The Cloud Ice Mountain Experiment (CIME) 1998: experiment overview and modelling of the microphysical processes during the seeding by isentropic gas expansion

The second field campaign of the Cloud Ice Mountain Experiment (CIME) project took place in February 1998 on the mountain Puy de Dôme in the centre of France. The content of residual aerosol particles, of H₂O₂ and NH₃ in cloud droplets was evaluated by evaporating the drops larger than 5 μm in a Counterflow Virtual Impactor (CVI) and by measuring the residual particle concentration and the released gas content. The same trace species were studied behind a round jet impactor for the complementary interstitial aerosol particles smaller than 5 μm diameter. In a second step of experiments, the ambient supercooled cloud was converted to a mixed phase cloud by seeding the cloud with ice particles by the gas release from pressurised gas bottles. A comparison between the physical and chemical characteristics of liquid drops and ice particles allows a study of the fate of the trace constituents during the presence of ice crystals in the cloud.In the present paper, an overview is given of the CIME 98 experiment and the instrumentation deployed. The meteorological situation during the experiment was analysed with the help of a cloud scale model. The microphysics processes and the behaviour of the scavenged aerosol particles before and during seeding are analysed with the detailed microphysical model ExMix. The simulation results agreed well with the observations and confirmed the assumption that the Bergeron–Findeisen process was dominating during seeding and was influencing the partitioning of aerosol particles between drops and ice crystals. The results of the CIME 98 experiment give an insight on microphysical changes, redistribution of aerosol particles and cloud chemistry during the Bergeron–Findeisen process when acting also in natural clouds.     

中等传输距离下的无线功率传输链路第1部分:实现工作状态最优化

中程无线功率传输（WPT）可以采用几种不同的方式实现,如通过电感或电容耦合、谐振或非谐振网络实现.本文主要研究了通过感应耦合谐振器实现的WPT链路,而且只着重研究了利用2个谐振器的链路（直接链路）并工作在主谐振频率下的情况.研究结果表明,当工作在主谐振频率下,可以根据网络参数来对传输效率或负载功率进行优化.     

A comparison of wetness indices for the prediction of observed connected saturated areas under contrasting conditions

For lack of other widely available spatial information, topography is often used to predict water fluxes and water quality in mesoscale watersheds. Such data have however proven to be misleading in many environments where large and flat valley bottoms and/or highly conducive soil covers determine water storage and water transport mechanisms. Also, the focus is generally on the prediction of saturation areas regardless of whether they are connected to the catchment hydrographic network or rather present in isolated topographic depressions. Here soil information was coupled with terrain data towards the targeted prediction of connected saturated areas. The focus was on the 30 km² Girnock catchment (Cairngorm Mountains, northeast Scotland) and its 3 km² sub‐catchment, Bruntland Burn in which seven field surveys were done to capture actual maps of connected saturated areas in both dry and humid conditions. The 1 km² resolution UK Hydrology of Soil Types (HOST) classification was used to extract relevant, spatially variable, soil parameters. Results show that connected saturated areas were fairly well predicted by wetness indices but only in wet conditions when they covered more than 30% of the whole catchment area. Geomorphic indices including information on terrain shape, steepness, aspect, soil texture and soil depth showed potential but generally performed poorly. Indices based on soil and topographic data did not have more predictive power than those based on topographic information only: this was attributed to the coarse resolution of the HOST classification. Nevertheless, analyses provided interesting insights into the scale‐dependent water storage and transport mechanisms in both study catchments. Copyright © 2013 John Wiley & Sons, Ltd.     

