimates of the direct aerosol radiative forcing in the spectral range 300–800 nm at the surface and at the top of the atmosphere (TOA) were also derived. At the surface, aerosols produce a decrease of the instantaneous downward irradiance with respect to an aerosol‐free atmosphere by 70.8, 37.2, and 39.1 W m−2, for 18 May (the aerosol optical depth is 0.511 at 415 nm), 25 (0.165) and 27 (0.224), respectively. The radiative forcing per unit optical depth at the surface is largest for aerosol of continental/marine origin, transported from North. The forcing at the TOA is negative, thus producing a cooling, in the desert dust case, and close to zero or positive for aerosol originating from North.
Tropospheric aerosols in the Mediterranean: 1. Microphysical and optical properties
Authors: Di Iorio T. , di Sarra A. , Junkermann W. , Cacciani M. , Fiocco G. , Fuà D.
Published: June 2003

Measurements of the aerosol properties were carried out at the island of Lampedusa, in the Mediterranean, in May 1999, as part of the Photochemical Activity and Ultraviolet Radiation modulating factors II campaign. Data from ground‐based lidar and Sun photometer, and particle counters aboard an instrumented ultralight aircraft, are used in this study. Three different cases, when all the measurements were available in cloud‐free conditions, were identified to derive the aerosol microphysical and optical properties. In one of these cases (18 May) the airmasses originated from Africa, and were loaded with a large amount of desert dust. In the other two cases (25 May and 27 May) the airmasses passed over Europe before reaching Lampedusa from North. The microphysical and optical properties of the aerosol strongly depend on the origin of the airmasses. The amount of particles in the 1–6 μm range of radii and the average aerosol surface area per unit volume are larger in the desert dust case than on 25 May and 27 May. The real part of the refractive index of the desert dust at 532 nm is between 1.52 and 1.58; its imaginary part is 5–7 × 10−3 and the single scattering albedo is about 0.7–0.75. The aerosol layer of 18 May closest to the surface, that probably contains a mixture of desert dust and marine aerosol, displays a smaller imaginary part (1.2 × 10−3) and a larger single scattering albedo (0.91). The aerosols originating from the North Atlantic and Europe have a real part of the refractive index between 1.35 and 1.49, and an imaginary part ranging from 8 × 10−4 to 1.8 × 10−2; the single scattering albedo at 532 nm (0.78–0.95) is larger than for desert dust values. The smallest value of the single scattering albedo (0.69) corresponds to an airmass originating from North, characterized by a large imaginary part of the refractive index. The asymmetry factor of the desert dust appears consistently larger for the desert dust (0.75–0.8) than for the other cases (0.61–0.72). The extinction‐to‐backscattering ratio, also derived from the measurements, is about 40 sr for the desert dust, and between 60 and 81 sr for the aerosol of northern origin. Simple estimates of the aerosol average direct shortwave radiative forcing at the top of the atmosphere indicate that all considered aerosol types induce a cooling. The radiative forcing per unit optical depth of the aerosol originating from North is about −37 Wm−2 over ocean and −(12–17) Wm−2 over land, while is −29 Wm−2 over ocean and −8 Wm−2 over land for desert dust. The largest forcing is however produced by the desert aerosols that generally display a considerably larger optical depth.
Deposition of coarse soil particles and ambient gaseous components dominating dew water chemistry
Authors: Takeuchi Masaki , Okochi Hiroshi , Igawa Manabu
Published: June 2003

