Science of Nowcasting Olympic Weather for Vancouver 2010 (SNOW-V10): a World Weather Research Programme Project

A World Weather Research Programme (WWRP) project entitled the Science of Nowcasting Olympic Weather for Vancouver 2010 (SNOW-V10) was developed to be associated with the Vancouver 2010 Olympic and Paralympic Winter Games conducted between 12 February and 21 March 2010. The SNOW-V10 international team augmented the instrumentation associated with the Winter Games and several new numerical weather forecasting and nowcasting models were added. Both the additional observational and model data were available to the forecasters in real time. This was an excellent opportunity to demonstrate existing capability in nowcasting and to develop better techniques for short term (0–6 h) nowcasts of winter weather in complex terrain. Better techniques to forecast visibility, low cloud, wind gusts, precipitation rate and type were evaluated. The weather during the games was exceptionally variable with many periods of low visibility, low ceilings and precipitation in the form of both snow and rain. The data collected should improve our understanding of many physical phenomena such as the diabatic effects due to melting snow, wind flow around and over terrain, diurnal flow reversal in valleys associated with daytime heating, and precipitation reductions and increases due to local terrain. Many studies related to these phenomena are described in the Special Issue on SNOW-V10 for which this paper was written. Numerical weather prediction and nowcast models have been evaluated against the unique observational data set now available. It is anticipated that the data set and the knowledge learned as a result of SNOW-V10 will become a resource for other World Meteorological Organization member states who are interested in improving forecasts of winter weather.     

Local Site Effects in the Town of Benevento (Italy) from Noise Measurements

— The study of ground motion amplification produced by surface geology is extremely interesting in the Benevento area, Southern Italy, as it is characterized by high seismic hazard. The present moderate-to-low seismicity makes the noise method appropriate to estimate the seismic site response in the area. The three components of seismic noise have been recorded in five sites in the Benevento metropolitan area characterized by different surface geology, in order to estimate the seismic site response. In evaluating site amplification effects we used the direct interpretation of amplitude spectra and standard spectral ratio techniques, evaluating sediment-to-bedrock, sediment-to-average and H/V spectral ratios. The temporal evolution of the noise spectra is analysed within one day, in order to assess the stationarity of the noise signal. The noise wavefield properties have been studied through polarization analyses in selected bands of frequency, where spectral peaks are observed to dominate, to better understand the real nature of those peaks. Results give evidence of low amplification levels, missing any correlation between spectral amplitudes and sediment thickness over the basement. We interpret this result as due to the poor impedance contrast between sediments and basement, which is characterized by low values of shear waves velocity. Moreover, sharp amplitude peaks are observed in the raw spectra of the sediment-sites, in the 2–4 Hz frequency band; a numerical simulation interprets this effect as possibly associated with a wide-scale structure, invoking the presence of a sharper impedance contrast at greater depth. At high frequencies the action of ambient noise sources, mainly active on horizontal components of motion, is retained dominant to generate the prominent peaks observed in the H/V spectral ratios; in some cases the presence of a near-surface low-velocity layer can contribute to amplify the seismic motion generated at these frequencies.     

The Alpine Rif Belt (Morocco): A Case of Mountain Building in a Subduction-Subduction-Transform Fault Triple Junction

