Australian Water Information Dictionary
Water forecasts: Dynamic streamflow
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 25% quartile

The 25% quartile of a set of numbers is the value in which 25% of the numbers are below it and 75% of the numbers are above it when the numbers are arranged in ascending (increasing) order.
Synonym: first quartile
This definition applies to:
 75% quartile

The 75% quartile of a set of numbers is the value in which 75% of the numbers are below it and 25% of the numbers are above it when the numbers are arranged in ascending (increasing) order.
Synonym: third quartile
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 ARMA

autoregressive moving average
A combined process of statistical time series analysis in terms of two polynomials, one for the autoregression and the second for the movingaverage.
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 Australian Water Availability Project

An operational data assimilation and modelling project that monitors the state and trend of the Australian terrestrial water balance at a resolution of 5 km. Using both measurements and modelling, the past history and present state of soil moisture are determined. The water fluxes that contribute to changes in soil moisture are incorporated in this project. These water fluxes include rainfall, transpiration, soil evaporation, surface runoff and deep drainage.
Source: Australian Water Availability Project
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 autocorrelation function

Describes the correlation between values of that process as a function of the time separation between them.
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 autoregressive moving average

A combined process of statistical time series analysis in terms of two polynomials, one for the autoregression and the second for the movingaverage.
This definition applies to:
 AWAP

Australian water availability project
An operational data assimilation and modelling project that monitors the state and trend of the Australian terrestrial water balance at a resolution of 5 km. Using both measurements and modelling, the past history and present state of soil moisture are determined. The water fluxes that contribute to changes in soil moisture are incorporated in this project. These water fluxes include rainfall, transpiration, soil evaporation, surface runoff and deep drainage.
Source: Australian Water Availability Project
This definition applies to:
 BATEA

Bayesian total error analysis
A generalised Bayesian framework for environmental model calibration and validation. BATEA permits the use of explicit probabilistic errors models which are used to describe the uncertainty associated with observed data, notably, in forcing inputs and outputs, e.g. rainfall and discharge data.
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 Bayesian

Refers to methods in probability or statistics, e.g. Bayesian Joint Probability, named after Thomas Bayes (c. 170261), who provided the first mathematical treatment of Bayesian inference.
Source: S E Fienberg, 2006, When Did Bayesian Inference Become "Bayesian"?, Bayesian Analysis, 1 (1), 140.
Related: Bayesian total error analysis
This definition applies to:
 Bayesian total error analysis

A generalised Bayesian framework for environmental model calibration and validation. BATEA permits the use of explicit probabilistic error models which are used to describe the uncertainty associated with observed data, notably, in forcing inputs and outputs, e.g. rainfall and discharge data.
Source: G Kuczera, D Kavetski, S Franks, M Thyer 2006, Towards a Bayesian total error analysis of conceptual rainfallrunoff models: Characterising model error using stormdependent parameters, Journal of Hydrology, 331:12,161177.
Related: Bayesian
This definition applies to:
 catchment

The land area draining to a point of interest, such as a water storage or monitoring site on a watercourse.
Related:
This definition applies to:
 Glossary for Water forecasts: Flood warning services
 Glossary for Water forecasts: Seasonal streamflow
 Glossary for Water forecasts: Dynamic streamflow
 Glossary for Water status: Australian Water Resources Assessment
 Glossary for Water status: Water in Australia
 Glossary for Water forecasts: 7day Streamflow Forecasts
 El Niño

Refers to the extensive warming of the central and eastern Pacific Ocean that leads to a major shift in weather patterns across the Pacific. In Australia (particularly eastern Australia), El Niño events are associated with an increased probability of drier conditions. See the Climate Glossary webpage on El Niño for more information.
Related:
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 El Niño Southern Oscillation

The oscillation between the El Niño climate phase and the La Niña phase, usually over several years. See the Australian Climate Influence webpage on ENSO for more information.
Related:
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 ensemble forecast

A set of multiple forecasts for the same period and location. The spread of multiple forecasts provides information about forecast uncertainty.
This definition applies to:
 ENSO

El Niño Southern Oscillation
The oscillation between the El Niño climate phase and the La Niña climate phase, or opposite phase, usually over several years. See the Weather and Climate page on ENSO for more information.
Related:
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 exceedance probability

The forecast probability that a particular variable such as streamflow volume will be exceeded.
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 first quartile

The first quartile of a set of numbers is the value in which 25% of the numbers are below it and 75% of the numbers are above it when the numbers are arranged in ascending (increasing) order.
Synonym: 25% quartile
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 GR4J

Modèle du Génie Rural à 4 Paramètres Journalier
A daily lumped fourparameter rainfallrunoff model, belonging to the family of soil moisture accounting models.
Source: Modèles Hydrologiques du Génie Rural
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 hindcast

A retrospective forecast using observed information to validate or test a mathematical model. Observed inputs for past events are entered into the model to see how well the output matches the observed streamflow volumes.
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 historical reference or historical probability distribution

A probability distribution created by sampling the historical streamflow data record. It is the reference forecast used when skill scores are calculated from hindcast modelling results.
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 Indian Ocean Dipole

A major contributor to rainfall variability over Australia. When the dipole is in a positive phase, the seasurface temperature (SST) around Indonesia is cooler than average while those in the western Indian Ocean are warmer than average. The positive phase increases easterly winds across the Indian Ocean, while convection in areas near Australia reduces. This results in suppressed rainfall over the Australian region. During a negative phase, warmer than average SST near Indonesia and cooler than average SST in the western Indian Ocean, result in more westerly winds across the Indian Ocean, greater convection near Australia and enhanced rainfall in the Australian region. See the Weather and Climate page on Indian Ocean for more information.
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 interquartile range (IQR)