Dew water characteristics are not as acidic as those of rainwater and fog water, and they are abundant in weak acid components. The dew water components are dominated by the coarse‐mode aerosol rather than the fine‐mode aerosol, and calcium carbonate, the component of soil, is the important chemical species raising the pH of the dew water. Carbon dioxide is deposited as calcium carbonate into dew water and is the only major component released from dew water. The total concentration of carbon dioxide increased with an increase in the dew water pH, while the degassing rate increased with the decrease in dew water pH. In the low‐pH region, the pε values in dew water are lower than those in rainwater, and the dew water is in a reductive state. The concentration of the representative oxidant, hydrogen peroxide, was much lower in the dew water than in the rainwater in Yokohama (dew water, 0.4 μM; rainwater, 13.1 μM in 1998). The representative conjugate base ions of a weak acid, sulfite and hydrogen sulfite ions, are easily oxidized by hydrogen peroxide, and the lower concentration of hydrogen peroxide in dew water may cause the higher concentration of sulfite ion in dew water than in rainwater. The dew water pH is higher than the rainwater and fog water pH, and a weak acid is easily dissolved into the dew water. Therefore these weak acid ions are more abundant in dew water than in rainwater and fog water.
Validation of total water vapor retrieval with an airborne millimeter wave radiometer over Arctic sea ice
Authors: Selbach Nathalie , Hewison Tim J. , Heygster Georg , Miao Jungang , McGrath Andrew J. , Taylor Jonathan P.
Published: June 2003

Measurements of the airborne SEPOR‐POLEX campaign in the Arctic in March 2001 were used to validate a total water vapor (TWV) algorithm. This is a modified version of an algorithm developed by Miao et al. [2001] using SSM/T2 data in the Antarctic. Data from a passive microwave radiometer with channels at 157, 183 ± 7, 183 ± 3, and 183 ± 1 GHz have been used. Dropsondes were launched from the aircraft during the flights to provide ground truth for the validation of the algorithm. The surface emissivity is assumed to be the same for the frequencies used. In general, there is a good agreement with TWV derived from dropsondes using the 183 GHz data only. This assumption leads to systematic errors in the estimation of TWV if the 157 GHz data are used in combination with measurements at 183 GHz. The high surface emissivity in regions of new ice is shown to lead to errors as a result of the strong influence of the surface. The difference in emissivity between 157 GHz and 183 GHz is larger over open water than over the sea ice, and therefore the error in TWV using the lower frequencies is larger in these regions.
Numerical simulation of radar surveillance for the ship target and oceanic clutters in two‐dimensional model
Authors: Jin Ya‐Qiu , Li Zhongxin
Published: June 2003

A fast iterative approach of generalized forward‐backward method with the spectrum acceleration algorithm (GFBM/SAA) is developed for solving electromagnetic field integral equation and is applied to numerical simulation of radar surveillance of the ship target and oceanic clutters in two‐dimensional (2‐D) model. Randomly rough surface is realized by the Monte Carlo method using the 1‐D Pierson‐Moskowitz spectrum. Numerical results of bistatic and backscattering from the ship target and oceanic clutters demonstrate the functional dependencies upon the situation of radar surveillance such as the incidence and observation angles, radar altitude, ship RCS, and other oceanic conditions.
Spatial variability of arsenic in 6000 tube wells in a 25 km2 area of Bangladesh
Authors: van Geen A. , Zheng Y. , Versteeg R. , Stute M. , Horneman A. , Dhar R. , Steckler M. , Gelman A. , Small C. , Ahsan H. , Graziano J. H. , Hussain I. , Ahmed K. M.
Published: June 2003

Arsenic concentrations measured by graphite furnace atomic absorption range from < 5 to 900 μg/L in groundwater pumped from 6000 wells within a 25 km2 area of Bangladesh. The proportion of wells that exceed the Bangladesh standard for drinking water of 50 μg/L arsenic increases with depth from 25% between 8 and 10 m to 75% between 15 and 30 m, then declines gradually to less than 10% at 90 m. Some villages within the study area do not have a single well that meets the standard, while others have wells that are nearly all acceptable. In contrast to the distribution of arsenic in the 8–30 m depth range which does not follow any obvious geological feature, the arsenic content of groundwater associated with relatively oxic Pleistocene sand deposits appears to be consistently low. The depth of drilling necessary to reach these low‐As aquifers ranges from 30 to 120 m depth within the study area.
Collapse‐sinkholes and radar interferometry reveal neotectonics concealed within the Dead Sea basin
Authors: Abelson Meir , Baer Gidon , Shtivelman Vladimir , Wachs Daniel , Raz Eli , Crouvi Onn , Kurzon Ittai , Yechieli Yoseph
Published: June 2003

