Atmosphere Notes
The Atmosphere The Earth's atmosphere is a thin layer of gases that surrounds the Earth. It composed of 78% nitrogen 21% oxygen 0.9% argon 0.03% carbon dioxide trace amounts of other gases..
Atmosphere The layer of gases that surrounds the Earth Consists of 4 layers; troposphere, stratosphere, mesosphere, and thermosphere
Layers of the Atmosphere
Troposphere The troposphere is the lowest region in the Earth's (or any planet's) atmosphere. On the Earth, it goes from ground (or water) level up to about 11 miles (17 kilometers) high. The weather and clouds occur in the troposphere. In the troposphere, the temperature generally decreases as altitude increases.
Stratosphere The stratosphere is characterized by a slight temperature increase with altitude and the absence of clouds. The stratosphere extends between 11 and 31 miles (17 to 50 kilometers) above the earth's surface. The earth's ozone layer is located in the stratosphere. Ozone, a form of oxygen, is crucial to our survival; this layer absorbs a lot of ultraviolet solar energy. Only the highest clouds (cirrus, cirrostratus, and cirrocumulus) are in the lower stratosphere.
Good Ozone = O3 ;found in stratosphere Bad Ozone = smog in troposphere
Mesosphere The mesosphere is characterized by temperatures that quickly decrease as height increases. The mesosphere extends from between 31 and 50 miles (50 to 80 kilometers) above the earth's surface.
Thermosphere Thermosphere: The thermosphere is a thermal classification of the atmosphere. In the thermosphere, temperature increases with altitude. The thermosphere includes the exosphere and part of the ionosphere.
Exosphere •The exosphere is the outermost layer of the Earth's atmosphere. The exosphere goes from about 400 miles (640 km) high to about 800 miles (1,280 km). The lower boundary of the exosphere is called the critical level of escape. This is where atmospheric pressure is very low (the gas atoms are very widely spaced) and the temperature is very low.
Ionosphere The ionosphere starts at about 43-50 miles (70-80 km) high and continues for hundreds of miles (about 400 miles = 640 km). It contains many ions and free electrons (plasma). The ions are created when sunlight hits atoms and tears off some electrons. Auroras occur in the ionosphere.
What happens to temperature as altitude increases? In the Troposphere the temperature decreases
What happens to air pressure as altitude increases? The air pressure decreases because the air gets less dense (thinner)
How do heating differences of earthly materials affect air movement? Because earthly materials heat up at different rates, some heat up quicker causing the air above them to warm up and rise. Cooler air moves in to replace the warmer air.
Thought Experiments: Conduction Conduction is the direct transfer of energy through direct contact between atoms. Thought Experiments: Conduction Which is colder coming out of the freezer: a metal spoon or a wooden spoon? Why? Which feels colder? Is snow a good conductor or a good insulator? Is the purpose of a good insulator to keep the cold out or to keep the heat in?
Thought Experiment: Being without a coat in winter Radiation The method by which the sun's energy reaches the earth. All objects radiate: hotter ones radiate more. Two objects at the same temperature, and the same size do not radiate the same amount of heat. Thought Experiment: Being without a coat in winter If you stood without a coat on a winter day with no wind, would you feel cold? (Hint: Think about radiation, convection, conduction.) What if the wind were blowing? Discuss the concept of wind chill.
Convection The motion or movement of large groups of molecules based on their relative densities or temperatures. (Warm air rises-less dense- and cool air moves in to replace it.) Thought Experiment: Convection on the Beach You are camped on the beach. You are offered a bet to predict the wind direction during the day and night. Would you bet? What do you predict? (Hint: Convective currents move air away from hot areas. Which heats up more, land or water? Which cools first?
How does the atmosphere affect the rate at which heated surfaces cool? The atmosphere holds heat in so the heated surfaces cool slower.
What are “greenhouse gases?” Carbon Dioxide Water Vapor Methane
What is the Greenhouse Effect? The greenhouse effect is an increase in the temperature of a planet as heat energy from sunlight is trapped by the gaseous atmosphere. Excess carbon dioxide and water vapor increase this global warming effect.
How does the Greenhouse Effect work? Solar Energy (sunlight) is short-wavelength radiation which easily penetrates the Earth's atmosphere and warms the Earth; only about one quarter of incoming sunlight is reflected by the atmosphere. The warmed Earth emits long-wavelength radiation (infrared waves or heat energy) back into space; these longer waves are mostly reflected back to Earth by the atmosphere.
METHANE CONCENTRATIONS (PPM)
HUMAN POPULATION (BILLIONS)
Charting the Evolution of the Earth’s Atmosphere Millions of Years Ago Percent
How did the evolution of living things affect the evolution of the atmosphere? As organisms started photosynthesis, oxygen was released into the atmosphere and CO2 was used up.
DEW POINT AND RELATIVE HUMIDITY LAB
DEW POINT The Dew point is temperature at which condensation or dew occurs. It is reached when the air is cooled to below its moisture capacity and becomes saturated.
DEW POINT AND RELATIVE HUMIDITY LAB If the air is saturated, no evaporation takes place from the wet-bulb, and the two thermometrs will show the same temperature. (relative humidity = 100%) If the air is holding a large amount of water vapor, little water evaporates from the wet-bulb thermometer and the difference between the two thermometers is small. (small depression) If the air is dry, water evaporates quickly from the wet-bulb thermometer and there is a large decrease in the wet-bulb temperature (large wet-bulb depression).
RELATIVE HUMIDITY Relative humidity is the amount of water vapor in the air compared with the amount of vapor needed to make the air saturated at the air's current temperature.
Why humidity can be less than 100% when it's raining Humidity is a measure of the amount of water vapor in the air, not the total amount of vapor and liquid. For clouds to form, and rain to start, the air does have to reach 100% relative humidity, but only where the clouds are forming or where the rain is coming from. This normally happens when the air rises and cools. Often, rain will be falling from clouds where the humidity is 100% into air with a lower humidity. Some water from the rain evaporates into the air it's falling through, increasing the humidity, but usually not enough to bring the humidity up to 100%.
The dewpoint temperature gives a much better estimate of the amount of moisture actually present in the air, which is very important in determining precipitation amounts and even how comfortable you feel Let's compare very cold, 10-degrees Fahrenheit air with a relative humidity of 100% with 72-degree tropical air, also with 100% relative humidity. In both cases, the relative humidity is 100%, but the cold air's dewpoint is 10 degrees and the warm air's dewpoint is 72 degrees. The higher the dewpoint temperature, the more moisture in the air.
Calculating DEW POINT STEP 1: Dry Bulb – Wet Bulb = Wet-Bulb Depression 68 – 66 = 2 STEP 2: Depression x Dry-Bulb Factor = X (2) X (1.79) = 3.58 STEP 3: Dry-Bulb x (X) = Dew Point (68) – 3.58 = 64.4 F
CALCULATING RELATIVE HUMIDITY (Absolute Humidity / Capacity) x 100 (5.5 g/m3 / 11 g/m3) x 100 = 50%
(Depression Factor) - DB Dry-bulb temperature Wet-bulb temperature Wet-bulb depression Dry-bulb factor Dew point temperature Relative humidity DB WB DB – WB See Chart 1 (Depression Factor) - DB See Chart 2 68F 65F 74F 52F 42F 32F 3 1.79 62.63 85%