tephi Documentation
Release 0.1.0
British Crown Copyright 2014, Met Office
March 01, 2017
Contents
1
User guide table of contents
1.1 Introduction . . . . . . . . . . . . . . .
1.1.1
Axes and lines of the tephigram
1.2 Tephigram plotting . . . . . . . . . . . .
1.2.1
Tephigram data . . . . . . . . .
1.2.2
Plotting tephigram data . . . . .
1.3 Tephigram customisation . . . . . . . . .
1.3.1
Isobar control . . . . . . . . . .
1.3.2
Saturated adiabat control . . . .
1.3.3
Humidity mixing ratio control .
1.4 Tephigram barbs . . . . . . . . . . . . .
1.4.1
Wind barbs . . . . . . . . . . .
1.4.2
Plotting barbs . . . . . . . . . .
1.4.3
Controlling the barbs . . . . . .
1.4.4
Moving the gutter . . . . . . . .
1.5 Glossary . . . . . . . . . . . . . . . . .
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3
3
4
9
9
11
17
18
24
30
35
35
36
40
41
43
i
ii
tephi Documentation, Release 0.1.0
This user guide gives a brief introduction to the tephigram plotting capability provided by tephi.
Warning: This module is currently in beta release and is liable to change.
Contents
1
tephi Documentation, Release 0.1.0
2
Contents
CHAPTER 1
User guide table of contents
Introduction
The tephigram is a thermodynamic or energy diagram, devised in 1915 by Sir William Napier Shaw, a former DirectorGeneral of the Met Office.
It is a graphical representation of the obervations of pressure, temperature and humidity, made in a vertical sounding
of the atmosphere, typically from radiosondes.
The axis of the tephigram are temperature (T) and entropy (𝜑), hence the name “T-𝜑-gram”. The axes and lines of the
tephigram are shown in Figure 1: The tephigram..
Fig. 1.1: Figure 1: The tephigram.
3
tephi Documentation, Release 0.1.0
Axes and lines of the tephigram
At first glance the tephigram appears to be a confusing mass of lines. However, on closer inspection five different
types of lines can be identified, all of which are now described.
Isotherms
Isotherms are lines of constant temperature, measured in units of o C. They are straight and parallel, running at 45o
across the tephigram from bottom left to top right of the plot.
The line representing the 0o C isotherm has a thick black dashed line-style.
Fig. 1.2: Figure 2: The isotherm lines.
The axis ticks to the left of the plot show the temperature values of each individual isotherm line.
Dry adiabats
Dry adiabats are lines of constant potential temperature, measured in units of o C. They are straight and parallel, running
at 45o across the tephigram from the top left to the bottom right of the plot.
The dry adiabats represent the rate at which unsaturated air will cool when rising or warm when sinking. The dry
adiabatic lapse rate (DALR) is the rate at which cooling occurs if there are no other factors increasing or decreasing
the temperature of a parcel as it rises.
The axis ticks at the bottom and to the right of the plot show the potential temperature value of each individual dry
adiabat line.
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Chapter 1. User guide table of contents
tephi Documentation, Release 0.1.0
Fig. 1.3: Figure 3: The dry adiabat lines.
1.1. Introduction
5
tephi Documentation, Release 0.1.0
Note that, as temperature (T) and entropy (𝜑) are the axes of the tephigram, the isotherms and dry adiabats perpendicularly bisect each other, and are not skewed.
Fig. 1.4: Figure 4: Relationship between the isotherm and dry adiabat lines.
Isobars
Isobars are lines of constant pressure, measured in units of millibars or hectopascals. They are almost horizontal and
straight and their vertical spacing increases as their value decreases. The highest valued isobar is at the bottom of the
plot and the lowest valued isobar is at the top, akin to our atmosphere.
The value of each individual isobar line is always shown within the plot beside the isobar line. By default, isobar lines
and text values are blue.
Humidity mixing ratio
Humidity mixing ratio lines are lines of constant saturation mixing ratio with respect to a plane water surface, measured
in units of g kg-1 . They run diagonally across the plot from bottom left to top right.
A humidity mixing ratio line represents the number of grams of water required to saturate 1 kg of air at a particular
temperature and pressure.
The value of each humidity mixing ratio line is always shown within the plot beside the line. By default, humidity
mixing ratio lines and text values are green.
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Chapter 1. User guide table of contents
tephi Documentation, Release 0.1.0
Fig. 1.5: Figure 5: The isobar lines.
1.1. Introduction
7
tephi Documentation, Release 0.1.0
Fig. 1.6: Figure 6: The humidity mixing ratio lines.
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tephi Documentation, Release 0.1.0
Pseudo saturated wet adiabats
Saturated adiabats are lines of constant equivalent potential temperature for saturated air parcels, measured in units
o
C. They run as vertically curved lines across the plot from top to bottom.
The saturated adiabats represent the rate at which saturated air will cool when rising i.e. the saturated adiabatic lapse
rate (SALR).
Fig. 1.7: Figure 7: The saturated adiabat lines.
The value of each saturated adiabat line is always shown within the plot beside the line. By default, saturated adiabat
lines are text values are orange.
Tephigram plotting
This section describes how to visualise one or more data sets as a tephigram.
Tephigram data
Throughout this user guide we will make use of three data sets to plot temperature profiles on a tephigram.
