ECMWF re-analysis

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The ECMWF re-analysis project is in two phases. The first, ERA-15 generated re-analyses from December 1978 to February 1994. The second, ERA-40, begins in 1957 (the IGY).

Numerical weather prediction models generate an "analysis" to begin their forecasts from. These analyses themselves are a valuable tool for meteorological and climatological analysis. However, they suffer from inconsistency, because the analysis system is being constantly improved. Hence, the idea developed to re-analyse all the old data, including much archived data that was not available to the original analyses, using a consistent modern analysis system. This allows for the correction of many historical hand-drawn maps where the estimation of features was common in areas of data sparsity. The ability is also present to create new maps of atmosphere levels that were not commonly used until more recent times.