—The Rif belt forms with the Betic Cordilleras an asymmetric arcuate mountain belt (Gibraltar Arc) around the Alboran Sea, at the western tip of the Alpine orogen. The Gibraltar Arc consists of an exotic terrane (Alboran Terrane) thrust over the African and Iberian margins. The Alboran Terrane itself includes stacked nappes which originate from an easterly, Alboran-Kabylias-Peloritani-Calabria (Alkapeca) continental domain, and displays Variscan low-grade and high-grade schists (Ghomarides-Malaguides and Sebtides-Alpujarrides, respectively), shallow water Mesozoic sediments (mainly in the Dorsale Calcaire passive margin units), and infracontinental peridotite slices (Beni Bousera, Ronda). During the Late Cretaceous?-Eocene, the Alboran Terrane was likely located south of a SE-dipping Alpine-Betic subduction (cf. Nevado-Filabride HP-LT metamorphism of central-eastern Betics). An incipient collision against Iberia triggered back-thrust tectonics south of the deformed terrane during the Late Eocene-Oligocene, and the onset of the NW-dipping Apenninic-Maghrebian subduction. The early, HP-LT phase of the Sebtide-Alpujarride metamorphism could be hypothetically referred to the Alpine-Betic subduction, or alternatively to the Apenninic-Maghrebian subduction, depending on the interpretation of the geochronologic data set. Both subduction zones merged during the Early Miocene west of the Alboran Terrane and formed a triple junction with the Azores-Gibraltar transform fault. A westward roll back of the N-trending subduction segment was responsible for the Neogene rifting of the internal Alboran Terrane, and for its coeval, oblique docking onto the African and Iberian margins. Seismic evidence of active E-dipping subduction, and opposite paleomagnetic rotations in the Rif and Betic limbs of the Gibraltar Arc support this structurally-based scenario.     

中国地震科学实验场:认识与实践

中国地震科学实验场提出的国家重大科技基础设施建议被列入《中华人民共和国国民经济和社会发展第十四个五年规划和2035年远景目标纲要》,不仅是实验场的一件大事,也是中国地震科技的一件大事.这一重大进展,是中国地震科学界近半个世纪的思考与尝试的结果.     

Contamination Assessment and Site-Management Tool (CAST): A Browser-Based Tool for Site Assessment

Groundwater dependency is increasing globally, while millions of potentially contaminated sites are yet to be characterized for contamination levels. In particular, groundwater contamination due to light nonaqueous phase liquids (LNAPLs) continues to be a global challenge. Mathematical approaches (i.e., analytical, semi-analytical, empirical, numerical) are preferred for an initial site assessment to circumvent the high characterization costs and limited site data availability. However, the site-specific nature of contamination restricts the generalization of any single approach. Hence, the requirement is for an easy-to-use computing interface that provides site-specific data management, the selection and use of multiple-model interfaces for computing, and site characterization, with extension for the latest models as they become available. This work provides one such interface called CAST or Contamination Assessment and Site-management Tool. CAST is an open-source browser-based (online/offline) tool that provides an interface for six different analytical models (e.g., BIOSCREEN-AT), a MODFLOW based numerical model, and two empirical models (including a hybrid numerical-analytical model). Additionally, CAST includes interfaces for site data management, their evaluation, and scenario-based modeling. CAST's development is in a modular format, which simplifies the addition of new computing or data interfaces. Furthermore, the entire code-base of CAST is based on open-source (dominantly Python programming) libraries and standards. This further simplifies the modification or extension of this tool. This paper introduces CAST, its different computing, and data management interfaces and provides examples of the tool's functionality primarily for the initial evaluation of contaminated sites.     

Evaluating Long-Term Evolution of Radionuclide Migration Conditions from a Repository at the Yenisei Site (Krasnoyarsk Krai)

The article considers the procedure aimed to identify and select the factors, events, and processes that can have an effect on the long-term safety of radioactive waste repository to be constructed at The Yenisei Site (Krasnoyarsk krai). The geological factors to be taken into account in the development of scenarios for safety assessment are determined. Tentative quantitative forecasts of radionuclide migration are made taking into account possible climate evolution and vertical rise of the territory. The sensitivity of radionuclide migration model to variations in these factors is assessed.     

