Announcements

1
Announcements
Quiz 2 - A take home portion was given out today,
Thursday, and is also available on the website on
the Quiz Results page. The take home portion is
due Tuesday, Nov 1. This portion will be worth up
to 20 points to be added directly to your Quiz 2
score.

• Homework 3 - Now due Thursday, Nov 3. Also, some
  changes
• Problem 1 is extra credit.
• An additional problem 11 has been added for
  regular credit and is posted on the website. You
  can just print the last page if you already have
  the original version of the homework or you did
  not get it today.

• Quiz 3 - Now Thursday, Nov 10. Also, note
• Review session Wed. 9 Nov, 4-5pm. Location TBD.
• Will cover material since Quiz 2, meaning through
  Thursday Nov 3 lecture. Essentially, chapters
  6-7.
• Will include some of your questions from this
  week and next.

2
Key Concepts
Stability Refresher How a parcel temperature
changes as it rises on the west side of the
Rockies and sinks on the east side in a Chinook
wind
Pressure Refresher Vertical pressure
gradients Hydrostatic balance Pressure and
Temperature
Thermal Circulation Refresher Land/Sea breeze
example revisited Apply concepts of pressure
refresher slides
3
Key Concepts
Thermal circulations - winds driven by horizontal
temperature differences which create horizontal
pressure gradients.

• Monsoons
• Asian Monsoon
• North American Monsoon
• Seasonal wind pattern
• Similar to a land/sea breeze but persist over
  longer time period

• Jet Streams
• Polar jet stream
• Subtropical jet stream
• Exist near the tropopause
• Geostrophic winds, in geostrophic balance
  (PGFCF)
• Result from temperature differences between
  tropics and subtropics (subtropical jet),
  subtropics and poles (polar jet)

4
Chinook and Stability
Chinook Winds - downslope wind on the leeward
side of the Rockies, compressional heating
height
Temperature inversion
Mtn top
Tleeward - conditionally unstable
Temperature
10C
18C
-12C
5
Pressure Refresher
Vertical Pressure Gradient - The Hydrostatic
Balance
Pressure decreases with height!
6
Pressure Refresher
Pressure and Temperature
500 mb
If 500 mb level starts out at 5000 meters /
18,000 ft and at -20C / -4F
7
Thermal Circulations
Thermal circulation - Land/Sea Breeze example
8
Thermal Circulations
Thermal circulation - Land/Sea Breeze example
Things to notice Expansion of warm column of
air Compression of colder column of
air Horizontal winds responding to these
expansions and compressions Vertical motions
(weak) replacing air added or removed from column
9
Thermal Circulations
Monsoons - winds that change direction seasonally
generally due to large land-sea temperature
differences, global scale
Cold land, warm ocean
Subsiding air in anticyclone
Downslope winds off inland plateau
Winds blow from land to sea
10
Thermal Circulations
Prevailing winds, westerlies
Warm land, cold ocean
Rising air in cyclone
Winds blow from sea to land
Humid air lifts by 1) meeting colder westerly
flow, 2) mountains
11
Thermal Circulations
North American Monsoon
500 mb
Spring season - deep anticyclone over land, fair
weather in southern US
Cold land, warm ocean
Subsiding air in anticyclone
Downslope winds off Sierra Madre
Winds blow from west over southern US
12
Thermal Circulations
North American Monsoon
Summer season - anticyclone shifts northeast,
rainy weather in southern US
500 mb
Warm land, cold ocean
Winds blow from south/southwest over southern US,
from east over Mexico, ocean to land breeze
Humid air rises in (1) upslope winds along Sierra
Madre, (2) upslope winds over SE Arizona
mountains, and (3) rising air above dry
subtropical sinking air.
13
Thermal Circulations
North American Monsoon
Percentage of Annual Rainfall
14
Global Regions
Regions of the world
Tucson, AZ (32 latitude)
15
Thermal Circulations
Polar jet stream
H
L
H
L
H
L
16
Thermal Circulations
Geostrophic wind review PGF directed from high to
low pressure, set up by north-south temperature
gradient CF bending wind to the right When equal,
no acceleration, geostophic balance
Polar jet stream