Measuring Ozone Concentrations with Beer-Lambert Law and Dobson Units

Why is measuring ozone important

The ozone layer's ability to filter harmful UV radiation depends on how much ozone is present.

Where are the highest ozone concentrations usually found

Between approximately 15–30 km in altitude.

Where is approximately 90% of atmospheric ozone found

In the stratosphere.

What are the two general approaches to measuring atmospheric ozone

In situ measurements and remote sensing.

What are in situ measurements

Direct measurements made by sampling the atmosphere.

Where can in situ ozone measurements be performed

From balloons, aircraft, or ground-based platforms.

What is an advantage of in situ ozone measurements

They are usually very accurate and can provide reliable vertical ozone profiles.

What is remote sensing

Indirectly determining total column ozone using electromagnetic radiation passing through the atmosphere.

What is passive remote sensing

Remote sensing that uses a natural light source, such as sunlight.

Where can remote sensing instruments be deployed

On satellites, aircraft, balloons, or ground-based platforms.

What is an ozonesonde

An instrument carried by a weather balloon to measure ozone concentrations at different altitudes.

How can an ozonesonde measure ozone using potassium iodide

Ozone oxidizes iodide ions, producing iodine and causing a measurable electrical current.

What is the ozonesonde potassium iodide reaction

2KI(aq) + O₃ + H₂O ↔ 2KOH(aq) + I₂(aq) + O₂.

What causes current to flow between the ozonesonde chambers

Ozone changes the electrical potential between the two chambers, creating a current as the system moves toward equilibrium.

What is the relationship between ozonesonde current and ozone concentration

The current is proportional to ozone concentration.

How can an ozonesonde also measure ozone through colorimetry

It measures the colour change caused by the formation of iodine.

What does the Beer-Lambert law describe

The relationship between light absorbance, the concentration of an absorbing substance, and the path length through the sample.

Why can ozone be measured using light absorption

Ozone absorbs UV radiation, so the amount of light absorbed can be used to estimate ozone concentration.

What does total column ozone (TCO) represent

The total amount of ozone in a vertical column of atmosphere above a given location.

What is a Dobson Unit (DU)

A unit used to express total column ozone.

What does one Dobson Unit represent

A 0.01 mm-thick layer of pure ozone at standard temperature and pressure.

Why is total column ozone useful

It provides a measure of the total ozone present above a location rather than the concentration at only one altitude.