Meteorology 301

 

 

Laboratory Exercise 1

 

 

Thermodynamic Diagrams:

Simple Plot of Sounding and Interpretation

 

 

 

 

 

 

 

 

 

 

 

Insert in ringed-three hole binder.  Work not

turned in in binder will not be accepted.

 

Point deductions for sloppy or late work.

 

 

 

 

 

 

 

 

 

 

 

PROCEDURE

 

1. This lab involves use of the National Weather Service's Training Module on Skew T-Log diagrams provided by the instructur for the course. 

 

2. Read pages 4-13 of the Training Module first.  Then complete the rest of the training module readings as appropriate.

 

Exercise 1.  Simple Plot of Sounding and Interpretation

 

There are two thermodynamic diagrams which are used operationally:  i.  the Skew T/Log P (discussed in the training module); and, ii. the Pseudoadiabatic Diagram.  The instructor will give you copies of both.

 

            A.        Plot the following temperatures on both to get a visual representation of the

                        ENVIRONMENTAL LAPSE RATE on a summer day in the Bay Area

                        when fog was present.

 

                      

  Pressure
  Temperature        
Dew Point 
Wind
1016.4  
16
12
270,13
1000
13
12
280,18
950
11
11
290,25
900
12
7
300,30
875
20
5
280,15
850
24
0
265,10
700
15
-5
265,10
500
10
-10
250,10

 Now plot the wind information (discussed in class).

 

You will learn in other classes that the typical summer sounding along the California coast shows

a nearly adiabatic mixed layer near the ground, surmounted by a "marine", subsidence inversion. 

The air above the inversion is also very stable but shows a slow temperature decrease with height. 

The fog is found in the upper half of the marine (or "mixed") layer and the lower half of the

inversion layer.  Wind speeds tend to increase with height through the marine layer and then

decrease rapidly above.

 

The inversion acts to "cap" whatever convection occurs in the mixed layer, as discussed in class.  It

is important to identify inversions or stable layers on soundings, for this reason.

 

            B.        Examine your two soundings.  Describe which "shows" inversions and stable layers

                        most  dramatically and how.


 

            C.        You will be given background on the importance of the dew point information in

                        class.  Using this, your diagrams and the material in the module, determine the

                        following:

 

                        Pressure          Actual Mixing Ratio   Saturation Mixing Ratio        RH(%)

 

                        1016.4                        

                        1000.0                        

                        950.0                          

                        900.0                          

                        875.0                          

                        850.0                          

                        700.0                          

                        500.0

 

Now you can determine how "prone" the atmosphere is for deep, mesoscale convection to occur. 

 

            D.        Determine the lifting condensation level, the level of free convection, the equilibrium level from the Skew T/Log P.

 

            E.         Determine the CCL and CT from the Pseudoadiabatic Diagram.  (Note: these determinations could have been made all onthe same chart or on both charts, the answers will be exactly the same.)