Infiltration at the Tai rain forest (Ivory Coast): Measurements and modelling

Infiltration experiments have been performed at three sites along a well-known catena under virgin tropical rain forest using a portable sprinkling infiltrometer. Experimentally determined infiltration curves are presented. Infiltration curves are also simulated on the basis of the Mein-Larson equation. The parameters for this model have been obtained from the infiltration curves (saturated conductivity) and simple soil moisture determinations (fillable porosity). The agreement between experimentally determined and modelled infiltration is reasonable, provided (a) saturated conductivity as derived from the experimental data is corrected, (b) a storage parameter, also derived from the experimental data, is added to the Mein-Larson model, and (c) the decline in soil porosity with depth is either small or occurs abruptly at shallow depth. Comparison of observed infiltration rates with rainfall intensity shows that Horton Overland Flow has to occur naturally at least on the middle and lower section of the catena. Despite the fact that most parameters can be estimated in principle from basic soil data, it remains advisable to obtain sprinkling infiltrometer field measurements, because of soil variability due to dynamic surface conditions, macroporosity, air entrapment, and irregularity of the wetting front.     

地震预警仪观测地脉动差异与评估场地条件的可行性研究

根据台站场地条件进行地震动参数校正,有助于提高地震预警的有效性和准确性。针对我国地震预警台网中部分台址场地条件信息不完整及观测仪器的多样性,通过采用不同灵敏度的力平衡式加速度仪、速度仪和MEMS烈度仪,同时进行大量不同类别场地的地脉动观测,多角度对比分析时、频差别,探讨基于地震预警仪观测地脉动评价场地条件的可行性。结果表明,加速度仪灵敏度越高,H/V谱比卓越频率越易识别;速度仪与力平衡式加速度仪观测的地脉动,三分向傅氏谱和H/V谱比的谱形与卓越频率均一致;与TAG-33M强震仪相比,TMA-53烈度仪观测的地脉动整体幅值略高,波形较差,但随着振幅增大趋于一致;在近80%的场地上,TAG-33M强震仪与TMA-53烈度仪观测的地脉动傅氏谱卓越频率相差＜0.5 Hz;当幅值均方根值＞0.05 Gal时,TAG-33M强震仪与TMA-53烈度仪观测的地脉动竖向和水平向傅氏谱均趋于一致;当幅值均方根值为0.02 Gal～0.05 Gal时,TAG-33M强震仪与TMA-53烈度仪观测的地脉动竖向和水平向傅氏谱谱形均有较高的相似性;当幅值均方根值＜0.02 Gal时,TAG-33M强震仪与TMA-53烈度仪观测的地脉动傅氏谱谱形相差较大,相似性低;依据TAG-33M强震仪观测地脉动H/V谱比的卓越频率判定场地类别,准确率达83.3%;TMA-53烈度仪观测地脉动的H/V谱比过于平坦,大多数场地上卓越频率识别困难。     

Sensitivity of the Weather Research and Forecasting (WRF) model to downscaling ratios and storm types in rainfall simulation

Accurate information of rainfall is needed for sustainable water management and more reliable flood forecasting. The advances in mesoscale numerical weather modelling and modern computing technologies make it possible to provide rainfall simulations and forecasts at increasingly higher resolutions in space and time. However, being one of the most difficult variables to be modelled, the quality of the rainfall products from the numerical weather model remains unsatisfactory for hydrological applications. In this study, the sensitivity of the Weather Research and Forecasting (WRF) model is investigated using different domain settings and various storm types to improve the model performance of rainfall simulation. Eight 24‐h storm events are selected from the Brue catchment, southwest England, with different spatial and temporal distributions of the rainfall intensity. Five domain configuration scenarios designed with gradually changing downscaling ratios are used to run the WRF model with the ECMWF 40‐year reanalysis data for the periods of the eight events. A two‐dimensional verification scheme is proposed to evaluate the amounts and distributions of simulated rainfall in both spatial and temporal dimensions. The verification scheme consists of both categorical and continuous indices for a first‐level assessment and a more quantitative evaluation of the simulated rainfall. The results reveal a general improvement of the model performance as we downscale from the outermost to the innermost domain. Moderate downscaling ratios of 1:7, 1:5 and 1:3 are found to perform better with the WRF model in giving more reasonable results than smaller ratios. For the sensitivity study on different storm types, the model shows the best performance in reproducing the storm events with spatial and temporal evenness of the observed rainfall, whereas the type of events with highly concentrated rainfall in space and time are found to be the trickiest case for WRF to handle. Finally, the efficiencies of several variability indices are verified in categorising the storm events on the basis of the two‐dimensional rainfall evenness, which could provide a more quantitative way for the event classification that facilitates further studies. It is important that similar studies with various storm events are carried out in other catchments with different geographic and climatic conditions, so that more general error patterns can be found and further improvements can be made to the rainfall products from mesoscale numerical weather models. Copyright © 2011 John Wiley & Sons, Ltd.     

