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Geophysical Anomaly
In the natural sciences, especially in atmospheric and Earth sciences involving applied statistics, an ''anomaly'' is a persisting deviation in a physical quantity from its expected value, e.g., the systematic difference between a measurement and a trend or a model prediction.Wilks, D.S. (1995) ''Statistical Methods in the Atmospheric science'', Academic Press. (page 42) Similarly, a standardized anomaly equals an anomaly divided by a standard deviation. A group of anomalies can be analyzed spatially, as a map, or temporally, as a time series. It should not be confused for an isolated outlier. There are examples in atmospheric sciences and in geophysics. Calculation The location and scale measures used in forming an anomaly time-series may either be constant or may themselves be a time series or a map. For example, if the original time series consisted of daily mean temperatures, the effect of seasonal cycles might be removed using a deseasonalization filter. Robust statistics ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Natural Sciences
Natural science is one of the branches of science concerned with the description, understanding and prediction of natural phenomena, based on empirical evidence from observation and experimentation. Mechanisms such as peer review and repeatability of findings are used to try to ensure the validity of scientific advances. Natural science can be divided into two main branches: life science and physical science. Life science is alternatively known as biology, and physical science is subdivided into branches: physics, chemistry, earth science, and astronomy. These branches of natural science may be further divided into more specialized branches (also known as fields). As empirical sciences, natural sciences use tools from the formal sciences, such as mathematics and logic, converting information about nature into measurements which can be explained as clear statements of the " laws of nature". Modern natural science succeeded more classical approaches to natural philosophy, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
El Niño
El Niño (; ; ) is the warm phase of the El Niño–Southern Oscillation (ENSO) and is associated with a band of warm ocean water that develops in the central and east-central equatorial Pacific (approximately between the International Date Line and 120°W), including the area off the Pacific coast of South America. The ENSO is the cycle of warm and cold sea surface temperature (SST) of the tropical central and eastern Pacific Ocean. El Niño is accompanied by high air pressure in the western Pacific and low air pressure in the eastern Pacific. El Niño phases are known to last close to four years; however, records demonstrate that the cycles have lasted between two and seven years. During the development of El Niño, rainfall develops between September–November. The cool phase of ENSO is es, La Niña, translation=The Girl, with SSTs in the eastern Pacific below average, and air pressure high in the eastern Pacific and low in the western Pacific. The ENSO cycle, including bo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bias (statistics)
Statistical bias is a systematic tendency which causes differences between results and facts. The bias exists in numbers of the process of data analysis, including the source of the data, the estimator chosen, and the ways the data was analyzed. Bias may have a serious impact on results, for example, to investigate people's buying habits. If the sample size is not large enough, the results may not be representative of the buying habits of all the people. That is, there may be discrepancies between the survey results and the actual results. Therefore, understanding the source of statistical bias can help to assess whether the observed results are close to the real results. Bias can be differentiated from other mistakes such as accuracy (instrument failure/inadequacy), lack of data, or mistakes in transcription (typos). Bias implies that the data selection may have been skewed by the collection criteria. Bias does not preclude the existence of any other mistakes. One may have a poo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Temagami Magnetic Anomaly
The Temagami Magnetic Anomaly, also called the Temagami Anomaly or the Wanapitei Anomaly, is a magnetic anomaly resulting from a large buried geologic structure in the Canadian Shield near Temagami, Ontario, Canada. It stretches from Lake Wanapitei in the west to Bear Island in Lake Temagami. The Aboriginal community of Teme-Augama Anishnabai lies partly within the Temagami Magnetic Anomaly, including the Temagami First Nation on Bear Island. Located nearby are a number of other geological structures, including the Sudbury Basin, the Lake Wanapitei impact crater, and the Temagami Greenstone Belt. Discovery and structure The Temagami Magnetic Anomaly is egg-shaped, long and wide. The central section has the greatest amplitude and an east-west strike. The western portion appears smoother in character while the eastern section is long and narrow. With an areal extent of 50 x 15 km, it reaches a magnitude of approximately 10,000 nanoteslas, making it one of the largest p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kursk Magnetic Anomaly
Kursk Magnetic Anomaly (russian: Курская магнитная аномалия) is a territory rich in iron ores located within the Kursk, Belgorod, and Voronezh oblasts in Russia, and constitutes a significant part of the Central Chernozyom Region. The Kursk Magnetic Anomaly is recognized as the largest magnetic anomaly on Earth. The Kursk Magnetic Anomaly (KMA) was first discovered in 1773 by the Russian astronomer and academic Pyotr Inokhodtsev while preparing the maps of the General Land Survey (russian: Генеральное межевание) at the behest of the Russian government. It was not investigated again until 1874 when I. N. Smirnov conducted the first geomagnetic survey of European Russia. In 1883, N. D. Pilchikov, an assistant professor at Kharkiv University, conducted a series of 71 observations of the Kursk Magnetic Anomaly. These revealed a much larger extent than previously measured and for the first time attributed the anomaly to the presence of i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bangui Magnetic Anomaly
