Local Topographic Effects Research Articles

CHESS-SCAPE: high-resolution future projections of multiple climate scenarios for the United Kingdom derived from downscaled United Kingdom Climate Projections 2018 regional climate model output

Abstract. In order to effectively model the potential impacts of future climate change, there is a requirement for climate data inputs which (a) are of high spatial and temporal resolution, (b) explore a range of future climate change scenarios, (c) are consistent with historical observations in the historical period, and (d) provide an exploration of climate model uncertainty. This paper presents a suite of climate projections for the United Kingdom that conform to these requirements: CHESS-SCAPE. CHESS-SCAPE is a 1 km resolution dataset containing 11 near-surface meteorological variables that can be used to as input to many different impact models. The variables are available at several time resolutions, from daily to decadal means, for the years 1980–2080. It was derived from the state-of-the art regional climate projections in the United Kingdom Climate Projections 2018 (UKCP18) regional climate model (RCM) 12 km ensemble, downscaled to 1 km using a combination of physical and empirical methods to account for local topographic effects. CHESS-SCAPE has four ensemble members, which were chosen to span the range of temperature and precipitation change in the UKCP18 ensemble, representing the ensemble climate model uncertainty. CHESS-SCAPE consists of projections for four emissions scenarios, given by the Representative Concentration Pathways 2.6, 4.5, 6.0 and 8.5, which were derived from the UKCP18 RCM RCP8.5 scenarios using time shifting and pattern scaling. These correspond to UK annual warming projections of between 0.9–1.9 K for RCP2.6 up to 2.8–4.3 K for RCP8.5 between 1980–2000 and 2060–2080. Little change in annual precipitation is projected, but larger changes in seasonal precipitation are seen with some scenarios projecting large increases in precipitation in the winter (up to 22 %) and large decreases in the summer (up to −39 %). All four RCP scenarios and ensemble members are also provided with bias correction, using the CHESS-met historical gridded dataset as a baseline. With high spatial and temporal resolution, an extensive range of warming scenarios and multiple ensemble members, CHESS-SCAPE provides a comprehensive data resource for modellers of climate change impacts in the UK. The CHESS-SCAPE data are available for download from the NERC EDS Centre for Environmental Data Analysis: https://doi.org/10.5285/8194b416cbee482b89e0dfbe17c5786c (Robinson et al., 2022).

Shaking table test for near-valley subway station - Part I: Seismic site effects

As a typical local irregular topography, valley would have a significant influence on the seismic distribution around the local site as well as on seismic responses of near-valley underground structures, which has been evidenced by ground motion observation and field seismic records. However, current knowledge on the seismic site effects of the valley is limited to analytical solutions or numerical methods, and lack of experimental data from physical models. In this paper, a physical model test method based on 1g shaking table for arc-shaped valley topography is proposed, and a series of shaking table tests are carried out to investigate the seismic site effects induced by the valley topography. Details of experimental setup include not only the dynamic similitude design, the laminar model container and the model soil, but also the design and fabrication of arc-shaped valley topography with three kinds of depth-to-width ratios, i.e. 1/3, 1/4, and 1/8, as well as procedure for simulation of seismic excitations considering harmonic waves and actual seismic records. The free-field test case without valley site is also involved and taken as a benchmark comparison to better understand the seismic site effects of valley terrain. Acceleration sensors are placed and embedded in the model soil with different buried depths and distances to the local valley site in order to record the overall free-field seismic responses as well as the local topography effects. Results show that the dynamic response on the surface of model soil exhibits strong spatial variability due to the impact of the local valley topography. Results also indicate the ground acceleration increases within the local site, and the amplification effect is most pronounced at the valley top. The influence of the valley on the acceleration response of the ground is more significant when the predominant frequency of the seismic motions is higher and closer to the natural frequency of the site under different seismic motions. Furthermore, when the depth-to-width ratio of the valley increases, the acceleration amplitude at the valley top gradually increases, and the predominant frequency of Fourier spectrum at the valley top is also amplified. Notably, the Arias intensity amplification factor of the surrounding strata increases significantly due to the local valley topography, and the Arias intensity is also increased with the depth-to-width ratio of the valley.

