Anomaly (natural sciences)

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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. [1] Similarly, a standardized anomaly equals an anomaly divided by a standard deviation. [1] 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.

Contents

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, resistant to the effects of outliers, are sometimes used as the basis of the transformation. [1]

Examples

Atmospheric sciences

In the atmospheric sciences, the climatological annual cycle is often used as the expected value. Famous atmospheric anomalies are for instance the Southern Oscillation index (SOI) and the North Atlantic oscillation index. SOI is the atmospheric component of El Niño, while NAO plays an important role for European weather by modification of the exit of the Atlantic storm track. A climate normal can also be used to derive a climate anomaly. [2]

Geophysics

See also

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<span class="mw-page-title-main">Outlier</span> Observation far apart from others in statistics and data science

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<span class="mw-page-title-main">Instrumental temperature record</span> In situ measurements that provide the temperature of Earths climate system

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<span class="mw-page-title-main">El Niño–Southern Oscillation</span> Climate phenomenon that periodically fluctuates between three phases

El Niño–Southern Oscillation (ENSO) is a global climate phenomenon that emerges from variations in winds and sea surface temperatures over the tropical Pacific Ocean. Those variations have an irregular pattern but do have some semblance of cycles. The occurrence of ENSO is not predictable. It affects the climate of much of the tropics and subtropics, and has links (teleconnections) to higher-latitude regions of the world. The warming phase of the sea surface temperature is known as El Niño and the cooling phase as La Niña. The Southern Oscillation is the accompanying atmospheric oscillation, which is coupled with the sea temperature change.

Anomaly may refer to:

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<span class="mw-page-title-main">Sea surface temperature</span> Water temperature close to the oceans surface

Sea surface temperature is the temperature of ocean water close to the surface. The exact meaning of surface varies in the literature and in practice. It is usually between 1 millimetre (0.04 in) and 20 metres (70 ft) below the sea surface. Sea surface temperatures greatly modify air masses in the Earth's atmosphere within a short distance of the shore. Local areas of heavy snow can form in bands downwind of warm water bodies within an otherwise cold air mass. Warm sea surface temperatures can develop and strengthen cyclones over the ocean. Tropical cyclones can also cause a cool wake. This is due to turbulent mixing of the upper 30 metres (100 ft) of the ocean. Sea surface temperature changes during the day. This is like the air above it, but to a lesser degree. There is less variation in sea surface temperature on breezy days than on calm days. The thermohaline circulation has a major impact on average sea surface temperature throughout most of the world's oceans.

<span class="mw-page-title-main">Arctic oscillation</span> Climatic cycle over Earths North Pole

The Arctic oscillation (AO) or Northern Annular Mode/Northern Hemisphere Annular Mode (NAM) is a weather phenomenon at the Arctic pole north of 20 degrees latitude. It is an important mode of climate variability for the Northern Hemisphere. The southern hemisphere analogue is called the Antarctic oscillation or Southern Annular Mode (SAM). The index varies over time with no particular periodicity, and is characterized by non-seasonal sea-level pressure anomalies of one sign in the Arctic, balanced by anomalies of opposite sign centered at about 37–45° N.

<span class="mw-page-title-main">Pacific decadal oscillation</span> Recurring pattern of climate variability

The Pacific decadal oscillation (PDO) is a robust, recurring pattern of ocean-atmosphere climate variability centered over the mid-latitude Pacific basin. The PDO is detected as warm or cool surface waters in the Pacific Ocean, north of 20°N. Over the past century, the amplitude of this climate pattern has varied irregularly at interannual-to-interdecadal time scales. There is evidence of reversals in the prevailing polarity of the oscillation occurring around 1925, 1947, and 1977; the last two reversals corresponded with dramatic shifts in salmon production regimes in the North Pacific Ocean. This climate pattern also affects coastal sea and continental surface air temperatures from Alaska to California.

