Combined solar and QBO effects on the modes of low-frequency atmospheric variability in the Northern Hemisphere

We examine joint effects of the solar activity and phase of the quasi-biennial oscillation (QBO) on modes of low-frequency variability of tropospheric circulation in the Northern Hemisphere in winter. The winter months (December–March) are stratified by the solar activity into two (below/above median) classes, and each of these classes is subdivided by the QBO phase (west or east). The variability modes are determined by rotated principal component analysis of 500 hPa heights separately in each class of solar activity and QBO phase. Detected are all the modes known to exist in the Northern Hemisphere. The solar activity and QBO jointly affect the shapes, spatial extent, and intensity of the modes; the QBO effects are, however, generally weaker than those of solar activity. For both solar maxima and minima, there is a tendency to the east/west phase of QBO to be accompanied by a lower/higher activity of zonally oriented modes and increased meridionality/zonality of circulation. This means that typical characteristics of circulation under solar minima, including a more meridional appearance of the modes and less activity of zonal modes, are strengthened during QBO-E; on the other hand, circulation characteristics typical of solar maxima, such as enhanced zonality of the modes and more active zonal modes, are more pronounced during QBO-W. Furthermore, the zonal modes in the Euro-Atlantic and Asian sectors (North Atlantic Oscillation, East Atlantic pattern, and North Asian pattern) shift southwards in QBO-E, the shift being stronger in solar maxima.     

Continuous gas monitoring in the West Bohemian earthquake area,Czech Republic: First results

Two stations monitoring concentrations of carbon dioxide and radon in soil gas (Oldřišská and Novy Kostel) and one station monitoring flow of carbon dioxide at a mofette (Soos) have been operated in the area of the West Bohemian earthquake swarms. We present preliminary results obtained on the base of four-year observations. We found that data are not influenced considerably by barometric pressure. Although the CO₂ concentration varies greatly, the long-term trends at stations Oldřišská and Novy Kostel are similar, which indicates that the CO₂ flow is controlled by common geogenic processes. Also temporal trends of CO₂ and Rn concentrations in soil gas at individual stations are analogous. We found diurnal variations of both CO₂ concentration in soil gas and the CO₂ flow at mofettes due to the earth tides. A response to tides of semi-diurnal period is insignificant in CO₂ concentration and only weak in the CO₂ flow. We also examined possible pre-seismic, co-seismic and post-seismic effects of the intensive 2008 earthquake swarm on the CO₂ concentration at Oldřišská and Novy Kostel, and on the CO₂ flow at Soos. However, all potential indications were insignificant and there has not been proven any influence of the swarm on the CO₂ concentration as well as on the CO₂ flow. Nevertheless, a gradual decrease of amplitudes of diurnal variations before the swarm and the lowest amplitudes during the swarm is a noteworthy phenomenon, which might indicate the strain changes of the rock associated with earthquake swarm.     

Geoelectrical and geological structure of the crust in Western Slovakia

Electrical resistivity of the Earth’s crust is sensitive to a wide range of petrological and physical parameters, and it particularly clearly indicates crustal zones that have been tectonically or thermodynamically disturbed. A complex geological structure of the Alpine nappe system, remnants of older Hercynian units and Neogene block tectonics in Western Slovakia has been a target of recent magnetotelluric investigations which made a new and more precise identification of the crustal structural elements of the Western Carpathians possible. A NW-SE magnetotelluric profile, 150 km long, with 30 broad-band and 3 long-period magnetotelluric sites, was deployed, crossing the major regional tectonic elements listed from the north: Brunia (as a part of the European platform), Outer Carpathian Flysch, Klippen Belt, blocks of Penninic or Oravicum crust, Tatricum and Veporicum. Magnetotelluric models were combined with previous seismic and gravimetric results and jointly interpreted in the final integrated geological model. The magnetotelluric models of geoelectrical structures exhibit strong correlation with the geological structures of the crust in this part of the Western Carpathians. The significant resemblance in geoelectrical and crustal geological structures are highlighted in shallow resistive structures of the covering formations represented by mainly Tertiary sediments and volcanics. Also in the deeper parts of the crust highly resistive and conductive structures are shown, which reflect the original building Hercynian crust, with superposition of granitoids or granitised complexes and lower metamorphosed complexes. Another important typical feature in the construction of the Western Carpathians is the existence of young Neogene steep fault zones exhibited by conductive zones within the whole crust. The most significant fault zones separate individual blocks of the Western Carpathians and the Western Carpathians itself from the European Platform.     

SfM-MVS Photogrammetry for Splash Erosion Monitoring under Natural Rainfall

An understanding of splash erosion is the basis to describe the impact of rain characteristics on soil disturbance. In typical splash cup experiments, splashed soil is collected, filtered, and weighed. As a way to collect additional data, our experiments have been supplemented by a photogrammetric approach. A total of three soils were tested across three sites, one in the Czech Republic and two in Austria, all equipped with rain gauges and disdrometers to measure rainfall parameters. The structure from motion multiview stereo (SfM-MVS) photogrammetric method was used to measure the raindrops impact on the soil surface. The images were processed using Agisoft PhotoScan, resulting in orthophotos and digital elevation models (DEMs) with a resolution of 0.1 mm/pix. The surface statistics included the mean surface height (whose standard deviation was used as a measure of surface roughness), slope, and other parameters. These parameters were evaluated depending on soil texture and rainfall parameters. The results show a linear correlation between consolidation and splash erosion with a coefficient of determination (R²) of approximately 0.65 for all three soils. When comparing the change in soil volume with rainfall parameters, the best correlation was found with the maximum 30-minintensity (I₃₀), resulting in R² values of 0.48 (soil A, silt loam, 26% clay), 0.59 (soil B, silt loam, 18% clay), and 0.68 (soil C, loamy sand, 12% clay). The initial increase in the sample volume for the lowest splashed mass corresponds with the increase in the clay content of each of the soils. Soil A swells the most. Soil B swells less. Soil C does not swell at all and consolidates the most. We derived the relationship between the photogrammetrically measured change in surface height and the splash erosion (measured by weight) by accounting for the effect of the clay content.     