Combining Weather Station Data and Short-Term LiDAR Deployment to Estimate Wind Energy Potential with Machine Learning: A Case Study from the Swiss Alps

Wind energy potential in complex terrain is still poorly understood and difficult to quantify. With Switzerland’s current efforts to shift to renewable energy resources, it is now becoming even more crucial to investigate the hidden potential of wind energy. However, the country’s topography makes the assessment very challenging. We present two measurement campaigns at Lukmanier and Les Diablerets, as representative areas of the complex terrain of the Swiss Alps. A general understanding of local wind flow characteristics is achieved by comparing wind speed measurements from a near-surface ultra-sonic anemometer and from light detection and ranging (LiDAR) measurements further aloft. The measurements show how the terrain modifies synoptic wind for example through katabatic flows and effects of local topography. We use an artificial neural network (ANN) to combine the data from the measurement campaign with wind speed measured by weather stations in the surrounding area of the study sites. The ANN approach is validated against a set of LiDAR measurements which were not used for model calibration and also against wind speed measurements from a 25-meter mast, previously installed at Lukmanier. The statistics of the ANN output obtained from multi-year time series of nearby weather stations match accurately the ones of the mast data. However, for the rather short validation periods from the LiDAR, the ANN has difficulties in predicting lowest wind speeds at both sites, and highest wind speeds at Les Diablerets.

Oceanic bottom mixed layer in the Clarion-Clipperton Zone: potential influence on deep-seabed mining plume dispersal

The oceanic bottom mixed layer (BML) is a well mixed, weakly stratified, turbulent boundary layer. Adjacent to the seabed, the BML is of intrinsic importance for studying ocean mixing, energy dissipation, particle cycling and sediment-water interactions. While deep-seabed mining of polymetallic nodules is anticipated to commence in the Clarion-Clipperton Zone (CCZ) of the northeastern tropical Pacific Ocean, knowledge gaps regarding the form of the BML and its potentially key influence on the dispersal of sediment plumes generated by deep-seabed mining activities are yet to be addressed. Here, we report recent field observations from the German mining licence area in the CCZ that characterise the structure and variability of the BML locally. Quasi-uniform profiles of potential temperature extending from the seafloor reveal the presence of a spatially and temporally variable BML with an average local thickness of approximately 250 m. Deep horizontal currents in the region have a mean speed of 3.5 cm s-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{-1}$$\\end{document} and a maximum speed of 12 cm s-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{-1}$$\\end{document} at 18.63 ms above bottom over an 11 month record. The near-bottom currents initially have a net southeastward flow, followed by westward and southward flows with the development of complex, anticyclonic flow patterns. Theoretical predictions and historical data show broad consistency with mean BML thickness but cannot explain the observed heterogeneity of local BML thickness. We postulate that deep pressure anomalies induced by passing surface mesoscale eddies and abyssal thermal fronts could affect BML thickness, in addition to local topographic effects. A simplified transport model is then used to study the influence of the BML on the interplay between turbulent diffusion and sediment settling in the transport of deep-seabed mining induced sediment plumes. Over a range of realistic parameter values, the effects of BML on plume evolution can vary significantly, highlighting that resolving the BML will be a crucial step for accurate numerical modelling of plume dispersal.

Analysis of the seismic effects of the local slope site of Longtoushan market town in Ludian Ms6.5 earthquake

In the Ludian Ms6.5 earthquake (Yunnan, China), Longtoushan market town and its vicinity showed significant differences in earthquake damage. To explain this phenomenon, this paper discusses the local engineering geological conditions, local topographic effects, and seismic response of the soil layer in Longtoushan market town. The results show that complex topography and varied engineering geological conditions will lead to significant differences in ground motion, and then lead to significant differences in building earthquake damage. Slope topography has an obvious influence on ground motion. From the foot of the slope to the top of the slope, the degree of influence gradually increases, and the influence in different directions is different, as shown: the closer to the top of the slope, the more significant the difference. This indicates that the serious damage to buildings built on the slope is caused by the amplification effect of local terrain and the differential effect of ground motion. Although the site belongs to Class II site, the near-surface geotechnical properties and their combination characteristics, the physical state and thickness of the overlying soil layer, the variation characteristics of shear wave velocity, the non-linear dynamic characteristics of the soil, and other factors play a decisive role in the amplification degree of ground motion. The significant difference in ground motion on the surface of the slope site leads to a significant difference in seismic damage to buildings on the site. The covering soil layer has a significant effect on the acceleration response spectrum. The conclusions obtained in this paper can provide a scientific basis for the site selection of engineering construction and seismic design of building structures.

