Anna Mani: Marvelous Meteorology

How one scientist’s measurements helped us save the ozone layer

Portrait of Anna Mani holding meteorology instruments with a background of clouds.
Portrait of Anna Mani by Weilu Shen

“We have only one life. First equip yourself for the job, make full use of your talents and then love and enjoy the work, making the most of being out of doors and in contact with nature.” These are the words of Anna Mani, a scientist who did just that and devoted her career to understanding the Earth’s atmosphere. Mani overcame numerous hurdles to become a prominent meteorologist. Her work to understand and measure the ozone layer in our atmosphere would later lay the groundwork to prevent a climate catastrophe and protect our planet.

"[Anna Mani's] unrelenting pursuit of technological independence for India, and her work on developing renewable energy sources has helped India and the rest of the world appreciate how we humans affect our Earth. Her work continues to inspire us to make sure that we leavethe Earth just the way we found it."


Watch the video or read more below!


Table of Contents:

Ozone: our planet's sunscreen

Weathering the storm

Essential ozone

Protecting our planet

 

Ozone: our planet’s sunscreen

You may have heard about the ozone layer before. Maybe you’ve heard of the “hole” in the ozone layer above Australia, or maybe you know that you need to wear more sunscreen on some days because there are higher UV levels. But why is the ozone layer so important, and what does it have to do with whether you wear sunscreen or not?

Image showing layers of Earth's atmosphere. Bottom layer is green land, followed by blue semi-circles for the troposphere, ozone layer, stratosphere, mesosphere, karman line, thermosphere, exobase, and exosphere.
The layers of Earth's atmosphere.

The Earth's atmosphere has many layers. You can think of it like an onion, where each layer is made up of a mixture of different gasses. The ozone layer of the atmosphere is called that because it contains large amounts of a molecule called ozone, made up of three oxygen atoms. The structure of this molecule allows it to absorb a significant amount of dangerous ultraviolet (UV) radiation from the Sun. UV radiation is dangerous because its wavelengths can reach deep inside living things and damage DNA, which can cause cancer. Without the ozone layer, the Earth would constantly be bombarded with a huge amount of this dangerous radiation. So we can think of the ozone layer as Earth’s personal sunscreen, protecting life on our planet.

Animation showing a photon interacting with an ozone molecule. Purple photon enters and hits ozone molecule with three atoms and two bonds. Ozone splits to an oxygen atom and O2 molecule, which then interacting with surrounding oxygen to form more ozone.
A photon interacting with an ozone molecule.

 

Weathering the storm

It took climate scientists a long time to realize how important this layer of gas is to our planet. One of the very first was a meteorologist named Anna Mani. Anna was born in Travancore, India in 1918, in what is a state now called Kerala. In her community, it was expected for women to get married, take care of households, and raise children single-handedly. But against her family’s wishes, Anna was determined to study science. She chose to study physics and chemistry at the Presidency College in Madras (which is now called Chennai). After she graduated in 1940, she pursued postgraduate research on how light is bent and absorbed by rubies and diamonds. But after five years, her university refused to award her a PhD for her work. So Anna switched fields and started studying meteorology.


Initially, Anna Mani worked to develop instruments for measuring weather phenomena like humidity, rainfall, air pressure, and wind speed. Mani wanted to standardize the way that India measured and monitored its weather, without relying on any imports from other countries. This was a pretty big feat because at this time India was still controlled by the British Empire. As a colony, much of their manufacturing was monitored by Britain and the country was often forced to import scientific instruments from Britain.



Photo of a man holding a weather instrument next to Anna Mani holding an Anemometer, which looks like a cage suspended by string.
Top left: Hygrometer (to measure humidity) and anemometer (to measure wind speed and direction). Top Middle: Rain gauge to measure rainfall. Top right: Barometer to measure air pressure. Bottom: Anna Mani holding an anemometer.

 

Essential ozone

Anna Mani also wanted to develop technology to harness solar energy for India. But she ran into a problem: there were no historical records for which parts of India got the most sunlight! So Mani decided to change course and take those measurements herself.

Cartoon of an ozonesonde, an instrument used to measure ozone. Illustration consists of two brown boxes. First box contains a tube that air flows through and a pump; second box contains two jars, one filled with iodide. Second box has leads with current coming off of it.
Cartoon of an ozonesonde, an instrument used to measure ozone.

