All atmospheric synoptic scale systems either thrive or die with the abundance or lack of divergence aloft. You can judge the intensity of of a system by how far it extends into the upper levels and if it has a vertical stack or a tilted stack.

An illustration of upper level divergence would be if you turned your ceiling fan on and had the rotation set for a clockwise rotation or blowing up toward the ceiling. When the air being pulled from the floor below the fan reaches the ceiling, it has no place to go but out. This is a picture of divergence aloft.

When an updraft occur in a weather system, it is either caused by low level convergence, a heated surface causing an updraft or the jet stream could act as an air flow being blown over a tube creating a vacuum.

## Divergence

The divergence of a wind field is a measure of the net removal of mass out of a volume of air above a given point.

### Convergence

The convergence of the wind field is a measure of the rate of the net addition of mass into a volume above a given point. The effect of convergence is to promote surface pressure and height rises.

## Main Components

Direction and speed are the main components of the wind flow patterns that cause divergence and convergence.

### Wind Direction

**Directional Diffluence**is the spreading of wind flow and contours, which results in mass being removed from an area.

Directional Confluenceis coming together of wind flow or contours which results is mass being added to the area.

### Wind Speed

**Speed divergence**is cause by winds rapidly increasing speed downstream on the pressure surface. High wind speeds will pull mass out of an area faster than it can be replaced by the slower wind speeds, thus decreasing the mass.

**Speed Convergence**is caused by winds rapidly decreasing speed downstream. The higher wind speeds push mass into an area faster than it can be removed by the slower wind speeds, thus increasing the mass.

Wind direction and speed will offset each other on constant pressure charts. As contour (or Isobar) spacing increases or decreases, wind speeds will increase or decrease to remain a balance of forces. Therefore, divergence (removal of mass), or convergence (addition of mass) are difficult to evaluate on a constant pressure chart. The vorticity chart is used to determine the vertical motions and if net divergence or convergence is occurring aloft.

## The Effects Of Convergence And Divergence

### The Chimney Effect

If divergence is occurring in the upper troposphere the atmosphere will attempt to compensate by initiating convergence in the lower troposphere, this is called the chimney effect.

### The Damper Effect

If convergence is occurring in the upper troposphere the atmosphere will attempt to compensate by initiating divergence in the lower troposphere, this is called the damper effect. This condition results in downward vertical motion and adiabatic warming, which could represent improving weather with increased stability. If convergence aloft is stronger than divergence at low levels, surface pressure and constant pressure surfaces will rise. If the convergence is weaker than the divergence, surface pressure and constant pressure surfaces will fall despite the downward vertical motions.

### Level Of Non-Divergence

Convergence or divergence aloft results in the opposite effect in the lower troposphere; therefore, there must exist at some level in the atmosphere a level of non-divergence (LND)

The LND is found under average conditions around 600mb and marks the level of transition from convergence to divergence and visa/versa. The height of the LND will be highly variable, based on the atmospheric stability.

Divergence in the upper levels and convergence in the lower levels results in upward vertical motion and adiabatic cooling, which could represent deteriorating weather as stability changes. If the divergence aloft is stronger than the convergence at the lower levels, surface pressure and constant pressure surfaces will fall. If the divergence aloft is weaker than the convergence in the lower levels, then the surface and constant pressure surfaces will rise.

### Horizontal Divergence & Convergence

At lower levels, within the boundary layer, friction disrupts the geostrophic balance of forces and causes winds to cross the isobars toward lower pressures. This is called**boundary layer convergence (BLC)**around surface lows and**boundary layer divergence (BLD)**around surface highs.In the upper levels, the gradient wind relationships produce the divergence and convergence associated with the atmospheric waves. Near the tropopause, strong convergence and divergence patterns are produced by the jet stream maxima.

Above the tropopause, due to changes in height of the tropopause caused by the replacement and displacement of mass, warm and cold pockets are found at 200mb and 300mb levels above areas of strong divergence and convergence.**Warm sinks**are warm pockets of stratospheric air evident to the 200mb chart, and found above strong upper level divergence which causes the height of the tropopause to sink with respect to the 200mb surface.**Cold domes**are cold pockets of tropospheric air evident on the 200mb chart, and found above strong upper level convergence which causes the height of the tropopause to raise with respect to the 200mb surface.

## Effects Of Temperature Advection

### Effect on Height of Constant Pressure Surfaces

The 1000mb surface and sea level pressure are found below the gradient level, while 700mb level lies above the gradient level when the surface is smooth and located near sea level.The 850mb surface may be above or below the gradient level, depending upon the elevation and roughness of the terrain, stability and wind shear. Typically, in the eastern half of the U.S. the 850mb surface is above the gradient level, temperature advection is typically a maximum somewhere between the gradient level and 500mb.

