Geography Test #3
maritime airmasses tend to be unstable; continental airmasses tend to be stable
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the vertical extent (e.g. cA vs. cP)?
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typical dewpoint (remember what dewpoint is, and why it changes)
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typical temperature
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What are the two precipitation processes and how do they differ?
1) Collision and coalescence process - Is the process of producing precipitation by liquid particles colliding and then joining. 2) Ice-Crystal process - Process that produces precipitation. The process involves tiny ice crystals in a supercooled cloud growing larger at the expense of the surrounding liquid. They differ because the collision has "warmer" temperature which keeps the drops from turning into crystals.
How do clouds develop?
1. Surface heating and free convection 2. Uplift along topography 3. Widespread ascent due to convergence of surface air 4. Uplift along weather fronts.
What are the lifting methods that can cause air to rise?
1. orographic lifting is caused when mountains cause the air to lift. The rising generates clouds that produce large amounts of precipitation. 2. Precipitation is caused by frontal wedging in many regions. It results where cooler, denser air acts as a barrier over which warmer, less dense air rises. 3. Convergence causes lifting when air masses flow together. 4. Unequal heating of Earth's surface may cause sections of air to warm, become less dense, and rise. When these air sections rise above the condensation level, clouds form, which may produce rain.
Dryline Front
A boundary that seperates warm, dry air from warm, moist air. It usually represents a zone of instability along which thunderstorms form.
Occluded Front
A complex frontal system that ideally forms when a cold front overtakes a warm front. When the air behind the front is colder than the air ahead of i, the front is called a cold occlusion. When the air behind the front is milder than the air ahead of it, it is called a warm occlusion.
Stationary Front
A front that is nearly stationary with winds blowing almost parallel and from opposite directions on each side of the front.
Warm Front
A front that moves in such a way that warm air replaces cold air.
What is Doppler radar?
A radar that determines the velocity of falling precipitation either toward or away from the radar unit by taking into account the doppler shift.
What is a jetstreak and how does its zones of convergence and divergence affect mid-latitude cyclones?
A region of high wind speed that moves through the axis of a jet stream. Areas of convergence and divergence form at specific regions around them.
What is a pineapple express?
A relatively common weather pattern that brings southwest winds to the Pacific Northwest or California along with warm, moist air is often called the Pineapple Express.
Cold Front
A transition zone where a cold air mass advances and replaces a warm air mass.
What are air masses?
An extremely large body of air whose properties of temperature and humidity are fairly similar in any horizontal direction at any altitude
How can stability be modified?
By the cooling of air and the warming of air. Cooling: Winds bringin in colder air, or clouds emitting infrared radiation to space. Warming: Solar heating of the surface, influx of warm air brought in by the wind, air moving over a warm surface.
How are fronts symbolized on maps?
Cold Front: Blue line with Blue Triangles Warm Front: Red line with red semi-circles Occluded Front: Purple line with purple triangles and semi circles. DryLine: Brown line with brown semi circles.
What are the five different air masses and how do they generally differ from one another?
Continental Arctic - Extremely cold, dry stable Move across NA Continental Polar - Cold, dry, stable Continental Tropical - Hot, dry, stable aloft. Maritime Polar - Cool, moist, unstable Maritime Tropical - Warm, moist, usually unstable.
Where are blizzards most commonly found?
Dakotas, Minnesota, Southcentral Canada.
What are the conditions that bring about a drought for the west coast, central and eastern United States?
Depending on jet streams weather on the West Coast can be very hot. The central area can also become hot because the storms are usually at full strength when they get to the central. The east can be very wet during the Winter due to lake effect and the storms from the Atlantic.
DewLR
Dewpoint
What is drought?
Drought is a period of abnormally dry weather sufficiently long enough to cause serious effects on agriculture and other activities in the affected area.
What is an Alberta Clipper?
Fast moving winter weather system originating in the lee of the candaian rockies that typically brings snow, high winds, and cold temps across the Northern US.
How do they form (wave cyclone)?
Forms on a front, and in maturing, produces an incresingly sharp, wavelike deformation of the front.
What are the key precipitation seasons that may indicate that a drought could be occurring for the western, central, and eastern United States?
If there is not a lot of rain during the winter it may be very likely that the US would have problems with drought.
How does an Alberta Clipper differ from a blizzard that forms along the Rockies?
It has less snow but low in density, easy to move around.
How are they represented on maps?
It is represented by red line with red semi-circles and a blue line with blue triangles.
How can the atmosphere be made less stable (more unstable)?
