The study of Earth’s atmosphere

Weather vs. Climate

• Weather: Wind, temperature, precipitation, cloud cover and air pressure. Can be localized.

• Climate:long-term wx conditions over a large area. Classification based upon temp. and precip.

Atmosphere

Composition:• 78 % Nitrogen• 21 % Oxygen• .036% Carbon Dioxide*• Rest: water vapor; dust; ozone; argon

* Has the most impact, meteorologically speaking

Refer to Atmosphere Layers Hand Out

(A)Troposphere: up to ~12km. Where we live, where wx occurs.

Temp.↓as altitude↑.

Rate of change:

6.5 oC/km.

Thinnest layer

(B)Stratosphere:

~12km-50km

Contains the O3 (Ozone) Layer

Stratosphere cont’d

As elevation increases, temperature increases due to the absorption of radiation by the O3 Layer

UV rays + O3 O2 + O O3

Ozone Layer and Stratosphere cont’d

This rxn in the OThis rxn in the O33 Layer causes UV rays to get absorbed. If Layer causes UV rays to get absorbed. If

the rxn is disrupted (as in below), then holes in the Othe rxn is disrupted (as in below), then holes in the O33 layer layer

form. This allows more UV rays to reach the earth’s surface, form. This allows more UV rays to reach the earth’s surface, increasing skin cancers, etc.increasing skin cancers, etc.

UV rays + OUV rays + O33 O + OO + O2 2 + CFC’s + CFC’s

CFCO + OCFCO + O22

The result:The result:

Depleting the Ozone Layer so there is less Ozone to Depleting the Ozone Layer so there is less Ozone to react w/the UV rays, more UV rays get to Earth’s react w/the UV rays, more UV rays get to Earth’s surfacesurface

Layers and layers continued

• C.)Mesosphere: extends to 80 km. As altitude Temp.

Upper part called mesopause. Avg temp. -90oC

Just one more layer……….

• D.)Thermosphere: (80-400 km) contains the ionosphere in its lower portion.

Temp. increases as altitude increases due to the absorption of short-wave, high-energy solar radiation

Not quite done yet………….

• Auroras occur in the ionosphere.

Energetic electrically charged particles (mostly electrons) accelerate along the magnetic field that surrounds the Earth.They collide with gas atoms and solar radiation, causing the atoms to give off light.

Heat Transfer

• Conduction: transfer of heat through matter by molecular activity. Energy is transferred through collisions of one molecule to another

Heat Transfer

• Convection: the movement of matter due to the differences in density which is caused by differences in temp.

Heat Transfer

• Radiation:transfer of heat energy through space via electromagnetic waves. Electromagnetic waves can travel in the absence of matter (mechanical waves, like sound, can not).

Meet ROYGBIV(Not who….what)

ROYGBIV stands for the electromagnetic spectrum (light)

• R=Red• O=Orange• Y=YellowY=Yellow• G=GreenG=Green• B=Blue• I= Indigo• V=VioletV=Violet

When “white” light (from the sun) is separated (like a rainbow), it separates into these colors

Wavelengthlong short

Red Orange YellowYellow Green Blue Indigo Violet

V

I

S

I

B

L

E

Low Frequency – Energy High

infrared Ultra-Violet

Weather Principles and Vocab……

!

• Pressure= Force/area

• Pressure is measured in Pascals (Pa)

• 1 Pa = 1 Newton (force)/m2 (area)

• AIR PRESSURE is measured in milli bars (mb)

• 1 mb = 100 Pa

• Standard air pressure at sea level = 1013.2 mb (aka 29.9 inches of mercury)

What is needed for What is needed for precipitation?precipitation?

• Temp. of pocket of airTemp. of pocket of air >Temp. of >Temp. of environmentenvironment ( (Tp>Te) Tp>Te) This causes:This causes:

• Vertical transportVertical transport, which causes , which causes InstabilityInstability.. Need pocket of air to rise .. Need pocket of air to rise in order for it to cool, condense and in order for it to cool, condense and precipitateprecipitate

• Condensation/MoistureCondensation/Moisture. USUALLY . USUALLY 75% relative humidity75% relative humidity

THEREFORE…..

• IN GENERAL, precipitation will not occur when a high pressure system is in control.

• If the pressure is high, then the air SUBSIDES (sinks)….if it sinks will not get the instability, etc needed for precipitation.

So what do you get w/a high pressure system?

• USUALLY…fair weather, light winds• Tp<Te=subsidence/stable condition

What gives “bad” weather/precipitation?

• IN GENERAL, a LOW PRESSURE system

• Tp>Te, causing the air to rise, get the instability, condensation, etc

Low Pressure SystemLow Pressure System• Pressure is low so Pressure is low so

the surrounding the surrounding air pressure, in air pressure, in contrast, is high.contrast, is high.

• High pressure High pressure wants to go to wants to go to lowlow

• That replacing air That replacing air rises….causes the rises….causes the instability and instability and condensation condensation needed for needed for precip/poor wxprecip/poor wx

What causes Pressure Differences?

Temp. differences Density differences

Pressure differences

So……WHAT causes the temp differences???????

• Uneven heating/ cooling of the Earth’s surface.

• These cause AIR MASSES that then cause FRONTS/FRONTAL SYSTEMS

Maritime Polar(mP)

Continental Polar cP)

cP

mP

Maritime Tropical (mT)

Continental Tropical (cT)

mT

Air Masses

Page 603 in book

Air MassesNames and Properties

• Maritime Polar (mP)

• Continental Polar (cP)

• Continental Tropical(cT)

• Maritime Tropical (mT)

• Moist (from off the ocean), cold from the “poles”

• Dry from off the continent(land), cold from the “poles”

• Dry from off the land; warm from equator

• Moist from off the ocean, warm from the equator

FRONTS

• Warm front

• Cold front

COLD AIR

WARM AIR

Warm Front

• Incoming air is warmer (less dense)than air it is “replacing”

• Warm “over runs” air it is replacing

• Often get cirrus clouds as warm front approaches

• Can get precip. Usually not “violent”(ex: showers, drizzle)

Cold Front

• Incoming air is colder (more dense) than the air it is replacing

• “Replaced” air rises quickly

• Get precip that could be violent (thunderstorms, tornadoes)

Stationary Front

• Unsettled wx stalls. Usually “drizzley”

• Overcast

Occluded Front

• Cold front catches up to warm front

• Weather can be VERY violent (more than a cold front) thunderstorms, tornadoes

Definitions:

• Dewpoint:The temperature at which air becomes totally saturated w/water

• Humidity: amount of water vapor in the air

• Relative Humidity: air’s water vapor content to its water vapor capacity. Capacity can change w/temp. HOW/WHY?

(temp. capacity )

Formula for RHYeah!!! Math in Science

Relative Humidity (RH)=

Absolute humidity/Capacity X 100=%

Ex: at 10oC capacity is 11.0g/cm3

The actual humidity(absolute)might be 5.5g/cm3, so……

5.5/11 x 100=50% RH