Flashcards in Atomosphere Deck (43):
What are the 5 layers of the Atmosphere?
How High dose the Troposphere extend?
Between 25,000ft-35,000ft at the polls and 50,000ft-65,000ft at the equator.
How is the atmosphere heated?
The atmosphere is not directly heated by the sun's radiation. The sun's radiation which is primarily short wave radiation is first directly absorbed by the surface of the earth. This heats the earth which in turn re-radiates the heat at a much longer wavelength which is absorbed by the atmosphere.
What are the 4 factors to unequal heating on the earth?
1. Seasonal variations which expose one hemisphere to more sunlight than another depending on the time of the year
2. Latitude variations
3. Diurnal (day/night) variations
4. Different surfaces on the earth absorbing and reflecting heat differently. For example, a dark rocky surface will absorb more sunlight directly than a surface covered in vegetation
is a standard atmosphere what is the environmental lapse rate?
1.98°C per 1,000 ft.
What is the standard lapse rate for calculations?
2°C per 1,000 ft
What is the dry adiabatic lapse rate?
3°C per 1,000 ft.
What is the wet or saturated adiabatic lapse rate?
1.1 to 2.8°C per 1,000 ft
What is the wet adiabatic lapse rate for calculations?
1.5°C per 1,000 feet
In a stable atmosphere what dose the lapse rate look like?
A stable atmosphere occurs when the environmental lapse rate is shallow or even negative. In this condition, it will be less than either the dry or wet adiabatic lapse rates. When the lapse rate is negative, the condition is known as an inversion. The atmosphere is stable because any air which rises will cool adiabatically and in doing so will cool more rapidly than the surrounding air which cools at the environmental lapse rate. Because rising air cools faster than its surroundings it will sink back after rising. This is a stable situation.
In an unstable atmosphere what dose the lapse rate look like?
An unstable atmosphere arises when the environmental lapse rate is steeper than both the dry adiabatic lapse rate and the wet adiabatic lapse rate. Under these conditions, any air which is forced to rise and cools adiabatically will end up being warmer than the surrounding atmosphere. As a consequence, it will then be lighter than the surrounding air which will then cause it to rise further and in doing so increase the temperature difference between itself and the surrounding air and so on.
in a conditionally or potentially unstable atmosphere what dose the lapse rate look like?
A conditionally (or potentially) unstable atmosphere arises when the environmental lapse rate is somewhere between the dry and adiabatic lapse rates. Under these conditions, air which is forced to rise a short amount, will cool at the dry adiabatic lapse rate and end up cooler than the surrounding air. This will cause it to sink back. In other words the situation will be stable. If however the air is forced to rise a considerable amount causing it to cool adiabatically to the dew point and beyond, where it then cools at the slower wet adiabatic lapse rate, it may end up warmer, and as a result lighter, than the surrounding air. This is then the familiar unstable situation.
What is the International Standard Atmosphere?
- Temperature at sea level is 15°C
- Environmental lapse rate is 2°C/1,000'
- Pressure at sea level is 29.92" Hg
- Atmospheric pressure drops by approximately 1" of mercury for every 1,000 feet that you climb in the lower atmosphere
- The height of the tropopause is 36,090 feet
What is HUMIDITY?
The higher the temperature of the air, the greater the quantity of water which it can hold
What is RELATIVE HUMIDITY?
RELATIVE HUMIDITY is the amount of water in the air relative to the maximum which it can hold at that temperature and pressure
What is DEWPOINT?
DEWPOINT: If air is cooled at constant pressure the temperature at which condensation begins is known as the dewpoint. The closer the dewpoint temperature is to the outside air temperature, the more likely it is that clouds will form.
What is Convection?
Convection - is the vertical movement of air
What is Advection?
Advection - is the horizontal movement of air
What is Sublimation?
Sublimation - when a solid changes phase directly to a gas without going through the liquid phase
What is Deposition?
Deposition - when a gas changes directly to a solid without going through the liquid phase
What is Isobars?
Isobars - these are lines of constant pressure
What is Isotachs?
Isotachs - these are lines of constant wind velocity
What are Contour lines?
Contour lines - these are lines joining points where the altitude at which a specified pressure occurs is constant
what 4 forces makes air move from high pressure areas to low pressure areas?
• The fundamental forces which arise from the
• Coriolis force which causes moving air to be deflected
to the right in the northern hemisphere and to the left
in the southern hemisphere
• Friction with surface of the earth. Friction forces are
greatest below approximately 3,000' AGL
• Acceleration or centrifugal forces when the air is
following a curved path
What was dose the CORIOLIS FORCES move in the northern hemisphere?
Deflected to the right
What way dose air move around low pressure areas?
Air circulates counter-clockwise around a low
pressure area in the northern hemisphere
What is an elongated low pressure area?
what can be expected in a low pressure area?
Surface lows are usually associated with
rising (or ascending) air and the arrival of
cloudy weather and precipitation
What way dose air move around a high pressure area?
Air circulates clockwise around a high pressure
system in the northern hemisphere
What is an elongated area of high pressure?
what can be expected in a high pressure area?
High pressure systems are normally associated
with descending (or subsiding) air, clear weather
and a gentle wind
What dose is mean when isobars are close together?
Generally speaking, the closer the isobars are together, the stronger the wind. At the surface, the wind will cross the isobars from high to low while higher up, it will blow essentially parallel to the isobars. The wind thus veers with increasing altitude
what is BUYS BALLOTS LAW?
In the northern hemisphere, if you stand with your back to the wind then the low pressure will be on your left-hand side
What happens to wind as it increases in altitude?
it veers and increases in speed
How dose the wind blow in relation to isobars below 3000 ft AGL?
Below 3,000' winds blow increasingly across the isobars
How dose the wind blow in relation to isobars above 3000 ft AGL?
Above 3,000' winds blow generally parallel to the isobars
What is a Gust?
Gust - A rapid increase in wind speed for a short period of time before returning to the average speed
what is a Squall?
Squall - A rapid increase in wind speed lasting for a minute or longer before returning to the average speed
what is Veering?
Veering - when the direction from which the wind blows increases, for example when the wind changes from a southerly to a south-westerly direction
What is Backing?
Backing - when the direction from which the wind blows decreases, for example when the wind changes from an easterly to a north easterly direction
what is a downburst?
A downburst is a very strong, localized downdraft from a thunderstorm.
What is a microburst?
A downburst which is less than 2 nautical miles in horizontal extent and persists for less than 5 minutes is known as a microburst.