Hybrid Forecasting of Wind for Air Pollution Dispersion over Complex Terrain

In case of an unplanned emission event from a nuclear power plant, the local population can be protected more efficiently when valid atmospheric dispersion model results are available. Atmospheric dispersion models use local meteorological variables as inputs. When atmospheric dispersion in the future is being predicted, a forecast of the local meteorological variables is needed. The most important variable in atmospheric dispersion modelling is wind, and accurately predicting ground level winds presents a challenge to numerical weather prediction models. We therefore develop hybrid models for forecasting local ground level wind at a single location where the terrain is complex and the average wind is weak and fluctuating. Wind speed and direction are modelled as west-east and south-north wind components. Each model is composed of a numerical weather prediction model and a Gaussian process statistical model that uses numerical weather predictions as some of its inputs and is trained on historical data to predict the output component. The most advanced Gaussian process models studied are of Gaussian process nonlinear autoregressive model with exogenous input (GPNARX) type. In addition to numerical weather predictions, they also use local meteorological variables, including the output variable, as their inputs. Numerical weather prediction results based on large scale information and fundamental knowledge of the system are thus supplemented by local measurements that better reflect the effects of local topography and land use. The models are tested by prediction and simulation. The wind components predicted by more advanced models are more accurate than raw or post-processed numerical weather prediction results. As an example, a model predicting 2D wind vector 1.5 h in advance achieves a NRMSE of 0.214 if it uses all the immediately available information. This is better than both the persistence model with NRMSE of 0.188 and post-processed NWP with NRMSE of 0.164. This demonstrates that hybrid modelling provides the best weather information for short-term and medium-term atmospheric dispersion forecasting. While the method is motivated by nuclear emission sources, it could also be applied to other pollution.

Hourly wind data for aeolian vibration analysis of overhead transmission line conductors

Fretting fatigue of conductors due to aeolian vibrations is an important phenomenon for the design and maintenance of electric transmission networks. The evaluation of exposure and susceptibility of a given span to aeolian vibrations requires information on the distribution of hourly wind speed and direction. Interpolation has been used to obtain wind data at non-instrumented locations; however, their accuracy is not adequate at locations far from stations and at locations in mountainous regions. Numerical Weather Prediction data sets provide wind information on a regular grid covering equally all regions; however, the spatial resolution is not adequate. A procedure is proposed using a mass-conserving diagnostic model (WindNinja) that incorporates a detailed map of local topography to improve predictions of wind direction. A second correction is proposed to account for local surface roughness as a function of wind direction and average canopy height from high-resolution LiDAR data. The proposed procedure is applied to nine meteorological stations and two experiment sites over southern Quebec, Canada. WindNinja was found to provide good estimates for the effects of local topography in mountainous regions. Wind speed after correction provides good agreement with hourly observations as well as with Weibull distributions fitted to the actual observations.

Determination and application of path duration of seismic ground motions based on the K-NET data in Sagami Bay, Japan

