Composition of Air

The air that is near the planet surface is a combination of gasses. Mostly, it is nitrogen with takes up about 78% of the total if there is no water vapor. Then, oxygen is second most abundant at 21%. In that tiny 1% sliver you have 0.97% inert gasses, 0.035% carbon dioxide, and the remaining are trace gasses. Carbon dioxide has been getting a lot of attention lately as a greenhouse gas. We will talk about that more later, but here let's look at what a few of the sources of it are and what uses it.

We exhale and carbon dioxide makes up about 6% of those gasses. The reason we exhale carbon dioxide is that it is one of two chemical byproducts of our body burning glucose for fuel. The other component is water vapor. Plants in turn need carbon dioxide and they use it to make glucose, among other things. 

  Layers of the Atmosphere

The collection of gases that surround the planet, known as the atmosphere, are divided up into five layers that are determined by changes in temperature of the gas with increasing altitude. These layers are separated by narrow pauses where with increasing altitude does not correspond to a change in the layer's temperature. Here is an image from the NOAA showing the changes in temperature (horizontal axis) with increasing altitude (vertical axis).

  Ozone Layer

Why You Don't Hear About the Ozone Layer Anymore

Much like you hear about climate change now, in the 80's the big fear was the ozone layer thinning until it could not protect us from solar radiation any more. So, why is it that we don't hear about this any more?

Time: 8:34

  Water and Atmosphere

Relative Humidity

You cannot live in Texas or nearby states without hearing about humidity. In this area of the country, humidity in the summer can make hot days quite oppressive to most. In the chart below, you see a thermometer set to Celsius. There are a few correlations of temperature and how much water in in units of grams that the air can hold before it will come out of the air and turn to dew (dewpoint). This held water is humidity. In the chart right beside it you will see a column of percentage humidity and the column beside it how most people describe as their perception of humidity.

When we get hot, we sweat. This cools us off. Why? Well, it is because the evaporation of water carries heat away. How well the evaporation of sweat occurs makes a difference in our ability too cool off. This is impacted by humidity in the air. When there is a lot of humidity, evaporation does not occur very well because the water is already holding water.