Weather Merit Badge – A rainy day will keep you from mowing the lawn or playing a baseball game. A serious heatwave could prevent your Scout troop from taking a hiking trip.
For people in some occupations, however, the weather forecast is vital. Planning ahead for weather conditions can mean the difference between profit and loss or even life and death.
Climate information helps experts lay out airport runways and determine the heating and cooling needs for houses, factories, or for the shipment of goods.
Climate records may be introduced as evidence in court to clarify the causes of accidents on highways, in the air, and at sea.
Climate can affect people’s health and social behavior as well as agricultural, commercial, and industrial pursuits the world over. That’s why we need to learn about the climate or weather.
Weather Merit Badge Requirements
- Define meteorology. Explain what weather is and what the climate is. Discuss how the weather affects farmers, sailors, aviators, and the outdoor construction industry. Tell why weather forecasts are important to each of these groups.
- Name five dangerous weather-related conditions. Give the safety rules for each when outdoors and explain the difference between a severe weather watch and a warning. Discuss the safety rules with your family.
- Explain the difference between high- and low-pressure systems in the atmosphere. Tell which is related to good and to poor weather. Draw cross-sections of a cold front and a warm front, showing the location and movements of the cold and warm air, the frontal slope, the location and types of clouds associated with each type of front, and the location of precipitation.
- Tell what causes wind, why it rains, and how lightning and hail are formed.
- Identify and describe clouds in the low, middle, and upper levels of the atmosphere. Relate these to specific types of weather.
- Draw a diagram of the water cycle and label its major processes. Explain the water cycle to your counselor.
- Identify some human activities that can alter the environment, and describe how they affect the climate and people.
- Describe how the tilt of Earth’s axis helps determine the climate of a region near the equator, near the poles, and across the area in between.
- Do ONE of the following:
- Make one of the following instruments: wind vane, anemometer, rain gauge, hygrometer. Keep a daily weather log for one week using information from this instrument as well as from other sources such as local radio and television stations, NOAA Weather Radio All Hazards, and internet sources (with your parent’s permission). Record the following information at the same time every day: wind direction and speed, temperature, precipitation, and types of clouds. Be sure to make a note of any morning dew or frost. In the log, also list the weather forecasts from radio or television at the same time each day and show how the weather really turned out.
- Visit a National Weather Service office or talk with a local radio or television weathercaster, private meteorologist, local agricultural extension service officer, or university meteorology instructor. Find out what type of weather is most dangerous or damaging to your community. Determine how severe weather and flood warnings reach the homes in your community.
- Give a talk of at least five minutes to a group (such as your unit or a Cub Scout pack) explaining the outdoor safety rules in the event of lightning, flash floods, and tornadoes. Before your talk, share your outline with your counselor for approval.
- Find out about a weather-related career opportunity that interests you. Discuss with and explain to your counselor what training and education are required for such a position, and the responsibilities required of such a position.
Earth and Atmosphere
Earth’s atmosphere can be thought of as an ocean. It is an ocean of air instead of water. The air is almost never at rest. Its restless movement is the source of everything people call weather. The study of the atmosphere and its weather is the science of meteorology.
1. Elements of the Atmosphere
The atmosphere is a mixture of gases, six of which are present in amounts large enough to be important in studying meteorology. Four of the six stay more or less in constant proportions, at least in the atmosphere’s lowest 8 miles or so.
The most abundant of these is nitrogen, making up about 78 percent of the atmosphere. Oxygen is next, at about 21 percent, followed by argon at about 1 percent, and carbon dioxide at about 0.03 percent.
Nitrogen, oxygen, and carbon dioxide are essential to life on Earth. If their proportions were to change significantly, all life would disappear. The atmosphere contains two other
Because their amounts change from time to time and place to place, they are called variable gases. One is water vapor, which can range from nearly zero to as high as about 4 percent of the total.
Most of the water vapor is concentrated in the lowest mile of the atmosphere. When it condenses to form clouds, rain, and snow, it is the most important part of the weather.
The other variable gas is ozone, most of which is found more than 6 miles above Earth. While ozone at sea level harms humans and plant life, its presence high in the atmosphere shields us from the sun’s ultraviolet rays.