Duration models are one of the important parameters in ground-motion simulations. This model varies in different study areas, and plays a critical role in nonlinear structural response analysis. Currently, available empirical models are being globally used in ground-motion simulations, with limited research focusing on path duration in specific regions. In this study, we collected 6,486 sets of three-component strong-motion records from 29 K-NET stations in the Sagami Bay, Japan, and its surrounding areas between January 2000 to October 2018. We extracted the effective duration of 386 pieces of ground-motion records by manually picking up the S-wave arrival time and calculating the significant duration. We then obtained the path duration model of the study area based on the empirical equation of dynamic corner frequency and source duration of [7]. Compared with the results of the available empirical models, the Fourier spectrum of the simulated ground motion from our effective duration model showed higher accuracy in the long-term range, with less fitting residuals. This path duration model was then applied to simulate two earthquakes of MW5.4 and MW6.2, respectively, in the region using the stochastic finite-fault method with a set of reliable source, path, and site parameters determined for the study area. The simulation results of most stations fit well with observation records in the 0–30 Hz frequency band. For the MW5.4 earthquake, the simulated ground motions at KNG005/KNG010/SZO008 stations were relatively weak in the mid to high frequency band (1–30 Hz) because the quality factor and geometric diffusion model used in the simulation were the averages of the entire Sagami Bay region, causing a bias in the results of a few stations owing to local crustal velocity anomalies and topographic effects. For the MW6.2 earthquake, the simulated ground motions were relatively weak at all SZO and TKY stations, mainly because of the close distance from these stations to the epicenter and the complex seismic-wave propagation paths. The analysis suggests that the differences between the simulation results of the two earthquakes were mainly related to complex geological conditions and seismic-wave propagation paths.

Effect of Local Topography on Cell Division of Staphylococcus spp.

Surface engineering is a promising strategy to limit or prevent the formation of biofilms. The use of topographic cues to influence early stages of biofilm formationn has been explored, yet many fundamental questions remain unanswered. In this work, we develop a topological model supported by direct experimental evidence, which is able to explain the effect of local topography on the fate of bacterial micro-colonies of Staphylococcus spp. We demonstrate how topological memory at the single-cell level, characteristic of this genus of Gram-positive bacteria, can be exploited to influence the architecture of micro-colonies and the average number of surface anchoring points over nano-patterned surfaces, formed by vertically aligned silicon nanowire arrays that can be reliably produced on a commercial scale, providing an excellent platform to investigate the effect of topography on the early stages of Staphylococcus spp. colonisation. The surfaces are not intrinsically antimicrobial, yet they delivered a topography-based bacteriostatic effect and a significant disruption of the local morphology of micro-colonies at the surface. The insights from this work could open new avenues towards designed technologies for biofilm engineering and prevention, based on surface topography.

Preliminary investigation on the extreme rainfall event during July 2021 in Henan Province and its multi-scale processes

<p indent="0mm">During July 17–22, 2021, a disastrous extreme rainfall event occurred in Henan Province, China, with the maximum 6-day accumulated rainfall obtained from meteorological observations being <sc>1122.6 mm</sc> (Hebi City). The maximum hourly rainfall reached <sc>201.9 mm</sc> (Zhengzhou city), which broke the record in the inland of China. The daily rainfall of 1/6 of the national rain gauge stations in Henan Province exceeded their respective records. In this study, a comprehensive review and a preliminary investigation on the multi-scale atmospheric processes are conducted by using rain gauge observations, sounding data, Doppler weather radar observations and the ERA5 reanalysis data. Results show that this extreme rainfall event was caused by the joint effect of multi-scale atmospheric systems in the middle and low latitudes, and the effect of local topography: (1) The western Pacific subtropical high is abnormally northerly and strong, as compared with the mean circulation in July during the 30-year period of 1991–2020. It prevented the tropical cyclone “In-fa” from moving northward, and was conducive to the westward movement of “In-fa” along its southern periphery. An easterly low-level jet formed between the subtropical high and “In-fa”, which strengthened the water vapor transport to East China. (2) The water vapor was transported from the South China Sea to the Northwest Pacific by the southwest monsoon, and then was carried northwards by the tropical cyclone “In-fa”. The water vapor over the Northwest Pacific was transported to Henan Province by the easterly jet on the north of “In-fa” and the southeast flow around the southwestern periphery of the western Pacific subtropical high. This abnormal remote water vapor transport associated with the tropical cyclone caused a positive anomaly in precipitable water in Henan. (3) In the upper troposphere, the location of Henan Province was in front of an upper-troposphere trough. In the lower troposphere, there was a low-level vortex or an inverted trough over Henan and its periphery. The synoptic conditions over Henan were conducive to the convergence and upward motion of lower-tropospheric atmosphere. In addition, the Funiu and Taihang mountain ranges favored the convergence of water vapor and the uplift of the approaching easterly or southeasterly airflow. (4) The subtropical high and the abnormally strong continental high connected and formed a “high-pressure dam”, which prevented mid-latitude cold air from moving southward. The extreme rainfall in Zhengzhou occurred in a warm-humid environment which resulted in a low-centroid precipitation resembling tropical precipitation. During the two days with the heaviest rainfall in Zhengzhou, convection was initiated continuously and merged into the main convective cluster from the southeast, south and southwest respectively, which helped maintain the mesoscale convective system in Henan for a long time.

