ATMO Lab Midterm

Temperature

Measure of the average kinetic energy of the molecules

• measured in Fahrenheit, Celsius, or Kelvin

Pressure

Force per unit area

• measured in units of millibars (mb)

Wind

air in motion relative to earth’s surface

• measured in mph kph (kilometers per hour), or knots

Humidity

associated with the amount of water vapor in the air

• measured in %

Wind Barbs

meteorological symbol used to convey wind speed and direction

Remember:

• shows were wind is COMING from (not where its going)

• ½ line= 5 knots, full line= 10 knots, triangle= 50 knots

Isopleth

A line of equal value (commonly for elevation, temperature, pressure, etc)

Rules:

• lines cannot cross or branch off

• lines must be drawn on a fixed interval (ex. every four mb)

• lines must be smooth

• lines should be drawn that all values on one side of the line are less than the value drawn and all values on the other side are greater than the value drawn.

Isobar

lines of equal pressure

• drawn using sea level pressure

• hint- unit of pressure is millibar and so isobars are lines of equal pressure!

Isotherm

lines of equal temperature

• hint- thermal relates to heat/temperature so isotherms are lines of equal temperature!

Steps for drawing Isopleths

1. identify areas of equal values (start with low/high values)

2. connect values nearby at FIXED intervals

3. go to the edge of the map and label on both sides WITH units

4. if the line can reasonably form a circle DO IT

Radiosondes

device attached to a ballon that collects temperature, pressure, and humidity, and wind

• results are plotted on a graph called a sounding

Troposphere

the lowest layer of the atmosphere where majority of the weather happens (and where we live)

• temperature usually decreases with height

• small inversions can occur in early morning hours

Tropopause

marks the altitude where the temperature stops decreasing with height

• height is usually around 11km, but is not constant around earth

Jet stream

narrow band of fast-moving air found near the tropopause

Troposphere Depth (aka height of the tropopause)

IS NOT CONSTANT

• height of the tropopause is greater at the equator and lower as you go towards the poles

• higher temp= greater depth, lower temp= smaller depth

Steps for unit conversions

1. identify unit type

2. multiply conversion factor

3. cancel unwanted unit

4. solve

Vertical Pressure Changes

Pressure decreases with height in ALL layers of the atmosphere

• pressure is the weight of the air above you → as height increases there is less air above you so pressure decreases

Surface pressure

the ACTUAL pressure observed at a location due to the weight of the air above it

Sea level pressure

the surface pressure corrected for altitude

• needed because if not then pressure would always be low in the mountains and high at sea level

Conversion from surface pressure to sea level pressure

pressure changes 10 mb for every 100 m (10mb/100m)

• 
  

Vertical changes in wind

wind speed generally increases with height (less friction)

• highest winds are usually found near the tropopause (jet stream)

Lapse rate

decrease of temperature with height

Inversion

increase of temperature with height

Latitude notation

northern hemisphere is considered positive, southern hemisphere is considered negative

• if the question asks for a latitude use N or S

• if you are calculating use + or -

Solar Radiation

energy from the sun

• the amount reaching earth’s surface changes over the year

Seasons

Caused by the 23.5-degree tilt in earth’s axis

Solar angle

Measures the suns position in the sky from the perspective of someone on Earth

• influences the amount of radiation received at any latitude on earth

• when comparing solar angles at different locations it is understood that the solar angles are computed for solar noon

Summer solstice

occurs on June 21st

• solar declination occurs at 23.5 degrees North

Winter Solstice

occurs on December 21st

• solar declination occurs at 23.5 degrees South

Fall/Spring Equinox

Fall= occurs September 21st

Spring= occurs March 21st

• solar declination occurs at 0 degrees (because the sun is directly over the equator)

Calculating the solar angle

Solar Angle= 90 degrees - (the latitude of a location) +(solar declination)

Solar declination

the latitude at which the Sun appears directly overhead at solar noon

• its value will vary between +23.5 and -23.5 (never above or below)

Insolation

amount of incoming solar energy during the daylight hours at a location

• largely dependent on the solar angle!

• higher the solar angle the more insolation

Greenhouse gas effect

greenhouse gasses absorb outgoing long-wave radiation and re-radiate the infrared energy back to earth

• problem= if there are to much GHGs in the atmosphere then our planet will get too warm

Greenhouse gases (three of them)

water vapor, carbon dioxide, and methane

• water vapor= most abundant

radiative equilibrium temperature

when the absorption of incoming shortwave solar radiation equals the emission of longwave radiation

Water Vapor effect on nighttime temperature

more water vapor= temperatures will remain higher vs less water vapor= temperatures will drop lower

• a cloudy night will be warmer than a clear sky night

Pressure Gradient

a change or difference in pressure between two locations

Pressure Gradient Force (PGF)

A force that causes air to travel from HIGH to LOW pressure

• drawn perpendicular to isobars

• strength is affected by the spacing of isobars (closer together= stronger PGF and stronger winds)

Coriolis Force (COR)

a force due to the rotation of earth which causes air to move to the right in the NH and the left in the SH relative to its original motion

• always points to the right of the direction of motion (in NH)

• faster winds= stronger force

• higher latitudes= stronger force

• COR changes the direction of ALREADY moving air but not the speed

Frictional force

force resisting the relative motion of the air

• only present at the surface

• points the opposite direction of the wind

Convergence

air flowing inward towards a point; associated with rising motion

Divergence

air flowing outward from a point; associated with sinking motion

Direction of wind above the surface

• PGF and COR are balanced (equal length) and arrows point in opposite directions

• wind direction is PARALLEL to the isobars

• friction is ignored

• if isobars are closer together → faster wind speeds

High and low pressure centers ABOVE the surface

Direction of wind at the surface

• PGF stays the same

• Friction IS included (opposite direction of wind)

• PGF and COR are not in balance (COR is weaker than PGF)

• Winds travel ACROSS the isobars towards low pressure

High pressure centers at the surface

• wind is in a clockwise direction

• divergence (air flowing away from high pressure center in different directions) at the surface leads to sinking air from above

Low pressure centers at the surface

• winds flow in a counterclockwise direction

• convergence (air flowing inward towards low pressure from different directions) leads to rising motion

• **** associated with cloud formation