Data mining is a valuable tool in meteorological applications. Properly selected data mining techniques enable researchers to process and analyze massive amounts of data collected by satellites and other instruments. Large spatial-temporal datasets can be analyzed using different linear and nonlinear methods. The Self-Organizing Map (SOM) is a promising tool for clustering and visualizing high dimensional data and mapping spatial-temporal datasets describing nonlinear phenomena. We present results of the application of the SOM technique in regions of interest within the European re-analysis data set. The possibility of detecting climate change signals through the visualization capability of SOM tools is examined.
As observational data has attained new legal status, allowing their integration into open Internet systems, and experimental data continues to be assembled in common and free platforms, state of the art, easy to access data repositories have been designed in Spain. These repositories have removed many obstacles to re-utilization of GIS and other data. European legislation has also made advances in opening biodiversity data, including a European space in the Latin-American grid infrastructure. Open access biomedical repositories attract commercial attention while astronomical, meteorological, and oncological institutions promote data quality and access. This paper describes recent approaches to open access data for science in Spain.
Africa is a rising star - one of the most desirable investment destinations in the world. Nonetheless, economic growth is uneven among African countries, and many obstacles must be overcome in order to realize the full potential of opportunity. To achieve long-term sustainable investment results, and ultimately progress towards Sustainable Development goals, many risks must be isolated, analyzed, and mitigated. This paper introduces the concept of Sustainability Risk, identifying a set of major risk components for Sub-Saharan Africa and building an integral measure to quantify the degree of remoteness of the forty-six Sub-Saharan Africa countries from the total set of threats considered. The countries are separated into distinct groups with similar characteristics in terms of Sustainability Risk, and an analysis for potential decision-making, based on the visualization of the countries' position in relation to the major sustainability threats, is performed for each group. The research identifies risks with maximum impacts.
Speech recognition and language analysis of spontaneous speech arising in naturally spoken conversations are becoming the subject of much research. However, there is a shortage of spontaneous speech corpora that are freely available for academics. We therefore undertook the building of a natural conversation speech database, recording over 200 hours of conversations in English by over 600 local university students. With few exceptions, the students used their own cell phones from their own rooms or homes to speak to one another, and they were permitted to speak on any topic they chose. Although they knew that they were being recorded and that they would receive a small payment, their conversations in the corpus are probably very close to being natural and spontaneous. This paper describes a detailed case study of the problems we faced and the methods we used to make the recordings and control the collection of these social science data on a limited budget.
Precision-Recall is one of the main metrics for evaluating content-based image retrieval techniques. However, it does not provide an ample perception of the properties of an image dataset immersed in a metric space. In this work, we describe an alternative metric named H-Metric, which is determined along a sequence of controlled modifications in the image dataset. The process is named homogenization and works by altering the homogeneity characteristics of the classes of the images. The result is a process that measures how hard it is to deal with a set of images in respect to content-based retrieval, offering support in the task of analyzing configurations of distance functions and of features extractors.
We review research on geomagnetic pulsations carried out using magnetic field measurements from the CHAMP low-Earth-orbit (LEO) satellite and ground-based stations in South Africa and Hungary. The high quality magnetic field measurements from CHAMP made it possible to extract and clearly resolve Pi2 and Pc3 pulsations in LEO satellite data. Our analyses for nighttime Pi2 pulsations are indicative of a cavity mode resonance. However, observations of daytime Pi2 pulsation events identified in ground station data show no convincing evidence of their occurrence in CHAMP data. We also studied low-latitude Pc3 pulsations and found that different types of field line resonant structure occur, namely discrete frequencies driven by a narrow band source and L-dependent frequencies driven by a broad band source.
In order to investigate quantitatively the accuracy of geomagnetic daily variation recorded by the FGE magnetometer, we analyzed the stability and precision of some groups' baseline values continuously recorded one day at seven observatories in 2009. The results show that the standard deviation and variable amplitude of the baseline values are small in D, H, and Z components, the standard deviation values are δD≤0.03', δH≤0.3nT, δZ≤0.3nT respectively, and the variable amplitude values are ΔD≤|0.05'|, ΔH≤|0.5'|, ΔZ≤|0.5'| respectively. Then we selected the baseline values continuously recorded one day at CDP and KSH observatories in 2009 and 2010 and analyzed the influence of absolute measurement intervals on the stability of the baselines.