Lost Horizon: Quantifying the Effect of Local Topography on Global 21 cm Cosmology Data Analysis

Abstract We present an investigation of the horizon and its effect on global 21 cm observations and analysis. We find that the horizon cannot be ignored when modeling low-frequency observations. Even if the sky and antenna beam are known exactly, forward models cannot fully describe the beam-weighted foreground component without accurate knowledge of the horizon. When fitting data to extract the 21 cm signal, a single time-averaged spectrum or independent multi-spectrum fits may be able to compensate for the bias imposed by the horizon. However, these types of fits lack constraining power on the 21 cm signal, leading to large uncertainties on the signal extraction, in some cases larger in magnitude than the 21 cm signal itself. A significant decrease in uncertainty can be achieved by performing multi-spectrum fits in which the spectra are modeled simultaneously with common parameters. The cost of this greatly increased constraining power, however, is that the time dependence of the horizon’s effect, which is more complex than its spectral dependence, must be precisely modeled to achieve a good fit. To aid in modeling the horizon, we present an algorithm and Python package for calculating the horizon profile from a given observation site using elevation data. We also address several practical concerns such as pixelization error, uncertainty in the horizon profile, and foreground obstructions such as surrounding buildings and vegetation. We demonstrate that our training-set-based analysis pipeline can account for all of these factors to model the horizon well enough to precisely extract the 21 cm signal from simulated observations.

Effects of local topography on the mobility of rock avalanches: A statistical analysis based on 36 cases from south-western China

Rock avalanches are the extremely rapid flow-like movements of dry debris with extreme destructive potential. The mobility of these landslides can be characterised with Fahrböschung (defined as the ratio of fall height H over runout distance L) and runout distance. Here we statistically analyze the effects of local topography on the mobility of rock avalanches using a database that includes 36 well-documented events that occurred in south-western China, half of which induced by the 2008 Wenchuan earthquake. The analysis is conducted by distinguishing the three basic confinement categories of the rock avalanches, i.e. L-confined (laterally confined), U-confined (unconfined) and F-confined (frontally confined). The results of simple linear regression for H/L ratio and of multiple linear regression for runout distance L indicate that runout distance is preferable as a measure of mobility compared with H/L ratio due to the higher coefficient of determination. Moreover, the box-plots of residuals of the logarithm of runout distance indicated that frontal confinement tends to reduce runout distance, while lateral confinement enhances it. However, additional statistical analyses should be conducted exploiting a larger database of rock avalanches from a wider variety of environments.

Estimates of abundance and biomass of cephalodia and their relationship to nitrogen deposition in some British populations ofLobaria pulmonaria(L.) Hoffm.

AbstractInternal cephalodia ofLobaria pulmonariawere examined in two British locations, one in western Scotland (Isle of Skye) and the other in England (Cumbria, Lake District), sites which were predicted to have contrasting levels of fixed nitrogen deposition. Cephalodia were found to occupy a small proportion of the total biomass averaging (&lt;1%) in both areas. Modelled nitrogen deposition in the sites in Cumbria was 3–6 times higher than in the Skye sites but the cephalodium relative biomass was not significantly different. It is suggested that local climatic and topographic effects might have reduced the estimated rate of nitrogen deposition at the former sites.

