The READER data set is continuously being revised as more observations are acquired, however as with any data set we expect READER to contain errors. The observations come from a variety of sources, each having its own probability of error. Real-time data is provided through the WMO Global Telecommunications System (GTS). Today, most of this is electronic, but early data was often read by observers, transmitted by voice over HF radio and hand punched onto telex tape. Each step could lead to the generation of errors and omissions. National operators may subsequently supply the complete data set in electronic form after local verification and on occasion re-calibration (the preferred means for inclusion in READER), but it is still subjected to further quality control to identify possible errors; not all are detected. On occasion, particularly for older observations, no synoptic observations are available, however a monthly mean from a CLIMAT message has been provided. Little verification is possible for these values. Finally errors may occur during compilation of the READER database. We welcome independent verification of the values presented here, and would particularly welcome contribution of the original synoptic data in order to provide uniform treatment for all stations. In addition to these issues, we note that the actual location of observing points at Antarctic stations, and indeed the location of the stations themselves, often changes over time.

The data are arranged into three sections

Surface station data Temperatures Pressures / Winds. A list of errors that are being investigated in surface station data can be accessed here

Surface aws data Temperatures Pressures / Winds. A list of corrections that have been made to the AWS tables can be accessed here

Upper air data Temperatures Heights / Winds

Temperatures are in degrees Celsius, pressures are in hecto-Pascals, wind speeds are in knots and heights are in metres

Data are displayed in different colours:

Black when the full synoptic data sets have been obtained from the national operator.

Green when the data have been obtained from the GTS, these should be considered as preliminary values.

Blue where the data have come from CLIMAT messages and only the monthly mean values are available.

Red where the percentage of observations are too low to calculate an accurate mean ( < 90 % for surface and < 30 % for upper air ).

The number in brackets after the value is the percentage of observations available. Since 3rd March 2009 the percentages are truncated values rather than rounded values.

A text based version of the table can be downloaded from the bottom of each web page but the data shown in red are not included in this text version.

Any comments on data format or style or to report any suspected errors then please contact Steve Colwell