The Dead Sea (DS) pull‐apart basin is one of the more seismically active segments of the DS Transform plate boundary. In the last decade, hundreds of collapse‐sinkholes have been formed along the DS coastlines in Israel and Jordan, causing severe damage to the regional infrastructure. The formation of these sinkholes is attributed to the dissolution of a buried salt layer by fresh groundwater due to the drop of the DS and the associated groundwater levels. Here we show that the sinkhole distribution, combined with gradual land subsidence measured by radar interferometry (InSAR) track young fault systems suspected as active, concealed within the fill of the DS rift. This notion is supported by (1) sinkholes clustering along discrete lineaments with a striking trend similarity to that of the exposed rift‐margin faults; (2) prominent discontinuities in seismic reflection profiles offsetting young sediments (several kyrs old) below sinkhole lines, and (3) straight boundaries of gradual subsidence features that coincide with or parallel sinkhole lines. Combined, the sinkhole lineaments and the InSAR measurements reveal a zigzag pattern of buried faults within the DS rift fill.
Global view of the nighttime low‐latitude ionosphere by the IMAGE/FUV 135.6 nm observations
Authors: Sagawa Eiichi , Maruyama Takashi , Immel Thomas J. , Frey Harald U. , Mende Stephen B.
Published: June 2003

The FUV Spectrographic Imager (FUV/SI) onboard the IMAGE satellite takes images at two wavelengths (121.8 nm: SI‐12 and 135.6 nm: SI‐13). The SI‐13 images of the low latitude region at night clearly show the intertropical FUV arcs corresponding to the equatorial anomaly (EA) in the ionosphere. The two‐minute cadence of the instrument provides a unique data set of the nighttime low‐latitude ionosphere. We compare the IMAGE observations of the OI 135.6 nm nightglow with the model emission intensities calculated by using the SAMI2 ionosphere model. The comparison shows that although both the FUV observation and the model give comparable emission intensities near the EA peak, the two differ in terms of their latitudinal and local time dependences. Large‐scale (∼1000 km) longitudinal wavy structures are often seen in OI 135.6 nm images. These structures drift eastward with a phase velocity of ∼100 m/s. The structure may be due to the plasma density perturbations generated by acoustic gravity waves through amplification by the spatial resonance and the Rayleigh‐Taylor (R‐T) instability. This is a common structure seen in the pre‐midnight sector of FUV/SI images regardless of longitude.
Strong ground motion and damage in the Taipei basin from the Moho reflected seismic waves during the March 31, 2002, Hualien, Taiwan earthquake
Authors: Chen Kou‐Cheng
Published: June 2003

The March 31, 2002, Hualien offshore earthquake (ML6.8, Mw7.0) caused minor damage near its epicenter but significant damage in Taipei, about 110 km from the epicenter. The recorded PGA values around the Taipei basin vary in a factor of 5. The high‐PGA values in the southeastern part of the basin correspond to the most significant damage area during the earthquake. Strong ground‐motion recordings from this event recorded at stations around the Taipei basin exhibit several distinct large‐amplitude seismic arrivals that can be interpreted as the PmP, SmP and SmS phases. The largest amplitude of the critically reflected S‐wave from the Moho (SmS) and the amplification of soft shallow sediments unique for each site are responsible for the maximum peak ground motion and the significant damage in the Taipei basin during the Hualien offshore earthquake.
Polar mesospheric clouds formed from space shuttle exhaust
Authors: Stevens Michael H. , Gumbel Jörg , Englert Christoph R. , Grossmann Klaus U. , Rapp Markus , Hartogh Paul
Published: June 2003