The Bangui magnetic anomaly is a local variation in the Earth's magnetic field centered at Bangui, the capital of Central African Republic. The magnetic anomaly is roughly elliptical, about , and covers most of the country, making it one of the "largest and most intense crustal magnetic anomalies on the African continent". The anomaly was discovered in the late 1950s, explored in the 1970s, and named in 1982. Its origin remains unclear. History In 1962, Raymond Godivier and Lucien Le Donche reported on a magnetic anomaly in Central African Republic, which they identified by analyzing their surface magnetic activity data of 1956. These results were confirmed and built upon by the high-altitude aeromagnetic surveys carried out by the US Naval Oceanographic Office, as well as by the satellite measurements conducted in 1964 with Cosmos 49 and in the 1970s with the Orbiting Geophysical Observatory at altitudes. This data was combined in 1973 and yielded a spatial map of Earth's magne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Anomaly
In geophysics, a magnetic anomaly is a local variation in the Earth's magnetic field resulting from variations in the chemistry or magnetism of the rocks. Mapping of variation over an area is valuable in detecting structures obscured by overlying material. The magnetic variation (geomagnetic reversals) in successive bands of ocean floor parallel with mid-ocean ridges was important evidence for seafloor spreading, a concept central to the theory of plate tectonics. Measurement Magnetic anomalies are generally a small fraction of the magnetic field. The total field ranges from 25,000 to 65,000 nanoteslas (nT). To measure anomalies, magnetometers need a sensitivity of 10 nT or less. There are three main types of magnetometer used to measure magnetic anomalies: # The fluxgate magnetometer was developed during World War II to detect submarines. It measures the component along a particular axis of the sensor, so it needs to be oriented. On land, it is often oriented vertically, wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iridium Anomaly
The term iridium anomaly commonly refers to an unusual abundance of the chemical element iridium in a layer of rock strata at the Cretaceous–Paleogene (K–Pg) boundary. The unusually high concentration of a rare metal like iridium is often taken as evidence for an extraterrestrial impact event. Anomaly characteristics The type locality of this iridium anomaly is near Raton, New Mexico. Iridium is a very rare element in the Earth's crust, but is found in anomalously high concentrations (around 100 times greater than normal) in a thin worldwide layer of clay marking the boundary between the Cretaceous and Paleogene periods, 66 million years ago. This boundary is marked by a major extinction event, including that of the dinosaurs along with about 70% of all other species. The clay layer also contains small grains of shocked quartz and, in some places, small weathered glass beads thought to be tektites. Meteorite impact theory A team consisting of the physicist Luis Alvarez, h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Free-air Anomaly
In geophysics, the free-air gravity anomaly, often simply called the free-air anomaly, is the measured gravity anomaly after a free-air correction is applied to account for the elevation at which a measurement is made. It does so by adjusting these measurements of gravity to what would have been measured at a reference level, which is commonly taken as mean sea level or the geoid. Applications Studies of the subsurface structure and composition of the earth's crust and mantle employ surveys using gravimeters to measure the departure of observed gravity from a theoretical gravity value to identify anomalies due to geologic features below the measurement locations. The computation of anomalies from observed measurements involves the application of corrections that define the resulting anomaly. The free-air anomaly can be used to test for isostatic equilibrium over broad regions. Survey methods The free-air correction adjusts measurements of gravity to what would have been meas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bouguer Anomaly
In geodesy and geophysics, the Bouguer anomaly (named after Pierre Bouguer) is a gravity anomaly, corrected for the height at which it is measured and the attraction of terrain. The height correction alone gives a free-air gravity anomaly. Definition The Bouguer anomaly g_B defined as: g_B = g_ - \delta g_B + \delta g_T Here, * g_F is the free-air gravity anomaly. * \delta g_B is the ''Bouguer correction'' which allows for the gravitational attraction of rocks between the measurement point and sea level; * \delta g_T is a ''terrain correction'' which allows for deviations of the surface from an infinite horizontal plane The free-air anomaly g_F, in its turn, is related to the observed gravity g_ as follows: g_F = g_ - g_\lambda + \delta g_F where: * g_\lambda is the correction for latitude (because the Earth is not a perfect sphere; see normal gravity); * \delta g_F is the free-air correction. Reduction A Bouguer reduction is called ''simple'' (or ''incomplete'') if the t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gravity Anomaly
The gravity anomaly at a location on the Earth's surface is the difference between the observed value of gravity and the value predicted by a theoretical model. If the Earth were an ideal oblate spheroid of uniform density, then the gravity measured at every point on its surface would be given precisely by a simple algebraic expression. However, the Earth has a rugged surface and non-uniform composition, which distorts its gravitational field. The theoretical value of gravity can be corrected for altitude and the effects of nearby terrain, but it usually still differs slightly from the measured value. This gravity anomaly can reveal the presence of subsurface structures of unusual density. For example, a mass of dense ore below the surface will give a positive anomaly due to the increased gravitational attraction of the ore. Different theoretical models will predict different values of gravity, and so a gravity anomaly is always specified with reference to a particular model. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Climate Normal
Climatological normal or climate normal (CN) is a 30-year average of a weather variable for a given time of year.Climate Variability and Climate Change ; WHAT IS THE DIFFERENCE? Michigan Sea Grant Most commonly, a CN refers to a particular , but it may also refer to a broader scale, such as a specific . More recently, CN have been reported for narrower scales, such as |