Rapid Exhumation in the Alpine Belt of the Betic-Rif (W Mediterranean): Tectonic Extrusion

—Extreme cooling rates (500 °C/m.y.) during the late stage, 22–18 Ma, orogenic evolution of the Alpine Betic-Rif belt are suggested to result from rapid exhumation caused by tectonic extrusion and concomitant extensional tectonics. The extrusional/extensional tectonic setting is controlled by the SW-NE trending break-off scar left in the lithosphere of the Alborán Sea and SE Spain after detachment of a lithospheric slab. The extruded material represents the collisional crustal nappe pile (together with fragments of underlying mantle, such as the Ronda peridotites) and the cause of the extrusion is the thermal softening within the crustal section during and after collision. The extrusion/extension took place under the influence of a NW-SE directed compressive regime, perpendicular to the collisional belt. At the same time the sub-lithospheric mantle still showed the E-W compressive regime of the collisional stage. The Alpine tectono-metamorphic evolution of the Betic-Rif belt in the W Mediterranean thus comprises two main stages: (1) continental collision with formation of primary nappes and high-pressure metamorphic parageneses, (2) tectonic extrusion with vertically directed tectonics (high pressure, very rapid decompression) and extensional tectonics with roughly horizontal, lateral transport and final emplacement of the extruded mélange in the form of a stack of detachment sheets (low pressure, very rapid cooling). This model for the Betic-Rif may offer important constraints to all rapidly exhumed convergent terranes.     

Application of Microtremor Horizontal-to-Vertical Spectral Ratio (MHVSR) Analysis for Site Characterization: State of the Art

Nakamura (Q Rep Railway Tech Res Inst 30:25–33, 1989) popularized the application of the horizontal-to-vertical spectral ratio (HVSR) analysis of microtremor (seismic noise or ambient vibration) recordings to estimate the predominant frequency and amplification factor of earthquake shaking. During the following quarter century, popularity in the microtremor HVSR (MHVSR) method grew; studies have verified the stability of a site’s MHVSR response over time and validated the MHVSR response with that of earthquake HVSR response. Today, MHVSR analysis is a popular reconnaissance tool used worldwide for seismic microzonation and earthquake site characterization in numerous regions, specifically, in the mapping of site period or fundamental frequency and inverted for shear-wave velocity depth profiles, respectively. However, the ubiquity of MHVSR analysis is predominantly a consequence of its ease in application rather than our full understanding of its theory. We present the state of the art in MHVSR analyses in terms of the development of its theoretical basis, current state of practice, and we comment on its future for applications in earthquake site characterization.     

Measurements of tidal gravity and load deformations on Unst (Shetlands)

Summary The tidal gravimetric factor due to the elastic yielding of the Earth has been determined by gravimetric measurements on Unst (Shetland Islands), extending over the time of one month. Its corrected value isG=1.205±0.03. The influence of applying different methods of harmonic analysis, and the effects of ambient temperature and pressures and of the sea tides on the gravimetric results are discussed. No significant difference inG for semi-diurnal and diurnal tides remains after the necessary corrections have been made. The amplitude of the semidiurnal load depression is about 2 cm and it is shown that the more distant North Atlantic tides have a greater effect than the regional tides near the Shetlands. An approximate calculation gives 4.3×10¹¹ CGS-units as the mean rigidity of the part of the Earth's crust yielding to the maritime loading differences in this region.     