The objective of this project is to develop a flexible observation mode for a geomagnetic abnormal phenomena tracking system. The instrument, based on ring core fluxgate magnetometer technology, improves the field environment performance. Using wireless technology provides on-the-spot mobile networking for the observational data, with efficient access to the earthquake precursor observation network. It provides a powerful detection method for earthquake short-term prediction through installation of a low-noise fluxgate magnetometer array, intensely observing the phenomenon of geomagnetic disturbances and abnormal low-frequency electromagnetic signals in different latitudes, then carrying out observational data processing and exploring the relationship between earthquake activity and geomagnetic field changes.
Based on the analysis of the Vr index from data from geomagnetic observatories in China and four geomagnetic observatories abroad, temporal-spatial distribution characteristics of Vr index were analyzed. The Vr index showed 27-day solar-cycle recurrences and significant seasonal variation. It also increased with latitude. Meanwhile, both local-time dependence and an obvious dusk-dawn asymmetry existed, which might be related to the asymmetric ring current, the partial ring current, and the field-aligned current.
The K index was devised by Bartels et al. (1939) to provide an objective monitoring of irregular geomagnetic activity. The K index was then routinely used to monitor the magnetic activity at permanent magnetic observatories as well as at temporary stations. The increasing number of digital and sometimes unmanned observatories and the creation of INTERMAGNET put the question of computer production of K at the centre of the debate. Four algorithms were selected during the Vienna meeting (1991) and endorsed by IAGA for the computer production of K indices. We used one of them (FMI algorithm) to investigate the impact of the geomagnetic data sampling interval on computer produced K values through the comparison of the computer derived K values for the period 2009, January 1st to 2010, May 31st at the Port-aux-Francais magnetic observatory using magnetic data series with different sampling rates (the smaller: 1 second; the larger: 1 minute). The impact is investigated on both 3-hour range values and K indices data series, as a function of the activity level for low and moderate geomagnetic activity.
The standard observatory procedure for determining a geomagnetic field's declination and inclination absolutely is the DI-flux measurement. The instrument consists of a non-magnetic theodolite equipped with a single-axis fluxgate magnetometer. Additionally, a scalar magnetometer is needed to provide all three components of the field. Using only 12 measurement steps, all systematic errors can be accounted for, but if only one of the readings is wrong, the whole measurement has to be rejected. We use a three-component sensor on top of the theodolites telescope. By performing more measurement steps, we gain much better control of the whole procedure: As the magnetometer can be fully calibrated by rotating about two independent directions, every combined reading of magnetometer output and theodolite angles provides the absolute field vector. We predefined a set of angle positions that the observer has to try to achieve. To further simplify the measurement procedure, the observer is guided by a pocket pc, in which he has only to confirm the theodolite position. The magnetic field is then stored automatically, together with the horizontal and vertical angles. The DI3 measurement is periodically performed at the Niemegk Observatory, allowing for a direct comparison with the traditional measurements.
The Japan Meteorological Agency (JMA) has developed an advanced system to monitor geomagnetic environments consisting of magnetometers and monitoring cameras. The new system calculates the magnetic moments and positions of sources of artificial disturbances and then visually identifies the sources. The intensity and location of a source of artificial disturbance are calculated assuming the source is a magnetic dipole. This new system was installed at two branch observatories operated by the JMA, which will enable the remote monitoring of sites for geomagnetic observations from the headquarters at Kakioka Magnetic Observatory.
The time accuracy of geomagnetic data is an important specification for one-second data distributions. We tested a procedure to verify the time accuracy of a fluxgate magnetometer by using a GPS pulse generator. The magnetometer was equipped with a high time resolution (100 Hz) output, so the data delay could be checked directly. The delay detected from one-second data by a statistical method was larger than those from 0.1-s- and 0.01-s-resolution data. The test of the time accuracy revealed the larger delay and was useful for verifying the quality of the data.
