The GHCN data base contains mean monthly station pressure data (in tenths of millibars) for 1873 stations throughout the world. The majority (83%) have data for fewer than 50 years, and only a small proportion (4%) have records in excess of 100 years. The longest period of record for any given station is 221 years (1768-1988 for Geneve-Cointrin, Switzerland). Most records (71%) end in the 1980s. No data are available for any station after 1988.
The density of stations in central Europe is extremely high, and moderately high in most of the rest of the world. Significant data gaps are evident in northern North America, the Sahara desert, the Arabian peninsula, the Gobi desert, the East Indies, and all of Antarctica. The global distribution of stations with 50 years or more of data is characterized by a low density of stations in most areas, except central North America, central Europe, and the Indian subcontinent. Stations with 100 years or more of data are primarily restricted to these same areas.
In general, the number of stations has increased over the past 250 years, particularly in third-world countries. The rate of increase has accelerated since the nineteenth century, owing to the widespread availability of reliable instrumentation and 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.
Nearly 75% of all stations are missing less than 10% of their data. Typically, these are the same stations in eastern North America and central Europe with the longest periods of record. In contrast, the data sparse areas of northern South America, northern Africa, and Asia are characterized by higher proportions of missing data.
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