In the

natural sciences Natural science or empirical 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 ...

, especially in atmospheric and

Earth sciences Earth science or geoscience includes all fields of natural science related to the planet Earth. This is a branch of science dealing with the physical, chemical, and biological complex constitutions and synergistic linkages of Earth's four spheres ...

involving applied statistics, an anomaly is a persisting deviation in a

physical quantity A physical quantity (or simply quantity) is a property of a material or system that can be Quantification (science), quantified by measurement. A physical quantity can be expressed as a ''value'', which is the algebraic multiplication of a ''nu ...

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 In statistics, the standard deviation is a measure of the amount of variation of the values of a variable about its Expected value, mean. A low standard Deviation (statistics), deviation indicates that the values tend to be close to the mean ( ...

. A group of anomalies can be analyzed spatially, as a map, or temporally, as a

time series In mathematics, a time series is a series of data points indexed (or listed or graphed) in time order. Most commonly, a time series is a sequence taken at successive equally spaced points in time. Thus it is a sequence of discrete-time data. ...

. It should not be confused for an isolated

outlier In statistics, an outlier is a data point that differs significantly from other observations. An outlier may be due to a variability in the measurement, an indication of novel data, or it may be the result of experimental error; the latter are ...

. 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 Robust statistics are statistics that maintain their properties even if the underlying distributional assumptions are incorrect. Robust Statistics, statistical methods have been developed for many common problems, such as estimating location parame ...

, resistant to the effects of

s, are sometimes used as the basis of the transformation.

Examples

Atmospheric sciences

In the atmospheric sciences, the climatological

annual cycle Annual may refer to: *Annual publication, periodical publications appearing regularly once per year **Yearbook A yearbook, also known as an annual, is a type of Annual publication, a book published annually. One use is to record, highlight, an ...

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 EL, El or el may refer to: Arts and entertainment Fictional entities * El, a character from the manga series ''Shugo Chara!'' by Peach-Pit * Eleven (''Stranger Things'') (El), a fictional character in the TV series ''Stranger Things'' * El, fami ...

, while NAO plays an important role for

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

weather Weather is the state of the atmosphere, describing for example the degree to which it is hot or cold, wet or dry, calm or stormy, clear or cloud cover, cloudy. On Earth, most weather phenomena occur in the lowest layer of the planet's atmo ...

by modification of the exit of the Atlantic

storm track ''Storm Track'' was the first magazine for and about storm chasing. The magazine was in circulation between 1977 and 2002. History and profile ''Storm Track'' was started in 1977 by chasing pioneer David K. Hoadley, David Hoadley following an ...

. A climate normal can also be used to derive a climate anomaly.{{Cite book, url=https://books.google.com/books?id=ypcMBwAAQBAJ&dq=climate+anomaly&pg=PA53, title=Dictionary of Global Climate Change, date=August 15, 2008, publisher=Springer Science & Business Media, isbn=9780585295732, via=Google Books

Geophysics

* Gravity anomaly, difference between the observed gravity and a value predicted from a model ** Bouguer anomaly, anomaly in gravimetry ** Free-air anomaly, gravity anomaly that has been computed for latitude and corrected for elevation of the station * Iridium anomaly, an unusual abundance of what is normally a very rare element in the Earth's crust *

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 ...

, local variation in the Earth's magnetic field ** Bangui magnetic anomaly, in central Africa ** Kursk Magnetic Anomaly, territory rich in iron ores located within Kursk Oblast, Belgorod Oblast, and Oryol Oblast **

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 Wanapite ...

, large buried geologic structure in the Temagami region of Ontario, Canada

References

Time series Climate and weather statistics Geophysics

Calculation

Examples

Atmospheric sciences

Geophysics

See also

References