A measure of statistical dispersion, being equal to the difference between the third and first quartiles. Also called the midspread or middle 50.
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 IOD

Indian Ocean Dipole
A major contributor to rainfall variability over Australia. When the dipole is in a positive phase, the seasurface temperature (SST) around Indonesia is cooler than average while those in the western Indian Ocean are warmer than average. The positive phase increases easterly winds across the Indian Ocean, while convection in areas near Australia reduces. This results in suppressed rainfall over the Australian region. During a negative phase, warmer than average SST near Indonesia and cooler than average SST in the western Indian Ocean, result in more westerly winds across the Indian Ocean, greater convection near Australia and enhanced rainfall in the Australian region. See the Weather and Climate page on Indian Ocean for more information.
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 La Niña

The extensive cooling of the central and eastern Pacific Ocean. In Australia (particularly eastern Australia), La Niña events are associated with an increased probability of wetter conditions. See the Climate Glossary webpage on La Niña for more information.
Related:
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 Modèle du Génie Rural à 4 Paramètres Journalier

A daily lumped fourparameter rainfallrunoff model, belonging to the family of soil moisture accounting models.
Source: Perrin, C., Michel, C., & Andréassian, V. 2003, Improvement of a parsimonious model for streamflow simulation. Journal of Hydrology, 279(1), 275289.
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 monsoon

The northern Australian monsoon season generally lasts from December to March. It is associated with the inflow of moist west to northwesterly winds into the monsoon trough, producing convective cloud and heavy rainfall over northern Australia. These moistureladen winds originate from the Indian Ocean and southern Asian waters. The northern Australian wet season encompasses the monsoon months but can extend several months either side. See the Weather and Climate page on the Australian monsoon for more information.
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 pie chart

A circular chart that is divided into sectors. A pie chart is used to display tercile forecasts with three sectors representing low flow, near median flow and high flow.
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 POAMA

predictive ocean atmosphere model for Australia
A stateoftheart seasonal to interannual forecast system consisting of coupled oceanatmosphere general circulation models (GCMs) along with sophisticated data assimilation and landsurface initialisation systems.
Source: POAMA
This definition applies to:
 Predictive Ocean Atmosphere Model for Australia

A stateoftheart seasonal to interannual forecast system consisting of coupled oceanatmosphere general circulation models (GCMs) along with sophisticated data assimilation and landsurface initialisation systems.
Source: POAMA
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 probabilistic forecast

A probabilistic streamflow forecast shows the range of possible streamflow volumes and how likely it is that they will occur.
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 quantile

Denotes one of a series of threshold values that divides a set of ordered data into groups with an equal number of data points in each. The terms tercile, quartile, quintile, decile and percentile refer to quantiles that divide the distribution of data into 3, 4, 5, 10 and 100 equal parts, respectively.
Related:
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 RMSE

root mean squared error
The square root of the average square error (SE) for a set of forecasts
The SE is the squared difference between the observed value and median of the forecast.
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 RMSEP

root mean squared error in probability
The square root of the average square error in probability (SEP) for a set of forecasts
The SEP is the squared difference between the historical probabilities of the observed value and median of the forecast.
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 root mean squared error

The square root of the average square error (SE) for a set of forecasts
The SE is the squared difference between the observed value and median of the forecast.
Related: root mean squared error in probability
Synonym: RMSE
This definition applies to:
 root mean squared error in probability

The square root of the average square error in probability (SEP) for a set of forecasts
The SEP is the squared difference between the historical probabilities of the observed value and median of the forecast.
Related: root mean squared error
Synonym: RMSEP
This definition applies to:
 Seasonal Streamflow Forecast

A forecast of total streamflow volumes predicted at a particular gauging station, or for the total of inflowing watercourses into a water storage. The forecast can be for a specific period, ranging from one to several months.
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 skill score

A statistical score used to assess the relative performance (skill) of a model against a reference forecast (e.g. climatology).
Skill Score =(Smod  Sref) / (Sperf  Sref)
Where
Smod = Score for the model forecast
Sref = Score for a reference forecast, e.g. climatology
Sperf = Score for a perfect forecast, usually 0 or 1
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 SOI

Southern Oscillation Index
An index calculated from the monthly or seasonal fluctuations in the air pressure difference between Tahiti and Darwin. See the Climate page on SOI for more information.
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 Southern Oscillation Index

An index calculated from the monthly or seasonal fluctuations in the air pressure difference between Tahiti and Darwin. See the Climate page on SOI for more information.
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 streamflow

The flow of water in streams, rivers and other channels.
Synonym: flow
This definition applies to:
 Glossary for Water forecasts: Seasonal streamflow
 Glossary for Water data: National Atlas of Groundwater Dependent Ecosystems
 Glossary for Water forecasts: Dynamic streamflow
 Glossary for Standards: National Industry Guidelines for hydrometric monitoring
 Glossary for Water status: Water in Australia
 Glossary for Water forecasts: 7day Streamflow Forecasts
 tercile

A set of data arranged in order with values that partition the data into three groups, each containing onethird of the total data. To define these terciles, the historical data is arranged in order from lowest to highest and then the data is partitioned into three equal groups. The lowest third of the data values are defined as the lowest tercile, the middle third of the values are the middle tercile and the upper third of the values are the upper tercile. A tercile is a specific form of quantile.
For example, if you had 100 data values, the lowest tercile would contain the 1st–33rd data values, the middle tercile the 34th–67th values and the upper tercile the 68th–100th values.
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 third quartile

The third quartile of a set of numbers is the value in which 75% of the numbers are below it and 25% of the numbers are above it when the numbers are arranged in ascending (increasing) order.
Synonym: 75% quartile
This definition applies to: