DEPARTMENT OF GEOSCIENCES                  NAME_________________________

SAN FRANCISCO STATE UNIV                                Meteorology 201

 

In-class Lab Assignment 4 Key (100 pts)

 

 

1.      Determine the morning stability at KOUN (Norman, OK) from the morning sounding for 1200 UTC 3 May 1999 (attached).

Estimate the height of the Lifting Condensation Level, Level of Free Convection, 500 mb Lifted Index, Equilibrium Level and determine if the sounding is unstable, stable or conditionally unstable with respect to a SURFACE LIFTED PARCEL. Be sure to indicate the parcel ascent curve, LCL, LFC and EL right on the diagram.
(30 points)

 

Detail of Sounding Analyses . Zoomed portion of sounding on right shows intersection of saturation mixing
ratio extending from surface dew point temperature and dry adiabat extending from surface temperature.
KOUN Sounding 12 UYC 3 May 1999 Closeup of LCL

This is a conditionally unstable sounding. The LCL is at about 930 mb (162 m AGL), the LFC is at about 700 mb (~3000 m AGL), and the EL is at about 240 mb (~10,500 m AGL). The Lifted Index is -2.4.

2.      Estimate the afternoon stability at KOUN (Norman, OK) from the morning sounding for 1200 UTC 3 May 1999 (second copy).  Estimate the Convective Temperature, Convective Condensation Level and determine if the sounding is potentially unstable.  Indicate the CT, CCL, parcel ascent curve, positive area on sounding (CAPE) (shaded red), and negative area on sounding (CINH) (shaded blue). (30 points)

 

 

Convective Temperature calcuation
Convective Temperature Calculation CCL_CAPE\

The procedure is to follow the saturation mixing ratio extending from the surface dew point temperature until it intersects the sounding at or above the nose of the inversion. This intersection point is the convective condensation level (CCL). Then, a dry adibat is drawn from the CCL to the surface. The temperature at the surface is called the Convective Temperature (CT). In this case, the CT is 28C and the CCL is at the 825 mb level (about 1400 m AGL). The diagram at above right shows the CAPE and CINH areas shaded in. Not the dramatic increase in CAPE (proportional to red area) from the morning sounding..

3.      Calculate the CAPE from the morning sounding using the method discussed in class. You'll be approximating the CAPE by summing up the indidividual contributions of layers approximately 1500 m thick. The table below should get you started. (Started in class) (30 points)

 

 

4. Using the results from (3) above, calculate the maximum vertical velocity at the EL in the morning.  (Started in class) (10 points)

 

 

Pressure (mb)

Elevation AGL (m)

~700

~3000

600

~4500

500

~6000

400

~7500

300

~9000

240

~10500

 

 

 

 

 

 

 

 

I used the procedure outlined in class. I created the formulas in Excel, but you could have done them on a calculator. I got a CAPE value of 1032 J/kg, and a vertical velocity at the EL of 45.5 m s-1. This is fairly close to the actual values, as shown on the actual sounding.

 

Spreadsheet Entries and Ascent Curve for KOUN 12 UTC 5/3/99

 

BuoyancyTable Asceny

 

 

 

4.     

 

 

 

 

 

 

 

 

 

 

 

 

 

CAPE

 

 

 

KOUN Sounding 12 UYC 3 May 1999

 

KOUN Sounding and Hodograph, 12 UTC 3 May 1999 (click on sounding to get larger version)