====== 203 - G - WX Theory ======


===== Composition of Atmosphere =====

21% Oxygen, 78% Nitrogen, and trace gasses

**Troposphere** (surface to tropopause) -  The altitude of the tropopause varies with 
latitude and with the season of the year; therefore, it takes 
on an elliptical shape as opposed to round. Location of the 
tropopause is important because it is commonly associated with 
the location of the jet stream and possible clear air turbulence.

Stratosphere - from tropopause to 160,000ft. Generally stable. Very little weather.


===== Characteristics of Various Air Masses =====

{{:courses:203:tp-c-06-04.jpg?direct&400|}}

{{:courses:203:tp-c-06-08.jpg?direct&400|}}

{{:courses:203:tp-c-06-09.jpg?direct&400|}}

{{:courses:203:tp-c-06-07.jpg?direct&400|}}

===== Characteristics of Frontal Systems =====

Frontal passage will be indicated by the following discontinuities:

1.	A temperature change (the most easily recognizable discontinuity)

2.	A continuous decrease in pressure followed by an increase as the front passes

3.	A shift in the wind direction, speed, or both.

===== Formation & Dangers of Thunderstorms =====


===== Formation of Fog & Clouds =====

Stability determines which of two types of clouds will be formed: cumuliform or stratiform.


Cumuliform clouds are the billowy-type clouds having considerable vertical development, which enhances the growth rate of precipitation. They are formed in unstable conditions, and they produce showery precipitation made up of large water droplets.

Stratiform clouds are the flat, more evenly based clouds formed in stable conditions. They produce steady, continuous light rain and drizzle made up of much smaller raindrops.

The base of a cloud (AGL) that is formed by vertical currents (cumuliform clouds) can be roughly calculated by dividing the difference between the surface temperature and dew point by 4.4 and multiplying the remainder by 1,000. The convergence of the temperature and the dewpoint lapse rate is 4.4°F per 1,000 feet.

===== Weather Hazards - Cold Weather Operation =====


===== Inflight Icing: Formation, Avoidance, and Escape =====


===== Turbulence & Clear Air Turbulence =====


A common location of **clear air turbulence (CAT)** and strong wind shear exists with a curving jet stream. This curve is created by an upper or lower low-pressure trough. The wind speed, shown by isotachs (lines of constant wind speed), decreases outward from the jet core. The greatest rate of decrease of wind speed is on the polar side as compared to the equatorial side. Strong wind shear and CAT can be expected on the low-pressure side or polar side of a jet stream where the speed at the core is greater than 110 knots. Air travels in a “corkscrew” path around the jet core with upward motion on the equatorial side. When high-level moisture is present, cirriform (cirrus) clouds may be visible, identifying the jet stream along with its associated turbulence.

===== Wind Shear, LLWS, Microbursts =====


===== Hydroplaning =====