We observe a plume of water vapor in the Arctic above 85 km and a day after an August shuttle launch. Our satellite observations reveal that a discrete region of polar mesospheric clouds (PMCs) appears a week after that launch. We calculate that the water contained in the observed PMCs is consistent with the amount injected by the shuttle. This is evidence for a source of PMCs not previously considered.
Left‐handedness in asthmatic children
Authors: Krommydas Georgios , Gourgoulianis Konstantinos I. , Andreou Georgia , Molyvdas Paschalis‐Adam
Published: June 2003

Left‐handedness has been associated with asthma and allergic disorders. The Geschwind–Behan–Galaburda (GBG) hypothesis could explain this association. In view of previous findings, we investigated the distribution of laterality scores among asthmatic children and controls aged 4–8 years old. Seventy families with asthmatic children were administered the International Study of Asthma and Allergy in Childhood (ISAAC) questionnaire and the Edinburgh Left‐handedness Inventory. A sample of 70 families with non‐asthmatic, healthy children was used as controls. The majority of children had mild asthma. Ambidexterity was the main feature in the asthmatic children. A statistically significant difference in the laterality quotient (LQ) distribution was found in the group of asthmatic children with allergic rhinitis (LQ mean value in the asthmatic children with allergic rhinitis: 42.85 vs. 79.50 in the rest of the asthmatic children). These results suggest that there is a tendency towards left‐handedness in asthmatic children and lend support to the GBG hypothesis.
H1‐antihistaminic activity of cetirizine and fexofenadine in allergic children
Authors: Simons F. Estelle R. , J. Semus Michael , Goritz Sandra S. , Simons Keith J.
Published: June 2003

The clinical pharmacology of H1‐antihistamines has not yet been optimally studied in children and other special groups of patients. Our objective was to determine the onset, extent, and duration of H1‐antihistaminic activity of cetirizine and fexofenadine in the pediatric population. We performed a prospective, randomized, placebo‐controlled, double‐blind, crossover, single‐dose study of these H1‐antihistamines in 15 allergic children, mean±SEM age 8.8±0.5 years. We used suppression of the histamine‐induced wheal and flare as the primary outcome. Compared with pre‐dose baseline, cetirizine 10 mg suppressed the wheals significantly (p≤0.05) from 2 to 24 h and the flares significantly from 1 to 24 h, achieving 77±SEM 10% to 86±9% suppression of the wheal from 2 to 7 h and 85±6% to 88±6% suppression of the flare from 2 to 24 h, inclusive. Compared with baseline, fexofenadine 30 mg did not suppress the wheals or flares significantly at any time, achieving 40±9% to 54±9% wheal suppression from 2 to 7 h and 45±11% to 68±9% flare suppression from 2 to 7 h, inclusive. Compared with placebo, cetirizine suppressed the wheals and flares significantly from 2 to 24 h. Compared with placebo, fexofenadine suppressed the wheals significantly at 4 and 6 h, and the flares from 4 to 7 h. Cetirizine suppressed the wheals and flares significantly more than fexofenadine at 2 h (wheals), and at 3 and 24 h (flares). Placebo did not suppress the wheals and flares significantly at any time. In children age 6–11 years, cetirizine 10 mg has a rapid onset of H1‐antihistaminic activity, a 24‐h duration of action, and greater H1‐activity than fexofenadine 30 mg. Higher doses of fexofenadine should be tested in children.
Skin reactivity to histamine and to allergens in unselected 9‐year‐old children living in Poland and Italy
Authors: Ronchetti Roberto , Haluszka Janusz , Martella Susy , Falasca Carlo , Guglielmi Francesco , Parmiani Silvano , Zakrzewski Janusz , Bednarek Anna Lesiak , Barreto Mario , Villa Maria Pia
Published: June 2003

