Air Masses and Source Regions

Question 1

Fronts

Answer 1

boundaries between different air masses

Question 1

Air Mass

Answer 1

large volumes of air with uniform temperature and humidity

Question 2

Source Regions

Answer 2

areas of the globe where air masses form
-air must remain over a source region for substantial length of time for an air mass to form

Question 3

Basic Characteristics

Answer 3

1. Moisture
   a. continental; forming over land, dry
   b. maritime; forming over ocean, humid
2. Temperature
   a. tropical; forming near the tropics in lower altitudes, warm
   b. Polar; cold
   c. Arctic; very cold

Question 4

Maritime Polar from Gulf of Alaska

Answer 4

-originates from Gulf of Alaska and grates down along the west coast of North America
-cold, humid, unstable
-trajectory into US depends on the position of the polar jet stream
a. when jet stream is dipping southward LA has poor weather, when facing northward LA has clear weather
-maritime polar air coming from the ocean gets enhanced as they are lifted up the mountain range and leads to precipitation
-large source of winter precipitation in California

Question 5

How does the jet stream change in the winter

Answer 5

it moves to the south and become stronger and the waves become more pronounced

Question 6

Maritime Polar from Atlantic

Answer 6

-cold, humid, unstable
-nor’easters

Question 7

Nor’easters

Answer 7

-dumps a lot of snow in New England
-caused when the polar het stream transports cold arctic air from Canada and meets with warm air from the Gulf of Mexico … when these meet over the cold Atlantic it leads to nor’easters

Question 8

Maritime Tropical

Answer 8

-warm, humid
-major source of precipitation and thunderstorms in the southeastern US

Question 9

Atmospheric Rivers

Answer 9

-relatively long. narrow regions in the atmosphere that transport most of the water vapor outside of the tropics
-air masses forming in maritime tropical region in the pacific that bring in warm humid maritime tropical air and carry high amounts of water vapor
-second major source of precipitation in California
-Pineapple Express from Hawaii

Question 10

Atmospheric River Synoptic Pattern Development

Answer 10

1. 7-10 days before event there is a ridge that is locked over west coast that prevents precipitation in SoCal, but heavy rain over western pacific
2. 2-5 days before event the ridge starts to break down because the jet split and from two jets; this opens up a southern corridor that allows the jet to route in weather off the pacific
3. Precipitation Event: southern portion of the jet stream takes over and allows the routing of the atmospheric river towards SoCal

Question 11

Why can’t air masses form in mid-latitudes?

Answer 11

They are too variable and don’t have quiet periods

Question 12

What happens when an air mass moves?

Answer 12

1. The region in which the air moves undergoes a major change in temperature and humidity
2. The air mass becomes more moderate

Question 13

How do cP air masses differ in the winter vs the summer?

Answer 13

In the winter snow radiation leads to cool temp that create stable conditions — prevents cloud formation so usually bright and sunny

More humid in the summer and leads to cumulus clouds but not much precipitation

Question 14

Where do cT air masses usually form?

Answer 14

in deserts over the Southwestern US and Northern Mexico

*unstable because of dryness