Meteorology

= = =Meteorology= The study of the entire atmosphere, including its weather. = The Atmosphere: =
 * Air is a mixture of many gases in earth's lower atmosphere
 * Nitrogen and Oxygen together form about 99% of dry air by volume
 * The remaining 1% is mainly argon and carbon dioxide

= Structure of the Atmosphere: = Troposphere- is the lowest layer of the atmosphere (0-12 km) in which all of earth's weather occurs. Tropopause- the top of the troposphere where the decrease in temperature stops Stratosphere- reaches from the tropopause to about 50 km above earth Ozone- ultraviolet rays make oxygen O3. The ozone layer absorbs sun's UV rays and protects us from burning. Stratopause- the top of the stratosphere where the temperature stops rising Mesosphere- temperature drops again Thermosphere- temperature rises again about 500 km from earth
 * Gradually decreases in temperature with an increase in altitude
 * Contains most water vapor
 * The jet stream is located between 6-12 km
 * Steady winds and few weather changes (Planes fly here!)
 * Steady increase in temperature with the increase of altitude, which is caused by absorption from the ozone

__**What is weather like outside?**__ Weather- is the state of the atmosphere at a given time and place. To try to predict weather you need to observe the clouds, wind, temperature, humidity, air pressure and precipitation over a period of time.

Energy from the sun results in changes in the weather. Heat moves thorough the atmosphere in three ways
 * __Heating of the Atmosphere__**
 * 1) Conduction- an object receives heat when it comes into contact with a hotter object. Ex. pan on a hot stove
 * 2) Radiation- hot bodies radiate energy in short waves, ultra violet, (sun); cold bodies radiate energy in longer waves (Earth)
 * 3) Convection- most effective; the rising of hot air and sinking of cold are results in a steady flow. Convection is very important in moving heat through the atmosphere

__**Insolation**__ Solar energy that reaches the earth; we receive one two billionth of the sun's rays.

Short ultra violet waves from the sun are able to reach the earth's surface, then longer infrared waves re-radiated by the earth's surface are trapped by greenhouse gasses. (CFC's and CO2) Normal Lapse Rate- the rate of cooling with altitude (1º celsius for every 160 meters) Temperature inversion- when the air is especially still cooler air because of its greater density, settles close to the ground, and the warmer air forms a blanket above it in a temperature inversion. Pollutants in the air, such as smoke and soot are also trapped close to the ground ** The amount of heat required to raise the temperature of something 1 degree Celsius.
 * __Greenhouse Effect__
 * __Specific Heat__**
 * Water has a very high specific heat compared to soil**

__**Re-Radiation-**__ to absorb short wave energy and give off long wave energy.
 * __Absorption-__** to take in energy and heat up
 * __Reflection-__** to bounce back energy

Good Absorbers- dark-colored; rough surface; dry soil Poor Absorbers- light colored; smooth surface; wet soil

Heating of Land and Water ** Thermometers are the instruments used to measure temperature Thermographs are self- recording thermometers Isotherms are lines drawn on maps connecting places with the same temperature
 * water warms much more slowly than land**
 * In water, the sun's rays go to a depth of many meters. On land, the sun's rays heat only the top few centimeters of soil.
 * Water can spread heat easily because it is a fluid
 * Some solar energy is used in the process of evaporation. Thus, less solar energy is available to raise the temperature.
 * Water cools more slowly than land because its heat is spread through a greater depth
 * __Temperature__**
 * Temperature is measure of the energy of molecules. The more energy the molecules in air have, the hotter it feels.
 * Temperature is measured in degrees (celsius, fahrenheit, kelvin)
 * the alcohol expands when heated

The capacity of air for holding water vapor **
 * __Evaporation__**
 * The change from liquid water to water vapor
 * Water vapor spreads throughout the troposphere by convection currents and winds.
 * __Humidity__
 * As air temperature increases so does the amount of water vapor it can hold
 * Specific Humidity- the amount of water vapor actually present in the air.
 * Relative Humidity- compares the actual amount of water vapor in the air (Specific Humidity) with the maximum amount of water vapor the air can hold at that temperature
 * Psychrometer- is the instrument used to determine relative humidity

__**Condensation**__ The change from water vapor to a liquid. This occurs when the temperature drops low enough that the capacity for water vapor in the air drops below the specific humidity. Examples: Dew- water vapor which condenses on surfaces, such as grass, in the form of a liquid. Clouds or Fogs- for when the water vapor condenses into droplets Air may be cooled below its dew point in many ways: Water Vapor needs to condense on something. Condensation Nuclei- tiny particles, such as salt, sulfate, or nitrate particles, on which water vapor condenses. >0ºC=Dew <0ºC=Frost
 * Dew Point- temperature at which saturation occurs
 * Contacting a colder surface
 * Radiating heat
 * Mixing with colder air
 * Expanding when it rises
 * When cooling occurs by contact with a colder surface, the water vapor condenses directly on that surface

