In this age of high tech, it's hard to imagine that a 75-year old instrument is used to measure the ozone hole. Hi, I'm Dave Thurlow and this is the Weather Notebook. As correspondent Allan Coukell reports, scientists in the Antarctica today are relying on a tried, true and older technology to measure escaping ozone in the atmosphere.
Herme Binney: "This is the Dobson. And the kind of cool thing about this is - look - it's "Dr Dobson's ozone meter, number 17..."
AC: "On Ross Island, Antarctica, a science technician is preparing to measure atmospheric gases using a Dobson Spectrophotometer. Herme Binney is with New Zealand's National Institute of Water and Atmospheric Research."
HB: "This is an instrument that measures the ozone levels. So we take the hatch off and I put up this pretty cool looking periscope here. (rattle) And we put in the lense here (clink), so we follow the sun, we move the table so it's pointing in the right direction."
AC: "So what happens? Light comes down the periscope."
HB: "Light comes down the periscope, hits the lens, and it pops into the instrument here. And what you're really trying to do is measure how strong that light is at various points. Because the atmosphere is like an enormous sponge. And what it does is every particular gas up there has a particular fingerprint frequency that it will soak up the light. So what we do is measure at that fingerprint, at that particular frequency, how much sunlight makes it through."
AC: "These days, much ozone monitoring is done from space, by orbiting satellites. But to calibrate the satellite readings, scientists still rely on the tried and tested measurements taken on the ground."
Thanks today to Allan Coukell of New Zealand. The Weather Notebook is a productin of the Mount Washington Observatory, with support from Subaru.