Currently, the tephigram module can only plot data from ascii text files. These files may contain pressure, temperature,
wind speed and wind direction data sets. Here pressure is measured in units of millibars or hectopascals, temperature
is measured in units of degrees celsius, wind speed is measured in knots and wind direction is measured in degrees
from north.
1.2. Tephigram plotting
9
tephi Documentation, Release 0.1.0
Note that the data set must consist of one or more pressure and temperature paired values, and optionally one wind
speed and wind direction pair for each pressure value. Thus any temperature value must be paired with a pressure
value, and wind speed and wind direction pairs must be paired with a pressure value.
Data from the text files is loaded into one collections.namedtuple() instance per text file. Each column of
data representing a given phenomenon in a text file is loaded into a single named tuple. The name of each tuple is set
using a list of strings passed to the loader. If not specified, the names default to (pressure, temperature).
For our example tephigram data sets we have a 2-dimensional dew-point data set:
>>> print dews
tephidata(
pressure=array([ 1006.,
924.,
900.,
850.,
800.,
755.,
710.,
700.,
600.,
500.,
470.,
459.,
400.,
300.,
250.], dtype=float32)
temperature=array([ 26.39999962, 20.29999924, 19.79999924, 14.5
,
12.89999962,
8.30000019, -5.
, -5.0999999 ,
-11.19999981, -8.30000019, -12.10000038, -12.5
,
-32.90000153, -46.
, -53.
], dtype=float32))
And a 2-dimensional dry-bulb data set, with each named tuple printed individually:
>>> print
[ 1006.
470.
151.
50.]
temps.pressure
924.
900.
850.
459.
400.
300.
150.
129.
117.
800.
250.
107.
755.
210.
100.
710.
200.
82.
700.
186.
80.
600.
178.
60.
500.
159.
54.
>>> print temps.temperature
[ 30. 22. 21. 18. 16. 12. 12. 11.
4. -4. -7. -7. -13. -29. -38.
-47. -51. -56. -57. -63. -63. -64. -69. -77. -79. -77. -78. -78. -72. -71.
-69.]
A convenience function, as introduced above, has been provided to assist with loading one or more text files of
pressure, temperature, wind speed and wind direction data; see tephi.loadtxt(). Here it is used to load the third
example data set that contains four columns of data, being pressure, temperature, wind speed and wind direction:
>>> import os.path
>>> import tephi
>>> winds = os.path.join(tephi.DATA_DIR, 'barbs.txt')
>>> columns = ('pressure', 'dewpoint', 'wind_speed', 'wind_direction')
>>> barbs = tephi.loadtxt(winds, column_titles=columns)
>>> barbs
tephidata(
pressure=array([ 1006.,
924.,
900.,
850.,
800.,
755.,
710.,
700.,
600.,
500.,
470.,
459.,
400.,
300.,
250.], dtype=float32)
dewpoint=array([ 26.39999962, 20.29999924, 19.79999924, 14.5
,
12.89999962,
8.30000019, -5.
, -5.0999999 ,
-11.19999981, -8.30000019, -12.10000038, -12.5
,
-32.90000153, -46.
, -53.
], dtype=float32)
wind_speed=array([ 0.,
1.,
5.,
5.,
7., 10., 12., 15., 25., 35., 40.,
43., 45., 50., 55.], dtype=float32)
wind_direction=array([
0.,
15.,
25.,
30.,
60.,
90., 105., 120., 180.,
240., 270., 285., 300., 330., 359.], dtype=float32))
Note: WMO upper-level pressure, temperature, humidity, and wind reports FM 35-IX Ext. TEMP, FM 36-IX Ext.
TEMP SHIP, FM 37-IX Ext. TEMP DROP and FM 38-IX Ext. MOBIL are currently not supported.
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Chapter 1. User guide table of contents
tephi Documentation, Release 0.1.0
Plotting tephigram data
Note: Tephigram subplots are currently not supported.
Plotting a single data set
The temperature profile of a single tephigram data set can easily be plotted.
import matplotlib.pyplot as plt
import os.path
import tephi
dew_point = os.path.join(tephi.DATA_DIR, 'dews.txt')
dew_data = tephi.loadtxt(dew_point, column_titles=('pressure', 'dewpoint'))
dews = zip(dew_data.pressure, dew_data.dewpoint)
tpg = tephi.Tephigram()
tpg.plot(dews)
plt.show()
1.2. Tephigram plotting
11
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36
200
0.002
34
32
.0
0.01
−
60
30
.0
90
T=
θ=
0.03
300
28
0.1
26
0.2
45
T=
22
20
1.0
2.0500
18
16
3.0
θ=
.0
30
−
5.0
.0
T=
60
14
12
600
7.0
10
9.0
12.0
8
6
.0
−
400
0.6
75
0.4
θ=
.0
24
700
16.0
4
θ=
2
20.0
28.0
36.0
44.0
−
15
.0
.0
45
800
T=
900
52.0
60.0
80.0
1000
θ=
.0
15
0. 0
.0
30
θ=
θ=
Plotting multiple data sets
Plotting more than one data set is achieved by over-plotting each data set individually onto the tephigram.