A New Set of Tools for the Generation of InSAR Visibility Maps over Wide Areas

Multi-temporal Interferometric Synthetic Aperture Radar (MTInSAR) is a solid and reliable technique used to measure ground motion in many different environments. Today, the scientific community and a wide variety of users and stakeholders consider MTInSAR a precise tool for ground motion-related applications. The standard product of a MTInSAR analysis is a deformation map containing a high number of point-like measurement points (MP) which carry information on ground motion. The density of MPs is uneven, and they cannot be extracted continuously at large scale due to geometrical distortions and unfavourable landcover. It is a good practice to assess the feasibility of the interferometric analysis ahead of data processing. This technical note proposes a ready-to-use set of tools aimed at updating existing methods for modelling the effects of local topography and land cover on MTInSAR approaches. The goal of the tools is to provide InSAR experts and non-experts with a fast and automatic way to derive visibility maps, useful for pre-processing screening of a target area, and to forecast the expected density of MP over a specified area. Moreover, the visibility maps are a valid support for users to better understand the available standard and advanced interferometric results. Two workflows are proposed: the first generates the so-called Rindex map (Ri_m) to estimate the influence of topography on MP detection, the second is used to derive a land cover-calibrated Ri_m seen as a probabilistic model for MP detection (MPD_m). The proposed set of tools was applied in the context of the Alpine arc, whose climatic, morphological, and land cover characteristics represent a challenging environment for any interferometric approach.

Satellite-Based Regionalization of Solar Irradiation in Vietnam by k-Means Clustering

AbstractThis study presents the application of k-means clustering to satellite-based solar irradiation in different regions of Vietnam. The solar irradiation products derived from the Himawari-8 satellite, named AMATERASS by the solar radiation consortium under the Japan Science and Technology Agency (JST), are validated with observations recorded at five stations in the period from October 2017 to September 2018 before their use for clustering. High correlations among them enable the use of satellite-based daily global horizontal irradiation for spatial variability analysis and regionalization. With respect to the climate regime in Vietnam, the defined 6-cluster groups demonstrate better agreement with the conventionally classified seven climatic zones rather than the four climatic zones of the Köppen classification. The spatial distribution and seasonal variation in the regionalized solar irradiation reflect interchangeable influences of large-scale atmospheric circulation in terms of the East Asian winter monsoon and the South Asian summer monsoon as well as the effect of local topography. Higher daily averaged solar radiation and its weaker seasonal variation were found in two clusters in the southern region where the South Asian summer monsoon dominates in the rainy season. Pronounced seasonal variability in solar irradiation in four clusters in the northern region is associated with the influence of the East Asian monsoon, resulting in its clear reduction during the winter months.

Topographic Correction of Geothermal Heat Flux in Greenland and Antarctica

AbstractWe present a new approach to account for the influence of subglacial topography on geothermal heat flux beneath the Greenland and Antarctic ice sheets. We first establish a simple empirical proportionality between local geothermal flux and topographic relief within a given radius, based on a synthesis of existing observations of these properties elsewhere on Earth. This analysis essentially yields a high‐pass filter that can be readily applied to existing large‐scale geothermal heat flux fields to render them consistent with known subglacial topography. This empirical approach avoids both the geometric limitations of existing analytic models and the complex boundary conditions required by numerical heat flow models, yet it also produces results that are consistent with both of those methods, for example, increased heat flux within valleys and decreased heat flux along ridges. Comparison with borehole‐derived geothermal heat flux suggests that our topographic correction is also valid for non‐ice‐covered areas of Earth and that a borehole location uncertainty of &gt;100 m can limit the value of its inferred heat flux. Ice‐sheet‐wide application of this approach indicates that the effect of local topography upon geothermal heat flux can be as important as choice of regional geothermal heat flux field across a small portion of Antarctica (2%) and a larger portion of Greenland (13%), where subglacial topography is best resolved. We suggest that spatial variability in geothermal heat flux due to topography is most consequential in slower‐flowing portions of the ice sheets, where there is no frictional heating due to basal sliding. We conclude that studies of interactions between ice sheets and geothermal heat flux must consider the effect of subglacial topography at sub‐kilometer horizontal scales.

