Meteorology

Alban Hoxhaj

Meteorology

The study of the entire atmosphere, including its weather.

The Atmosphere


 * Air is a mixture of many gases in earths 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 of the atmosphere (0-12 KM) in which all of Earth's weather occurs.


 * Gradually decreases in temperature with an increase in altitude
 * Contains all water vapor
 * The jet stream is located between 6-12 KM

Tropopause- The top of the troposphere where the decrease in temperature stops.

Stratosphere- Reaches from the tropopause to about 50 KM above Earth.
 * 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 layer

Ozone- Ultraviolet rays make oxygen 03. The ozone layer absorbs sun's UV rays 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.

WHAT IS THE 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.

HEATING OF THE ATMOSPHERE Energy from the sun results in changes in the weather. Heat moves through the atmosphere in three ways.


 * Conduction- An object receives heat when it comes into contact with a hotter object. (EX. A plan)
 * Radiation- Hot bodies in short waves (sun); cold bodies radiate energy in longer waves (Earth)
 * Convection- Most effective; the rising of hot air and sinking of cold air 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.

Greenhouse Effect

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 (1 degree C 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. pollution in the air, such as smoke and soot, also trapped close to the ground.

Smog trapped by temperature inversion
 * Warm air over cool traps smog in valley.

SPECIFIC HEAT

The amount of heat required to raise the temperature of something 1 Degree Celsius.


 * Water has a high specific heat compared to soil.*

Absorption- To take in energy and heat up.

Reflection- To bounce back energy.

Re-Radiation- To absorb short wave energy and give off long wave energy.

HEATING OF LAND AND WATER

Which Heats Up Faster???

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 of the water.
 * water cools more slowly than land because its heat is spread through a greater depth.

Temperature

Temperature is a 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)

Thermometers are the instruments used to measure temperature Thermographs are self-recording thermometers.
 * The alcohol expands when heated.

Isotherms are lines drawn on maps connecting places with the same temperature.

Evaporation the change from liquid water to water vapor.

water vapor is spread throughput the troposphere by convection currents and winds.

Humidity

The capacity of air for holding water vapor

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

Dew Point- temperature at which saturation occurs.

Clouds or fogs-form when the water vapor condenses into droplets.

air may be cooled below its dew point in many ways:


 * Contacting a colder surface
 * Radiating heat
 * mixing with colder air
 * expanding when it rises

Water Vapor needs to condense on something!! Condensation Nuclei- tiny particles, such as salt, sulfate, or nitrate particles, on which water vapor condenses.

When cooling occurs by contact with a colder surface, the water vapor condenses directly on that surface Above 0 degrees Celsius = Dew Below 0 degrees Celsius = Frost

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 the lightest air movement.

Radiation fogs- at night the ground loses heat rapidly. Light winds mix the cold bottom air with the air a short distance from the surface. When the whole layer of air is cooled below the dew point, A fog forms. (Common in humid valleys and near rivers and lakes)

Advection Fogs- Result when warm, moist air blows over cool surfaces (Example Coastal California)

Clouds Clouds from when air above the surface cools below the dew point.

Precipitation Is 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.

Raindrops form from tiny droplets and then grow by bumping into and combining with other droplets.

Sleet forms when raindrops fall through the freezing air and fall to the ground as pellets of ice.

Hailstones begin as a frozen raindrops and grows by collecting smaller ice particles or liquid cloud droplets.

Acid Rain forms when water condenses on sulfate and nitrate.

Barometer Is an instument used to measure air temperature.

Mercury Barometer

Millibar- Is a metric unit of pressure


 * 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 4 MB

High Pressure area (high)- The area of the largest pressure. The pressure in a high is greater than the surrounding air.

Low Pressure Area (low)- This area has a 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 sigh of precipitation.

Wind

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 pressure.

Global Wind Belts

Wind flows from high pressure at the poles to low pressure at the equator. - The wind is deflected by the Earth's rotation, called the coriolus effect.

Air Masses

An AIR MASS is a 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 he characteristics of the surface below.

Air Masses have two characteristics

Temperature depends on whether it comes from the tropics or polar regions.

The Humidity the air mass depends on whether it comes from land or sea.

Air masses are named from their source region

c- Continental (Dry) T-Tropical

m- Maritime (Moist) P- Polar A- Arctic

Boundaries between air masses are called fronts.

COLD FRONT

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.

Warm 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 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 fronts.

Occluded 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 in front of Nimbostratus and cummonimbus 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.