import matplotlib.pyplot as plt
import os.path
import tephi
dew_point = os.path.join(tephi.DATA_DIR, 'dews.txt')
dry_bulb = os.path.join(tephi.DATA_DIR, 'temps.txt')
column_titles = [('pressure', 'dewpoint'), ('pressure', 'temperature')]
dew_data, temp_data = tephi.loadtxt(dew_point, dry_bulb, column_titles=column_titles)
dews = zip(dew_data.pressure, dew_data.dewpoint)
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Chapter 1. User guide table of contents
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temps = zip(temp_data.pressure, temp_data.temperature)
52
tpg = tephi.Tephigram()
tpg.plot(dews)
tpg.plot(temps)
plt.show()
48
5. 0
44
12
−
0. 0
21
T=
θ=
50
40
0. 0
18
10
36
θ=
0. 0
100
T=
−
0.01
32
75
−
T=
.0
50
−
20.0
400
36.0
52.0
500
4
80.0
θ=
600
0. 0
T=
12.0
12
8
7.0
θ=
12
0. 0
16
15
20
28
0.4200
1.0
24
3.0
300
θ=
.0
0.1
90
.0
700
−
25
.0
800
T=
900
1000
θ=
.0
60
θ=
θ=
.0
30
0. 0
Note that, by default the tephigram will automatically center the plot so that all temperature profiles are visible, also
see Anchoring a plot.
Customising a temperature profile
All keyword arguments passed
matplotlib.pyplot.plot().
1.2. Tephigram plotting
to
tephi.Tephigram.plot()
are
simply
passed
through
to
13
tephi Documentation, Release 0.1.0
This transparency allows full
100 control when plotting a temperature profile on the tephigram.
import matplotlib.pyplot as plt
import os.path
import tephi
32
0.01
.0
Dew-point temperature
−
60
30
.0
90
T=
θ=
0.03
300
28
0.1
26
0.2
45
T=
22
20
1.0
2.0500
18
16
3.0
θ=
.0
30
−
5.0
.0
T=
60
14
12
600
7.0
10
9.0
12.0
8
6
.0
−
400
0.6
75
0.4
θ=
.0
24
700
16.0
4
20.0
θ=
2
28.0
−
15
.0
.0
45
800
900
T=
0.002
dew_point = os.path.join(tephi.DATA_DIR, 'dews.txt')
38
dew_data = tephi.loadtxt(dew_point, column_titles=('pressure', 'dewpoint'))
dews = zip(dew_data.pressure, dew_data.dewpoint)
tpg = tephi.Tephigram()
36
tpg.plot(dews, label='Dew-point temperature', color='blue', linewidth=2, linestyle='--', marker='s')
plt.show()
200
34
36.0
44.0
52.0
60.0
80.0
1000
θ=
.0
15
0. 0
.0
30
θ=
θ=
14
Chapter 1. User guide table of contents
tephi Documentation, Release 0.1.0
Tephigram axis ticks
By default the isotherm and dry adiabat axis ticks are automatically located and scaled based on the tephigram plot
and zoom level, which may be changed interactively.
However, fixed axis tick locations can easily be configured for either axis if required.
import matplotlib.pyplot as plt
import os.path
import tephi
dew_point = os.path.join(tephi.DATA_DIR, 'dews.txt')
dew_data = tephi.loadtxt(dew_point, column_titles=('pressure', 'dewpoint'))
dews = zip(dew_data.pressure, dew_data.dewpoint)
tpg = tephi.Tephigram(isotherm_locator=tephi.Locator(10), dry_adiabat_locator=tephi.Locator(20))
tpg.plot(dews)
plt.show()
1.2. Tephigram plotting
15
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200
0.002
34
32
0.01
30
57
θ=
.0
0.03
.0
T=
28
88
−
300
0.1
26
0.2
T=
−
47
.0
24
0.4
400
0.6
22
.0
37
−
.0
T=
68
18
2.0500
16
3.0
14
12
5.0
600
27
.0
10
−
θ=
20
1.0
7.0
9.0
12.0
T=
8
700
16.0
20.0
.0
2
28.0
T=
−
17
.0
800
900
36.0
44.0
52.0
60.0
80.0
1000
T=
−
7. 0
48
4
θ=
6
θ=
θ=
.0
28
8. 0
The above may also be achieved without using a tephi.Locator:
tpg = tephi.Tephigram(isotherm_locator=10, dry_adiabat_locator=20)
Anchoring a plot
By default, the tephigram will automatically center the plot around all temperature profiles. This behaviour may not
be desirable when comparing separate tephigram plots against one another.
To fix the extent of a plot, simply specify an anchor point to the tephigram.
import matplotlib.pyplot as plt
import os.path
16
Chapter 1. User guide table of contents
tephi Documentation, Release 0.1.0
import tephi
dew_point = os.path.join(tephi.DATA_DIR, 'dews.txt')
dew_data = tephi.loadtxt(dew_point, column_titles=('pressure', 'dewpoint'))
dews = zip(dew_data.pressure, 200
dew_data.dewpoint)
tpg = tephi.Tephigram(anchor=[(1000, 0), (300, 0)])
tpg.plot(dews)
plt.show()
0.01
42
40
38
0.03
36
0.1
300
34
0.2
45
−
5. 0
T=
10
.0
θ=
32
0.4
0.6
30
400
1.0
28
θ=
2.0
.0
30
T=
−
5.0
.0
500
90
26
3.0
24
7.0
22 9.0
20
600
12.0
.0
15
−
.0
28.0
700
36.0
14
44.0
12
T=
20.0
75
16
θ=
16.0
18
800
10
52.0
60.0
80.0
θ=
8
60
6
.0
900
4
θ=
θ=
.0
45
.0
30
.0
15
0. 0
T=
1000
θ=
θ=
0. 0
2
Tephigram customisation
This section discusses how finer control of the tephigram isobars, saturated adiabats and humidity mixing ratio lines
and text can be achieved.