Valley Winds at the Local Scale: Correcting Routine Weather Forecast Using Artificial Neural Networks

In regions of complex topography, local flows are difficult to forecast on a routine basis, especially in stable conditions, due to the coarse resolution of operational models. The Cadarache valley (southeastern France) features this sort of complex topography. The Weather Research and Forecasting (WRF) model is run daily to forecast the weather in this region with a horizontal resolution of 3 km. Such a resolution cannot resolve all topography details of the small Cadarache valley, and therefore its local wind patterns. Other variables, however, that are less dependent on the subgrid topography, are satisfactorily forecasted, and used as inputs to an artificial neural network (ANN) designed to reproduce wind observations inside the valley from WRF forecasts. A variable selection procedure identified 5 key input variables that best drive the ANN. With respect to the WRF output, the ANN significantly improves forecasted low-level winds, both for speed and direction. This study demonstrates the potential for the ANN technique to be used as a correcting tool to forecast weather conditions at the local scale when numerical modeling is performed at a resolution too coarse to take into account the effect of local topography.

Extreme Rainfall over Complex Terrain: An Application of the Linear Model of Orographic Precipitation to a Case Study in the Italian Pre-Alps

Intense meteorological events are the primary cause of geohazard phenomena in mountain areas. In this paper, we present a study of the intense rainfall event that occurred in the provinces of Lecco and Sondrio from 11 to 12 June 2019. The aim of our work is to understand the effect of local topography on the spatial distribution of rainfall and to attempt the reconstruction of a realistic rainfall field relative to that extreme event. This task represents a challenge in the context of complex orography. Classical rain-gauge interpolation techniques, such as Kriging, may be too approximate, while meteorological models can be complex and often unable to accurately predict rainfall extremes. For these reasons, we tested the linear upslope model (LUM) designed for estimating rainfall records in orographic precipitation. This model explicitly addresses the dependence of rainfall intensification caused by the terrain elevation. In our case study, the available radio sounding data identified the convective nature of the event with a sustained and moist southern flow directed northward across the Pre-Alps, resulting in an orographic uplift. The simulation was conducted along a smoothed elevation profile of the local orography. The result was a reliable reconstruction of the rainfall field, validated with the ground-based rain gauge data. The error analysis revealed a good performance of the LUM with a realistic description of the interaction between the airflow and local orography. The areas subjected to rainfall extremes were correctly identified, confirming the determinant role of complex terrain in precipitation intensification.

Assessing the interaction of seismically loaded adjacent valleys using time-domain approach

Amplification or attenuation of seismic waves while passing through the soil medium can be due to soil type and its stratification or local topographic effects. Such aspects have been theoretically explained in many researches by means of ground response analysis. The results of seismic ground response analysis provide the necessary and realistic information for seismic design of structures and soil-structure interaction problems. In present study, two-dimensional finite element method is applied to evaluate the ground response of valley environments and estimation their interaction effects using time-domain approach. In this regard different cases include free field condition, single valley and double valleys environments are considered. Numerical simulations of seismic wave propagation for these cases are carried out and compared with each other. The results show that irregular topography can greatly amplify the seismic waves. On the other hand, if there are adjacent topographies, due to interaction of them, the amplification effect can be substantially increased. This amplification can be attenuated by moving away from the valley center to free field conditions.

Local topography effects on the surface temperatures on Mars – Application to the case of Recurring Slope Lineae (RSL)

Recurring Slope Lineae (RSL) are dark linear recurrent features which incrementally lengthen and fade each year on Martian slopes. Their activity during warmest seasons rises the question of modern martian water related process. To investigate this question, this study focuses on the thermal context of slopes hosting RSL. The paper presents a numerical study of surface and subsurface temperatures at high spatial resolution (1 m/pix) of three well-described RSL sites: Palikir Crater, Coprates Chasma and Rauna Crater. We then compare our local thermal simulations to quantitative measurements of the length and timing of RSL lengthening and fading in these three sites. We underline that RSL sites surface temperatures are poorly correlated with RSL morphology's changes. Indeed, lineae lengthening occurs while surface temperature are under the melting point of pure water (273 K) for at least two sites: Coprates Chasma and Rauna Crater, for two different sets of surface physical properties. We also highlight the significant differences in temperature range while lengthening occurs for all the sites, from ~220 K in Coprates Chasma site to a maximum of ~300 K in Palikir Crater. RSL are sometimes associated with signals in topography, involving significant heating variations of the surface, which can yield to the formation of local winds. Facing the thermal inconsistency between wet triggering processes and RSL reported activity, we suggest that RSL are more probably dry processes.