MSC 243 HOMEWORK #4 – DUE NOV 8, 2011
INTERPRETING DATA FROM A SOUNDING
Before doing the exercises, read the following sections in the SkewT manual
linked to Lecture 8 on our course website: 2.1
2.5 (lines on chart), 4.1
4.4
(meteorological
quantities),
4.18,
4.19,
4.20,
4.22,
4.23,
4.24 (CCL/Conv
Temp/LCL/LFC/CIN/CAPE/EL), 5.1 (Parcel Theory), 5.4, 5.5a,b,c (Instability).
Next,
go
through
Slides
111
on
the
COMET
module
http://www.meted.ucar.edu/mesoprim/cape/cape.htm
(you may need to sign up)
Goal
: To use data from a sounding to forecast the potential for convection, showers, thundershowers,
and severe weather.
Data:
Included are data from soundings from Miami FL (KMIA) and Manzanillo Mexico (MMZO) and
2 blank SkewT diagrams on which to plot the data for each sounding.
Answer each question for
both soundings.
If
you
want
some
extra
blank
SkewT
diagrams,
you
can
download
them
from
http://meteora.ucsd.edu/wx_pages/stuff/Blank_SkewT.pdf
1. The first step is to plot the temperature, dewpoint and winds on the skewT diagrams.
a. Using a pencil, plot the temperatures and dewpoints on the skewT diagrams. Connect the
temperature dots and dewpoint dots to produce 2 separate lines.
See SkewT charts at back
b. Plot wind barbs at each pressure level.
See SkewT charts at back
c. Is it dry or humid at each location?
Both locations are humid.
d. Are there any inversions in the soundings – if so, where?
KMIA: Very minor inversion between 479 mb and 466.5 mb (check data)
MMZO: Very minor inversions around 630 mb and 535 mb.
Neither of the upperlevel inversions
are significant.
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View Full Document2. The next step is to find the LCL (Lifting Condensation Level) where the cloud base exists,
and the maximum surface temperature.
a. What is the average mixing ratio for the lowest 100mb of the sounding?
What is the average
potential temperature?
KMIA: Average mixing ratio is around 16g/kg.
Average potential temperature is around 22C or
295K.
MMZO: Average mixing ratio is around 18g/kg.
Average potential temperature is around
28.5C or 301.5K.
b. The LCL is the pressure level at which these two lines of average mixing ratio and average
potential temperature intersect.
Indicate the LCL on the diagram and note down its pressure
level.
KMIA: approx. 980 mb.
MMZO: approx. 920 mb.
c. To estimate the maximum surface temperature or potential temperature, follow a dry adiabat
from the LCL down to the ground level, and write down the temperature reading at the ground.
This is the potential temperature.
An air parcel at this temperature at the ground would rise
adiabatically to the LCL, at which point it would become saturated.
The air parcel would then
no longer rise at the dry adiabatic lapse rate, but the moist adiabatic lapse rate.
KMIA: around 24C
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 Fall '08
 Majumdar,S
 Heat, Atmospheric thermodynamics, Thunderstorm, Thermodynamic diagrams, MMZO

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