Meteorology 400/800

# Laboratory Exercise 1

Thermodynamic Diagrams:

## Simple Plot of Sounding Showing Marine Layer

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 application of the knowledge and skills you received in Metr 201 with respect to sounding interpretation and buoyancy. We will also explore

the Penn State primer on Skew T-Log diagrams, sounding interpretation and sounding code.

2. Read pages 4-13 of the NOAA Training Center Training Modul and pages 30-31of Vasquez first.  Then complete the following exercises.

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. Plot the wind information on th right margin, as discussed in class.

 Pressure Temperature Dew Point Wind 1015.0 13.8 11.5 220,04 1000 12.6 11.4 225,04 981 11.2 11.2 230,05 944 10 10 220,05 925 19.8 -2.2 315.02 850 18.4 -30.6 185,08 700 9.6 -39.4 200,12 500 -7.9 -55.9 310,06

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.

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.        Compare the fully plotted KOAK sounding for 12 UTC 12 Sep 2005 with that for

00 UTC 24 July 2005 at KMSP. Briefly describe and discuss how the soundings VISUALLY compare

D.       In Metr 200 and 201, you were 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 for the 12 UTC 25 Aug 2009 sounding data given above:

 Pressure Mixing Ratio Saturation Mixing Raio Relative Humidity 1015.0 1000 981 944 925 850 700 500

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

E.        Using RAOB, plot KOAK sounding for 12 UTC 12 Sep 2005 and that for 00 UTC 24 July 2005 at KMSP. Text Files: Oakland and Minneapolis.

F.         With Chris's help, use RAOB to determine the LCL and LFC and the stability (absolutely stable, absolutely unstable, conditionally unstable).

G.         On hard copy of each, determine the CCL (in mb) and CT (deg C). How realistic is it that the afternoon temperature

would achieve the CT?