Plotting the average distance of weather stations from the equator

Weather stations further away from the equator will obviously record colder temperatures, so if there is an increase in high latitude stations over time this could bias graphs of average temperatures accordingly.

To investigate if there is any latitude bias within the data we can use the following command:

    tempgraph --ghcn v2.mean --countrycodes v2.country.codes --start 1900 --wmo wmo.txt --equatordist graph_dist_to_equator.png

We can also perform the same analysis for particular countries, or groups of countries:

    tempgraph --ghcn v2.mean --countrycodes v2.country.codes --start 1900 --wmo wmo.txt --equatordist graph_dist_to_equator.png --countries "uk,france,germany,spain"

An example for the entire data set is shown below: