Density of Stations Reporting Daily Precipitation

The following plots give the density of stations reporting the daily precipitation throughout a particular time interval.

1860-1899

1900-1939

1940-1979

1980-2019

We can see the addition of station data to the archive over time and the expanding spatial coverage of measurements. The United States has the densest network or stations in the archive. The density across the globe increases in each time interval with Australia and the United States having some of the highest concentration of stations in the archive. Of note is the change in coverage over South America from 1940-1979 to 1980-2019; the coverage moves from the Eastern side of the continent to the Central and Western side. Each density plot has the same scale.

There are only 57 stations that record the daily precipitation (PRCP) over the enire time frame of 1860-1899. There are 5970 stations reporting PRCP throughout 1900-1939, 13169 stations reporting PRCP throughout 1940-1979, and 12509 stations reporting PRCP throughout 1980-2019.

Menne et. al. (2012) present similar plots in their paper; however, for our plots, a station is included in the density plot for the years 1900-1939 only if the station is active for the entire 40 years of that time interval. The benefit of this approach is that it gives more of an indication of how consistently areas of the globe are covered by reporting stations over time. Stations than only record data for a small time frame would be excluded from this plot. The drawback of this approach is that it would exclude stations that report from say 1920-1970 since the endpoints do not span one of the chosen cut-offs in the graphs.

The final plot given below gives the density of stations reporting PRCP in 2018.

Menne, M.J., I. Durre, R.S. Vose, B.E. Gleason, and T.G. Houston, 2012: *An overview of the Global Historical Climatology Network-Daily Database*. Journal of Atmospheric and Oceanic Technology, 29, 897-910, doi:10.1175/JTECH-D-11-00103.1.