1.3. Tephigram customisation
17
tephi Documentation, Release 0.1.0
Isobar control
Isobar lines
The default behaviour of the tephigram isobar line is controlled by the tephi.ISOBAR_LINE dictionary:
>>> print tephi.ISOBAR_LINE
{'color': 'blue', 'linewidth': 0.5, 'clip_on': True}
This is a dictionary of key and value pairs that are passed through as keyword arguments to
matplotlib.pyplot.plot().
Updating the ISOBAR_LINE dictionary will subsequently change the default behaviour of how the tephigram isobar
lines are plotted.
import matplotlib.pyplot as plt
import os.path
import tephi
dew_point = os.path.join(tephi.DATA_DIR, 'dews.txt')
dew_data = tephi.loadtxt(dew_point, column_titles=('pressure', 'dewpoint'))
dews = zip(dew_data.pressure, dew_data.dewpoint)
tephi.ISOBAR_LINE.update({'color': 'purple', 'linewidth': 3, 'linestyle': '--'})
tpg = tephi.Tephigram()
tpg.plot(dews)
plt.show()
18
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200
0.002
36
34
32
.0
0.01
−
60
30
.0
90
T=
θ=
0.03
300
28
0.1
26
0.2
45
T=
22
20
1.0
2.0500
18
16
3.0
θ=
.0
30
−
5.0
600
.0
T=
60
14
12
7.0
10
9.0
12.0
8
6
.0
−
400
0.6
75
0.4
θ=
.0
24
700
16.0
4
θ=
2
20.0
28.0
36.0
−
15
.0
.0
45
800
T=
900
44.0
52.0
60.0
80.0
1000
θ=
.0
15
0. 0
.0
30
θ=
θ=
Isobar text
Similarly, the default behaviour of the tephigram isobar text is controlled by the tephi.ISOBAR_TEXT dictionary:
>>> print tephi.ISOBAR_TEXT
{'color': 'blue', 'va': 'bottom', 'ha': 'right', 'clip_on': True, 'size': 8}
This is a dictionary of key and value pairs that are passed through as keyword arguments to
matplotlib.pyplot.text().
Updating the ISOBAR_TEXT dictionary will change the default behaviour of how the tephigram isobar text is plotted.
import matplotlib.pyplot as plt
import os.path
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import tephi
dew_point = os.path.join(tephi.DATA_DIR, 'dews.txt')
dew_data = tephi.loadtxt(dew_point, column_titles=('pressure', 'dewpoint'))
dews = zip(dew_data.pressure, dew_data.dewpoint)
tephi.ISOBAR_TEXT.update({'color': 'purple', 'size': 12})
tpg = tephi.Tephigram()
tpg.plot(dews)
plt.show()
38
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28
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T=
22
20
1.0
500
2.0
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16
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.0
30
−
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.0
T=
60
600
θ=
14
12
7.0
10
8
6
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12.0
700
16.0
4
20.0
θ=
2
.0
−
400
0.6
75
0.4
θ=
.0
24
28.0
−
15
.0
.0
45
800
T=
900
36.0
44.0
52.0
60.0
80.0
1000
θ=
.0
15
0. 0
.0
30
θ=
θ=
Isobar frequency
The frequency at which isobar lines are plotted on the tephigram is controlled by the tephi.ISOBAR_SPEC list:
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>>> print tephi.ISOBAR_SPEC
[(25, 0.03), (50, 0.1), (100, 0.25), (200, 1.5)]
This line specification is a sequence of one or more tuple pairs that contain an isobar pressure line step and a zoom
level.
For example, (25, 0.03) states that all isobar lines that are a multiple of 25 mb will be plotted i.e. visible, when
the zoom level is at or below 0.03.
The overall range of isobar pressure levels that may be plotted is controlled by the tephi.MIN_PRESSURE and
tephi.MAX_PRESSURE variables:
>>> print tephi.MIN_PRESSURE
50
>>> print tephi.MAX_PRESSURE
1000
Note that, it is possible to set a fixed isobar pressure line step for a tephigram plot by setting the associated zoom level
to None. This is opposed to relying on the plot zoom level of the tephigram to control line visibility.
For example, to always show isobar lines that are a multiple of 50 mb, irrespective of the zoom level,
import matplotlib.pyplot as plt
import os.path
import tephi
dew_point = os.path.join(tephi.DATA_DIR, 'dews.txt')
dew_data = tephi.loadtxt(dew_point, column_titles=('pressure', 'dewpoint'))
dews = zip(dew_data.pressure, dew_data.dewpoint)
tephi.ISOBAR_SPEC = [(50, None)]
tpg = tephi.Tephigram()
tpg.plot(dews)
plt.show()
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30
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300
28
0.1
26
350
0.2
45
T=
22
18
2.0500
.0
30
−
T=
6
5.0
.0
10
60
12
θ=
16
3.0
14550
8
20
450
1.0
600
7.0
9.0
650
12.0
700
4
16.0
28.0
.0
45
800
.0
20.0
θ=
750
2
.0
−
400
0.6
75
0.4
θ=
.0
24
−
15
850
T=
900
36.0
44.0
52.0
60.0
80.0
950
1000
θ=
.0
15
0. 0
.0
30
θ=
θ=
It is also possible to control which individual isobar lines should be fixed via the tephi.ISOBAR_FIXED list:
>>> print tephi.ISOBAR_FIXED
[50, 1000]
By default, the isobar lines at 50 mb and 1000 mb will always be plotted.