There is a need to develop secular variation (SV) models using satellite data as the use of ground data is not always possible. Ground data has many limitations including limited data points and lack of data over ocean areas that are not easily accessible. Two regional geomagnetic field modelling techniques, namely polynomial surface modelling (PolyM) and Spherical Cap Harmonic Analysis (SCHA), were applied to CHAMP satellite data recorded between 2001 and 2005 to investigate the use of satellite data to develop a geomagnetic SV model over southern Africa. The resulting regional models of this investigation were validated against the two widely used global field models IGRF 10 and CHAOS-2 using the available ground survey data obtained during the same period over southern Africa. The results suggest that the regional field models can be derived based entirely on satellite data. However, the regional SV models can be improved using both high quality satellite and ground survey data, since they lack the high quality of a global field model like CHAOS-2.
NGII(National Geography Information Institute) of Korea consigned KIGAM(Korea Institute of Geoscience & Mineral Resources) to do absolute geomagnetic measurements on 32 geomagnetic repeat stations evenly distributed on the southern part of Korean Peninsula in the year 2010 and to produce geomagnetic field components' distribution maps for the year 2010.0. The result of the processing of the measured data, i. e., the geomagnetic field components' distribution, shows a near similarity with that calculated from IGRF-11 although the latter was processed without any real geomagnetic data measured on the Korean Peninsula as an input. This implies that we installed the repeat stations on sites with good geomagnetic conditions and that our result in accordance with the IGRF represents well the regional distribution trend, i. e., it is dominated by relatively long wavelength components.
Long-term precise magnetic observations are being carried out at the Eilat test site as a part of active tectonic fault multi-sensor geophysical monitoring. The gradiometer system comprises three highly sensitive potassium total field sensors with short bases - up to 50 m. The gradiometer time series contain residuals of external magnetic field variations, which are essentially homogeneous over such short distances. Mutual regression analysis of the gradiometer and the vector magnetometer time series was proved to be an effective tool in reduction of the influence of external homogeneous variation on gradiometer readings. Monitoring results together with time dependence of regression coefficients are analyzed.
The knowledge transfer project called "Magnetic Valley" that was launched in 2009 is presented below. This project is funded by the Belgian government to investigate and develop products and services that will improve the socio-economic development in the area around the "Centre de Physique du Globe de l'IRM".
Good magnetic observatories are needed more than ever for global modeling and navigation. Magnetic satellite missions, once said to be the death of ground based observations, are now demanding quality data from fixed observations points on the Earth.
The COMPASS (COmprehensive Magnetic Processes under the African Southern Sub-continent) program forms part of a collaboration project between Germany and South Africa, called Inkaba ye Africa, and aims to investigate the regional geomagnetic field in this area, particularly its evolutionary behaviour. Results obtained from field surveys conducted by the Hermanus Magnetic Observatory (HMO) and the Helmholtz GeoForschungsZentrum (GFZ) in South Africa, Namibia, and Botswana, in addition to geomagnetic field data from the 4 continuous recording magnetic observatories in southern Africa at Hermanus, Hartebeesthoek, Keetmanshoop and Tsumeb, were used to model the geomagnetic field time variation by means of a polynomial approach.
An experimental validation of the in-situ calibration procedure, which allows estimating parameters of observatory magnetometers (scale factors, sensor misalignment) without its operation interruption, is presented. In order to control the validity of the procedure, the records provided by two magnetometers calibrated independently in a coil system have been processed. The in-situ estimations of the parameters are in very good agreement with the values provided by the coil system calibration.
Despite the advance of technology, the fully automatic recording of absolute magnetic field vector variation at observatories remains an elusive goal. Primary difficulties are the long term stability of sensor orientation and the stable operation of the sensor system. In standard practice, definitive data are produced through the combination of continuous operation of a variometer and the occasional absolute measurements that are used for calibration of the variometer data. A single, automatic instrument that can continuously acquire absolute vector measurements with 1-second resolution is desired. We introduce a device that will fulfil these requirements. Data are acquired using Serson's method: the ambient magnetic field is modulated by superposed fields. This method has been applied, mostly in connection with Proton magnetometers, for many years. In general it requires that the applied fields have a strength on the order of the Earth's magnetic field. But the sampling rate is limited for most xisting systems. In contrast, our system only requires applied fields of about 5000nT, and the switching rate of polarities is 5Hz. This is possible because we use a fast self oscillating Cs-magnetometer. The self oscillating Cs-magnetometer is calibrated by a Cs-He cell during times without additional fields (tandem-magnetometer).