Modeling of the Guagua Pichincha volcano (Ecuador) lahars

Lahars, here defined as debris flows of volcanic origin, are rapid mass movements that pose a serious threat to cities located in the vicinity of many volcanoes. Quito, capital city of Ecuador and placed at the foot of the Pichincha volcano complex, is exposed to serious inundation hazard as part of the city is built on numerous deposits of large lahars that have occurred in the last 10,000 years.The objective of this paper is to model the potential lahars of the Pichincha volcano to predict inundation areas within the city of Quito. For this purpose two models that apply different approaches were utilized and their results were compared.The programs used were LAHARZ, a semi-empirical model conceived by the United States Geological Survey (USGS), and FLO-2D, a hydraulic model distributed by FLO Software Inc. LAHARZ is designed as a rapid, objective and reproducible automated method for mapping areas of potential lahar inundation (Proc. First Int. Conf. on Debris Flow Hazards Mitigation, San Francisco, USA, ASCE, 1998, p. 176). FLO-2D is a two-dimensional flood routing model for simulating overland flow on complex surfaces such as floodplains, alluvial fans or urbanized areas (FLO-2D Users manual, version 99.2). Both models run within geographical information systems (GIS).Fieldwork was focused on collecting all available information involved in lahar modeling. A total of 49 channel cross-sections were measured along the two main streams and stratigraphic investigations were carried out on the fans to estimate the volume of previous events. A global positioning system was utilized to determine the coordinates of each cross-section. Further data collection concerned topography, rainfall characteristics and ashfall thicknesses. All fieldwork was carried out in cooperation with the Instituto Geofisico of the Escuela Politecnica Nacional.Modeling in a GIS environment greatly aided the exportation of results for the creation of thematic maps and facilitated model comparison. Evaluation of the models was performed by comparing simulation results against each other and against the geometry of existing lahar deposits.     

Migrating sand waves

A simple mathematical model is described, which reproduces the major features of sand waves' appearance and growth and in particular predicts their migration speed. The model is based on the linear stability analysis of the flat configuration of the sea bottom subject to tidal currents. Attention is focused on the prediction of the complex growth rate that bottom perturbations undergo because of both oscillatory fluid motions and residual currents. While the real part _r of controls the amplification or decay of the amplitude of the bedforms, the imaginary part _i is related to their migration speed. Previous works on the migration of the sand waves (Németh etal. 2002) consider a forcing tide made up by the M2 constituent (oscillatory period equal to 12 h) plus the residual current Z0 and predict always a downcurrent migration of the bedforms. However, field cases exist of upcurrent-migrating sand waves (downcurrent/upcurrent-migrating sand waves mean bedforms moving in the direction of the steady residual tidal current or in the opposite direction, respectively). The inclusion of a tide constituent characterized by a period of 6 h (M4) is the main novelty of the present work, which allows for the prediction of the migration of sand waves against the residual current Z0. Indeed, the M4 tide constituent, as does also the residual current Z0, breaks the symmetry of the problem forced only by the M2 tide constituent, and induces sand-wave migration. The model proposed by Besio etal. (2003a) forms the basis for the present analysis. Previous works on the subject (Gerkema 2000; Hulscher 1996a,b; Komarova and Hulscher 2000) are thus improved by using a new solution procedure (Besio etal. 2003a) which allows for a more accurate evaluation of the growth rate for arbitrary values of the parameter r, which is the ratio between the horizontal tidal excursion and the perturbation wavelength. Responsible Editor: Jens Kappenberg     

Effects of trace metal and exposure to air on serotonin and dopamine levels in tissues of the mussel Perna perna

We evaluated levels of serotonin (5HT) and dopamine (DOPA) in muscle and digestive glands of the mussel, Perna perna, collected at different times of day; exposed to air for 24 h, followed by re-submersion; and after exposure to different metals. Mussels collected at different periods of day showed little oscillation in 5HT and DOPA levels. Mussels exposed to metals showed significant changes in 5HT and DOPA levels in digestive gland and muscle, as did mussels exposed to air. Our data suggest that analyses of 5HT and DOPA in tissues of mussels could serve as a tool to evaluate the presence and effects of heavy metal contamination in mussels. Care in data interpretation is required, however, since other environmental factors such as exposure of mussels to air (i.e. at low tides) can also cause changes in DOPA and 5HT levels. Additional research is necessary to separate such natural environmental effects from effects of contaminants.     

