physics

Norwegian cyclone model

Norwegian cyclone model 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 Norwegian cyclone model rather than just read about it. In short: The older of the models of extratropical cyclone development is known as the Norwegian cyclone model, developed during and shortly after World War I within the Bergen School of Meteorology. In this theory, cyclones develop as they move up and along a frontal boundary, eventually occluding and reaching a barotropically cold environment.

Key takeaways

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

Reference excerpt

The older of the models of extratropical cyclone development is known as the Norwegian cyclone model, developed during and shortly after World War I within the Bergen School of Meteorology. In this theory, cyclones develop as they move up and along a frontal boundary, eventually occluding and reaching a barotropically cold environment. It was developed completely from surface-based weather observations, including descriptions of clouds found near frontal boundaries. Developed from this model was the concept of the warm conveyor belt, which transports warm and moist air just ahead of the cold front above the surface warm front.

Development of the theory Polar front theory is attributed to Jacob Bjerknes, derived from a coastal network of observation sites in Norway during World War I. This theory proposed that the main inflow into a cyclone was concentrated along two lines of convergence, one ahead of the low and another trailing behind the low. The convergence line ahead of the low became known as either the steering line or the warm front. The trailing convergence zone was referred to as the squall line or cold front. Areas of clouds and rainfall appeared to be focused along these convergence zones. The concept of frontal zones led to the concept of air masses. The nature of the three-dimensional structure of the cyclone would wait for the development of the upper air network during the 1940s.

Evolution

A wave along a frontal boundary, in the form of a broad area of low pressure, develops as an upper level disturbance moves towards that portion of the boundary. Precipitation will begin to form ahead of the surface low, within the cold sector of the cyclone poleward of the warm front. As the low deepens, both the cold and warm fronts around the low become better defined. As the low matures, it couples with the upper level disturbance moving into the cyclone's cold sector. The cold front catches up to the westward portion of the warm front, forming an occluded front. Eventually, the cyclone stacks with the upper level disturbance, becoming isolated within the cold sector, and begins to weaken as it becomes far removed from the original temperature discontinuity along the cold and warm fronts. At this point, it becomes a cold-core low. The frontal boundary becomes weaker and surrounds the equatorward portion of the cyclone, waiting for the next upper level disturbance to form a new low pressure area.

Conveyor belt

A conveyor belt, also referred to as the warm conveyor belt, describes the flow of a stream of warm moist air originating within the warm sector of an extratropical cyclone ahead of the cold front which slopes up above and north of the surface warm front. The idea of the conveyor belt originated in 1969. The left edge of the conveyor belt is sharp due to the higher density air moving in from the west forcing a sharp slope to the cold front. An area of stratiform precipitation develops north of the warm front along the conveyor belt. Active precipitation north of the warm front implies potential for greater development of the cyclone. A portion of this conveyor belt turns to the right (left in the Southern Hemisphere), aligning with the upper level westerly flow. However, the western portion of this belt wraps around the northwest (southwest in the Southern Hemisphere) side of the cyclone, which can contain moderate to heavy precipitation. If the air mass is cold enough, the precipitation falls in the form of heavy snow. Theory from the 1980s talked about the presence of a cold conveyor belt which originates north of the warm front and flows along a clockwise path (in the northern hemisphere) into the main belt of the westerlies aloft, but there has been conflicting evidence as to whether or not it actually exists.

Illustrations

Worked examples

Example 1 — a first encounter with Norwegian cyclone model

Start with the simplest possible case. Write down what Norwegian cyclone model 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 Norwegian cyclone model 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 Norwegian cyclone model 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 Norwegian cyclone model

In research: Norwegian cyclone model 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 Norwegian cyclone model 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: Norwegian cyclone model is common in secondary-school and first-year university syllabi. It links to neighbouring topics Extratropical cyclones, Synoptic meteorology and weather, so understanding it makes those chapters shorter.
In everyday life: Look for Norwegian cyclone model 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.

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How to study Norwegian cyclone model in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Norwegian cyclone model means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Norwegian cyclone model out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Norwegian cyclone model in simple terms?

Why does Norwegian cyclone model 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 Norwegian cyclone model?

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 Norwegian cyclone model.