__**Fogs**__ Surface layers of air a few hundred meters thick which are cooled below the dew point. As water vapor condenses tiny droplets stay suspended in the air by lightest air movement __Radiation Fogs__- at night the ground loses heat rapidly. Light winds mix the cold bottom air with the air short distance from the surface. When the whole layer of air is cooled below the dew point, a fog forms. (Common in humid valleys near river and lakes) __Advection Fogs__- result when warm, moist air blows over cool surfaces (Ex. coastal california) __Clouds__- clouds form when air above the surface cools below the dew point __Precipitation__- the falling of any form of water from the air to the earth's surface/
 * Occurs when cloud droplets grow into drops heavy enough to fall to earth
 * 1) Raindrops- form from tiny droplets and then grow by bumping into and combining with other droplets.
 * 2) Sleet- forms when raindrops fall through the freezing air and fall to the ground as pellets of ice
 * 3) Hailstones- begin as a frozen raindrop and grows by collecting smaller ice particles or liquid cloud droplets
 * 4) Acid Rain- forms when water condenses on sulfate and nitrate.

The weight of the atmosphere per unit area Differences in air pressure cause the earths wind and weather changes
 * __Air Pressure__**
 * Pressure decreases with Altitude*

Millibar (MB)-** a metric unit of pressure
 * Barometer-** an instrument used to measure air pressure
 * Aneroid Barometer-** measures pressure with a thin metal can
 * Mercury Barometer
 * Standard sea-level pressure is 1013.2 MB**
 * Isobar-** lines that join points having the same air pressure at a given time
 * Each line is worth 4MB
 * High Pressure Area (High)-** the area of the largest pressure. The pressure in a high is greater then the surrounding air,
 * Low Pressure Area (Low)-** this area has lower pressure than the surrounding area
 * Pressure Gradient-** the rate of change for air pressure between two points
 * Rising Barometer-** greater pressure usually means cooler, drier weather (sinking air)
 * Falling Barometer-** less pressure because the air is warm and moist and rises. This can be a sign of precipitation

The horizontal movement of air from areas of high air pressure to areas of low air pressure. The closer the spacing between isobars the stronger the winds Winds blow across isobars, from high to low air pressure.
 * __Wind__**

Wind flows from high pressure at the poles to low pressure at the equator An air mass is huge section of the lower troposphere that has the same kind of weather (temperature and moisture properties) throughout The best source regions for air masses are large flat areas where air can be stagnant long enough to take on the characteristics of the surface below
 * __Global Wind Belts__**
 * MOIST AIR IS LESS DENSE, LIKE WATOR VAPOR*
 * The wind is deflected by the earth's rotation, called Coriolus effect
 * __Air Masses__**

Air Masses have two characteristics: c- continental m- maritime T- tropical P- polar A- arctic Boundaries between air masses are called fronts 1) Cold air is advancing and replacing warm air 2) Cold fronts are steeper and move faster than warm fronts 3) The air rises upward rapidly forming cumulonimbus 4) Heavy precipitation and thunderstorms which start and end quickly are associated with cold fronts 5) Precipitation covers 75-100 miles and occurs both before and after a cold front passes at the surface 6) Cold fronts travel at speeds between 25-30 MPH 7) As soon as the front passes the temperature will decrease and the wind speed may rise
 * Temperature depends on whether it comes from the tropics or polar regions
 * The humidity of the air mass depends on whether it comes from land or sea
 * Ai masses are named from their source region
 * __Cold Front__**

1) Warm air is advancing and replacing cold air 2) Warm fronts move slower; warm air moves up a gentle frontal surface 3) Warm air may travel 1000 KM before rising 2 or 3 KM 4) First cirrus and cirrostratus clouds form and then there are altostratus clouds. Finally, steady rain falls from nimbostratus clouds. 5) Precipitation can occur for 225-275 miles ahead of where the front touches the ground 6) Warm fronts travel at speeds between 20-25 MPH 7) Warmer temperatures follow the passing warm front 1) A cold front is advancing and combining with a warm front 2) Occluded fronts move the slowest of all (20 MPH) 3) These fronts are associated with cirrus and stratus clouds front of nimbostratus and cumulonimbus clouds 4) Precipitation occurs for about 400 miles, most of which is in front of the frontal boundary 5) Cool air is in front, as warm air is forced up by the cold air which follows the passing occluded front
 * __Warm Front__**
 * __Occluded Front__**