ArticleslgStudy

physics

Skew-T log-P diagram

Skew-T log-P diagram is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Skew-T log-P diagram rather than just read about it. In short: A skew-T log-P diagram is one of four thermodynamic diagrams commonly used in weather analysis and forecasting. In 1947, Nicolai Herlofson proposed a modification to the emagram that allows straight, horizontal isobars and provides for a large angle between isotherms and dry adiabats, similar to that in the tephigram.

Skew-T log-P diagram — main illustration
Skew-T log-P diagram — illustration

Key takeaways

  • Skew-T log-P diagram belongs to physics; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Skew-T log-P diagram to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Skew-T log-P diagram from memory before moving on to harder problems.

Reference excerpt

A skew-T log-P diagram is one of four thermodynamic diagrams commonly used in weather analysis and forecasting. In 1947, Nicolai Herlofson proposed a modification to the emagram that allows straight, horizontal isobars and provides for a large angle between isotherms and dry adiabats, similar to that in the tephigram. This made the diagram useful for analysis techniques that were then being adopted by the United States Air Force. Such a diagram has pressure plotted on the vertical axis, with a logarithmic scale (thus the "log-P" part of the name), and the temperature plotted skewed, with isothermal lines at 45° to the plot (thus the "skew-T" part of the name). Plotting a hypothetical set of measurements with constant temperature for all altitudes would result in a line angled 45° to the right. In practice, since temperature usually drops with altitude, the graphs are usually mostly vertical (see examples linked to below). The major use for skew-T log-P diagrams is the plotting of radiosonde soundings, which give a vertical profile of the temperature and dew point temperature throughout the troposphere and lower stratosphere. The isopleths on the diagram can then be used to simplify many tedious calculations involved, which were previously performed by hand or not at all. Many skew-T log-P diagrams also include a vertical representation of the wind speed and direction using wind barbs. Important atmospheric characteristics such as saturation, atmospheric instability, and wind shear are critical in severe weather forecasting, by which skew-T log-P diagrams allow quick visual analysis. The diagrams are widely used by glider pilots to forecast the strength of thermals and the height of the base of the associated cumulus clouds.

See also

Thermodynamic diagrams Tephigram Emagram Stüve diagram Meteogram

Bibliography

Iribarne, J. V.; Godson, W. L. (1981). Atmospheric Thermodynamics (2nd ed.). Dordrecht, the Netherlands: D. Reidel Publishing Company. ISBN 978-90-277-1297-4. Petty, G. W. (2008). A First Course in Atmospheric Thermodynamics. Sundog Publishing. ISBN 978-0-9729033-2-5. Rogers, R. R.; Yau, M. K. (1989). Short Course in Cloud Physics (3rd ed.). Butterworth-Heinemann. ISBN 978-0750632157.

External links Downloadable/printable skew-T log-P diagrams in PDF format NOAA observed sounding archive Printable blank skew-T log-P diagrams in multiple densities on-line course about skew-T NOAA Skew-T log-P page Archived 2021-04-27 at the Wayback Machine

Illustrations

Skew-T log-P diagram: Annotated skew-T log-P diagram. The X-axis number labels are for the diagonal temperature lines in blue, and the Y-axis has pressure in millibars.
Annotated skew-T log-P diagram. The X-axis number labels are for the diagonal temperature lines in blue, and the Y-axis has pressure in millibars.

Worked examples

Example 1 — a first encounter with Skew-T log-P diagram

Start with the simplest possible case. Write down what Skew-T log-P diagram claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Skew-T log-P diagram before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Skew-T log-P diagram ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Skew-T log-P diagram

In research
Skew-T log-P diagram appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Skew-T log-P diagram in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Skew-T log-P diagram is common in secondary-school and first-year university syllabi. It links to neighbouring topics Atmospheric science stubs, Atmospheric thermodynamics, Meteorological diagrams, so understanding it makes those chapters shorter.
In everyday life
Look for Skew-T log-P diagram outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.
Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “Skew-T log-P diagram” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Skew-T log-P diagram in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Skew-T log-P diagram means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Skew-T log-P diagram out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Skew-T log-P diagram in simple terms?

A skew-T log-P diagram is one of four thermodynamic diagrams commonly used in weather analysis and forecasting. In 1947, Nicolai Herlofson proposed a modification to the emagram that allows straight, horizontal isobars and provides for a large angle between isotherms and dry adiabats, similar to th…

Why does Skew-T log-P diagram matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Skew-T log-P diagram?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Skew-T log-P diagram.

Tags

  • Atmospheric science stubs
  • Atmospheric thermodynamics
  • Meteorological diagrams

Keep exploring