HSC CHEMISTRY 2015​.

Monitoring the Ozone Layer

 

Australian Bureau of Meterology measurements:

 

Dobson Spectrophotometer:

Ground based instrument which records the amount of U.V radiation reaching the earth. 2 different (but very close) frequencies are measured; one which ozone doesn’t absorb and another that ozone does absorb. The intensity of the absorbed radiation hitting reaching the spectrophotometer depends on the amount of concentration of ozone above.

Advantages=1% accuracy and provides quick (3-4hours) and specific measurements of ozone concentrations

Disadvantages=localised measurements – only determines net column ozone amounts.

 

Weather Balloons

Helium filled balloon, equipped with a ‘sonde’ which measures the concentration of Ozone as well as the correlating altitude as it rises to typically 30km. The sonde uses reactions of ozone and a Potassium Iodide solution inside the sonde. Electrodes in the solution measure the small electrical currents which depend on the concentration of ozone.

Advantages=altitude specific measurements,  

Disadvantages=controlled by the weather; their location is determined by winds thus can’t be aimed at a specific coordinate

 

NASA measurements:

 

Satellite:

There has been a range of satellite instruments measuring atmospheric ozone concentrations including. NIMBUS, TOMS & OMI but the most recent is the Ozone Mapping Profile Suite (OMPS) aboard the Suomi NPP satellite.

This works similarly to the Dobson spectrophotometer, as it measures the light that has been reflected off the atmosphere and as some of this light is absorbed by Ozone and thus the concentration can be calculated. It is called a profiler as it is able to record a profile of the different ozone concentration at varying altitudes. This means they are able to produce global pictures of ozone concentration.

Advantage=Global Monitor, provides a profile of the whole atmosphere as well as a daily column ozone amount, monitors the chemistry of ozone destruction, real-time measurements.

Disadvantage=Expensive to get into space

 

Dobson Unit: Unit of measurement for ozone in a column of air (≈0.3cm thick). 1DU is the amount of ozone that can be spread in a layer 0.01mm thick at 0°C and atmospheric pressure.

The normal amount of ozone is 300DU (3mm thick)