Anomalous curvature of equipotential surfaces due to variations in the Earth's rotation

Summary The anomalies of the Gaussian curvature of geopotential equipotential surfaces due to variations in the Earth's rotation vector have been derived theoretically.

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am mmuu ¶rt; aau a uu nmunmuaa, a auauu ma au u.

     

Bestimmung der Dimensionen des Erdellipsoids aus den Europäischen Astronomischgeodätischen Netzen

Резюме Сообщаются результаты исследований по выводу размеров земного эллипсоида по градусным измерениям стран Европы, выполненном двумя методами: методом площадей на основе принципа развертывания (решение I) и методом площадей на основе принципа проектирования (решение II). В гл. I рассматривается теория обоих методов. В классическую теорию метода площадей на основе принципа развертывания (раздел 2) не вносятся существенные изменения. Но коэффициенты соответствующих уравнений градусных измерений, являющиеся функциями геодезических координат и длины и азимута геодезической линии, преобразованы и представлены в виде функций только геодезических координат концов этой линии. Это внесло боляшое облегчение в вычислительную работу, т. к. главные члены формул получили простой вид, а поправочные члены оказалось возможным решить графическим путем. В теории метода площадей на основе принципа проектирования (раздел 3) выведено выражение для поправки большой полуоси эллипсоида в виде функции координат центра нового эллипсоида и поправки сжатия. Точность этого выражения порядка расстояния старого и нового эллипсоидов в исходном пункте. В разделе 4 дана теория преобразования системы уклонений отвеса при методе развертывания в систему уклонений отвеса при методе проектирования, исходя из исследований Молоденского [4] (способ I), и используя дифференциальные формулы при методах развертывания и проектирования (способ II). Гл. II содержит очень краткое описание градусных измерений, выполненных в странах Европы. В гл. III изложены некоторые числовые результаты всей выполненной работы. В гл. IV даются некоторые выводы и заключения на основе полученных результатов. Прежде всего отмечается практически полное совпадение значений параметров эллипсоида, выведенных методом площадей на основе принципа развертывания и методом площадей на основе принципа проектирования. Влияние эффекта развертывания на величину большой полуоси эллипсоида при выводе на основе принципа проектирования и с использованием обычной системы смешанных уклонений отвеса в Европе равно применро 15м (табл. 4). Относительно вывода сжатия эллипсоида отмечается, что его точность мала вследствие неблагоприятного расположения использованных градусных измерений. Этот факт иллюстрирустся тем, что изменение сжатия на 1 единису в его знаменателе вызывает изменение большой полуоси лишь в 4–8м (табл. 5). По выводу элементов ориентировки эллипсоида отмечается, что во всех решенных вариантах их значения практически одинаковы, и что влияние эффекта развертывания здесь ничтожно. Наиболее достоверными считаются результаты вывода в варианте В, т. е. Без использования наблюдений астрономических азимутов. Средние из значений параметров, выведенных при использовании принципа проектирования и принципа развертывания в этом варианте даны уравнениями (32)–(34). Приведенные результаты показывают, что ни эллипсоид Бесселя и ни эллипсоид Хейфорда не подходят для астрономо-геодезических сетей Европы. Можно заключить, что для этой цели эллипсоид Красовского более подходит, чем какой—нибудь другой из известных эллипсоидов. Как известно, в европейских странах народной демократии этот эллипсоид уже применяется. Его применение в Европе является научно обоснованным.

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Anschrift: Kostelní 42, Praha 7.     

Phase-coherent oscillatory modes in solar and geomagnetic activity and climate variability

Oscillatory modes with the period of approximately 7–8 yr were detected in monthly time series of sunspot numbers, geomagnetic activity aa index, NAO (North Atlantic Oscillation) index and near-surface air temperature from several mid-latitude European locations. Instantaneous phases of the modes underwent synchronization analysis and their statistically significant phase coherence, beginning from 1950s, has been observed. Thus the statistical evidence for a coupling between solar/geomagnetic activity and climate variability has been obtained from continuous monthly data, independent of the season, however, confined to the temporal scale related to oscillatory periods about 7–8 yr.     

Deflections of the vertical on the territory of Europe from satellite data

amu n¶rt;ma u ma mum au n¶rt;¶rt; m unu¶rt;a, amu n u amu uu, u n nmu ¶rt;a [2]; ¶rt;am nu uum, n m uum ¶rt;um au mau u ma ¶rt; muu¶rt;a.     

Interferometric evidence for the observation of ground backscatter originating behind the CUTLASS coherent HF radars

Interferometric techniques allow the Super-DARN coherent HF radars to determine the elevation angles of returned backscatter, giving information on the altitude of the scatter volume, in the case of ionospheric backscatter, or the reflection altitude, in the case of ground backscatter. Assumptions have to be made in the determination of elevation angles, including the direction of arrival, or azimuth, of the returned signals, usually taken to be the forward look-direction (north) of the radars, specified by the phasing of the antenna arrays. It is shown that this assumption is not always valid in the case of ground backscatter, and that significant returns can be detected from the backward look-direction of the radars. The response of the interferometer to backscatter from behind the radar is modelled and compared with observations. It is found that ground backscatter from a field-of-view that is the mirror image of the forward-looking field-of-view is a common feature of the observations, and this interpretation successfully explains several anomalies in the received backscatter.     

