Weather

Weather is the condition of the atmosphere at a particular time and place.

Earth's Atmosphere

Earth’s atmosphere is a thin layer of gases that surround the planet Earth’s atmosphere is a thin layer of gases that surround the planet. The atmosphere is made up of 78% nitrogen, 21% oxygen, 1% other gases, as well as water vapor, dust particles, smoke, salt, and other chemicals. We call the combination of gases in our atmosphere air.

The atmosphere is divided into layers that are determined by temperature change.

Troposphere The layer we live in is the Troposphere. The troposphere starts at Earth’s surface and extends upward for 9 to 20 km. This layer is where water vapor and clouds are and where weather happens. Even though this is the thinnest layer, it contains most of the air, 80% of the total mass of the atmosphere. The air temperature drops as you go higher up in the troposphere. At its upper limits, the temperature of the troposphere is about -60°C. The average temperature is 25°C. Mt. Everest, the highest landform on earth, rises 8.85 km. in the troposphere.

Jet Stream The jet stream, a fast-flowing river of wind, travels generally west to east between the lower stratosphere and the upper troposphere. Many military and commercial jet aircraft fly in this zone when going west to east.

Stratosphere The stratosphere is located 10 to 50 km above earth’s surface. This layer contains a layer of ozone (O3), a form of oxygen, that absorbs high-energy ultraviolet (UV) radiation from the sun. The temperature stays cold in the stratosphere except in the ozone layer where it rises to 0°C.

Mesosphere The mesosphere is located 50 to 80 km above Earth’s surface. The temperature plunges here reaching its coldest temperature of around -90°C. This is the layer in which meteors burn up while entering Earth’s atmosphere, producing what we call shooting stars.

Thermosphere The thermosphere is located 80 to 300 km above Earth’s surface. This is an extremely thin layer of air. It is the first layer of the atmosphere to get heated by the sun. When the sun is extra active with sunspots or flares, the temperature in the thermosphere can surge up to 1500°C. The thermosphere is divided into two layers, the ionosphere and the exosphere.

Ionosphere The ionosphere is located in the lower part of the thermosphere from about 60 to 300 km above Earth’s surface. The ionosphere has a large number of electrically charged ions which create the Aurora Borealis in the north and the Aurora Australis in the south.

Exosphere The exosphere is the uppermost layer of Earth’s atmosphere, 500 to 10,000 km above Earth’s surface. Atmospheric gases, atoms, and molecules can escape into space from this layer. Satellites that are used to monitor the weather, send telephone and T.V. signals, and that carry telescopes orbit the earth in the exosphere.

What Affects the Atmosphere?

Air has the properties of mass, density, and pressure.

Altitude is the distance above sea level Altitude is the distance above sea level. Air pressure decreases as altitude increases. As air pressure decreases, so does density. The composition of the atmosphere remains the same until the exosphere.

Barometer A barometer is an instrument used to measure changes in atmospheric air pressure.

The troposphere is heated by the sun’s energy in 3 ways: radiation, conduction, and convection.

Radiation Radiation is the direct transfer of energy through empty space by electromagnetic waves.

Convection Convection is the transfer of heat by movement of currents within a fluid.

Conduction Conduction is the direct transfer of heat from one substance to another substance that it is touching.

The Earth’s surface absorbs solar energy becoming warmer than the air The Earth’s surface absorbs solar energy becoming warmer than the air. Air near the Earth’s surface is warmed by radiation and conduction of the heat from the surface. Then convection causes the air near the ground that is heated to have more energy. The air molecules move faster, bumping into other air molecules, and moving farther apart. This air becomes less dense. The warmer air moves upward and the cooler air moves downward.

A wind is the horizontal movement of air from an area of high pressure to an area of lower pressure.

Coriolis Effect The way Earth’s rotation makes winds in the Northern Hemisphere curve to the right and winds in the Southern Hemisphere curve to the left.

The water cycle also effects weather The water cycle also effects weather. The water cycle is the movement of water through the Earth’s atmosphere. Water on Earth’s surface absorbs energy from the sun. When water has enough energy, it changes from a liquid to a gas called water vapor. This process is called evaporation. The water vapor rises up through the troposphere where it cools and condenses forming clouds.

Precipitation is any form of water that falls from clouds and reaches Earth’s surface. Common types of precipitation include rain, sleet, freezing rain, hail, and snow.