The National Centers for Atmospheric Prediction (NCEP) and the National Center for Atmospheric Research (NCAR) have accomplished different re-analysis projects which aim on the generation of global data sets for a long time period for different atmospheric parameters. The here presented NCEP1 reanalysis has been used in numerous publications and has, therefore, in addition to the recent re-analysis products the advantage of very long time series.
The re-analysis is created with a model similar to the one used for weather forcasts. This model is initialised with measured data from different sources, including observations from weather stations, ship, aircraft, radiosondes, and satellite. Using one model for the whole re-analysis period generates homogeneous data that can be used for long term studies.
NCEP/NCAR has produced several re-analyses, that are described on their web-page. Here we give an introduction to the NCEP/NCAR Reanalysis I (1948-present). This free data set is updated continuously and has therefore many users worldwide. There is a large number of available parameters in several height levels, NCEP divided into 7 groups on its website, after level or properties:
Using the NCEP search funktion can also be convenient to search for parameters in various data sets. ICDC has a selection of ground-level parameters put together, which are listed in the following table.