Several studies have shown a higher prevalence of positive skin‐prick tests to airborne allergens in Western than in Eastern European countries. We have recently reported that skin histamine reactivity significantly increased in Italy over the past 15 years. Population differences in skin histamine reactivity could, at least in part, explain the reported differences in positive allergen skin tests. To test this hypothesis we compared histamine skin reactivity and the prevalence of allergen positive skin‐prick tests in a sample of Italian and Polish schoolchildren. A total of 336 unselected 9‐year‐old‐schoolchildren (198 in Italy and 138 in Poland) underwent skin‐prick tests with three different histamine concentrations (10, 1 and 0.2 mg/ml) and with a panel of common airborne allergens according to the ISAAC protocol, phase two. Mean wheals elicited by skin‐prick tests with the three serial concentrations of histamine were significantly larger (p < 0.001) and shifted more toward higher values (p < 0.001) in Italian than in Polish children. The differences were greater for the intermediate histamine concentration tested (1 mg/ml) than for the highest concentration (10 mg/ml). Skin‐prick tests for airborne allergens were more frequently positive in Italian children: wheals ≥ 3 mm induced by any allergen [odds ratio (OR) 1.69; confidence interval (CI) 0.98–2.92] by Dermatophagoides pteronyssinus (OR 1.92; CI 0.97–3.80) and by D. farinae (OR 3.15; CI 1.16–8.63). Labeling as positive allergen wheal reactions half the size of the 10 mg/ml histamine wheal or larger reduced but did not abolish the Italian–Polish differences. The significantly higher skin histamine reactivity observed in Italian children could help to explain why allergen skin‐test reactions differ in the East and West European populations. Moreover, differences in nonallergen‐specific factors among populations should be considered in the interpretation of skin test results (e.g. cut‐off points). To obtain meaningful results, epidemiological studies of allergies should include serial histamine dilutions.
Early acquisition of serum and saliva antibodies reactive to enteropathogenic Escherichia coli virulence‐associated proteins by infants living in an endemic area
Authors: Carbonare Cristiane Barros , Carbonare Solange Barros , Carneiro‐Sampaio Magda Maria Sales
Published: June 2003

Enteropathogenic Escherichia coli (EPEC) is the most common etiological agent of acute diarrhea among infants living in poor social conditions in Brazil and other developing countries. This infection is rare in breast‐fed infants, as well as in children older than 2 years. Over the past few years, our group has attempted to identify antibodies to EPEC virulence proteins in human milk and to establish the in vitro protective role of these antibodies. In the present study, we report the identification of antibodies to EPEC virulence proteins in sera and saliva from children of different ages, living in slums in the city of São Paulo, Brazil. Using EPEC and bacterial constructs (pET) for immunoblotting (IB) analysis, antibodies reacting to the main adhesins (intimin, bundle‐forming pilli) and cell‐signaling proteins (EPEC secreted proteins – Esp A, Esp B) were detected in sera from adults and children older than 1 year. Almost all children older than 1 year presented recognition patterns similar to those of adults in IB assays for serum IgG and secretory IgA antibodies, using EPEC outer membrane and other antigenic preparations. As previously observed for human milk, all samples from adults and older children recognized the 94 kDa molecular weight adhesin intimin strongly. In most children, previous EPEC symptomatic diarrhea could not be confirmed; however, almost all of them have presented one or more diarrhea episodes during their lifetime. These results suggest that reduction of EPEC infection frequency after 2 years of age may be associated with the development of anti‐EPEC antibody repertoires.
Tumor suppressor protein p53 and anti‐p53 autoantibodies in pediatric rheumatological diseases
Authors: El‐Sayed Zeinab Awad , Farag Dalia Helmy , Eissa Sanaa
Published: June 2003

