Properties of the Atmosphere Heat vs Temperature Temperature measure of how rapidly or slowly molecules move around Higher the temperature faster particle movement Heat is the transfer of energy that occurs because of a difference in temperature between substances ID: 772044
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Properties of the Atmosphere
Heat vs. Temperature Temperature – measure of how rapidly or slowly molecules move around. Higher the temperature = faster particle movement Heat - is the transfer of energy that occurs because of a difference in temperature between substances .
Heat vs. Temperature Heat is the transfer of energy that fuels atmospheric processes, while temperature is used to measure and interpret that energy. Temperature is measured in: Degrees Fahrenheit Degrees CelsiusKelvins
Temperature Units In the U.S. Fahrenheit ( oF) is the most common unit to measure temperature.Celsius ( oC ) is the unit used in textbook where the difference from freezing to boiling is 100o. Kelvin (K) is the SI unit for temperature. Absolute zero, 0 Kelvin, is the coldest anything can be. It is equal to -273oC and is the temperature which molecular motion stops!!
Vertical Temperature Changes Dew Point: the temperature to which air must be cooled at constant pressure to reach saturation. Often called the “ condensation temperature ” Condensation: occurs when matter changes state from a gas to a liquid The height that condensation occurs is called the lifted condensation level (LCL) and often corresponds to the base of the clouds.
Dew Point If dew point is close to the air temperature then the relative humidity is high
Air Pressure The Earth’s atmosphere exerts a downward force due to the weight of the atmosphere. Air pressure – pressure exerted on a surface by the weight of the atmosphere Units – N/m 2 or mb (1 mb = 100 N/m 2 ) The higher you go in the atmosphere the less air pressure.
Density of Air Density of air decreases with increasing altitude because the molecules are further apart . Near sea level density is 1.2 kg/m 3
Pressure-Temperature-Density Relationship In the atmosphere, the temperature, pressure, and density of air are related.
Air Pressure and Temperature Warmer air = higher pressureParticles move faster and exert a greater force
Air Pressure and Density At the same temperature, air with higher density exerts more pressure than air with lower density. More gas particles means more collisions.
Temperature and Density At the same pressure, warmer air is less dense than cooler air. Heat causes particles to move faster and spread apart.
Temperature Inversion An increase in temperature with height in an atmospheric layer Called a temperature inversion because the temperature/altitude relationship is inverted or turned upside down.
Cause and Effects of Temperature Inversion Land is not radiating thermal energy to lower layers of atmosphere Example – cold, clear winter night when air is calm Leads to fog, low-level clouds, and trapping pollutants close to the Earth’s surface
Wind Wind – movement of air; caused by cold, dense air rushing towards warm, less dense air
Wind and Pressure Difference Air moves from regions of higher density to areas of lower density Air pressure increases as density increases, so air moves from areas of high pressure to low pressure as well
Wind Speed and Altitude Wind moves slower near the Earth’s surface due to friction Wind speed is measured in: Miles per hour (mph) Kilometers per hour (km/h) At sea – in knots (1 knot = 1.85 km/h)
Humidity Humidity – amount of water vapor in the atmosphere at a given location Two ways to express – relative humidity and dew point
Relative Humidity Water molecules are constantly evaporating into the atmosphere and condensing to form clouds and precipitation. If rate of evaporation > rate of condensation then the amount of water vapor increases Relative humidity – The ratio of water vapor in the air to how much water vapor that volume of air is capable of holdingRelative humidity is expressed as a percentage (100% when fully saturated)