LAYERS OF THE ATMOSPHERE
BACKGROUND
THE ENVELOPE OF GASES SURROUNDING THE EARTH IS THE ATMOSPHERE. FIVE DISTINCT LAYERS ARE CLASSIFIED BY
TEMPERATURE CHANGES. IN ADDITION, CHEMICAL COMPOSITION, MOVEMENT, AND DENSITY ARE USED TO CHARACTERIZE THE 5
LAYERS. EACH LAYER IS BOUNDED BY PAUSES WHERE CESSATION OCCURS.
I. TROPOSPHERE
THE TROPOSPHERE BEGINS AT THE EARTH'S SURFACE AND EXTENDS 15 Km ABOVE EARTH. THIS IS THE LAYER OF THE ATMOSPHERE
IN WHICH WE LIVE. THE TROPOSPHERE HOLDS ~ 80% OF THE ATMOSPHERE’S GASSES. ALMOST ALL WEATHER OCCURS IN THIS
REGION.
AS THE DENSITY OF THE GASES IN THE TROPOSPHERE DECREASE WITH HEIGHT, THE AIR BECOMES THINNER. THE TEMPERATURE IN
THE TROPOSPHERE DECREASES WITH HEIGHT. IN THE TROPOSPHERE, THE TEMPERATURE DROPS FROM (17°C) TO (-51°C).
THE TRANSITION BOUNDARY BETWEEN THE TROPOSPHERE AND THE LAYER ABOVE IS CALLED THE TROPOPAUSE. THE TROPOPAUSE
IS A COLD TRAP FOR RISING WATER VAPOR.
II. STRATOSPHERE
THE STRATOSPHERE EXTENDS FROM THE TOP OF THE TROPOSPHERE TO 50 Km ABOVE EARTH. THIS LAYER HOLDS ~19% OF THE
ATMOSPHERE'S GASES AND VERY LITTLE WATER VAPOR. THE TROPOSPHERE IS WHERE JETS FLY.
THE TEMPERATURE INCREASES WITH HEIGHT IN THE STRATOSPHERE. HEAT IS PRODUCED DURING THE FORMATION OF OZONE.
OZONE IS A PRODUCT OF THE REACTION BETWEEN THE SUN’S ENERGY AND OXYGEN RESULTING IN AN INCREASE IN THE
TEMPERATURE FROM (-51°C) TO (-15°C).
THE TRANSITION BOUNDARY WHICH SEPARATES THE STRATOSPHERE FROM THE LAYER ABOVE IS CALLED THE STRATOPAUSE.
III. MESOSPHERE
THE MESOSPHERE EXTENDS FROM THE TOP OF THE STRATOSPHERE TO 90 Km ABOVE EARTH. AS A RESULT OF THE RARIFIED AIR
(ESPECIALLY THIN), TEMPERATURE DECREASES FROM (-15°C) TO (-120°C).
HOWEVER, THE GASES IN THE MESOSPHERE ARE STILL THICK ENOUGH TO PROTECT THE EARTH FROM METEORS HURTLING INTO THE
ATMOSPHERE. THE METEORS BURN UP LEAVING FIERY TRAILS IN THE NIGHT SKY.
THE TRANSITION BOUNDARY WHICH SEPARATES THE MESOSPHERE FROM THE LAYER ABOVE IS CALLED THE MESOPAUSE.
IV. THERMOSPHERE
THE THERMOSPHERE EXTENDS UP TO 600 Km ABOVE EARTH. THIS IS THE LAYER WHERE THE SPACE SHUTTLE AND SPACE STATION
ORBITS.
THE GASES OF THE THERMOSPHERE BECOME INCREASINGLY THINNER. THE TEMPERATURE INCREASES WITH HEIGHT AND CAN
REACH AS HIGH AS 2,000°C NEAR THE TOP BECAUSE OF THE ABSORPTION OF THE SUN’S ENERGY. DESPITE THE HIGH TEMPERATURE,
THIS LAYER OF THE ATMOSPHERE WOULD FEEL VERY COLD BECAUSE OF THE EXTREMELY THIN AIR. THE TOTAL AMOUNT OF ENERGY
FROM THE VERY FEW MOLECULES IS NOT ENOUGH TO BURN.