To enhance the quality and near real time production of K-based planetary magnetic activity indices, such as am, and longitude-sector indices, aλ, there is a requirement for local three-hourly K index values from the South Atlantic observatory at Port Stanley. We describe the computer algorithm used to estimate the solar regular variation, SR, and techniques used to establish the parameters required to derive the K indices. We analyse the results by comparing the distributions of K values with observatories at similar geomagnetic latitude and thus with likely similar levels of geomagnetic activity. We also look for biases by comparing the indices directly to those from nearby observatories. Both sets of results show a good overall agreement. However adjustment of input parameters will be necessary if improved agreement with the indices from the other observatories is required.
Principal component analysis is applied to analyze the horizontal component of geomagnetic data for the Panzhihua Ms 6.1 earthquake. We investigate temporal variations in eigenvalues and find that only the first principal component has good correlation with the Ap index for which the cross-correlation correlation R is larger than 0.6, which may imply solar-terrestrial activity. Both the second and third principal components show clear daily variation, being high during work hours and low at night and on weekends. The mean eigenvalue of the third component at night (00:00-04:00 LT) increased about 40 days before the earthquake and returned to normal 10 days before the earthquake. These features are likely to be correlated with the earthquake.
Magnetic disturbances due to the traffic are tentatively modelled assuming that the sources are moving dipoles. The influencing section of the road ("useful" portion) should be modelled in 3D. The parameters of the model (time of closest position to the magnetometer, velocity, including its sign, dipole moment) are fairly accurately estimated. The fit is improved with the incorporation of a small induction effect.
The island Tristan da Cunha is located in the South Atlantic Anomaly, and until recently the area has been one of the largest gaps in the global geomagnetic observatory network. As part of the Danish project SAADAN we set up a geomagnetic observatory on the island. Here we report on how we established the observatory in 2009 and on its operation in 2010.
This paper analyzes the baselines of 8 geomagnetic observatories in the China Magnetic Observatory Network. The baselines of similar variometers were measured by two different fluxgate theodolites during the same time period. The results demonstrate that two baseline values measured by two independent absolute instruments did not completely coincide for the same components even though the differences between pillars and instruments had been corrected. The baseline values were still not smooth, and there existed obvious wave variations for the D, H, and Z components. The causes of this inconsistency might be the differences between the two pillars installed with two independent absolute instruments and instrument problems in some of the observatories. In other words, the difference in the geomagnetic field between two points in the same observational area is not a constant.
We report here on the new realization of an automatic fluxgate theodolite able to perform unattended absolute geomagnetic declination and inclination measurements: the AUTODIF MKII. The main changes of this version compared with the former one are presented as well as the better specifications we expect now. We also explain the absolute orientation procedure by means of a laser beam and a corner cube and the method for leveling the fluxgate sensor, which is different from a conventional DIflux theodolite.
In this study, using one-minute definitive data published by a number of INTERMAGNET observatories, we apply a number of time- and frequency-domain techniques to characterise the global, natural geomagnetic signal and isolate the artificial noise at an individual observatory. With the aim of developing an analytical tool that can be used to identify observatory noise against the natural signal, we report on the suitability of these techniques to detect common observatory noise types.
The temporal and spatial distribution of SqH in China was analyzed based on geomagnetic digitized data from the geomagnetic observation network. It was found that; 1) there was obvious prenoon-postnoon asymmetry of SqH in summer and equinox; 2) in summer, equinox, and winter, the averaged foci of Sq were located at 27° N, 29° N, and 35° N, respectively. However, in a single quiet day, the Sq foci might reach a latitude north of 50° N and south of 19° N; 3). There were some inconsistencies in the behavior of the SqH distributions in two longitudinal chains, such as the reverse of SqH variations in the same latitudinal chain and the increase (decrease) of the daily ranges from east to west. All these demonstrated that there might be latitudinal migration of the Sq focus or changes in current intensity during the longitudinal migration of the Sq focus from east to west.
The following PDF indicates errata for the original article entitled " Principal Component Analysis of Geomagnetic Data for the Panzhihua Earthquake (Ms 6.1) in August 2008" by Junhui Li, Qi Li, Dongmei Yang, Xingzhou Wang, Dequan Hong and Kang He.