A climate index is here defined as a calculated value that can be used to describe the state and the changes in the climate system. The climate at a defined place is the average state of the atmosphere over a longer period of, for example, months or years. Changes on climate are much slower than on the weather, that can change strongly day by day.
The first classical climate indices of the atmosphere have been defined already about approximately a hundred years ago, for example the North Atlantic Oscillation (NAO). It is determined from monitoring station data or identified by means of objective analysis as teleconnection or EOF analysis.
Each climate index has a definition equation that uses the so-called climatic elements. Those are measurable parameters, which primarily influence the characteristics of the climate system, for example atmospheric parameters such as air pressure, air temperature, precipitation or solar radiation, or non-atmospheric parameters like the sea surface temperature or the ice cover fraction.
Climate indices allow a statistical study of variations of the dependent climatological aspects, such as analysis and comparison of time series, means, extremes and trends.
In addition to the classical representation climate indices is the goal of this project, to calculate more climate indices such as mean values, trends, anomalies and correlations from the at ICDC available data of different climate parameters and make them available. In the process of this project a list of climate indices is presented, which is constantly extended. Each climate index is described and combined with results that are either already available on the net or were computed by ICDC.