GEOG220 exam 2
What is the equation for relative humidity?
(specific humidity/saturation specific humidity) x 100%
What are some characteristics of The Coriolis Force?
-Causes the wind to deflect to the right of the direction motion in the northern hemisphere and to the left of the direction motion in the southern hemisphere -The Coriolis force is at maximum at the poles and goes to zero at the equator -The Coriolis force is proportional to the wind speed. The greater the wind speed the greater the deflection caused by the Coriolis Force
Rain
-Cold aloft (in the air) and a warm surface -Snow-->Rain
What circumstances are needed for advection fog?
-Cold surface and warm moist air moves over the surface
What is Conditional Instability?
-DALR>ELR>MALR -Conditional instability occurs when the ELR is between the MALR and DALR -We are saying that the environment is cooling slower than a dry air parcel, but faster than a moist air parcel -Stratiform clouds and/or clouds of vertical development severe weather may form
Freezing Rain
-Destructive--> mostly North East -Snow--> Snow melts--> Rain--> Glaze -Temperature above freezing in the middle of the atmosphere -Do not have time to refreeze
What is DALR?
-Dry Adiabatic Lapse Rate -As long as the air in a rising or sinking parcel remains UNSATURATED, the rate of adiabatic cooling or warming remains constant -The cooling or warming rate is called DALR
What happens during Radiation fog? and when does it occur?
-Earth's surface cools rapidly -Has to do with earth and LWR -Apparent in the early morning, fall through spring -Also in clear, calm night
What is ELR?
-Environmental Lapse Rate -The temperature change with height of surrounding atmosphere is the ELR -This is simply the temperature change we would feel as we climbed a mountain--IT IS NOT A PARCEL LAPSE RATE -The ELR is usually different than the DALR and MALR--it varies from one time to another in the atmosphere -As you go higher the temperature gets colder
What occurs during evaporation?
-Evaporation from water to cold air -Warm water and cold air above -Examples: seeing your breath, steam
How do you calculate the Convective Cloud Base?
-Find the difference between the T and Td (both in Celsius) and multiplying the difference by 125 m, we can find the approximate height of the Convective Cloud Base -H(meters)= 125m (T-Td) (in Celsius) -H(feet)= 222ft (T-Td) (in fahrenheit)
Sleet
-Hits and bounces off surfaces so it's less destructive -Small ice pellets= fine transportation -Middle layers of atmosphere where temperature is above freezing, but closer to the earth's surface there is a thicker area of below freezing temperatures
Composition and Formation of Middle Clouds
-In middle latitude these clouds usually have bases between 6500 ft and 23,000 ft and are composed of water droplets and/or ice crystals
Composition and Formation of Low Clouds
-In middle latitudes low clouds usually have their bases below 6500 ft and are composed mainly of water droplets. However, during winter they may contain ice crystals and snow
What is the average DALR?
-It has a value of approximately 10 degrees C/1000 m
What is dew point temperature?
-It is the temperature of the air when it reaches its saturation point (100% relative humidity) -Knowing the dew point temperature tells you the specific humidity of the atmosphere (using the SSH curve)
What occurs during Low-Level Convergent with Low Pressure Cloud Development?
-Low pressure is higher at the surface -At places where there is high pressure the air is leaving the surface...Flow going upward -High pressure piling down at the surface -When the air converges it forms clouds
What is MALR?
-Moist Adiabatic Lapse Rate -The rate at which a saturated air parcel will cool -It is NOT a constant. It varies greatly depending upon the amount of water vapor present in an air parcel (and hence in the temperature of the parcel). This is because a warm saturated parcel will be holding more water vapor than a cold, saturated parcel -Values range from 2 degrees C to 9.5 degrees C/1000 m
What occurs during upslope fog?
-Moist air rises up and over a mountain barrier and therefore cools down as it rises
Where is friction most important?
-Near the earth's surface
What occurs during Convection Cloud Development?
-Refers to the vertical movement of the atmosphere due to density differences between an air parcel and the surrounding atmospheric environment
What are condensation nuclei?
-Small particles that range in size from less than a tenth of a micrometer to greater than a micrometer. However, those most favorable for the growth of cloud droplets have sizes of about 0.1 micrometer or greater -They also have very small masses, less than one-trillionth of a grain--they stay in the air for a very long time
What kind of clouds are considered clouds of vertical development? and what are they composed of?
-Stratiform and Cumuliform -They have bases as low as 1000 ft and tops as high as 65,000 ft (12 miles). They are composed of both water droplets and ice crystals...billions and billions of each
What forces are important to Atmospheric Motion?
-The Pressure Gradient Force -Coriolis Force -Frictional Force
What is Absolute Stability?
-The atmosphere is always absolutely stable when the ELR is less than the MALR -ELR<MALR<DALR -We are saying that the environment is cooling slower than a saturated air parcel
What is Absolute Instability?
-The atmosphere is in a condition of absolute instability when the ELR is greater than the DALR -ELR>DALR>MALR -Clouds of vertical development, potentially heavy precipitation, severe weather -We are saying that the environment is cooling faster than a dry air parcel -Usually will occur only in thin layers of the atmosphere
What is the average ELR?
