The following description is from the abstract of the documentation file for this data set:
Abstract: The Global Historical Climatology Network (GHCN) - Daily represents a compilation of global daily data into a single and consistent format. This dataset is a continuation of the Global Daily Climatology Network (GDCN, TD9101) which is no longer under development. The data set will serve the needs of researchers, weather-sensitive businesses, agriculture, and policy makers whose are dependent upon complete and accurate analysis of daily temperature and precipitation. Data within the GHCN-Daily have been extensively checked through a series of quality control procedures to ensure erroneous values have been removed and/or identified.
Documentation for this data set can be found in the following PDF: GHCN_Daily_V1.pdf
The GHCN Daily data can be found here.
COUNTRY CODES (Country_Code)
The key to the three-digit country codes used in this data set can be found in Appendix A of GHCN_Daily_V1.pdf.
DATA MEASUREMENT FLAG (DMFlag-Pr, DMFlag-Tx, DMFlag-Tn)
(Note: Flags can apply to Tx = Maximum Temperature, Tn = Minimum Temperature, Pr = Total Precipitation)
| - | No data measurement information (Tx,Tn,Pr) | |
| 65 | - | Accumulated precipitation value (Pr) |
| 67 | - | Begin or continuing precipitation accumulation (Pr) |
| 69 | - | Estimated value provided by source (Pr) |
| 74 | - | Source provided accumulated precipitation value, however
no information on accumulation period was provided (Pr) |
| 84 | - | Trace accumulation reported by source (Pr) |
| 82 | - | Daily value derived from the hourly data (i.e. highest
hourly or synoptic-reported temperature). (Tx, Tn) |
| - | No quality control information (Tx, Tn, Pr) | |
| 68 | - | Duplicate value. (Tx, Tn, Pr) |
| 88 | - | Exceeds known world daily extreme for that particular
element (Krause and Flood, 1997). (Tx, Tn, Pr) |
| 73 | - | Internal consistency error. The minimum temperature
value is greater than same day maximum temperature value. (Tx, Tn) |
| 75 | - | Streak value. Note: 0.0 mm precipitation values
are excluded. (Tx, Tn, Pr) |
| 71 | - | Gap value (see temperature quality control section).
(Tx, Tn) |
| 79 | - | Temperature value is greater than or equal to 4.0
bi-weight standard deviations from the period biweight mean. (Tx, Tn) |
| 77 | - | Manually edited value set to missing. (Tx, Tn, Pr) |
DUPLICATE STATIONS
With millions of days of daily data, direct comparison of all station data to all other station data was not feasible due to computational time limitations. However, a station to station duplicate identification check was developed that compares the 15th day (for all years) of each month to the 15th day of each corresponding month. The comparison was only done between the same element (e.g. compare STN A TMIN to STN B TMIN). The purpose of this test is to identify potential station pairs that have 100% of the same data on the 15th day of each month for all non-missing days. The test requires that at least 60 comparisons (12 months x 5 years) of data are present before a duplicate can be declared. Appendix F lists the station pairs and the element that are potentially duplicated.
Note: A portion of the stations were given new id numbers to facilitate their entry into the Data Library. A list of these stations, along with their original and new id numbers, can be found here.
Note: The data and metadata within the Global Historical Climatology Network - Daily Version 1.0 are governed by the following:
"The following data and products have conditions placed on their commercial use. The non-U.S. data cannot be redistributed within or outside of the U.S. for any commercial activities."