The tumor suppressor protein p53 plays an important role in cell cycle regulation. One of the major features in rheumatic diseases is the abnormal proliferation of lymphocytes. p53 expression in peripheral blood mononuclear cells (by flowcytometry) and serum anti‐p53 antibodies (by ELISA) were therefore measured in 18 children and adolescents with juvenile rheumatoid arthritis (JRA) and 17 with systemic lupus erythematosus (SLE) in comparison to 20 healthy controls, to determine their role. p53 expression in patients was insignificantly higher than that of controls (2.28 ± 2.71% vs. 1.08 ± 1.02%, respectively, p > 0.05) with 29.4% of the patients showing values above a cut‐off level of 2.55% (95th percentile of controls). SLE patients with active disease had significantly higher p53 expression compared to controls and to patients with quiescent disease although no significant correlation with ESR or complement 3 was detected. Seropositivity to anti‐p53 antibodies was observed in none of controls but in 22.8% of patients, all of whom, except one, had active disease. Seropositivity to anti‐p53 antibodies was more prominent in lupus nephritis than in other presentations of SLE (p < 0.05). The mean p53 expression in seropositive patients was insignificantly higher than in seronegatives. p53 expression and seropositivity to anti‐p53 were slightly higher in SLE than in JRA and were not significantly affected by the mode of therapy. Thus, the overexpression of p53 in some patients with active SLE and JRA might explain the abnormal proliferation of autoreactive lymphocytes that perpetuates the inflammatory response. The presence of anti‐p53 antibodies might cause malfunctioning of p53 protein interfering with its regulatory functions.
The prevalence, characteristics of and early life risk factors for eczema in 10‐year‐old children
Authors: Kurukulaaratchy Ramesh , Fenn Monica , Matthews Sharon , Hasan Arshad S.
Published: June 2003

Eczema is a common infantile disease but its nature and extent during later childhood remains unclear. In a whole‐population birth cohort study (n = 1456) we examined prevalence and characteristics of eczema amongst 10‐year‐old children. At this age 1373 (94%) children completed ISAAC questionnaires, 1043 (72%) skin prick testing and 953 (65%) serum inhalant IgE antibody screening. At 10 years of age prevalence of eczema ever was 41.0% and for current eczema was 13.7% (combined current itchy rash and eczema ever). Most current eczema (71.0%) began before 4 years of age, but was associated with low morbidity at 10 years. Amongst children with diagnosed eczema at 4 years of age, 56.3% had current eczema at 10 years. Atopy (positive skin test) and other allergic states were associated with current eczema (p < 0.001). Risk factor analysis for current eczema identified independent significance for atopy (p = 0.01), rhinitis (p = 0.04) and food allergy (p = 0.01) at 4 years, plus maternal asthma (p = 0.03). Diagnosed rhinitis at 4 years emerged as a significant predictor of persistent disease. Eczema is not simply a transient infantile condition but a common problem at 10 years of age, often reflecting persistent disease from early childhood. Inherited predisposition towards atopy is the predominant risk factor for this state.
The effect of montelukast on allergen‐induced cutaneous responses in house dust mite allergic children
Authors: Sekerel Bulent Enis , Akpinarli Akgul
Published: June 2003

The benefits of a leukotriene modifier on allergen‐induced cutaneous responses have not been studied in children. We hypothesized that a leukotriene‐receptor antagonist would provide protection against allergen‐induced early and/or late phase cutaneous responses in susceptible children. In a randomized, double‐blind, placebo‐controlled, cross‐over study in 6‐ to 15‐year‐old house dust mite allergic children, we compared the benefit of either montelukast or a matching placebo for 2 days on cutaneous responses induced by intradermal injection of house dust mite extract. Responses were measured as the mean of the longest diameter and its longest perpendicular of the induration response after 10, 20 min, 4 h and 6 h of the challenge. A total of 30 children were randomized to placebo or montelukast. The mean decline from baseline was significantly greater (p = 0.04) in the montelukast‐treated children [−5.20 mm (−12.03–1.63)][median (95% CI)] than in the placebo‐treated children [0.13 mm (−6.46–6.73] at 6th hour of the challenge, as was the mean diameter (p = 0.04), but did not differ in the remaining time points. We concluded that in house dust mite allergic children, montelukast 5 mg provided significant improvement in allergen‐induced cutaneous late‐phase responses, suggesting its contribution to allergic skin responses and its potential therapeutic value.
Correction of bronchial challenge data for age and size may affect the results of genetic association studies in children
Authors: Child Frances , Lenney Warren , Clayton Sadie , Davies Siobhan , Jones Peter W. , Strange Richard C. , Fryer Anthony A.
Published: June 2003

