The GHCN data base contains total monthly precipitation data (in tenths of millimeters) for 7533 stations throughout the world. A slight majority (55%) have records in excess of 50 years, and a significant proportion (13%) have records in excess of 100 years. The longest period of record for any given station is 291 years (1697-1987 for Kew, United Kingdom). Most records (76%) end in the 1980s. No data are available for any station after 1990.
The density of stations in central North America, central Europe, sub-Saharan Africa, and eastern Australia is extremely high, and moderately high in eastern Europe and Asia. Significant data gaps are evident in northern North America, central South America, the Sahara desert, the Arabian peninsula, the Tibetan plateau, the East Indies, and all of Antarctica. The global distribution of stations with 50 years or more of data is characterized by a lower density of stations in most areas and the appearance of additional data gaps over southern Africa, central Asia, and western Australia. Stations with 100 years or more of data are concentrated in eastern North America, central Europe, and eastern Australia.
In general, the number of stations has increased over the past 300 years, particularly in third-world countries. The rate of increase has accelerated since the late nineteenth century, owing to the increased habitation of areas that were previously less populated. The sharp increase in the number of stations in 1951 is due to the inclusion of the 1951-1960 version of the WWR data set in the WMSSC. The decrease in the number of stations after 1971 results from the inclusion of only three of the six volumes of the 1971-1980 WWR publication (i.e., three volumes have yet to be prepared and thus could not be included). The continuing decrease in the number of stations through the 1980s results from the fact that most of the data sets from which the GHCN was compiled were produced during the late 1980s, and in the case of the African data sets, in the early 1980s or late 1970s.
Nearly 72% of all stations are missing less than 10% of their data. Typically, these are the same stations in central North America, central Europe, and eastern Australia with the longest periods of record. In contrast, the data-sparse areas of South America and northern Africa are characterized by higher proportions of missing data.
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