Weather Flashcards
standard day
standard air temperature is 15º C (59º F), and standard air pressure is 29.92” Hg, or inches of mercury (1013 millibars)
Absolute Altitude
the height above ground level (AGL)
True Altitude
the height above mean sea level (MSL)
Density Altitude
how we measure the density of air
Higher Density Altitude Occurs at
Higher elevations, Lower atmospheric pressures
Higher temperatures, Higher humidity
Lower Density Altitude Occurs at:
Lower elevations, Higher atmospheric pressures
Lower temperatures, Lower humidity
Convective Currents
Different surfaces radiate heat in varying amounts. Plowed ground, rocks, sand, and barren land give off a large amount of heat; water, trees, and other areas of vegetation tend to absorb and retain heat. land and rock push air up and water and vegetation push air down.
Sea Breeze
during the day land heats up faster than the water so you get breezes coming in from the ocean. air going up over land then going down over water in a circular pattern.
Land Breeze
At night the opposite happens. water the air goes up and the air goes down. breezes going out to the water. and moves up and then inland
Evaporation Fog
is the changing of liquid water to water vapor. After a rain, as the rainwater disappears from the ground, it evaporates into the atmosphere.
Sublimation Fog
is the changing of ice directly to water vapor, completely bypassing the liquid stage. If you’ve ever seen dry ice, you’ve seen sublimation at work.
Relative Humidity
Relative humidity is the actual amount of moisture in the air compared to the total amount of moisture the air could hold at that temperature. flying in an environment with relative humidity readings of 75 to 90 percent would decrease the performance of your aircraft.
Temperature and Dew Point
The dew point, given in degrees, is the temperature at which the air can hold no more moisture, so it’s at 100% humidity. As moist, unstable air rises, clouds often form at the altitude where temperature and dew point reach the same value.
Fog
Fog typically occurs when the temperature of air near the ground is cooled to the air’s dew point. Remember, the dew point is the temperature at which the air will have 100% humidity – it’s fully saturated with water vapor. At this point, the water vapor in the air condenses and becomes visible in the form of fog.
Radiation Fog
Radiation fog happens when the surrounding air reaches its dew point, and the ground cools rapidly due to terrestrial radiation. It’ll form on clear nights, with relatively little to no wind present. quickly burns off during the day.
Advection Fog
Advection fog is common in coastal areas 1) where sea breezes can blow moist air over cooler land masses, and 2) when air masses move inland from the coast.
Upslope Fog
moist, stable air is forced up sloping land features like a mountain range. Like advection fog, upslope fog requires wind for formation and continued existence.
Steam Fog
Steam fog is common over bodies of water during the coldest times of the year, and because of that, it’s also known as sea smoke.
Ice Fog
Ice fog occurs in cold weather when the temperature is way below freezing, and water vapor forms directly into ice crystals.
SIGMET Advisories
it’s a weather advisory that contains information about significant weather events like thunderstorms and severe turbulence.
AIRMET Advisories
reports weather of lower intensities that are potentially unsafe to pilots. Less severe weather: things like moderate turbulence and icing, sustained surface winds of 30 knots or more, or widespread restricted visibility.
Thunderstorm Phases
They form when there is: High Humidity, Unstable Conditions (change of temperature as air raises) Lifting Force An initial upward boost to start the process A thunderstorm makes its way through three distinct stages before dissipating
Unstable air
Cumuliform clouds, Turbulent air, Good visibility
Showery precipitation
Stable air
Stratiform clouds, Smooth air, Fair-to-poor visibility in haze and smoke, Continuous precipitation
