Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Observations of changes in the frequency distribution of total column ozone (DU, Dobson units) in Antarctica in September for Syowa (Top), Halley Bay (Middle), and Faraday (Bottom), which are stations with long records since 1960. Symbols show the midpoints of bins used. DU, Dobson units.
