USING
INDIRECT MODEL OUTPUT TO DETERMINE DIFFERENTIAL THICKNESS ADVECTION (TERM C)
In this section, you will
examine the most common method of determining thickness (temperature) advection
using wind barbs and temperature field plots.
Obtain the image pictured below by following these steps:
1)
Check the box next to “Wind Barbs” under the “WIND PLOTS” section of the
“Displays” menu.
2) Click
on Wind Barbs.
a)
In the “Wind Barbs; Level: 500 hectopascals” window that appears, change the
“Levels:” to 850 hectopascals.
b)
Close the “Wind Barbs; Level: 850 hectopascals” window.
3)
Under the “GEOPOTENTIAL HEIGHT PLOTS” section of the “Displays” menu, check the
box next to “850 hPa Geopotential Height Contours.”
4)
Under the “THICKNESS PLOTS” section of the “Displays” menu, check the boxes
corresponding to these plots:
a) “1000-500 hPa Thickness Contours”
b) “1000-500 hPa Colored Thickness”
850 hPa Temperature Advection
Q18 - Is the wind at 850 hPa geostrophic. How can you tell? Why are the 850 hPa winds assumed to be the
advecting winds? To answer this
question, consider that the thickness plot is for the 1000-500 hPa layer.
Q19 - From the labels over southeast
Q20 - Do the solenoids in the vicinity of the location
diamond depict strong thickness advection?
How can you tell?
Q21 - Consider the idealistic scenario of temperature
advection pictured below. The blue area
represents a “pool” of cold air; the red area represents a “pool” of warm
air. In the presence of a west wind
(depicted by the wind barb), what will happen to the localized temperature at
the location diamond? What kind of advection
(warm air or cold air) is present?
Applying this physical
approach to determining temperature advection at a point, what kind of
thickness (temperature) advection is present at the location diamond over western
5)
Uncheck the boxes corresponding to the following in the “Displays” menu:
a) “1000-500 hPa Thickness Contours”
b) “1000-500 hPa Colored Thickness”
c) “850 hPa Geopotential
Height Contours”
The
850 hPa wind barbs will remain on the map.
Obtain the image of
upper-level thickness advection pictured below by following these steps:
1) Click on Wind Barbs
under the “WIND PLOTS” heading in the “Displays” menu.
a)
In the “Wind Barbs; Level: 850 hectopascals” window that appears, change the
“Levels:” to 400 hectopascals.
b)
Close the “Wind Barbs; Level: 400 hectopascals” window.
2)
Under the “THICKNESS PLOTS” section of the “Displays” menu, check the boxes
corresponding to following parameters:
a) “500-300 hPa Thickness Contours”
b) “500-300 hPa Colored Thickness”
500-300 hPa Thickness Advection
Q22 - Is the atmosphere between 500 and 300 hPa
baroclinic or barotropic? What does this
tell you about the temperature advection within this layer? If you were to determine the vertical
distribution of temperature advection within the troposphere, what levels would
be most important to examine?
Typically, thermal advection
is very small in the upper troposphere (above 500 hPa). Thus, it is really the low level advection
that determines the 500-hPa geopotential tendency.
3)
Uncheck the following:
a) “Wind Barbs” under “WIND PLOTS”
b) “500-300 hPa
Thickness Contours” and “500-300 hPa Colored Thickness” under “THICKNESS PLOTS”
A
blank map with only the location diamond present over western