Structure of the Atmosphere Meteorology is the study of the atmosphere- including weather. Weather is the condition of the atmosphere. It can change from time to time and place to place. Climate is the type of weather an area has over a long period of time.
Layers of the atmosphere: separated by the variation of temperature patterns.
In these two models, you can see how most of the atmosphere is concentrated near the surface due to the pull of gravity.
We live in the troposphere.
Gets colder as you go up.
All weather occurs here
All water vapor in the atmosphere is here
Temperatures get warmer as you go up.
Home of the Ozone layer.
Mesosphere & Thermosphere
Upper layers of the atmosphere.
The air is very thin here.
Atmospheric Variables- things that can be measured and change from moment to moment.
(Click the link to go down to that section)
Energy always go from high to low.
There is no such thing as “cold”.
Cold is just an absence of heat.
Ice doesn’t add cold to something.
It sucks the heat into it.
Heat flows from hot to cold
(source to sink).
Heat Transfers: Radiation -the transfer of heat in the form of light.
The Greenhouse Effect
IR (infrared) light that is re-radiated from the ground is stopped from reaching space by extra “greenhouse gasses” in the air.
CO2 from burning fossil fuels.
Clearing of trees.
Fart gas from cows (methane).
Conduction- Heat transfers from one object to another through touch.
Caused by density differences:
Hot air expands and gets less dense.
Cold air contracts and gets more dense.
The weight of the air above you. The more air that is above you the more pressure you will feel.
Sinking air pushes down more- cold air is usually high pressure.
Rising air pushes down less- hot air is usually low pressure.
When converting from millibars to station model code, use only the last three digits and throw out the decimal point.
When converting from station model code to millibars:
Write your code twice
Write a 10 in front of one
and a 9 in front of the other
Insert the decimal point between the last two numbers
Look on the reference Tables so see which one is possible
(Short Method: if the code is 500 or higher put a 9 in front, therwise put a 10)
Wind travels from high pressure to low.
The gradient between isobars determines the wind speed.
Big Difference in Pressure
(Steep Gradient) = fast wind
Small Difference in Pressure
(Gentle Gradient) = gentle winds
The Coriolis Effect
The Coriolis Effect deflects things to their right in the Northern Hemisphere.
Caused by the rotation of the Earth.
High Pressure flows outward and clockwise (cw) (in the N. Hemisphere)
Low Pressure flows inward and counterclockwise (ccw)(in the N. Hemisphere)
The Right Hand Rule
Your thumb (of your right hand) represents the rising or sinking of low or high pressure.
Your fingers wrap around your palm the way that the wind spirals around the pressure system.
Low Pressure sucks so low has inward flow while highs are outward.
Winds are named for the direction that they come from
On a map direction is shown with a line showing where it came from.
Water Content & Humidity
The amount of water in the air is called humidity. The actual amount of water vapor in the air is the absolute humidity.
The ability of air to hold water changes depending on the temperature.
Relative humidity tells "how full" the air is with water.
It is expressed in %.
100% is full and can't hold any more.
It is saturated.
Water gets into the air by evaporation or sublimation.
Evaporation is changing from a liquid to a gas.
Sublimation is changing from a solid (snow or ice) to a gas. (sublime means to skip a step)
To get the water out of the air it either condenses or sublimes.
Two images of snow.now is not frozen rain. It is an ice crystal that forms directly from
water vapor by the process of sublimation.
Photos by Phil Medina, Stony Brook, NY 2005
(Right-click to view the full sized pictures)
These two images show frost forming from water vapor coming out of a warm sewer drain.
Photos by Phil Medina, Yaphank, NY 2004
condense-changing from gas to liquid.- dew
Condensation nucleus – a small piece of dust, smoke, or salt that acts as a surface for codensation.
precipitation- water that condenses in the atmosphere falls to the surface.
Precipitation cleans out the atmosphere by pulling down the condensation nuclei (pollution)
Measuring Relative Humidity
The “Dry Bulb”
Don’t let it fool you. It is just a thermometer.
It measures the air temperature.
The “Wet Bulb”
Has a little wet booty tied to the bottom.
Gets cool when water evaporates.
On A Dry Day...
A lot of moisture will evaporate.
The wet bulb will be a lot cooler than the dry bulb.
On A Humid Day...
A little bit of moisture will evaporate.
The wet bulb will not be much cooler than the dry bulb.
Cyclone- any inward and counterclockwise air circulation around a low pressure center.
Types of Cyclones:
a small, compact storm with strong winds.
Extremely localized low pressure center.
99.9% in Northern Hemisphere spin ccw.
Come from strong thunderstorms.
Can be predicted a few minutes early with Doppler radar.
Fujita Scale is based on the width and wind speed of the funnel.