Lifting a layer of air makes it more unstable.
What is lake effect snow and how does it develop and where does it tend to occur?
Localized snow-storms that form on the downwind side of a lake. Such storms are common in late fall and early winter near the Great Lakes as cold, dry air picks up mositure and warmth from the unfrozen bodies of water.
How can the atmosphere be made more stable?
Lowering an entire layer of air makes it more stable.
What is the lifting condensation level?
Marks the base of the cloud that has formed as air is lifted.
What are four major drought types, and what do they mean?
Meteorlogical drought - When dry weather patterns dominate an area. Hydrological drought - When low water supply becomes evident, especailly in streams, reservoirs, and groundwater levels. Agricultural drought - When crops become affected. Socioeconomic drought - Relates the supply and demand of various commodities to drought.
What are the PDSI, the Crop Moisture Index, and the Additional Precipitation Needed to Bring PDI to -0.5 maps and what do they indicate?
PDSI takes into account the average temperature and precipitation values to define drought severity. The map shows that white is normal, and in California most of the state in a moderate to extreme drought. Meaning we need lots of rain to help decrease the drought.
What weather fronts and airmasses are associated with mid-latitude cyclones?
Polar Fronts, Frontal Wave, Wavy Cyclone, Open wave
What are the different precipitation types (hail, rain, sleet, freezing rain)
Rain - The drop must have a diameter equal to, or greater than 0.5mm. Anything smaller is drizzle. Sleet - Is when a snowflake starts to melt when falling, but then hits a cold patch and then is frozen making it sleet. Freezing Rain - Rain that falls in liquid form and then freezes upon striking a cold object or ground. Can produce a coat of ice on the ground. Hail - Are large pieces of ice ranging in size.
What weather events are often associated with mid-latitude cyclones during the winter/spring and spring/summer?
Rain and winds
Understand the concept of stability - unstable, stable, and neutral (air neither rises nor does it sink)
Stable - Air make take on air, but is more than likely to return back to its normal location. Unstable - Air make take on air but it will not return back to its normal location. Neutral - The air stays in a neutral spot.
Where do mid-latitude cyclones usually form and where do they not?
Tend to form: Eastern Slope of the Rockies, Great Basin Area, Gulf of Mexico, Atlantic Coast east of the Carolinas.
DALR
The Lapse rate of a dry mass of air which expands and cools as it rises.
What are stable, unstable and conditionally unstable atmospheres?
The atmosphere is always absolutely stable when the environmental lapse rate is less than the moist adiabatic rate. Absolutely instability results when the environmental lapse rate is greater than the dry adiabatic rate. Conditional instability means that if unsaturated air could be lifted to a level where it becomes saturated, instability would result.
How is rainfall intensity determined using Doppler radar.
The intensity is determined by the brightness of the color. Green indicates moderate, yellow indicates heavier, and red indicates the heaviest.
What are mid-latitude cyclones?
The mid-latitude cyclone is a synoptic scale low pressure system that has cyclonic (counter-clockwise in northern hemisphere) flow that is found in the middle latitudes it is not a tropical storm or a hurricane.
What are ice storms, and what damage do they do?
The substantial accumulation of freezing rain or freezing drizzle. They cause damage to telephone lines, roads, freeways.
How are air masses modified?
They are modified when air masses travel over a large body of water.
How do upper-air winds affect mid-latitude cyclones?
They create jet streams
What are the influences of mountains upon precipitation?
They promote convection and forcing air to rise along their windward slopes.
What are some of the problems that blizzards might cause for people who have to deal with them?
Trouble getting to work, hyperthermia
MALR
When heat is added during condensation offsets some of the cooling due to expansion, the air no longer cools at the dry adiabatic rate.
What phenomena constitute a blizzard?
When the storms has sustained winds greater or equal to 35mph, and must last for a long period of time
In terms of temperature and windchill?
Wind chills down to -50 def F
Generally speaking, what is their typical lifespan?
a couple of days
What are their two-letter abbreviations?
cA cP cT mP mT
Where do air masses form?
formed by uneven heating and cooling of the Earth by the sun. This causes pressure differences in different areas of the globe. The movement of air masses is just the flow of high pressure air masses to low pressure areas.
In terms of the characteristics of the snow?
less snow
What causes Fresno to experience very cold temperatures (arctic outbreak)?
mP
What airmasses can influence Fresno?
mT, Mp
How is precipitation measured?
precipitation is measured in the amount of rain that falls per inches in a given year.
How does Fresno recover from such cold temperatures?
windflow