-The average ELR is 6.5 degrees C/1000 m
What is the Average MALR?
-The average MALR is 6 degrees C/1000 m
What does condensation or deposition occur in the atmosphere?
-There are approximately 100,000 particles in the atmosphere in a volume the size of an index finger -These particles are so small that they can't be seen with the human eye, but they are there. Many of them can serve as condensation nuclei
How are the isobars positioned in a large pressure gradient?
-They are crowded together
How are the isobars positioned in a weak pressure gradient?
-They are far apart
What occurs during Orographic Ascent Cloud Development?
-Think mountain homework -There are different way clouds form -When there's some sort of topography (mountain) that forces the air upward and it cools, reaches dew point, then forms a cloud
What are HYDROPHOBIC nuclei?
-WATER REPELLING condensation nuclei -Resist condensation even when the relative humidity is 100%
What are HYGROSCOPIC nuclei?
-WATER SEEKING condensation nuclei -Condensation can begin on these when the RH is less than 100%
When do Divergence winds occur?
-We now know that air near the earth's surface crosses the isobars away from high pressure. Thus, the atmosphere diverges near the center of the high - ←H→ down from the sun
When do Convergence winds occur?
-We now know that air near the earth's surface crosses the isobars toward low pressure. Thus, the atmosphere converges near the center of the low - →L← L moves up to the clouds
Explain the Concept of Stability
-When a parcel of air is warmer than the environmental temperature then it will continue to rise -When the air is unstable you get thunderstorms -When the parcel is warmer than the surrounding it's unstable -It's stable when the parcel is colder than its surroundings and it will sink
When is the air in hydrostatic balance?
-When the force of gravity and the VPGF are in exact balance, the air is said to be in hydrostatic equilibrium -The majority of the atmosphere is in hydrostatic balance at all times
What is a vertical pressure gradient?
-When there is high pressure at the surface and low pressure at upper levels -GRAVITY balances the VPGF
What occurs during Frontal Uplift Cloud Development?
-When you have a front coming along -Cold air is more dense than warm air which forces the warm air up above it
Composition and Formation of High Clouds
-in middle latitudes high clouds generally form about 20,000 ft and are composed mainly of ice crystals
Sub Tropical Front
A belt of strong upper-level winds lying above regions of subtropical high pressure. Unlike the polar front jet stream, it travels in lower latitudes and at slightly higher elevations, owing to the increase in height of the tropopause at lower latitudes
What is Newton's Second Law of Motion?
Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object).
What is a Coriolis Force?
An apparent force that arises because the earth rotates
In what kind of clouds does Ice-Crystal Process occur?
Cold Clouds
What is Newton's First Law of Motion?
Every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force
What is adiabatic expansion?
Forcing air to rise--it cools down due to adiabatic expansion
In what direction does wind always blow?
From Hight to Low Pressure
What does knowing the air temperature tell you?
It tells you the "holding capacity" of the air at that time, the saturation specific humidity (using the SSH curve)
What is the equation for mixing ratio?
Mass of Water Vapor in the Air (g) / Mass of Dry Air (kg)
What is the equation for specific humidity?
Mass of Water Vapor in the Air (g) / Total Mass of Air (kg)
What is the equation for absolute humidity?
Mass of Water Vapor in the Air (g) / Volume of Air (m^3)
What is an adiabatic process?
One in which no heat transfer takes place between a parcel and the environment. This makes adiabatic very special... you get a chance in temperature without a transfer of heat energy.
What is the equation for pressure gradient?
Pressure Gradient= Change in Pressure/Change in Distance
What is the equation for relative humidity?
Specific Humidity / Saturation Specific Humidity
Snow
The atmosphere is below freezing all the way up to the earth's surface
Polar Front
The polar front jet is usually located somewhere between 35 degrees N and 65 degrees N, depending on the season
What is pressure gradient force?
The strength of the PGF is directly proportional to the PF. Therefore, a large PG gives high wind speeds and a small PG gives low wind speeds
Vapor Pressure- How is it distributed according to Dalton's Law
Total Pressure= 1000 mb According to Dalton's Law: 78% Nitrogen- 780 mb 21% Oxygen- 210 mb 1% Water Vapor- 10 mb High Vapor Pressure, Higher WV Content Lower Vapor Pressure, Lower WV Content
In what kind of clouds does Collision and Coalescence occur?
Warm Clouds
**A very important rule in meteorology is that warm air has the capacity to hold more water vapor than cold air**
Warm air has a higher saturation vapor pressure
Geostrophic Winds
When Pressure Gradient Force, Coriolis Force, and Friction all come into balance
How/At what temp. does frost form (hoar frost)?
at 26 degrees F; When the air temperature cools to the dew point temperature (which is below freezing) (some times people call frost point temp. instead of dew point), water vapor in the air can turn directly to ice without going through the liquid stage. This process is called deposition. This is hoar frost.
How/At what temp. does dew form (bead frost)?
at 34 degrees F; When dew point forms and the temperature subsequently falls below the freezing point, the dew freezes into beads of ice that we call frost. This is one way that frost from (bead frost)
What is moisture needed for in our atmosphere?
clouds, precipitation, an important energy source for all types of atmospheric storms