2. Vertical Structure of the Atmosphere
A cross section of the atmosphere shows that it consists of four main layers. There is no “top” to Earth’s atmosphere. Instead, it gradually thins until it vanishes into the vacuum of space.
The lowest layer of Earth’s atmosphere is called the troposphere. This layer varies in depth from about 10 miles at the equator to only 4 miles over the North and South poles. It is within this layer that most weather occurs.
The troposphere is constantly stirred by the motions that produce weather, so the mixture of gases is nearly constant. Earth’s surface, which is warmed by the sun, in turn warms the air of the lower troposphere.
As a result, temperatures in this layer tend to decrease as altitude increases. On average, for every 1,000 feet gained, the air temperature will decrease by roughly 3.5 degrees Fahrenheit.
The layer above the troposphere is the stratosphere. This layer extends to a height of about 30 miles. In the stratosphere, the atmosphere is quite thin and the mixture of gases begins to change.
The small amount of ozone in the stratosphere is vital to life on Earth because it absorbs the sun’s harmful ultraviolet radiation.
The boundary between the troposphere and stratosphere is called the tropopause, a lid on the weather-filled troposphere.
Temperature begins to increase with height above the tropopause because an increasing number of ozone molecules absorb the sun’s ultraviolet radiation.
Above the stratosphere is the mesosphere, which extends about 30 to 50 miles. Temperature decreases with height in this coldest layer of the atmosphere.
The next layer is the thermosphere. Because of the sun’s rays, air temperatures in this layer can reach more than 1,800 degrees.
3. The Origin of Wind
In prehistoric times, humans became aware that the weather cloudy or clear skies, warm or cold air depended on wind direction and speed. During the 1600s, people learned that air has weight.
Scientists discovered that air becomes lighter when it is warm and heavier when it is cold. Because the pressure that anything exerts on the surface of Earth depends on its weight, air temperature affects air pressure.
Air temperature also is a factor in how winds arise. If air in one place is heated so that it is warmer than the air around it, that air tends to rise. As it does, air must flow in from around the heated region to replace the air that is rising.
If you live near a seacoast, you may see this process operate every day. During the day, the land heats more rapidly than the ocean. This heat warms the air over the land and makes it rise.
Cooler air from the ocean flows in to replace it. In turn, the rising air overland flows out to sea at some level above the surface to replace the air flowing inland. This creates a sea breeze.
At night, the opposite happens. The land cools more rapidly than the ocean. Air flows from land to sea at the surface, and the cycle is reversed. The circulation that results is a land breeze.
Similar circulations can develop around mountains, creating mountain and valley breezes. The winds that create the weather all arise in this way, as a result of unequal heating. However, it is not always easy to understand why winds behave the way they do.
4. Global Wind and Pressure Systems
Warm air near the equator, in the tropics, tends to rise and flow toward the poles (poleward). Along the way, the air cools and begins to sink. Because the equatorial regions are warm, they tend to form a belt of relatively low pressure.
The regions of sinking air tend to be associated with relatively high pressure, in what are called the “horse latitudes,” or subtropics. In a similar fashion, air over the poles tends to sink, being colder and heavier.
This sinking sends the air flowing into the subpolar regions, where it warms and rises, forming a belt with relatively low pressure at the surface. (Remember, warm air brings about low pressure, and cold air brings about high pressure because it weighs more.)
The middle latitudes lie between the belt of subpolar lows and the subtropic highs. Most of the United States can be found in the Northern Hemisphere’s middle latitudes. The Southern
Hemisphere also has middle latitudes.
The air tends to flow poleward at the surface of Earth, and toward the equator (equatorward) aloft, completing the transition between the polar and equatorial circulations.
People readily adapt to routine weather changes that occur with the passage of air masses. Sometimes, however, the weather can become so violent that people need to take special precautions.
Forecasters with the National Weather Service issue watches, warnings, and advisories to alert the public to potentially violent or hazardous weather. There is an important difference between a watch and a warning.
A watch means that hazardous weather is possible or that conditions are favorable for it to develop. A warning is a more urgent notice that hazardous conditions already exist or are heading your way.
