Atmospheric Pressure Data Set Information

Last update 7 February 2010

Monthly mean air pressure data are often needed to make corrections to the monthly mean sea level data from the PSMSL, and this file mentions some of the sources of air pressure data suitable for the corrections. Note that in many (or probably most) studies of mean sea level data, it will be necessary to make use of gridded fields of air pressures, rather than of station pressure time series, owing to the lack of station data near to gauges in many parts of the world.

A more detailed set of information on air pressure data availability can be found from the web pages of the GCOS-AOPC/OOPC Working Group on Surface Pressure. This group has the aim of making historical and recent air pressure data sets as accessible as possible. Its web pages contain links to many gridded data sets, databases of individual station series and air pressure-related climate indices (more than have been mentioned below). Developments in this field, especially in data archaeology, are taking place rapidly and group's web page should be consulted for the latest news.

(1) UK Met Office/Hadley Centre Data Sets

In our opinion, the most suitable gridded data set at the present time for sea level studies of the late-19th and 20th centuries is HADSLP2. This contains a set of global 5 degree latitude-longitude fields covering 1850-2004. It can be obtained from the Met Office's HADSLP2 page.

The description of HADSLP2 on the Hadley Centre web site reads as follows: The Met Office Hadley Centre's mean sea level pressure (MSLP) data set, HadSLP2, is a unique combination of monthly globally-complete fields of land and marine pressure observations on a 5 degree latitude-longitude grid from 1850 to 2004. This product is also available in an updated form using NCEP/NCAR reanalysis fields, giving the near real time product, HadSLP2r.

For a detailed description of the dataset see:
R. Allan and T. Ansell, “A new globally complete monthly historical gridded mean sea level pressure dataset (HadSLP2): 1850–2004,” Journal of Climate 19, no. 22 (2006): 5816–5842.


EMULATE is a set of daily 5-degree fields for the North Atlantic and Europe spanning 1850-2003. This data set is called EMSLP and has been produced by the EMULATE collaboration, of which the Met Office is a partner (Ansell et al, 2005. Journal of Climate, in press). EMSLP will be available from the EMULATE web site at the University of East Anglia Climatic Research Unit and from the Hadley Centre web site . The UEA CRU EMULATE web site also contains the daily pressures for the 86 stations which were used to make the fields.

(3) Climatic Research Unit at the University of East Anglia

The Met Office and the University of East Anglia (UEA) Climatic Research Unit (CRU) also provide a data set of monthly mean air pressures on a 5 x 10 (lat x lon) degree grid for 1873 onwards for north of 15 North. See the CRU web site for more details. This might be expected to be eventually superceded by some of the newer products mentioned above (particularly EMSLP).

(4) NCEP/NCAR and ECMWF Reanalysis Projects

Two major sets of meteorological products, including gridded monthly mean air pressures, are available through the so-called meteorological 'Reanalysis Projects'. These provide global data sets for the past half-century at higher spatial resolution than HADSLP2, for example.

These data sets are available from the National Centers for Environmental Prediction - National Center for Atmospheric Research (NCEP-NCAR) (Kistler et al., 2001. The NCEP-NCAR 50 year reanalysis: monthly means CD-ROM and documentation. Bulletin of the American Meteorological Society, 82, 247-267) and the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA-40) (Uppala et al., 2004. ERA-40: ECMWF 45-year reanalysis of the global atmosphere and surface conditions 1957-2002. ECMWF Newsletter, No.101, 2-21. Reading: European Centre for Medium Range Weather Forecasts).

The data sets can be downloaded from NOAA and ECMWF respectively.

Large differences are found between the monthly mean air pressures of the two data sets at higher southern latitudes and especially for the 1950s and 1960s (e.g. see Bromwich, D.H. and Fogt, R.L., Journal of Climate, 2004, and Ponte, R.M., Journal of Atmospheric and Oceanic Technology, in press).

(3) National Climatic Data Center (NCDC)

The NCDC and the World Data Center for Meteorology can provide a number of relevant products, including station data.

There is the Monthly Climatic Data for the World (MCDW TD 9645) database which is derived from a combination of efforts. This dataset contains monthly means of air pressures etc. at meteorological stations (often airports).

Note that the MCDW database is now incorporated into a dataset called the Global Historical Climatological network (GHCN) which is available via WDCM web pages although with restrictions on distribution. That data base contains monthly temperature (mean), total precipitation, sea-level pressure, and station-level pressure for thousands of stations.

One can access the GHCN version 1, which has the pressure information up to 1990 at Oak Ridge National Laboratory. This is provided free of charge from CDIAC as the NDP-041 dataset. This link leads to a written report, the GHCN V1 digital data sets, and FORTRAN and SASTM data retrieval programs.

Version 2 of the data set on the web does not at the time of writing include air pressure data, but air pressures are available from an ftp site. e.g.

cd /pub/data/ghcn/v2
mget *slp*

Another data set in this category is the NCAR World Weather Records (link available from the AOPC surface pressure web site, from 'Related links' - Data), see for example This is an extremely useful site and contains MSLP series from all over the world (many of which were used in HadSLP2).

(4) NOAA-CIRES Climate Diagnostics Center

The Climate Diagnostics Center (CDC) (which has now merged into the NOAA Earth System Research Laboratory, ESRL) web pages provide several important links.

For example, COADS data consist of 2 deg square monthly summaries of many variables (1 deg for later data). Some information goes back to the late 1700s, with more from the 1850s. provides ordering information, product description etc. allows one to manipulate, composite and correlate various data sets.

(5) Joint Institute for the Study of the Atmosphere and Ocean

The Joint Institute web site provides an extensive range of data sets and web links, including versions of COADS and NCEP products and climate indices.

(6) KNMI Climate Explorer

The KNMI Climate Explorer project

similarly allows for an extensive range of data sets and web links to many of the products described above. (Simple registration is needed for this site.)

The PSMSL is grateful to Tara Ansell, UK Met Office for advice on the availability of air pressure data sets.