Science With Mr. Milstid

One of the most important, but often overlooked, aspects of the world around us is the weather. It has an impact on everything in our lives – from what we wear day to day, to whether or not we are able to eat!

So what is it, really?
Weather is the condition of the atmosphere at a certain time and place. It is affected by the amount of wind, moisture, pressure and temperature in the air.

In order to fully understand weather, we need to be able to understand wind.
Wind is, very simply, moving air. It is also one of the driving factors of weather – it causes and carries weather phenomena from place to place.

What causes wind?
Wind is caused by the uneven heating and cooling of the earth’s surface - both globally and locally.

For instance:
As solar energy reaches the Earth, areas around the equator heat up more than the poles. Air in this region expands as it warms, creating areas of low air pressure, which rise. The warmer the temperature of air, the lower the pressure.
Air around the poles receives less solar radiation, and are cooler than air around the poles. These regions of cooler air condense, sink and create areas of high air pressure. The cooler the temperature of air, the higher the air pressure.

Wind is created by the convection that occurs as a result: low pressure (warmer) air rises; High pressure (cooler) air sinks, and rushes in to fill the space left by the rising low pressure air.

So our definition of wind, then, can be changed to: air moving from areas of high pressure to areas of low pressure.
Incidentally, the greater the difference in pressure (and temp) between two pockets of air, the higher the force/speed of wind.

So, quite obviously, we’ve been studying the atmosphere in the 7th grade. We’ve learned about the layers and composition of the atmosphere, pressure and temperature changes throughout the atmosphere, and methods of heating in the atmosphere (convection, conduction, radiation). Most importantly, we’ve spent time discussing the value of the atmosphere: it provides a blanket of stable gases which allow us to breath, provides us with moisture, shields us from harmful radiation from the sun, and protects us from severe shifts in temperature.

Unfortunately (at times) for us humans, changes can be caused to the atmosphere, and the general conditions of the world as a consequence, by pollution.

Air pollution is: the contamination of the atmosphere by the introduction of foreign substances by human and natural sources.

There are two main types of air pollution:

1. Primary Pollutants
2. Secondary Pollutants

Primary Pollutants
These are pollutants that are directly put into the air by human or natural sources.
They can include gases like carbon dioxide and carbon monoxide, dust, sea salt, smoke from forest fires, volcanic ash and gas, and chemicals from human activity.

Secondary Pollutants
Secondary Pollutants occur when primary pollutants react with atmospheric gases to make new, hazardous substances.

For example – when the car exhaust produced by vehicles reacts with sunlight in the atmosphere, it produces smog, which can be hazardous to breath, etc.

Effects of Pollution
There are myriad effects of air pollution.
Just a few of them are:
Acid Precipitation
Air Pollution can mix with water in the air to create acid rain.
Acid rain can damage plants, animals and ecosystems around the world.

Damage to the Ozone Layer
As air pollutants (such as CFCs) are added to the atmosphere, they may damage the ozone layer. As the ozone layer is damaged, and begins to be perforated, it can let in excess UV radiation, which itself can be damaging to life on earth.

We will discuss the effects of air pollution on human health, and global climate change in future classes.

Or, view the whole class set at Flickr

The atmosphere is a layer of gases surrounding the Earth. But, it is also much more.
It is a moving source of life for every creature of the planet. While the atmosphere is mainly composed of nitrogen (N₂), it also contains gases such as oxygen (O₂) and carbon dioxide (CO₂) that plants and animals need to survive.
It has specialized molecules like ozone (O₃) that filter out harmful radiation from space.
The atmosphere also protects us from the vacuum of space. Without the atmosphere, our world would be as barren and dead as the Moon or Mercury, not to mention extremely cold!

 

Atmospheric Composition
The atmosphere is made up of just a few main molecules:

The rest of it is made of things called trace elements like water vapor, ozone, and other particles and molecules floating around.

Layers of the Atmosphere
There are 5 layers in the atmosphere.
From the earth up, they are:

1. Troposphere
2. Stratosphere
3. Mesosphere
4. Thermosphere
5. Exosphere

Almost all weather occurs in the Troposphere, the lowest layer of the atmosphere, which extends from the surface up to 8 to 16 kilometers above Earth’s surface (lowest toward the poles, highest in the tropics). Earth’s surface captures solar radiation and warms the troposphere from below, allowing it to be habitable.

Temperatures in this layer decrease with elevation/altitude (by about 6.5°C with each kilometer of altitude).

At the top of the troposphere is the Tropopause, a layer of cold air (about -60°C), which forms the top of the troposphere and creates a “cold trap” that causes atmospheric water vapor to condense.

The next atmospheric layer, the Stratosphere, extends upward from the Tropopause to 50 kilometers. In the Stratosphere temperatures increase with altitude because of absorption of sunlight by stratospheric ozone.
(About 90 percent of the ozone in the atmosphere is found in the stratosphere in a section called the Ozone Layer. The Ozone Layer is important because it absorbs harmful UV radiation, preventing it from reaching the surface of the earth.)

At the top of this layer is the Stratopause, where temperatures peak at about -3°C.

In the third atmospheric layer, the Mesosphere, temperatures once again fall with increasing altitude, to a low of about -93°C.

Above this layer is the Thermosphere, where temperatures again warm with altitude, rising higher than 1700°C.

The highest layer of the atmosphere is the Exosphere. This layer is not well defined: it blends into space.

Figure 1 below shows the pattern of temperature fluctuations across layers of the atmosphere.

Figure 1. Structure of the atmosphere

See larger image

Source: © 2006. Steven C. Wofsy, Abbott Lawrence Rotch Professor of Atmospheric and Environmental Science, lecture notes.

Atmospheric pressure in the atmosphere changes with elevation consistently across all layers of the atmosphere: as elevation increases, pressure decreases because the total weight of air above you lowers.
Figure 1 illustrates this trend as well. This fact is what causes pressure changes in your ears while flying in an airplane.

With the PSSA science exam coming up in an increasingly short period of time, I’ve created a set of interactive flashcards online.

Follow this link to Quizlet.

On this site, you can review key terms, print a neatly formatted set of vocabulary flashcards, test yourself, randomly rearrange and review flashcards, etc. Seriously, it will help.
Also, if you sign up (for free) on this site, it will keep track of your top score on flashcard reviews, and compare it to those of your classmates. Competition anyone?!?