Weather and Micrometeorology

Question 1

By setting a ______________ it’s easier to make calculations To communicate the properties of an Atmosphere. 

Answer 1

Standard, for standard day

Question 2

Standard air temp = ____________________
Standard air pressure = ____________________
= at these conditions, density altitude equals pressure altitude

Answer 2

Standard air temp = 15 degrees C/59F
Standard air pressure = 29.92 in Hg
= at these conditions, density altitude equals pressure altitude

Question 3

the height above ground level, same as AGL

Answer 3

Absolute altitude

Question 4

Theheight above mean sea level. The vertical distance of the aircraft above sea level. MSL.

Answer 4

True altitude

It’s the “true” altitude your aircraft is flying at.

Question 5

how to measure air. The altitude where your aircraft “feels” like it’s flying. Propellers and wings need air to hold onto.

Answer 5

Density altitude

Density alt is higher - thinner air, reduced aircraft performance. Less air to grab into
Density alt is low - thicker air

Question 6

The altitude when the barometric pressure scale is set to 29.92 inHg (inches of mercury); ___________________ will be the same as density altitude during standard conditions

Answer 6

Pressure Altitude

Question 7

All three of these reduce aircraft climb and take off performance.

Answer 7

High temp, high relative humidity, and high density altitude

Question 8

Q1: If the outside air temperature (OAT) at a given altitude is warmer than standard, the density altitude is
A) lower than pressure altitude.
B) higher than pressure altitude.
C) equal to pressure altitude.

Answer 8

B) higher than pressure altitude.

If the outside air temperature is warmer than standard air temperature, then the density altitude will be higher than pressure altitude.

Question 9

Density altitude is defined by
A) humidity and braking friction forces.
B) headwind and landing weight.
C) pressure altitude and ambient temperature.

Answer 9

C) pressure altitude and ambient temperature.

Density altitude is the altitude relative to the standard atmosphere conditions at which the air density would be equal to the indicated air density at the place of observation. Those standard conditions include pressure altitude and ambient temperature.
Pressure altitude = density altitude on a “standard day”

Question 10

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. This uneven heating of the air creates small areas of local circulation.
They can cause that bumpy, turbulent air when flying at lower altitudes.

Answer 10

Convective Currents

Question 11

Shores of large bodies of water, land will heat up faster than water. Air over land becomes warmer and less dense. It rises and is replaced by cooler denser air flowing in from over the water.

Answer 11

Sea Breeze

Obstructions on the ground can affect the flow of the wind
Ground topography and large buildings can break up wind flow and create wind gusts.
Man made structures, or mountains, canyons, etc.
Depends on structures and speed of the wind
Scout out flight environment

Question 12

The stronger the wind, the greater the downward pressure

Answer 12

Katabatic wind

Question 13

Sudden drastic change in wind speed and or directions over a relatively small area
Can occur at all altitudes and directions
Characterized by directional wind changes of 180 degrees and speed of 50+ knots
Are expected in areas of low-level temperature inversion, frontal zones, and clear air turbulence.

Answer 13

Wind Shear

Question 14

___________________ is commonly associated with passing frontal systems, thunderstorms, and temperature inversions with strong upper level winds (greater than 25 knots).

Answer 14

Wind shear

Question 15

Occurs within <1 mile horizontally and within 1,000 ft vertically for fifteen minutes
Can cause severe down drafts of up to 6,000 ft per min
Can cause hazardous wind direction changes

Answer 15

Microbursts

Question 16

Always be alert of __________________, especially near thunderstorms

Answer 16

wind shear

Question 17

Every _____ increase in temperature doubles the amount of moisture the air can hold. Conversely, a decrease of ______ cuts the capacity in half.

Answer 17

20°F

20°F

Question 18

Water is present in air in three states: liquid, solid, and gas.
When water changes from one state to another, there are heat exchanges.
changes occur through the processes of
___________________ - changing of liquid water to water vapor. After rain, water evaporates into the atmosphere.
__________________ - changing of ice directly into water vapor. Ex: dry ice
Condensation
Deposition
Melting
Freezing

Answer 18

Evaporation

Sublimation

Question 19

amount of water vapor present in atmosphere at that time

Answer 19

Humidity

Question 20

The actual amount of moisture in the air compared to the total amount of moisture the air could hold at that temperature.

Answer 20

Relative Humidity

Ex: if the current relative humidity is 65 percent, the air is holding 65 percent of the total amount of moisture that it is capable of holding at that temperature and pressure

Question 21

___________________ is the temperature at which the air can hold no more moisture, so it’s at 100% humidity.

Answer 21

Dew Point

Clouds form at the altitude where temp and dew point reach the same value.
Typically, when the temperature and the dew point converge, you will have fog.

Question 22

A cloud that begins within 50 feet of the surface terrain.

Answer 22

Fog

Question 23

___________________ typically forms in low-lying areas like a mountain valley. It 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.

Answer 23

Radiation fog

Then, as the sun rises in the morning and the temperature increases, radiation fog lifts and eventually burns off. Also, an increase in wind speed can speed up the dissipation of radiation fog.

Question 24

____________________ 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. Think about the beautiful and foggy winter beaches of northern California, Oregon, or Washington.

Answer 24

Advection fog

Unlike radiation fog, wind is required for advection fog to occur. Winds of up to 15 knots allow the fog to form and intensify; above a speed of 15 knots, the fog usually lifts and forms low stratus clouds. This type of fog can persist for days.

Question 25

_____________ occurs, well, up a slope, when moist, stable air is forced up sloping land features like a mountain range. Like advection fog, this kind of fog requires wind for formation and continued existence. And unlike radiation fog, which can burn off with the sun, upslope fog can persist for days.

Answer 25

Upslope fog

Question 26

_________________ is common over bodies of water during the coldest times of the year, and because of that, it’s also known as sea smoke. This forms when cold, dry air moves over warm water. As the water evaporates, it rises and resembles smoke. Low-level turbulence can occur (and icing can become hazardous) with the presence of it.

Answer 26

Steam fog

Question 27

____________ occurs in cold weather when the temperature is way below freezing, and water vapor forms directly into ice crystals. It’s unlikely that you’d be operating an unmanned aircraft in this environment, but it’s still kind of interesting to think about. Conditions favorable for the formation of _____________ are low-lying areas where the temperature is really cold, usually –25°F or colder. This happens mostly in the arctic regions, but during winter seasons, ice fog can also form at middle latitudes.

Answer 27

Ice fog

Question 28

_________ forms when dew point is 0C, and when the temp of your propellers surface is below the dew point. It decreases lift capacity of aircraft, disrupts smooth flow

Answer 28

Frost

Question 29

An _________________________________ is an observation of current surface weather reported in a standard international format. They are primarily used by pilots as part of their pre-flight weather briefing, and also by meteorologists to help aid with forecasting. Normally issued hourly.

Answer 29

Aviation Routine Weather Report (METAR)