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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 month of year, but it may also refer to a broader scale, such as a specific meteorological season. More recently, CN have been reported for narrower scales, such as day of year and even hourly scale. Climatological normals are used as an average or baseline to evaluate climate events and provide context for year-to-year variability. Normals can be calculated for a variety of weather variables including temperature and precipitation and rely on data from
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 month of year, but it may also refer to a broader scale, such as a specific meteorological season. More recently, CN have been reported for narrower scales, such as day of year and even hourly scale. Climatological normals are used as an average or baseline to evaluate climate events and provide context for year-to-year variability. Normals can be calculated for a variety of weather variables including temperature and precipitation and rely on data from
weather station
A weather station is a facility, either on land or sea, with instruments and equipment for measuring atmospheric conditions to provide information for weather forecasts and to study the weather and climate. The measurements taken include tempera ...
s. Variability from the 30-year averages is typical and climate variability
Climate variability includes all the variations in the climate that last longer than individual weather events, whereas the term climate change only refers to those variations that persist for a longer period of time, typically decades or more ...
looks at the magnitude of extremes. Climatological standard normals are overlapping periods updated every decade: 1971–2000, 1981–2010, 1991–2020, etc.
The term "normal" first appeared in the literature by Heinrich Wilhelm Dove
Heinrich Wilhelm Dove (6 October 1803 – 4 April 1879) was a Prussian physicist and meteorologist.
Early years
Dove was born in Liegnitz in the Kingdom of Prussia. Dove studied history, philosophy, and the natural sciences at the University of ...
in 1840 and the concept was formalized by the International Meteorological Committee in 1872. The use of the 30 year period of normals began in 1935 with the 1901-30 period. The continued use of 30 year normals has increasingly been called into question due to substantial evidence that the stationarity
In addition to its common meaning, stationary may have the following specialized scientific meanings:
Mathematics
* Stationary point
* Stationary process
* Stationary state
Meteorology
* A stationary front is a weather front that is not moving ...
of climate statistics can no longer be taken for granted due to climate change
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...
. This has led to alternative definitions such as "Optimal Climate Normal" and the "Hinge Fit" approach to supplement the standard 30 year normals which are still commonly used.
See also
* Climate anomaly *Climatology
Climatology (from Ancient Greek, Greek , ''klima'', "place, zone"; and , ''wiktionary:-logia, -logia'') or climate science is the scientific study of Earth's climate, typically defined as weather conditions averaged over a period of at least 30 ...
* Seasonality
References
{{reflist Climate and weather statistics