In the course of this work, she began studying the ozone layer. To do that, she built an instrument called an ozonesonde. An ozonesonde is made up of an air pump that directs air through a small space filled with a chemical called iodide. When iodide mixes with ozone, it generates an electrical signal that can be measured. If there is a higher concentration of ozone, or the layer is thicker, these chemicals will react more strongly and generate a greater signal. Anna Mani attached these instruments to huge balloons and floated them up to the atmosphere 30 miles above the Earth to measure the thickness and concentration of ozone in different regions.



Illustration of large white balloon over a background of grass, palm trees, and blue sky. A small group of people is in the background on the grass.
Illustration of Anna Mani and others releasing a balloon tied to an ozonesonde.

With her ozonesondes, Mani made the first precise seasonal measurements of the ozone content in the tropical regions of Earth. She was one of the first scientists to precisely measure the thickness of the ozone layer globally and helped contribute to the discovery that the thickness of the layer changes depending on air pollution and your location on Earth. From her research, she was able to understand that this layer of the atmosphere was critical to life on Earth. This came a full twenty years before the larger scientific community realized how important this layer was in protecting life on Earth from dangerous radiation from the Sun.


In the 1980s, the global scientific community discovered that humans were polluting the air with certain chemicals that were causing the ozone layer to get thinner. This discovery depended on the technology and historic measurements made by Anna Mani. This “hole” in the ozone was a huge environmental crisis. A thinner layer meant that more of the Sun’s dangerous UV radiation was reaching us on earth. This discovery led to the regulation of chemicals that were harming the Earth’s protective sunscreen. Since those environmental protections passed, the ozone layer has slowly been recovering, once again protecting us from those harmful rays.

Photo of five people with Anna Mani in the center of four men, looking up into the sky.
Photo of Anna Mani and others releasing an ozonesonde into the atmosphere.

 

Protecting our planet

Anna Mani developed instruments that produced some of the most precise measurements ever taken of solar radiation. Her work helped lay the foundations for the development of green technology to harness solar and wind energy. Her unrelenting pursuit of technological independence for India, and her work on developing renewable energy sources has helped India and the rest of the world appreciate how we humans affect our Earth. Her work continues to inspire us to make sure that we leave the Earth just the way we found it.


Credits

Written by Lindsey Oberhelman

Edited by Manasvi Verma and Caroline Martin

Portrait by Weilu Shen

Illustrations by Helena Almazan

Video by Manasvi Verma, Caroline Martin, Taylor Contreras, and Madelyn Leembruggen

Other contributions by Yanting Teng and Katherine Fraser


Sources

Primary Sources:

Celebrating Women in STEM: Anna Mani

Anna Mani: The Weather Woman of India


Other Resources:

An illustrated children's book with Anna Mani's story.


Photo Credits:

Anna Mani and others releasing an ozonesonde

Illustration of Anna Mani and others releasing a balloon tied to an ozonesonde

Hygrometer and anemometer

Rain gauge

Barometer

Anna Mani holding an Anemometer

 

Learn more about Earth's atmosphere!


Define (10-20 minutes): The ozone layer acts like the Earth’s sunscreen. It shields life on Earth from intense harmful UV radiation from the sun. Take a few minutes to think about what life may be like without the ozone layer.


Create (30-45 minutes): Following the Earth Atmosphere Lab Worksheet. Create a model of the Earth’s atmosphere using household supplies. Use the model to answer some questions.


Monitor (4 months): Track the temperature, wind speeds, and precipitation in a weather journal every day for four months (you can use your local weather station to collect this data, or make the measurements yourself!). Once the four months are over, look up the historic averages for your region during the four months you measured. How does it compare?

  • Are the temperatures similar? If not, are they higher or lower than average?

  • Is your region getting equal, higher, lower amounts of rain than usual?

  • Wind speeds are an important measurement for renewable energy engineers. It helps them determine where they can use wind energy generation. On average a wind turbine needs wind speeds of 12-14 km/h, but 50-60 km/h is ideal. Is your area suitable for wind turbines?

Construct (45-60 minutes): Anna Mani is well known for constructing different weather monitoring instruments. Follow the Make Your Own Barometer Guide to construct your own instrument that can monitor air pressure.


Challenge (1-2 hours): How can the ozone layer break down? Follow along with this lab.