Isobar line extent
The extent of each tephigram isobar line is controlled by the tephi.MIN_THETA and tephi.MAX_THETA variables:
>>> print tephi.MIN_THETA
0
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>>> print tephi.MAX_THETA
250
For example, to change the isobar line extent behaviour to be between 15 o C and 60 o C,
import matplotlib.pyplot as plt
import os.path
import tephi
dew_point = os.path.join(tephi.DATA_DIR, 'dews.txt')
dew_data = tephi.loadtxt(dew_point, column_titles=('pressure', 'dewpoint'))
dews = zip(dew_data.pressure, dew_data.dewpoint)
tephi.MIN_THETA = 15
tephi.MAX_THETA = 60
tpg = tephi.Tephigram()
tpg.plot(dews)
plt.show()
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θ=
0.03
300
28
0.1
26
0.2
45
T=
22
20
1.0
2.0 500
18
16
3.0
θ=
.0
30
−
5.0
.0
T=
60
14
12
600
7.0
10
9.0
12.0
8
6
.0
−
400
0.6
75
0.4
θ=
.0
24
700
16.0
4
θ=
2
20.0
28.0
−
15
.0
.0
45
800
T=
900
36.0
44.0
52.0
60.0
80.0
1000
θ=
.0
15
0. 0
.0
30
θ=
θ=
Saturated adiabat control
Saturated adiabat lines
The default behaviour of the tephigram pseudo saturated wet adiabat line is controlled by the
tephi.WET_ADIABAT_LINE dictionary:
>>> print .WET_ADIABAT_LINE
{'color': 'orange', 'linewidth': 0.5, 'clip_on': True}
This is a dictionary of key and value pairs that are passed through as keyword arguments to
matplotlib.pyplot.plot().
Updating the WET_ADIABAT_LINE dictionary will change the default behaviour of all saturated adiabat line plotting.
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import matplotlib.pyplot
as plt
import os.path
import tephi
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22
20
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2.0500
18
16
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θ=
.0
30
−
5.0
600
.0
T=
60
14
12
7.0
10
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6
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75
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.0
24
700
16.0
4
20.0
θ=
2
28.0
−
15
.0
.0
45
800
900
T=
0.002
dew_point = os.path.join(tephi.DATA_DIR, 'dews.txt')
dew_data = tephi.loadtxt(dew_point, column_titles=('pressure', 'dewpoint'))
dews = zip(dew_data.pressure, dew_data.dewpoint)
tephi.WET_ADIABAT_LINE.update({'color': 'purple', 'linewidth': 3, 'linestyle': '--'})
tpg = tephi.Tephigram()
tpg.plot(dews)
plt.show()
200
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52.0
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θ=
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0. 0
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Saturated adiabat text
The default behavour of the tephigram saturated adiabat text is controlled by the tephi.WET_ADIABAT_TEXT
dictionary:
>>> print .WET_ADIABAT_TEXT
{'color': 'orange', 'va': 'bottom', 'ha': 'left', 'clip_on': True, 'size': 8}
This is a dictionary of key and value pairs that are passed through as keyword arguments to
matplotlib.pyplot.text().
Updating the WET_ADIABAT_TEXT dictionary will change the default behaviour of how the text of associated saturated adiabat lines are plotted.
import matplotlib.pyplot as plt
import os.path
import tephi
dew_point = os.path.join(tephi.DATA_DIR, 'dews.txt')
dew_data = tephi.loadtxt(dew_point, column_titles=('pressure', 'dewpoint'))
dews = zip(dew_data.pressure, dew_data.dewpoint)
tephi.WET_ADIABAT_TEXT.update({'color': 'purple', 'size': 12})
tpg = tephi.Tephigram()
tpg.plot(dews)
plt.show()
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300
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45
400
T=
0.6
22
20
1.0
18
30
−
T=
5.0
600
.0
14
60
7.0
9.0
12.0
700
16.0
20.0
θ=
28.0
.0
45
800
−
15
.0
2
4
6
10
12
16
3.0
θ=
.0
2.0500
8
.0
0.4
75
−
24
θ=
.0
0.2
T=
900
36.0
44.0
52.0
60.0
80.0
1000
θ=
.0
15
0. 0
.0
30
θ=
θ=
Saturated adiabat line frequency
The frequency at which saturated adiabat lines are plotted on the tephigram is controlled by the
tephi.WET_ADIABAT_SPEC list:
>>> print .WET_ADIABAT_SPEC
[(1, 0.05), (2, 0.15), (4, 1.5)]
This line specification is a sequence of one or more tuple pairs that contain a saturated adiabat temperature line step
and a zoom level.
For example, (2, 0.15) states that all saturated adiabat lines that are a multiple of 2 o C will be plotted i.e. visible,
when the zoom level is at or below 0.15.
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The overall range of saturated adiabat levels that may be plotted is controlled by the tephi.MIN_WET_ADIABAT
and tephi.MAX_WET_ADIABAT variables:
>>> print tephi.MIN_WET_ADIABAT
1
>>> print tephi.MAX_WET_ADIABAT
60
Note that, it is possible to set a fixed saturated adiabat temperature line step for a tephigram plot by setting the
associated zoom level to None.