Site Effect Study in Urban Area: Experimental Results in Grenoble (France)

—?Three methods are used to determine the site effect in the town of Grenoble, located in the Western Alps. First we use the classical spectral ratio method in 14 sites to calculate the transfer function of the basin. We find an amplification of 10 in the frequency range of 0.25 to 10?Hz. Second, we compare these results with the H over V spectral ratio method, and propose a map of resonance frequency of the basin. We find a lower resonance frequency in the center of the basin than on the edge, that is consistent with the structure deduced from a gravity Bouguer anomaly map. Finally we use the empirical Green's function method to simulate a M _w 5.5 earthquake at a distance of 20?km from the town. The simulated acceleration reaches the level of 2?m/s² in the center of the basin compared to 0.2?m/s² on the edges. The simulated ground motion we compute is smaller than the French seismic codes on the edge of the valley but significantly larger in the center.     

High Latitude Magnetic Impulse Events (MIEs): Polarization Peculiarities and Excitation Conditions

Polarization characteristics (polarization type, ellipticity ε, tilt angle τ of the polarization ellipse’s major axis) of high-latitude magnetic impulse events (MIEs) observed at the latitude of the dayside polar cusp are studied. It is established that all impulses are elliptically polarized, being right-polarized in 43% of cases (R-type) and left-polarized in 57% of cases (L-type). The right-polarized MIEs on the ground are more pronounced in the azimuthal direction, whereas the left-polarized events are more clearly marked in the meridional direction. The MIEs of both polarization types have the properties of intermittent processes. It is shown that diurnal and seasonal variations in the occurrence frequency and amplitudes of the events depend significantly on the type of their polarization. The R- and L-type impulse events are predominantly observed during the descending and ascending phase of the solar cycle, respectively. Solar wind high-speed streams (HSSs) are more favorable for exciting right-polarized impulses, whereas left-polarized impulse events are more efficiently excited by coronal mass ejection (CME). It is established that R-type impulses emerge in the conditions when the orientation of the interplanetary magnetic field vector is close to the radial direction against the development of moderate magnetospheric substorms whereas the L-type impulses appear when IMF is perpendicular to the Sun–Earth line in the absence of substorms. The behavior of the characteristics of impulse events significantly depends on the value of the IMF Bz-component and on the angle θ_xB = arccos(Bx/B). It is conjectured that excitation of the two groups of impulses is caused by the IMF structures in the solar wind stream with the characteristic configuration in the ecliptic plane, which determine the polarization type and properties of MIEs.     

Temperature and Pressure Dependencies of Thermal Transport Properties of Rocks: Implications for Uncertainties in Thermal Lithosphere Models and new Laboratory Measurements of High-Grade Rocks in the Central Fennoscandian Shield

Measurements on thermal conductivity and diffusivity as functions of temperature (up to 1150 K) and pressure (up to 1000 MPa) are presented for Archaean and Proterozoic mafic high-grade rocks metamorphosed in middle and lower crustal pressures, and situated in eastern Finland, central Fennoscandian Shield. Decrease of 12–20% in conductivity and 40–55% in diffusivity was recorded between room temperature and 1150 K, which can be considered as typical of phonon conductivity. Radiative heat transfer effects were not detected in these samples. Pressure dependencies of the samples are weak if compared to crystalline rocks in general, but relatively typical for mafic rocks.The temperature and pressure dependencies of thermal transport properties (data from literature and the present study) were applied in an uncertainty analysis of lithospheric conductive thermal modellings with random (Monte Carlo) simulations using a 4-layer model representative of shield lithosphere. Model parameters were varied according to predetermined probability functions and standard deviations were calculated for lithospheric temperature and heat flow density after 1500 independent simulations. The results suggest that the variations (uncertainties) in calculated temperature and heat flow density values due to variations in the temperature and pressure dependencies of conductivity are minor in comparison to the effects produced by typical variations in the room temperature value of conductivity, heat production rate or lower boundary condition values.     

