Hindcast
Encyclopedia
A hindcast is a way of testing a mathematical model
. Known or closely estimated inputs for past events are entered into the model to see how well the output matches the known results. Hindcasting is also known as backtesting
.
An example of hindcasting would be entering climate
forcings (events that force change) into a climate model
. If the hindcast accurately showed weather events that are known to have occurred, the model would be considered successful.
In oceanography
and meteorology
, hindcasting usually refers to a numerical model
integration of a historical period where no observations have been assimilated
. This distinguishes a hindcast run from a reanalysis
. Oceanographic observations of salinity
and temperature
as well as observations of surface wave parameters
such as the significant wave height
are much scarcer than meteorological observations, making hindcasting more common in oceanography than in meteorology. Also, since surface waves represent a forced system where the wind is the only generating force, wave hindcasting
is often considered adequate for generating a reasonable representation of the wave climate
with litte need for a full reanalysis.
The ECMWF re-analysis
is an example of a combined atmospheric reanalysis coupled with a wave model integration where no wave parameters were assimilated, making the wave part a hindcast run.
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Mathematical model
A mathematical model is a description of a system using mathematical concepts and language. The process of developing a mathematical model is termed mathematical modeling. Mathematical models are used not only in the natural sciences and engineering disciplines A mathematical model is a...
. Known or closely estimated inputs for past events are entered into the model to see how well the output matches the known results. Hindcasting is also known as backtesting
Backtesting
Backtesting is the process of evaluating a strategy, theory, or model by applying it to historical data. Backtesting can be used in situations like studying how a trading method would have performed in past stock markets or how a model of climate and weather patterns would have matched past...
.
An example of hindcasting would be entering climate
Climate
Climate encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elemental measurements in a given region over long periods...
forcings (events that force change) into a climate model
Climate model
Climate models use quantitative methods to simulate the interactions of the atmosphere, oceans, land surface, and ice. They are used for a variety of purposes from study of the dynamics of the climate system to projections of future climate...
. If the hindcast accurately showed weather events that are known to have occurred, the model would be considered successful.
In oceanography
Oceanography
Oceanography , also called oceanology or marine science, is the branch of Earth science that studies the ocean...
and meteorology
Meteorology
Meteorology is the interdisciplinary scientific study of the atmosphere. Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the 18th century. The 19th century saw breakthroughs occur after observing networks developed across several countries...
, hindcasting usually refers to a numerical model
Computer simulation
A computer simulation, a computer model, or a computational model is a computer program, or network of computers, that attempts to simulate an abstract model of a particular system...
integration of a historical period where no observations have been assimilated
Data assimilation
Applications of data assimilation arise in many fields of geosciences, perhaps most importantly in weather forecasting and hydrology. Data assimilation proceeds by analysis cycles...
. This distinguishes a hindcast run from a reanalysis
Meteorological reanalysis
A meteorological reanalysis is a meteorological data assimilation project which aims to assimilate historical observational data spanning an extended period, using a single consistent assimilation scheme throughout....
. Oceanographic observations of salinity
Salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
and temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
as well as observations of surface wave parameters
Ocean surface wave
In fluid dynamics, wind waves or, more precisely, wind-generated waves are surface waves that occur on the free surface of oceans, seas, lakes, rivers, and canals or even on small puddles and ponds. They usually result from the wind blowing over a vast enough stretch of fluid surface. Waves in the...
such as the significant wave height
Significant wave height
In physical oceanography, the significant wave height is defined traditionally as the mean wave height of the highest third of the waves , but now usually defined as four times the standard deviation of the surface elevation...
are much scarcer than meteorological observations, making hindcasting more common in oceanography than in meteorology. Also, since surface waves represent a forced system where the wind is the only generating force, wave hindcasting
Wind wave model
In fluid dynamics, wind wave modeling describes the effort to depict the sea state and predict the evolution of the energy of wind waves using numerical techniques...
is often considered adequate for generating a reasonable representation of the wave climate
Climate
Climate encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elemental measurements in a given region over long periods...
with litte need for a full reanalysis.
The ECMWF re-analysis
ECMWF re-analysis
The ECMWF re-analysis project is a meteorological reanalysis project.The first reanalysis product, ERA-15, generated re-analyses for approximately 15 years, from December 1978 to February 1994. The second product, ERA-40 begins in 1957 and covers 45 years to 2002...
is an example of a combined atmospheric reanalysis coupled with a wave model integration where no wave parameters were assimilated, making the wave part a hindcast run.
See also
- ForecastingForecastingForecasting is the process of making statements about events whose actual outcomes have not yet been observed. A commonplace example might be estimation for some variable of interest at some specified future date. Prediction is a similar, but more general term...
- ClimateClimateClimate encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elemental measurements in a given region over long periods...
- ECMWF re-analysisECMWF re-analysisThe ECMWF re-analysis project is a meteorological reanalysis project.The first reanalysis product, ERA-15, generated re-analyses for approximately 15 years, from December 1978 to February 1994. The second product, ERA-40 begins in 1957 and covers 45 years to 2002...
- NCEP re-analysisNCEP/NCAR ReanalysisThe NCEP/NCAR Reanalysis reanalysis data set is a continually updating gridded data set representing the state of the Earth's atmosphere, incorporating observations and numerical weather prediction model output dating back to 1948...
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