These files are associated with GHCN v2 precipitation:
New monthly data are added to v2.prcp a few days after the end of the month. Please note that sometimes these new data are later replaced with data with different values due to, for example, occasional corrections to the transmitted data that countries will send over the Global Telecommunications System.
readme.prcp.V2 is this brief documentation file.
The files ending with .Z are compressed. To uncompress the files use the command: uncompress filename. For more information, email: email@example.com.
v2.prcp is the raw data file.
The data are monthly total precipitation recorded at the station in tenths of mm. (Divide by 10 to get millimeters.)
Each line of the data file has:
This file does not contain any duplicates of the stations, however, it does have a duplicate number which indicates whether there are duplicates in the companion file. A 1 in the duplicate number indicates there are no duplicates and a 0 indicates that there are duplicates in the file v2.prcp.duplicates.
v2.prcp_adj is the adjusted data file.
This file contains far fewer station records than the raw data set, It has the same format as the raw data file, but contains data that has been adjusted for inhomogeneities. Not only are these station records free of inhomogeneities, they also contain additional records for some stations, particularly those in the former Soviet Union.
v2.prcp.inv Raw data set metadata file.
This metadata file contains the station id, station name, country, latitude, longitude, elevation, first and last record year for station, and number of years with at least one month of data between the first and last year.
The format is as follows:
v2.prcp.adj.inv Adjusted data set metadata file.
This file has the same format as the raw metadata file, but contains only those stations that are in the adjusted data set.
There is only one way to calculate the total monthly precipitation. Yet, when putting this data base together we found some station time series with non-trivial differences. While the metadata would indicated that they were the same station and the many data points that were identical would indicate that they were the same station, there were also some data points that were significantly different. If we could not determine which time series was the correct time series for that station, we preserved them both by putting the longest one in the regular file and the additional time series in this duplicate file. The number of stations with duplicates is fairly small (2,039)compared to the number of stations in all of the GHCN precipitation data set (20,614). But for specific times at some stations, these duplicate time series provide very different signals.
In the future, we will be evaluating the effects of using different duplicates in various types of analyses. Personally, I do not use the data in the duplicate file when performing large-scale analyses. However, if we're doing an analysis that uses only a few dozen stations, we would definitely see whether there were alternate time series for some of these stations and whether these duplicates provided different results. The answer in most cases will probably be no, but this duplicate file is made available to provide users with as much information as possible.
Like GHCN temperature data, the precipitation data base has undergone a series of Quality Control tests. The final test removed individual data points we determined were most likely erroneous (e.g., due to errors in digitizing). This final QC step is very important because some very bad values can make it into any data base. However, any QC approach that can detect most of the bad values will also flag some valid extreme precipitation data points. Therefore, we can say with confidence, that some of the data points that failed our QC are valid. This file has the data points that failed our QC and were removed from the data file and is provided for users who might have additional corroborating information such as an old news report of an unusual flood near an isolated station. Without such information, we do not recommend using these data points.
v2.prcp.failed.qc.duplicates is the same as #5 but for the duplicate time series.
v2.country.codes lists the countries of the world and GHCN's numerical country code.
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