Notes for Metr 356

    11/10/04

Frank Sanchez

 

Readings:

Reader: 248-253; 267-269; 292-293; Section VI (296-307); Section VIII (319-381); 335-365.

Class WebSite: Read through Divergence page

 

Reviewed:

First we reviewed thermal and dynamic pressure systems. We went through several examples of thermal lows. Looked at links of images Conceptual Divergence 1 and  Conceptual Divergence 2 in order to further our discussion on how High and Low pressure systems are formed.

 

We reviewed the image of the cross-section of advection fog.

 

Thermal Pressure Systems:

 

We then talked about how air is cooled as it increases in altitude.

5.5¡ per 1000 ft.

 

Nature Does Not Like Vacuuums Part I: At a given level, air tends to move horizontally  from higher values of pressure to lower values of pressure (Note:  due to Coriolis Effect the air really "spirals" from  higher values of pressure to lower values of pressure).

 

Divergence aloft  tends to be associated with falling surface pressures (formation  of surface lows), whereas convergence aloft tends to be associated  with rising surface pressures (formation of surface highs)

 

Nature Does Not Like Vacuums Part II: Divergence in the upper troposphere is associated  with rising air from beneath and convergence in the upper troposphere  is associated with sinking air beneath.

 

In discussing these rules, we established that low-pressure systems are concurrent with the eastern side of troughs due to divergence. We know this because the isobars related to the Jet Stream separate on the eastern side of the trough showing that air is expanding. So a low pressure is formed underneath this divergence. Going back to Rule #1 of understanding wind patterns: Nature does not like vacuums. So air rushes in to fill to void.

 

By examining the jet streams and the ridges and troughs, we are able to make good assumptions as to where low pressure should be forming.

 

We then looked at another link and images to further this example. We saw a real life example for October 29th 2004. We looked at the Jet Stream and how it correlated with the wave cyclone that was forming in South Dakota.