A. THE IONOSPHERE
A SUBLAYER OF THE TERMOSPHERE IS THE IONOSPHERE. THE IONOSPHERE IS MADE OF ELECTRICALLY CHARGED GAS
PARTICLES (IONIZED) BY THE ABSORPTION OF RADIATION. THE IONOSPHERE EXTENDS FROM 60-300 Km ABOVE THE EARTH.
THE IONOSPHERE IS DIVIDED INTO 3 LAYERS: THE F-LAYER, E-LAYER, AND D-LAYER. DURING THE DAYTIME THE F-LAYER
SPLITS INTO 2 LAYERS THEN RECOMBINES AT NIGHT.
THE E-LAYER WAS DISCOVERED FIRST. IN 1901, GUGLIELMO MARCONI TRANSMITTED A SIGNAL BETWEEN EUROPE AND
NORTH AMERICA AND SHOWED THAT IT HAD TO BOUNCE OFF AN ELECTRICALLY CONDUCTING LAYER ABOUT 100 Km
ALTITUDE. IN 1927, SIR EDWARD APPLETON NAMED THAT CONDUCTING LAYER THE (E)LECTRICAL-LAYER. ADDITIONAL
CONDUCTING LAYERS DISCOVERED LATER WERE SIMPLY CALLED THE D-LAYER AND F-LAYER.
SINCE THE IONOSPHERE'S EXISTENCE IS DUE TO RADIATION FROM THE SUN STRIKING THE ATMOSPHERE, IT CHANGES IN
DENSITY FROM DAYTIME TO NIGHTTIME. ALL 3 LAYERS ARE MORE DENSE DURING THE DAYTIME. AT NIGHT, ALL LAYERS
DECREASE IN DENSITY WITH THE D-LAYER UNDERGOING THE GREATEST CHANGE. AT NIGHT THE D-LAYER ESSENTIALLY
DISAPPEARS.
AS SEEN AROUND THE 1900'S, THE IONOSPHERE HAS THE IMPORTANT QUALITY OF BOUNCING RADIO SIGNALS TRANSMITTED
FROM THE EARTH. THE IONOSPHERE’S EXISTENCE IS WHY PLACES ALL OVER THE WORLD CAN BE REACHED VIA RADIO.
AS THE RADIO SIGNAL IS TRANSMITTED, SOME OF THE SIGNAL WILL ESCAPE THE EARTH THROUGH THE IONOSPHERE. THE
GROUND WAVE IS THE DIRECT SIGNAL WE HEAR. GROUND WAVES WEAKEN QUICKLY AND IS HEARD AS A FADING SIGNAL.
THE REMAINING WAVES ARE CALLED SKYWAVES. SKYWAVE WAVES BOUNCE OFF THE IONOSPHERE AND CAN BOUNCE FOR
MANY 1000'S OF Km DEPENDING UPON THE ATMOSPHERIC CONDITIONS.
B. MAGNETOSPHERE
ANOTHER SUBLAYER OF THE IS THE MAGNETOSPHERE. THE EARTH’S MAGNETIC FIELD CREATES THE MAGNETOSPHERE.
THE SHAPE OF THE MAGNETOSPHERE IS A RESULT OF BEING BLASTED BY THE SUN’S SOLAR WIND. THE MAGNETOSPHERE
PREVENTS THE SUN’S PARTICLES FROM HITTING THE EARTH AND PROTECTING LIFE.
V. EXOSPHERE
THE EXOSPHERE IS THE OUTERMOST LAYER OF THE ATMOSPHERE. IT EXTENDS FROM THE TOP OF THE THERMOSPHERE TO 10,000 Km
ABOVE EARTH. IN THIS LAYER, SATELLITES ORBIT AND ATOMS AND MOLECULES ESCAPE INTO SPACE.