Site Response for the RSM Seismic Network and Source Parameters in the Central Apennines (Italy)

—?Thirty-three earthquakes which occurred in the Central Apennines (Italy) with Ml ranging from 2.4 to 3.7 have been spectrally analysed using digital recordings from twelve stations of the Rete Sismometrica Marchigiana (RSM) network. Data corrected for geometrical spreading and quality factor Q have been inverted by means of the Generalised Inversion Technique. Site responses have been compared with those obtained by H/V ratio. Site amplifications have been observed both at stations placed on Pleistocene sediments and at one station located at 1800?m altitude. Source parameters have been calculated by fitting the spectra with an automatic procedure adopting the ω² source model. The seismic moments range from 9.23?×?10¹⁹ to 4.28?×?10²¹ dyne-cm with an average M ₀ (S) to M ₀ (P) ratio of 1.13?±?0.38. The stress drops are generally low and they vary between 1.1 and 10.2?bar when estimated by using S source spectra, and between 0.5 and 7.1?bar when the P-source spectra are fitted. For the considered range of seismic moments we observe that the stress drop does not have significant dependence on event size.     

Site response study in Abruzzo (Central Italy): underground array versus surface stations

In this site response study we examined local earthquakes recorded at surface stations of a local seismic network and at a temporary underground seismic array installed in a tunnel underneath the Gran Sasso Massif in Abruzzo (central Italy). This allowed us to compare the seismic site response beneath the mountain and on the surface in similar geological environment (soft rock sites). We applied spectral ratios method on different segments of the seismograms and used different reference spectra in the 1–20 Hz frequency band. We found little or no amplification effects at most of the surface stations whereas site transfer functions evaluated with respect to underground sites show an amplification factor up to 6 in the 1–8 Hz frequency range. Coda spectral ratios estimated at soft rock sites are confirmed as good estimates of shear wave transfer function.     

Model of the Ionospheric Trough for Daytime Winter Conditions Based on Data from Interkosmos-19 and Champ Satellites

Geomagnetism and Aeronomy - The principles and algorithm for the construction of an empirical model of the ionospheric trough for quiet (Kр = 2) daytime (06−18 LT) winter conditions in...     

Measurements and Observations in the XXI century (MOXXI): innovation and multi-disciplinarity to sense the hydrological cycle

To promote the advancement of novel observation techniques that may lead to new sources of information to help better understand the hydrological cycle, the International Association of Hydrological Sciences (IAHS) established the Measurements and Observations in the XXI century (MOXXI) Working Group in July 2013. The group comprises a growing community of tech-enthusiastic hydrologists that design and develop their own sensing systems, adopt a multi-disciplinary perspective in tackling complex observations, often use low-cost equipment intended for other applications to build innovative sensors, or perform opportunistic measurements. This paper states the objectives of the group and reviews major advances carried out by MOXXI members toward the advancement of hydrological sciences. Challenges and opportunities are outlined to provide strategic guidance for advancement of measurement, and thus discovery.     

Assimilation and High Resolution Forecasts of Surface and Near Surface Conditions for the 2010 Vancouver Winter Olympic and Paralympic Games

A dynamical model was experimentally implemented to provide high resolution forecasts at points of interests in the 2010 Vancouver Olympics and Paralympics Region. In a first experiment, GEM-Surf, the near surface and land surface modeling system, is driven by operational atmospheric forecasts and used to refine the surface forecasts according to local surface conditions such as elevation and vegetation type. In this simple form, temperature and snow depth forecasts are improved mainly as a result of the better representation of real elevation. In a second experiment, screen level observations and operational atmospheric forecasts are blended to drive a continuous cycle of near surface and land surface hindcasts. Hindcasts of the previous day conditions are then regarded as today’s optimized initial conditions. Hence, in this experiment, given observations are available, observation driven hindcasts continuously ensure that daily forecasts are issued from improved initial conditions. GEM-Surf forecasts obtained from improved short-range hindcasts produced using these better conditions result in improved snow depth forecasts. In a third experiment, assimilation of snow depth data is applied to further optimize GEM-Surf’s initial conditions, in addition to the use of blended observations and forecasts for forcing. Results show that snow depth and summer temperature forecasts are further improved by the addition of snow depth data assimilation.