Meaningful studies of asthma genetics require careful definition of airway hyperresponsiveness (AHR). In children, several studies have emphasized the need for correction of bronchial challenge data for baseline parameters, such as age, gender, lung function and atopic status, when undertaking airway responsiveness measurements. However, few studies have suggested how this should be performed in practice. This study describes a method for the correction of dose–response slopes (DRS) and PC20 values for baseline parameters in children, and illustrates the effect of such corrections on the association of AHR with the glutathione S‐transferase GSTP1 Ile105Val polymorphism in children. Skin prick and methacholine challenge testing, measurement of total serum IgE concentration and GSTP1 genotyping were performed in 145 unrelated British children aged 7–18 years. Correction of bronchial challenge results, expressed as both DRS and PC20 values, for age, gender, baseline lung function and atopic status was performed using linear regression and discriminant analysis, respectively. Adjusting bronchial challenge results for the age and size of the child altered AHR status, defined as a PC20 methacholine <8 mg/ml, in 37% of children. Correction for baseline parameters also resulted in a significant reduction in mean DRS (original uncorrected DRS 83.6, corrected DRSc 27.4). This had a marked effect on the results of the association study, unmasking a previously unidentified association between the GSTP1 genotype and AHR in children. Age and size adjustment of bronchial challenge data has a significant effect on AHR status and may influence the results of genetic association studies in children.
Asthma, lung function and allergy in 12‐year‐old children with very low birth weight: A prospective study
Authors: Mai Xiao‐Mei , Gäddlin Per‐Olof , Nilsson Lennart , Finnström Orvar , Björkstén Bengt , Jenmalm Maria  C. , Leijon Ingemar
Published: June 2003

We assessed the relationship between very low birth weight (VLBW) (≤1500 g) and the development of asthma, lung function and atopy. The study groups comprised 74 of all 86 (86%) VLBW and 64 of all 86 (74%) matched term children who were prospectively followed for 12 years. A questionnaire on asthmatic and allergic symptoms was completed and skin prick tests, spirometry and hypertonic saline provocation tests were performed at 12 years of age. Cytokine secretion was analysed in stimulated blood leukocyte cultures in 28 VLBW and 23 term children. A history of asthma was more frequent among the VLBW children, as compared with the term children at age 12 (22% vs. 9%, p = 0.046). Among the VLBW children, very preterm birth (gestational age: week 25 to 29) (RR 2.5, 95%CI 1.1–5.8), neonatal mechanical ventilation (RR 2.8, 95%CI 1.2–6.4) and neonatal oxygen supplementation (RR 4.3, 95%CI 1.3–14.0) were significantly associated with a history of asthma by the age of 12 years in univariate analyses. In multivariate logistic regression, neonatal oxygen supplementation ≥ 9 days was the only remaining significant risk factor for a history of asthma (adjusted OR 6.7, 95%CI 1.0–44). The VLBW children who required mechanical ventilation during the neonatal period were more likely to have bronchial hyperresponsiveness than those not requiring mechanical ventilation (60% vs. 28%, p = 0.050). The spirometric values were similar among the VLBW and the term children at 12 years. Very low birth weight was not significantly related to allergic rhinoconjunctivitis, eczema or positive skin prick tests. Furthermore, the levels of IL‐4, IL‐5 and IFN‐γ in stimulated cell cultures were similar in the VLBW and the term children. A history of asthma by 12 years of age was twice as common among the VLBW as the term children, and neonatal oxygen supplementation seemed to be associated with the increased risk. Furthermore, mechanical ventilation during the neonatal period was associated with bronchial hyperresponsiveness at age 12. Very low birth weight per se was not, however, related to atopy.