air masses and fronts l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Air masses and fronts PowerPoint Presentation
Download Presentation
Air masses and fronts

Loading in 2 Seconds...

play fullscreen
1 / 58

Air masses and fronts - PowerPoint PPT Presentation


  • 134 Views
  • Uploaded on

Air masses and fronts. Textbook, Chapter 9. Discussion. How do precipitation systems form?. How does this precipitation form?. How does this precipitation form?. mountains. How does this precip form?. How does this storm form?. let’s revisit the lifting mechanisms …. Five Mechanisms.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Air masses and fronts' - lavi


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
air masses and fronts

Air masses and fronts

Textbook, Chapter 9

slide2

Discussion

How do precipitation systems form?

slide6

How does this

precip form?

slide7

How does this storm form?

let’s revisit the lifting mechanisms …

five mechanisms
Five Mechanisms

1. Convective ascent

spontaneous buoyant

Cumulus

clouds …

d uplift forced by jet stream
(d) Uplift forcedby jet stream

Upper-level divergence

cloud precipitation formation mechanisms
Cloud & precipitation formation mechanisms
  • Buoyant ascent [bubble ascent]
  • Forced ascent [layer ascent]
    • Orographic
    • Frontal
    • Low-level convergence (friction)
    • Upper-level divergence (jet stream)
  • Many clouds are the result of several simultaneous processes.
slide15

1. Buoyant ascent

  • We’ve talked about stability and parcel ascent (Chapter 4, Lab 7).
  • Remember that in a conditionally unstable atmosphere, a cloud will continue to rise as long as its core temperature exceeds that of the surroundings
cumulus growth
cumulus growth

stable

environmental

lapse rate

stable

condi-

tionally

unstable

stable

conditionally

unstable

moist

dry

Cumulus humilis Cumulus congestus Cumulonimbus

cloud precipitation formation mechanisms18
Cloud & precipitation formation mechanisms
  • Buoyant ascent [bubble ascent]
  • Forced ascent [layer ascent]
    • Orographic
    • Frontal
    • Low-level convergence (friction)
    • Upper-level divergence (jet stream)
  • Many clouds are the result of several simultaneous processes.
a orographic clouds
(a)Orographic clouds

Altocumulus lenticularis, Greenland

slide20

The Foehn or Chinook effect

Quantifying the Foehn effect

(web link)

slide22

Pop quiz: when a good westerly wind blows and heavy snowfall occurs over the Cascades, then in Yakima on the east side it will be ……. than in Seattle on the west side.

A: sunnier but cooler

B: sunnier, warmer, drier, and windier

C: sunnier, cooler, more damp, and calmer

D: cloudier, cooler, more damp, and windier.

Yakima

Seattle

cloud precipitation formation mechanisms23
Cloud & precipitation formation mechanisms
  • Buoyant ascent [bubble ascent]
  • Forced ascent [layer ascent]
    • Orographic
    • Frontal
    • Low-level convergence (friction)
    • Upper-level divergence (jet stream)
b uplift along fronts
(b) Uplift along fronts

A front is a sudden transition between airmasses

continental maritime
cP

cT

mP

mT

continental maritime

Types of airmasses

polar

tropical

slide29
Air masses have distinct lapse rates, and therefore also distinct cloud and precipitation characteristics
pop quiz what airmass is this32
Pop quiz: what airmass is this ?

cP

cT

mP

mT

Hint: this happens in winter

warm fronts
Warm fronts

The cold air recedes …

warm front clouds
Warm front clouds

Where is the cold air??

cold front clouds
Cold front clouds
  • stable air ahead of cold front

light rain or dry

(2) unstable air ahead

of cold front

occluded fronts
Occluded fronts

Stage I

Stage II

slide41

Cold occlusion

(eastern US)

Warm occlusion

(western US)

Fig. 9.18

stationary fronts
Stationary fronts

Current analysis

drylines
drylines

Thunderstorms, sometimes severe ones, can be triggered along the dryline.

cloud precipitation formation mechanisms46
Cloud & precipitation formation mechanisms
  • Buoyant ascent [bubble ascent]
  • Forced ascent [layer ascent]
    • Orographic
    • Frontal
    • Low-level convergence (friction)
    • Upper-level divergence (jet stream)
c low level convergence into lows or trofs
(c) Low-level convergence into lows or trofs
  • Tropical lows (hurricanes)
    • extract their energy from latent heat release
  • Mid-latitude lows
  • extract most of their energy from the jet stream
slide48

Tropical cyclogenesis

LOW-LEVEL CONVERGENCE

INTO A TROF

slide52

Tropical cyclones have different names in different oceans

There spin is always cyclonic,

i.e. ccw in the north and cw in the south

slide53
Where do hurricanes form?
    • Away from the equator
    • Where the SST is at least 80F

August SST

slide54

Hurricane Effects:

Wind: causes most damage, but limited mortality.

Storm surge: a historical killer, now mitigated by evacuation.

Rain and Inland Flooding: take more lives than wind, but do less damage.

slide56

Hurricane mortality and damage, United States 1900-2008

coastal

Hurricanes are covered in the textbook in Chapter 8

slide57
Lows, and convergence, uplift, clouds, and precipitation, also occur at higher latitudes.What energizes them?
answer the jet stream
Answer: the jet stream !!
  • Buoyant ascent [bubble ascent]
  • Forced ascent [layer ascent]
    • Orographic
    • Frontal
    • Low-level convergence (friction)
    • Upper-level divergence (jet stream)

THIS WILL BE COVERED IN CHAPTER 10

End of Chapter 9