For example, to always show saturated adiabat lines that are a multiple of 5 o C, irrespective of the zoom level,
import matplotlib.pyplot as plt
import os.path
import tephi
dew_point = os.path.join(tephi.DATA_DIR, 'dews.txt')
dew_data = tephi.loadtxt(dew_point, column_titles=('pressure', 'dewpoint'))
dews = zip(dew_data.pressure, dew_data.dewpoint)
tephi.WET_ADIABAT_SPEC = [(5, None)]
tpg = tephi.Tephigram()
tpg.plot(dews)
plt.show()
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.0
0.01
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60
30
.0
90
T=
θ=
0.03
300
0.1
45
T=
400
0.6
.0
0.4
75
−
25
θ=
.0
0.2
20
1.0
2.0500
θ=
153.0
60
.0
30
−
T=
.0
5.0
600
7.0
10
9.0
12.0
700
5
16.0
20.0
θ=
28.0
36.0
−
15
.0
.0
45
800
T=
900
44.0
52.0
60.0
80.0
1000
θ=
.0
15
0. 0
.0
30
θ=
θ=
It is also possible to control which individual saturated adiabat lines should be fixed via the
tephi.WET_ADIABAT_FIXED variable:
>>> print tephi.WET_ADIABAT_FIXED
None
By default, no saturated adiabat lines are fixed. To force saturated adiabat lines with a temperature of 15 o C and 17
C always to be plotted,
o
import matplotlib.pyplot as plt
import os.path
import tephi
dew_point = os.path.join(tephi.DATA_DIR, 'dews.txt')
dew_data = tephi.loadtxt(dew_point, column_titles=('pressure', 'dewpoint'))
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θ=
0.03
300
28
0.1
26
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45
T=
22
20
1.0
2.0500
30
−
5.0
.0
12
18
60
.0
16
153.0
17
θ=
14
T=
.0
−
400
0.6
75
0.4
θ=
.0
24
600
7.0
10
9.0
12.0
8
6
700
16.0
4
20.0
θ=
2
28.0
36.0
44.0
−
15
.0
.0
45
800
900
T=
0.002
dews = zip(dew_data.pressure, dew_data.dewpoint)
tephi.WET_ADIABAT_FIXED = [15, 17]
tpg = tephi.Tephigram()
tpg.plot(dews)
plt.show()
200
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60.0
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θ=
.0
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θ=
θ=
Humidity mixing ratio control
Humidity mixing ratio lines
The default behaviour of the tephigram
tephi.MIXING_RATIO_LINE dictionary:
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mixing
ratio
line
is
controlled
by
the
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>>> print tephi.MIXING_RATIO_LINE
{'color': 'green', 'linewidth': 0.5, 'clip_on': True}
This is a dictionary of key and value pairs that are passed through as keyword arguments to
matplotlib.pyplot.plot().
Updating the MIXING_RATIO_LINE dictionary will change the default behaviour of all humidity mixing ratio line
plotting.
import matplotlib.pyplot as plt
import os.path
import tephi
dew_point = os.path.join(tephi.DATA_DIR, 'dews.txt')
dew_data = tephi.loadtxt(dew_point, column_titles=('pressure', 'dewpoint'))
dews = zip(dew_data.pressure, dew_data.dewpoint)
tephi.MIXING_RATIO_LINE.update({'color': 'purple', 'linewidth': 3, 'linestyle': '--'})
tpg = tephi.Tephigram()
tpg.plot(dews)
plt.show()
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28
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T=
22
20
1.0
2.0500
18
16
3.0
θ=
.0
30
5.0
.0
−
60
14
12
T=
.0
−
400
0.6
75
0.4
θ=
.0
24
600
7.0
10
9.0
12.0
8
6
700
16.0
4
θ=
2
20.0
28.0
36.0
44.0
−
15
.0
.0
45
800
T=
900
52.0
60.0
80.0
1000
θ=
.0
15
0. 0
.0
30
θ=
θ=
Humidity mixing ratio text
The default behaviour of the tephigram
tephi.MIXING_RATIO_TEXT dictionary:
humidity
mixing
ratio
text
is
controlled
by
the
>>> print tephi.MIXING_RATIO_TEXT
{'color': 'green', 'va': 'bottom', 'ha': 'right', 'clip_on': True, 'size': 8}
This is a dictionary of key and value pairs that are passed through as keyword arguments to
matplotlib.pyplot.text().
Updating the MIXING_RATIO_TEXT dictionary will change the default behaviour of how the text of associated
humidity mixing ratio lines are plotted.
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import matplotlib.pyplot
as plt
import os.path
import tephi
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.0
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60
30
.0
90
T=
θ=
0.03
300
28
0.1
26
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T=
400
0.6
22
1.0
20
2.0500
18
.0
30
−
T=
5.0
10
.0
600
60
14
θ=
3.016
12
7.0
8
6
.0
0.4
75
−
24
θ=
.0
0.2
700
4
9.0
12.0
16.020.0
28.0
θ=
2
−
15
.0
.0
45
800
900
T=
0.002
dew_point = os.path.join(tephi.DATA_DIR, 'dews.txt')
dew_data = tephi.loadtxt(dew_point, column_titles=('pressure', 'dewpoint'))
dews = zip(dew_data.pressure, dew_data.dewpoint)
tephi.MIXING_RATIO_TEXT.update({'color': 'purple', 'size': 12})
tpg = tephi.Tephigram()
tpg.plot(dews)
plt.show()
200
36.0
44.0
52.060.0
80.0
1000
θ=
.0
15
0. 0
.0
30
θ=
θ=
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Humidity mixing ratio line frequency
The frequency at which humidity mixing ratio lines are plotted on the tephigram is controlled by the
tephi.MIXING_RATIO_SPEC list:
>>> print tephi.MIXING_RATIO_SPEC
[(1, 0.05), (2, 0.18), (4, 0.3), (8, 1.5)]
This line specification is a sequence of one or more tuple pairs that contain a humidity mixing ratio line step and a
zoom level.