Watches and warnings are issued for events such as winter storms, tornadoes, severe thunderstorms, high winds, and flash floods. The National Weather Service issues advisories when conditions are expected to cause serious inconveniences.
A common type of advisory alerts motorists to hazards such as slippery roads caused by
1. Winter Storms
During the winter, some cyclones (low-pressure areas) develop into unusually intense storms that bring heavy snow, strong winds, and cold temperatures.
When the wind is strong enough (above 35 miles per hour) and visibility is reduced to less than a quarter mile by snow or blowing snow, the event is termed a blizzard.
Even if a snowstorm does not quite qualify as a blizzard, a combination of snow, wind, and cold can be deadly for people caught unprepared.
Another winter event that can be quite severe is freezing rain (or drizzle), or an ice storm.
If ice coatings build up enough, tree branches can break, often crashing into power and telephone lines already burdened with ice. Roads become ice-covered and treacherous.
Even without snow or ice, extreme cold can be dangerous. Bitter cold can be even more hazardous when accompanied by high wind because of the two increase the rate of heat loss from exposed skin.
The result can be frostbite, which is damage to the skin from freezing, or hypothermia, a dangerous lowering of body temperature.
Thunderstorms are most common in the tropics and subtropics and during the warm season in the middle latitudes, but they can occur in winter and at polar latitudes. They form when warm, moist air creates updrafts that form large precipitation drops in clouds.
As this precipitation develops, positive and negative electrical charges separate and build up in different parts of the clouds and on the ground beneath the clouds.
When charges have built up enough, they can “jump the gap” between regions of opposite charge, discharging the areas. This discharge is what we see as lightning.
Some lightning flashes strike the ground, but most are from one part of a cloud to another. Lightning ground strikes, fairly common in the United States, can be deadly. In the United States about 90 people die each year from being struck by lightning.
Thunder is caused by the great heat generated during the brief time (less than a second) that a lightning discharge occurs. The heat causes the air to expand rapidly, as in an explosion.
You hear thunder after you see lightning because of the difference between the speed of sound and the speed of light. Sound travels at a speed of 1,100 feet per second, but light travels at a speed of about 186,000 miles per second.
Therefore, you will see lightning flash almost instantly, but the sound of thunder will take longer to reach you.
Floods are an unavoidable part of life along rivers. The torrential rains of thunderstorms or tropical cyclones can cause flooding. Some floods occur when winter or spring rains combine with melting snows to fill river basins with too much water too quickly.
Such events usually take several days to develop. Other floods arise suddenly as the result of heavy localized rainfall. These flash floods can become raging torrents very fast, sometimes in less than an hour, and can sweep away everything in their path.
Areas of rugged terrain are particularly vulnerable to flash floods. Picturesque river valleys in the mountains can be swept without warning by floods from rains falling some distance away.
When camping, stay clear of natural streambeds during the time of year when rainstorms are common.
If you camp on low ground, you might be caught unawares, especially when asleep at night. In case of a flood in rugged terrain, climb to high ground immediately, even if it means abandoning your gear.
If the floodwaters are already rising, do not get into motor vehicles and attempt to drive away from the flood danger. Never enter a flooded low spot on the road or trail if you do not know how deep the water is, especially if the water is rising.
Make a Wind Vane
- Aluminum baking dish, pie tin, or tray
- Sturdy wooden garden stake (at least 3 feet tall and 1 inch thick)
- 12-inch piece of wood about 1⁄2 inch thick
- Nail (2 to 3 inches long)
- Electric or hand drill
- Thick metal washer
- Small saw
|Step 1 – Select a location for your wind vane. Then use the mallet to carefully drive the garden stake into the ground.|
|Step 2 – Use the saw to cut a halfinch slot at each end of the 12-inch piece of wood.|
|Step 3 – With an adult helping you, place the piece of wood on top of the stake, as shown, and drill through the wood and the stake. Use a drill bit that is slightly larger in diameter than the nail you will be using.|
|Step 4 – Place the washer on top of the stake and insert the nail through the wood and into the stake. The wood should turn easily on the axis of the nail.|