<span class="mw-page-title-main">Kursk Magnetic Anomaly</span> Magnetic anomaly in Russia due to extensive presence of iron ore

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The environmental isotopes are a subset of isotopes, both stable and radioactive, which are the object of isotope geochemistry. They are primarily used as tracers to see how things move around within the ocean-atmosphere system, within terrestrial biomes, within the Earth's surface, and between these broad domains.

<span class="mw-page-title-main">Climate system</span> Interactions that create Earths climate and may result in climate change

Earth's climate system is a complex system with five interacting components: the atmosphere (air), the hydrosphere (water), the cryosphere, the lithosphere and the biosphere. Climate is the statistical characterization of the climate system. It represents the average weather, typically over a period of 30 years, and is determined by a combination of processes, such as ocean currents and wind patterns. Circulation in the atmosphere and oceans transports heat from the tropical regions to regions that receive less energy from the Sun. Solar radiation is the main driving force for this circulation. The water cycle also moves energy throughout the climate system. In addition, certain chemical elements are constantly moving between the components of the climate system. Two examples for these biochemical cycles are the carbon and nitrogen cycles.

Upper-atmospheric models are simulations of the Earth's atmosphere between 20 and 100 km that comprises the stratosphere, mesosphere, and the lower thermosphere. Whereas most climate models simulate a region of the Earth's atmosphere from the surface to the stratopause, there also exist numerical models which simulate the wind, temperature and composition of the Earth's tenuous upper atmosphere, from the mesosphere to the exosphere, including the ionosphere. This region is affected strongly by the 11 year Solar cycle through variations in solar UV/EUV/Xray radiation and solar wind leading to high latitude particle precipitation and aurora. It has been proposed that these phenomena may have an effect on the lower atmosphere, and should therefore be included in simulations of climate change. For this reason there has been a drive in recent years to create whole atmosphere models to investigate whether or not this is the case.

<span class="mw-page-title-main">Atlantic multidecadal oscillation</span> Climate cycle that affects the surface temperature of the North Atlantic

The Atlantic Multidecadal Oscillation (AMO), also known as Atlantic Multidecadal Variability (AMV), is the theorized variability of the sea surface temperature (SST) of the North Atlantic Ocean on the timescale of several decades.

The Gulf Stream separates from the US coast near Cape Hatteras and then travels eastwards across the North Atlantic, becoming the North Atlantic current at about 55°W. In the region between 75°W and 55°W it is subject to meanders and is frequently accompanied by eddies. The northern edge of the current is marked by a sharp fall in temperature. This is also the case at much greater depths, so that the warm current is pressed up against a wall of cold water, called the 'north wall'. Monthly charts of the path of the north wall of the Gulf Stream have been available from surface, aircraft and satellite observations since 1966 and these have been used in several studies of the path's variability.

<span class="mw-page-title-main">Bangui magnetic anomaly</span> Local variation of the Earths magnetic field in central Africa

The Bangui magnetic anomaly is a local variation in the Earth's magnetic field centered at Bangui, the capital of the Central African Republic. The magnetic anomaly is roughly elliptical, about 700 km × 1,000 km, 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.

<span class="mw-page-title-main">Temperature anomaly</span>

Temperature anomaly is the difference, positive or negative, of a temperature from a base or reference value, normally chosen as an average of temperatures over a certain reference or base period. In atmospheric sciences, the average temperature is commonly calculated over a period of at least 30 years over a homogeneous geographic region, or globally over the entire planet.

The multivariate ENSO index, abbreviated as MEI, is a method used to characterize the intensity of an El Niño Southern Oscillation (ENSO) event. Given that ENSO arises from a complex interaction of a variety of climate systems, MEI is regarded as the most comprehensive index for monitoring ENSO since it combines analysis of multiple meteorological and oceanographic components.

References

  1. 1 2 3 Wilks, D.S. (1995) Statistical Methods in the Atmospheric science, Academic Press. ISBN   0-12-751965-3 (page 42)
  2. Dictionary of Global Climate Change. Springer Science & Business Media. August 15, 2008. ISBN   9780585295732 via Google Books.