REMINDERS: Problem Set 2: Due Friday (Jan 31) Midterm 1: Next Wednesday, Feb 5

- Lecture material covering chapters 1-5 - Multiple Choice, Short Answers, Definitions - Practice midterm will be on course website - Closed-book, no notes, no calculator. - No scantron or blue book necessary

UPCOMING REVIEW SESSION:

- Tuesday, Feb 4, 6:30-8:00pm in HSS 1330

In general, Fog and Clouds form when air cools to saturation point as Temp DECREASES, qsat DECREASES, so RH INCREASES

RH = (q / qsat) x 100% if Temp decreases enough, RH ==> 100% (saturation) and condensation occurs. There are a variety of cooling mechanisms. Radiational cooling of surface can lead to Radiation Fog...

Radiation Fog in the San Joaquin Valley January 2004

FOG

SNOW S.F.

L.A.

Advection Fog in San Francisco

Advection Fog Also occurs when warm moist air moves over cold land surface Southeast U.S. is prone to this type of fog in winter

A

B

O Two unsaturated air parcels at A and B

When A and B mixed end up at point O. Now on saturated side of curve => condensation occurs and get Mixing Fog

RH<100%! RH<100%!q! q!

q!qsat!

RH>100%!

Temperature

Spec

ific

Hum

idity

Saturation Curve

Below  curve:    RH  <  100%  (not  saturated)  Above  curve:    RH  >  100%  ==>  condensation  occurs  

MIXING FOG

Cirrus Clouds - High and Optically Thin - Composed of Ice Crystals

Altocumulus – Mid level clouds

Stratocumulus Clouds – Low level clouds

Stratocumulus

Cumulus Clouds – Vertically developed

Cumulus Clouds – Vertically developed

Cumulus Clouds – Vertically developed “Supercell” System – Tornado Producer

Nimbus cloud – Precipitating

Virga – Precipitation that evaporates before reaching ground

Color Enhanced Infrared Image Assign colors (or shades of gray) to different temperatures

January 19, 2004 10AM PST

Infrared Visible

Stability

Is the Atmosphere Stable or Unstable? Question we ask to see if air will rise. If air rises, clouds may form.

Stable: Air parcel pushed up a little, but returns to original level Unstable: Air parcel pushed up a little,

and continues to rise.

Clicker Question

Which of these situations is more unstable?

(A) (B)

cold air

cold air warm air

warm air

Set Clicker Frequency to AD

Also must consider that as air moves up (or down) in the atmosphere, it's temperature will change. ==> changes in pressure cause expansion or compression