For example, (4, 0.3) states that every fourth humidity mixing ratio line will be plotted i.e. visible, when the zoom
level is at or below 0.3.
The overall range of humidity mixing ratio levels that may be plotted is controlled by the tephi.MIXING_RATIOS
list:
>>> print tephi.MIXING_RATIOS
[0.001, 0.002, 0.005, 0.01, 0.02, 0.03, 0.05, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8, 1.0, 1.5, 2.0,
Note that, it is possible to control which individual humidity mixing ratio lines should be fixed i.e. always visible, via
the tephi.MIXING_RATIO_FIXED variable:
>>> print tephi.MIXING_RATIO_FIXED
None
By default, no humidity mixing ratio lines are fixed. To force humidity mixing ratio lines 4.0 g kg-1 and 6.0 g
kg-1 always to be plotted independent of the zoom level,
import matplotlib.pyplot as plt
import os.path
import tephi
dew_point = os.path.join(tephi.DATA_DIR, 'dews.txt')
dew_data = tephi.loadtxt(dew_point, column_titles=('pressure', 'dewpoint'))
dews = zip(dew_data.pressure, dew_data.dewpoint)
tephi.MIXING_RATIO_FIXED = [4.0, 6.0]
tpg = tephi.Tephigram()
tpg.plot(dews)
plt.show()
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0.002
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34
32
.0
0.01
−
60
30
.0
90
T=
θ=
0.03
300
28
0.1
26
0.2
45
T=
22
20
1.0
2.0500
18
16
3.0
.0
30
−
10
.0
5.0
600
60
T=
θ=
4.0
14
12
6.0
7.0
9.0
12.0
8
6
.0
−
400
0.6
75
0.4
θ=
.0
24
700
16.0
4
θ=
2
20.0
28.0
−
15
.0
.0
45
800
T=
900
36.0
44.0
52.0
60.0
80.0
1000
θ=
.0
15
0. 0
.0
30
θ=
θ=
Tephigram barbs
This section discusses how wind barbs may be plotted on a tephigram.
Wind barbs
Tephigram plots may be decorated with barbs to indicate wind speed and wind direction at specific pressure levels.
The following barb symbology has been adopted, as defined and used by the Met Office since 1 January 1955. See
Met Office National Meteorological Library and Archive, Fact Sheet No. 11 - Interpreting weather charts.
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Calm
1-2 knots
3-7 knots
8-12 knots
13-17 knots
18-22 knots
23-27 knots
28-32 knots
33-37 knots
38-42 knots
43-47 knots
48-52 knots
53-57 knots
58-62 knots
63-67 knots
68-72 knots
73-77 knots
78-82 knots
83-87 knots
88-92 knots
93-97 knots
98-102 knots
Wind direction is indicated by the orientation of the barb on the plot, where north is 0o , east is 90o , south is 180o and
west is 270o .
Plotting barbs
A profile must be first plotted before the barbs are associated with that profile.
import matplotlib.pyplot as plt
import os.path
import tephi
dew_point = os.path.join(tephi.DATA_DIR, 'dews.txt')
dew_data = tephi.loadtxt(dew_point, column_titles=('pressure', 'dewpoint'))
dews = zip(dew_data.pressure, dew_data.dewpoint)
tpg = tephi.Tephigram()
profile = tpg.plot(dews)
barbs = [(0, 0, 900), (1, 30, 850), (5, 60, 800),
(10, 90, 750), (15, 120, 700), (20, 150, 650),
(25, 180, 600), (30, 210, 550), (35, 240, 500),
(40, 270, 450), (45, 300, 400), (50, 330, 350),
(55, 360, 300)]
profile.barbs(barbs)
plt.show()
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.0
0.01
−
60
30
.0
90
T=
θ=
0.03
300
28
0.1
26
0.2
45
T=
22
20
1.0
2.0500
18
16
3.0
θ=
.0
30
−
5.0
600
.0
T=
60
14
12
7.0
10
9.0
12.0
8
6
.0
−
400
0.6
75
0.4
θ=
.0
24
700
16.0
4
θ=
2
20.0
28.0
−
15
.0
.0
45
800
T=
900
36.0
44.0
52.0
60.0
80.0
1000
θ=
.0
15
0. 0
.0
30
θ=
θ=
A single barb is specified using a triple denoting the wind speed, wind direction and pressure level. For example, the
following triple (10, 90, 750) represents a wind speed of 10 knots, directly from the east, and at an atmospheric
pressure of 750 mb.
