Ensemble Forecast

Definition

Ensemble forecasting is a method used in or within numerical weather prediction. Instead of making a single forecast of the most likely weather, a set (or ensemble) of forecasts is produced. This set of forecasts aims to give an indication of the range of possible future states of the atmosphere.

History

The attempt to conceive the quantum-theoretical description as the complete description of the individual systems leads to unnatural theoretical interpretations, which become immediately unnecessary if one accepts the interpretation that the description refers to ensembles of systems and not to individual systems. — Albert Einstein[4]

In his 1926[5] paper introducing the concept of quantum scattering theory Max Born proposed to view "the motion of the particle follows the laws of probability, but the probability itself propagates in accord with causal laws", where the causal laws are Schrödinger's equations. As related in his 1954 Nobel Prize in Physics lecture [6] Born viewed the statistical character of quantum mechanics as an empirical observation with philosophical implications.

Einstein maintained consistently that the quantum mechanics only supplied a statistical view. In 1936 he wrote "“the 𝜓 function does not in any way describe a condition which could be that of a single system; it relates rather to many systems, to ‘an ensemble of systems’ in the sense of statistical mechanics.”[7] However Einstein did not provide a detailed study of the ensemble, ultimately because he considered quantum mechanics itself to be incomplete primarily because it was only an ensemble theory.[8] Einstein believed quantum mechanics was correct in the same sense that thermodynamics is correct, but that it was insufficient as means of unifying physics.[9]