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Glossary of Terms

This glossary provides definitions for terms commonly used throughout our documentation. If you encounter any term in our docs that you're unfamiliar with, it might be explained here.


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Atmospheric Reanalysis

A reanalysis dataset is a comprehensive archive of weather and climate changes over time, produced using a combination of observational data and numerical models. It synthesizes a record of previous weather and climate states.



Climate refers to the average weather conditions in a specific area, encompassing variables like temperature, precipitation, and wind, over an extended period. It provides a detailed view of the longer-term state of the atmosphere, contrasting fast-changing weather patterns.


The Coupled Model Intercomparison Project (CMIP) is a structure for coordinated climate model testing, enabling scientists to compare outcomes from varying climate models.


Deterministic Forecasts

A type of prediction that gives a specific outcome based on certain initial conditions (model input). It always provides the same result for the same starting conditions. No randomness is involved.



The European Centre for Medium-Range Weather Forecasts (ECMWF) is an independent, intergovernmental organization supported by numerous European nations, focusing on providing accurate medium-term weather forecasts. ECMWF utilizes cutting-edge numerical models and a wealth of observational data, thereby fulfilling this purpose.

Ensemble Forecast

A prediction method that uses multiple scenarios or models to forecast an outcome, providing a range of possible outcomes to account for uncertainties. Ensemble forecasts offer a more comprehensive view, leading to enhanced accuracy and reliability. By capturing a variety of potential outcomes, they offer users more actionable insights and can better flag potential extreme events, giving a richer understanding than a single deterministic forecast.


GFS Models

Global Forecast System (GFS) models are a suite of numerical weather prediction models deployed for global weather forecasting. These models emulate Earth's atmospheric behaviour to anticipate future weather conditions.



A heatwave is a prolonged period of excessively hot weather, which may be accompanied by high humidity, especially in oceanic climate countries. To be considered a heatwave, these high temperatures have to be outside the historical averages for a given area. Definitions of a heatwave vary due to the different climate conditions in each location, but it is typically defined by temperatures that are higher than the 90th percentile of the historical temperature distribution over a period of at least two to three days.



The National Oceanic and Atmospheric Administration (NOAA) is a U.S. government agency tasked with weather monitoring and forecasting, oceans and atmospheric analysis. NOAA plays a vital role in weather research and environmental safeguarding.



Reanalysis is a scientific method used in climate studies where past observational data (from satellites, weather stations, ships, aircraft, etc.) is combined with modern weather forecasting models to generate a consistent, comprehensive, and accurate record of past atmospheric conditions. This process allows scientists to produce a coherent representation of the historical climate over regions where direct observations might be sparse or inconsistent. By merging observations with models, reanalysis datasets provide a detailed and reliable picture of weather and climate over time, making them valuable tools for understanding climate trends, variations, and other atmospheric phenomena.


Standardized Precipitation Index

The Standardized Precipitation Index, or SPI, is an index that measures the amount of precipitation in a region over a specific period, such as 1, 3, 6, or 12 months, compared to the historical average for that same period. The result is a standardized value that indicates how much wetter or drier it is relative to the typical conditions. By quantifying deviations in precipitation, the SPI can signal drought conditions when values are negative or excessive wetness when values are positive. It is a versatile index used globally for drought monitoring, agricultural planning, and managing water resources.



Weather depicts the state of the atmosphere at a particular moment and location, including factors like temperature, humidity, precipitation, wind, and others. It describes short-term atmospheric conditions that typically vary day-to-day.