Droplet Concentration and Size Distribution in Haze and Fog

Fog (haze) droplet concentrations and size distributions were measured at five sampling sites representing rural and urban regions and a highly polluted marine-urban environment. Droplet imprints in a thin gelatine layer were evaluated and compared to the measurement by light scattering instruments. This enabled conditions for the application of the logarithmic-normal size distribution and for the classification of typical fog droplet size distributions to be established. In particular, the parameters featuring the width and asymmetry of a size distribution were suggested and calculated. Advantages and drawbacks of the applied droplet sampling and evaluation technique are discussed in more detail.     

Numerical Simulations of Tsunami Waves and Currents for Southern Vancouver Island from a Cascadia Megathrust Earthquake

The 1700 great Cascadia earthquake (M = 9) generated widespread tsunami waves that affected the entire Pacific Ocean and caused damage as distant as Japan. Similar catastrophic waves may be generated by a future Cascadia megathrust earthquake. We use three rupture scenarios for this earthquake in numerical experiments to study propagation of tsunami waves off the west coast of North America and to predict tsunami heights and currents in several bays and harbours on southern Vancouver Island, British Columbia, including Ucluelet, located on the west coast of the island, and Victoria and Esquimalt harbours inside Juan de Fuca Strait. The earthquake scenarios are: an 1100-km long rupture over the entire length of the subduction zone and separate ruptures of its northern or southern segments. As expected, the southern earthquake scenario has a limited effect over most of the Vancouver Island coast, with waves in the harbours not exceeding 1 m. The other two scenarios produce large tsunami waves, higher than 16 m at one location near Ucluelet and over 4 m inside Esquimalt and Victoria harbours, and very strong currents that reach 17 m/s in narrow channels and near headlands. Because the assumed rupture scenarios are based on a previous earthquake, direct use of the model results to estimate the effect of a future earthquake requires appropriate qualification.     

Highly reducing conditions during Alpine metamorphism of the Malenco peridotite (Sondrio,northern Italy) indicated by mineral paragenesis and H2 in fluid inclusions

During regional metamorphism of the Malenco serpentinized peridotite (Sondrio, northern Italy), the mineral assemblage pentlandite-awaruite-magnetite-native copper-antigorite-brucite-olivine-diopside is formed. The opaque assemblage indicates very reduced fluids with fO₂ values 4 log units below QFM. Primary fluid inclusions were trapped in diopside overgrowth, contemporaneous with the opaque assemblage. These metamorphic fluids are saline aqueous solutions (about 10.4 mol% NaCl equivalent) and contain molecular H₂ of approximately 1 mol%, as shown by micro-Raman analysis and microthermometry. The fluids are interpreted to have been formed during deserpentinization at the olivine-in isograd under strong reducing conditions.     

Chinese tombs oriented by a compass: Evidence from paleomagnetic changes versus the age of tombs

Extant written records indicate that knowledge of an ancient type of compass in China is very old — dating back to before the Han dynasty (206 BC-220 AD) to at least the 4th century BC. Geomancy (feng shui) was practised for a long time (for millenia) and had a profound influence on the face of China’s landscape and city plans. The tombs (pyramids) near the former Chinese capital cities of Xi’an and Luoyang (together with their suburban fields and roads) show strong spatial orientations, sometimes along a basic South-North axis (relative to the geographic pole), but usually with deviations of several degrees to the East or West. The use of the compass means that the needle was directed towards the actual magnetic pole at the time of construction, or last reconstruction, of the respective tomb. However the magnetic pole, relative to the nearly ‘fixed’ geographic pole, shifts significantly over time. By matching paleomagnetic observations with modeled paleomagnetic history we have identified the date of pyramid construction in central China with the orientation relative to the magnetic pole positions at the respective time of construction. As in Mesoamerica, where according to the Fuson hypothesis the Olmécs and Maya oriented their ceremonial buildings and pyramids using a compass even before the Chinese, here in central China the same technique may have been used. We found a good agreement of trends between the paleodeclinations observed from tomb aligments and the available global geomagnetic field model CALS7K.2.     

Diurnal dynamics of streamflow in an upland forested micro‐watershed during short precipitation‐free periods is altered by tree sap flow

Diurnal variations in streamflow are becoming acknowledged as a way of analysing how changing climatic conditions and land use affects watersheds but also as a way to understand watersheds as a whole. Yet not many studies from uplands below 900 mm mean annual precipitation zone are available from European countries. During the 2012 growing season, a sampling campaign took place in an upland forested micro‐watershed, Czech Republic (65 ha). Tree sap flow, rainfall and temperature were measured continuously, while streamflow at the discharge point and soil moisture were estimated from short‐term measurements. Short precipitation‐free periods lasting several days were identified for evaluation of trends in diurnal dynamics of both sap flow and streamflow. The results demonstrated that during these periods, the main factor altering streamflow was almost exclusively tree sap flow. A decrease in streamflow was observed during the day and an increase at night. The decline in sap flow after sunset was accompanied by a continuous increase in streamflow throughout the night up to its initial maximum in the morning. The amplitude in diurnal variations reached 18%. The observed time lag between the diurnal variations of sap flow and streamflow was approximately 2 h. Relatively low changes in diurnal dynamics of streamflow pointed out a strong regulatory role of the forest in buffering water discharge from the catchment. Copyright © 2015 John Wiley & Sons, Ltd.