Note that, the barbs default to the same colour as their associated profile.
import matplotlib.pyplot as plt
import os.path
import tephi
dew_point = os.path.join(tephi.DATA_DIR, 'dews.txt')
dry_bulb = os.path.join(tephi.DATA_DIR, 'temps.txt')
column_titles = [('pressure', 'dewpoint'), ('pressure', 'temperature')]
dew_data, temp_data = tephi.loadtxt(dew_point, dry_bulb, column_titles=column_titles)
dews = zip(dew_data.pressure, dew_data.dewpoint)
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temps = zip(temp_data.pressure, temp_data.temperature)
tpg = tephi.Tephigram()
dprofile = tpg.plot(dews)
dbarbs = [(0, 0, 900), (15, 120, 600), (35, 240, 300)]
dprofile.barbs(dbarbs)
tprofile = tpg.plot(temps)
tbarbs = [(10, 15, 900), (21, 45, 600), (25, 135, 300)]
tprofile.barbs(tbarbs)
plt.show()
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Barbs may also be plotted using wind speed and wind direction data (associated with a pressure level) in a text file.
import matplotlib.pyplot as plt
import os.path
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import tephi
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winds = os.path.join(tephi.DATA_DIR, 'barbs.txt')
column_titles = ('pressure', 'dewpoint', 'wind_speed', 'wind_direction')
barb_data = tephi.loadtxt(winds, column_titles=column_titles)
dews = zip(barb_data.pressure, barb_data.dewpoint)
barbs = zip(barb_data.wind_speed, barb_data.wind_direction, barb_data.pressure)
tpg = tephi.Tephigram()
profile = tpg.plot(dews)
profile.barbs(barbs)
plt.show()
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Controlling the barbs
All keyword arguments passed to tephi.isopleths.Profile.barbs() are simply passed through to
matplotlib.pyplot.barbs().
This transparency allows full control when plotting barbs on the tephigram.
import matplotlib.pyplot as plt
import os.path
import tephi
dew_point = os.path.join(tephi.DATA_DIR, 'dews.txt')
dew_data = tephi.loadtxt(dew_point, column_titles=('pressure', 'dewpoint'))
dews = zip(dew_data.pressure, dew_data.dewpoint)
tpg = tephi.Tephigram()
profile = tpg.plot(dews)
barbs = [(0, 0, 900), (1, 30, 850), (5, 60, 800),
(10, 90, 750), (15, 120, 700), (20, 150, 650),
(25, 180, 600), (30, 210, 550), (35, 240, 500),
(40, 270, 450), (45, 300, 400), (50, 330, 350),
(55, 360, 300)]
profile.barbs(barbs, length=8, pivot='middle', color='green', linewidth=3)
plt.show()
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Moving the gutter
By default, the barbs are plotted on the right hand side of the tephigram. The position of the barb gutter can easily be
controlled via the gutter keyword argument to tephi.isopleths.Profile.barbs().
import matplotlib.pyplot as plt
import os.path
import tephi
dew_point = os.path.join(tephi.DATA_DIR, 'dews.txt')
dew_data = tephi.loadtxt(dew_point, column_titles=('pressure', 'dewpoint'))
dews = zip(dew_data.pressure, dew_data.dewpoint)
tpg = tephi.Tephigram()
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profile = tpg.plot(dews)
barbs = [(0, 0, 900), (1, 30, 850), (5, 60, 800),
(10, 90, 750), (15, 120, 700), (20, 150, 650),
(25, 180, 600), (30, 210, 550), (35, 240, 500),
(40, 270, 450), (45, 300, 400), (50, 330, 350),
(55, 360, 300)]
profile.barbs(barbs, gutter=0.9)
plt.show()
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The gutter keyword argument represents the proportion of the plot width that the barb gutter is offset from the right
hand side axis. By default the gutter is set to 0.1.
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Glossary
Anchor A sequence of two (pressure, temperature) pairs that specify the bottom left-hand corner and the top righthand corner of the plot. The pressure data points must be in units of mb or hPa, and the temperature data points
must be in units of o C.
Dry adiabat A line of constant potential temperature, measured in units of o C. The zeroth dry adiabat line is an axis
of the tephigram, see Dry adiabats.
Humidity mixing ratio A line of constant saturation mixing ratio with respect to a plane water surface, measured in
g kg-1 , see Humidity mixing ratio.
Isobar A line of constant pressure, measured in millibars or hectopascals, see Isobars.
Isotherm A line of constant temperature, measured in o C. The zeroth isotherm line is an axis of the tephigram, see
Isotherms.
Line specification A sequence of one or more tuple pairs containing a line step value and a zoom level value. Used
to control the frequency at which the tephigram plots isobar lines, humidity mixing ratio lines, and saturated
adiabat lines. Note that, specifying a zoom level of None forces the associated lines always to be visible.
Line step The first value in the tuple pair of a line specification. An integer that denotes Nth step multiples. i.e. a line
step of 25 denotes all lines that are a multiple of 25, or every 25th item from an enumerated list of values.
Pseudo saturated wet adiabat A line of constant equivalent potential temperature for saturated air parcels, measured
in units of o C, see Pseudo saturated wet adiabats.
Saturated adiabat See pseudo saturated wet adiabat.
Zoom level An inverted zoom level fraction that is a ratio of current tephigram plot display width over the original
plot display width.
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Index
A
Anchor, 43
D
Dry adiabat, 43
H
Humidity mixing ratio, 43
I
Isobar, 43
Isotherm, 43
L
Line specification, 43
Line step, 43
P
Pseudo saturated wet adiabat, 43
S
Saturated adiabat, 43
Z
Zoom level, 43
45