Effect of subsurface water level on gully headcut retreat in tropical highlands of Ethiopia

Gully erosion is a major cause of soil loss and severe land degradation in sub-humid Ethiopia. The objective of this study was to investigate the role and the effect of subsurface water level change on gully headcut retreat, gully formation and expansion in high rainfall tropical regions in the Ethiopian highlands. During the rainy seasons of 2017–2019, the expansion rate of 16 fixed gullies was measured and subsurface water levels were measured by piezometers installed near gully heads. During the study period, headcut retreats ranged from 0.70 to 2.35 m, with a mean value of 1.49 ± 0.56 m year⁻¹, and average depth of the surface water level varied between 1.12 and 2.82 m, with a mean value of 2.62 m. Gully cross-section areas ranged from 2.90 to 20.90 m², with an average of 9.31 ± 4.80 m². Volumetric retreat of gully headcuts ranged from 4.49 to 40.55 m³ and averaged 13.34 ± 9.10 m³. Soil loss from individual gullies ranged from 5.79 to 52.31 t year⁻¹ and averaged 17.21 ± 11.74 t year⁻¹. The headcut retreat rate and sediment yield were closely related over the three study seasons. Elevated subsurface water levels facilitated the slumping of gully banks and heads, causing high sediment yield. When the soil was saturated, bank collapse and headcut retreat were favoured by the combination of elevated subsurface water and high rainfall. This study indicates that area exclosures are effective in controlling subsurface water level, thus reducing gully headcut retreat and associated soil loss.     

Seismic performance of masonry walls retrofitted with steel reinforced grout

An innovative solution for the seismic protection of existing masonry structures is proposed and investigated through shake table tests on a natural scale wall assemblage. After a former test series carried out without reinforcement, the specimen was retrofitted using Steel Reinforced Grout. The strengthening system comprises horizontal strips of ultra‐high strength steel cords, externally bonded to the masonry with hydraulic lime mortar, and connectors to transversal walls, applied within the thickness of the plaster layer. In order to assess the seismic performance of the retrofitted wall, natural accelerograms were applied with increasing intensity up to failure. Test results provide a deep understanding of the effectiveness of mortar‐based composites for improving the out‐of‐plane seismic capacity of masonry walls, in comparison with traditional reinforcements with steel tie‐bars. The structural implications of the proposed solution in terms of dynamic properties and damage development under earthquake loads are also discussed.Copyright © 2015 John Wiley & Sons, Ltd.     

Predicting the equilibrium bed slope in natural streams using a stochastic model for incipient sediment motion

In this paper, a method to predict the equilibrium bed slope in natural streams based on the incipient motion criterion is proposed. The method is based on the criterion suggested by Gessler to simulate the grain size distribution of the armour coat using the concept of critical shear stress of a sediment mixture. In particular, a different expression of the probability for a single particle size to be part of the armour coat is firstly proposed; then, a simple two‐steps criterion is suggested to estimate the safety factor required by the proposed approach. The method is applied in three different Italian regions (Calabria, Basilicata, and Tuscany) and required several field campaigns involving the survey of 251 stream reaches upstream of grade‐control structures. The area including five Calabrian streams is firstly used to test the suitability of the two‐steps approach. In this area, considering the detailed information about the particle size of bed material, the effect of using a simplified grain size distribution for each torrent is also checked. The method is then applied within the two additional areas (Basilicata and Tuscany) in order to check the geographic influence on the prediction of the stable longitudinal profile. A comparison between measured and estimated values of the equilibrium bed slope showed a good agreement for the Calabrian streams, where the number of the investigated stream reaches is greater, and satisfactory results for the torrents located in Basilicata and Tuscany where the field data set is more limited. The overall results encourage the extension of the proposed method to additional field data and suggest the use of this approach by hydraulic designers in order to stabilize the longitudinal profile of natural streams. Copyright © 2011 John Wiley & Sons, Ltd.     

A parameterization of the wavelength of tidal dunes

The idealized model of Besio et al. (On the formation of sand waves and sand banks. Journal of Fluid Mechanics 2006; 557: 1–17) is used to predict the wavelength of tidal dunes (sand waves) generated by tidal currents in estuaries and shallow seas. The predictions are then analysed and a formula is proposed to estimate the wavelength of tidal dunes as a function of the parameters of the problem. The wavelength of the dunes is found to increase when the water depth is increased and/or the strength of the tidal current is decreased. On the other hand, the size of the bottom material (if medium sand is considered) and the tidal ellipticity are found to have a relatively small influence on the length of the bottom forms. The formula proposed provides results which are consistent with field observations of different authors. Copyright © 2011 John Wiley & Sons, Ltd.