Recent remote sensing applications for hydro and morphodynamic monitoring and modelling

It is not new to recognize that data from remote sensing platforms is transforming the way we characterize and analyse our environment. The ability to collect continuous data spanning spatial scales now allows geomorphological research in a data rich environment and this special issue [coming just eight years after the 2010 special issue of Earth Surface Processes and Landforms (ESPL) associated with the remote sensing of rivers] highlights the considerable research effort being made to exploit this information, for studies of geomorphic form and process. The 2010 special issue on the remote sensing of rivers noted that fluvial remote sensing articles made up some 14% of the total river related articles in ESPL. A similar review of articles up to 2017 reveals that this figure has increased to around 25% with a recent proliferation of articles utilizing satellite‐based data and structure from motion photogrammetry derived data. It is interesting to note, however that many studies published to date are proof of concept, concentrating on confirming the accuracy of the remotely sensed data at the expense of generating new insights and ideas on fluvial form and function. Data is becoming ever more precise and researchers should now be concentrating on analysing these early data sets to develop increased geomorphic insight, to challenge existing paradigms and to advance geomorphic science. The prospect of this occurring is increased by the fact that many of the new remote sensed platforms allow accurate spatial data to be collected cheaply and efficiently, reducing the need for substantial research funding to advance river science. Fluvial geomorphologists have never before been in such a liberated position. As techniques and analytical skills continue to improve it is inevitable that the prediction that remotely sensed data will revolutionize our understanding of geomorphological form and process will prove true, altering our ideas on the very nature of system functioning in the process. © 2018 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.     

Ground-air temperature tracking and multi-year cycles in the subsurface temperature time series at geothermal climate-change observatory

Long-term observations of air, near-surface (soil) and ground temperatures, collected between 1994 and 2011, monitored in the Geothermal Climate Change Observatory at Spo?ilov, Prague (GCCO) are analyzed to better understand the relationship between these quantities and to describe the mechanism of heat transport at the land-atmosphere boundary layer. The 17 years long monitoring series provided a surprisingly small mean ground-air temperature offset of only 0.31 K with no clear annual course and with the offset value changing irregularly even on a daily scale. Such value is substantially lower than similar values (1–2 K and more) found elsewhere, but it may be well characteristic for a mild temperate zones, when all so far available information referred rather to more southern locations. As many other observed geophysical data, temperature time series consist of a systematic pattern (usually a set of identifiable components) contaminated by random noise, which makes the identification of the proper pattern difficult. To identify the existing systematic patterns (cycles) of the temperature-time series at several depth levels in the investigated depth interval 0–40 m, the observed data were processed with the help of the Fast Fourier Transform (FFT) and Recurrence Quantification Interval (RQI) analysis. The latter represents recently developed powerful technique to uncover hidden periodicities in a noisy time environment. At low frequency band the RQI may provide far finer resolution than the conventional FFT technique. The results proved considerable similarity for all investigated depth levels. In addition to the annual wave all measured series proved to have a more complex pattern including predominantly 8-year and 11 years long periodicities. The results were compared with similar analysis of the meteorological air temperature series as well as with the results of other similar studies. The potential dynamics explaining the occurrence of the 8-year wave is briefly discussed.     

Mapping hydraulic biotopes using terrestrial laser scan data of water surface properties

For more than a decade, habitat mapping using biotopes (in‐channel hydraulically‐defined habitats) has underpinned aquatic conservation in the UK through (a) providing baseline information on system complexity and (b) allowing environmental and ecological change to be monitored and evaluated. The traditional method used is the subjective river habitat or corridor survey. This has recently been revised to include the floodplain via GeoRHS, but issues still exist concerning development of a national database due to the labour intensive nature of the data collection, subjectivity issues between samplers, temporal changes, the fuzzy nature of perceived habitats and habitat boundaries. This paper takes an innovative approach to biotope definition using high resolution spatial data to define water surface roughness for two representative reaches of the River South Tyne, Cumbria, and the River Rede, Northumberland, UK. Data was collected using a terrestrial laser scanner (TLS) and hydraulic variability simply expressed through assigning a local standard deviation value to a set of adjacent water surface values. Statistical linkage of these data with biotope locations defined visually in the field allowed complete mapping of the surveyed reach defining habitat and biotope areas to the fine scale resolution of the TLS data. Despite issues of data loss due to absorption and transmission through the water, the reflected signal generated an extremely detailed and objective map of the water surface roughness, which may be compared with known biotope locations as defined by visual identification in the field. The TLS accuracy achieved in the present study is comparable with those obtained using hyperspectral imagery: with 84% of the pool/glide/marginal deadwater amalgamated biotope, 88% of riffles, 57% of runs and 50% of the amalgamated cascade/rapid biotope successfully plotted. It is clear from this exercise that biotope distribution is more complex than previously mapped using subjective techniques, and based upon the water surface roughness delimiters presented in this study, the amalgamation of pools with glides and marginal deadwaters, riffles with unbroken standing waves, and cascades with rapids, is proposed. Copyright © 2010 John Wiley & Sons, Ltd