### Cold Air Advection (CAA)

Cold air advection is when wind flow is displacing warm, less dense air with cold, dense air. Therefore it will tend to sink (subsidence), Because the cold air is more dense, surface pressures and the 1000mb height surface will rise. Heights above the level of maximum CAA will fall. Heights and pressures below the level of maximum CAA will rise. The resulting effect is a decrease in thickness. Because the cold air sinks and causes subsidence, the vertical motion is downward.

### Warm Air Advection (WAA)

Warm air advection is when wind flow is replacing cold dense air with warm, less dense air. Because the warm air is less dense, surface pressures and the 1000mb height surface will fall. Heights above the level of maximum WAA will rise. Heights and pressures below the level of maximum WAA will fall. The result is an increase in thickness. Since the air is warm and less dense, the vertical motion is upward.

## Effect of WAA & CAA on Upper Level Ridges & Troughs

**Warm air advection**at the gradient level into a ridge will build it at the upper levels (height rises), while cold air advection into a ridge will weaken it at upper levels (height falls)

**Cold air advection**at the gradient level into a trough will deepen it at the upper levels (height falls), while warm air advection into a trough will fill it at the upper levels (height rises).

### Combined Effects

The vertical motion is estimated by combining the results of the possible combinations of cold air advection, warm air advection at the gradient level, and convergence and divergence above the LND. When forces oppose each other, then the result is indeterminable. Represented by ? below.

Temperature advection can be determined by analyzing thickness charts, such as the 1000mb-500mb or the 1000mb-850mb thickness charts, as well as the 850mb chart (700mb in mountainous regions) for determination of WAA or CAA.

The thermal wind relationship can also be applied to determine the temperature advection through a given layer of the atmosphere when the thickness or 850mb charts are not available.

Garry Ward

Served in the United States Marine Corps as a weather observer and advanced to a weather forecaster. Stationed at the most active air field on the east coast and provided meteorological and oceanographic support to aircraft squadrons traveling around the world.

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## FAQs

### What is convergence and divergence in meteorology? ›

convergence and divergence, in meteorology, **the accumulation or drawing apart of air, as well as the rate at which each takes place**. The terms are usually used to refer specifically to the horizontal inflow (convergence) or outflow (divergence) of air.

### What does divergence mean in weather? ›

Divergence occurs **when a stronger wind moves away from a weaker wind or when air streams move in opposite directions**. When divergence occurs in the upper levels of the atmosphere it leads to rising air.

### What weather does convergence cause? ›

Convergence lines form rows of **showers or thunderstorms** over a more local area. Sea breezes colliding can trigger development of a convergence line. The heavy rain caused in a short period of time can cause severe flooding.

### Does convergence bring good weather? ›

From Figure 3, we can see that **convergence at the upper part of the troposphere together with divergence at the lower level will lead to downward motion of air and bring fine weather**. If the opposite occurs, upward motion of air will be developed, leading to the formation of cloud and even rain.

### What is divergence and convergence? ›

**Divergence generally means two things are moving apart while convergence implies that two forces are moving together**. In the world of economics, finance, and trading, divergence and convergence are terms used to describe the directional relationship of two trends, prices, or indicators.

### How do divergence and convergence contribute to storms? ›

Convergence and divergence **roughly determine where air will be sinking or rising**. Rising air is associated with clouds and precipitation; sinking air is associated with clear, calm conditions and good weather.

### What causes divergence? ›

Divergence is when the price of an asset is moving in the opposite direction of a technical indicator, such as an oscillator, or is moving contrary to other data. Divergence warns that the current price trend may be weakening, and in some cases may lead to the price changing direction.

### What is the divergence definition? ›

Definition of divergence

1a : **a drawing apart (as of lines extending from a common center)** b : difference, disagreement.

### What is meant by the term convergence? ›

Definition of convergence

1 : **the act of converging and especially moving toward union or uniformity** the convergence of the three rivers especially : coordinated movement of the two eyes so that the image of a single point is formed on corresponding retinal areas. 2 : the state or property of being convergent.

### Is high pressure convergent or divergent? ›

Air Flow: Convergence vs. Divergence - YouTube

### How does convergence rainfall occur? ›

They are a form of convective precipitation that occurs **when air rises over land or sea**, unlike cold, warm or occluded fronts (dynamic precipitation) that depend on different air masses colliding. Sometimes showers form less randomly in lines or bands when winds blow from different directions and collide.

### Where are convergence zones? ›

The location of the Inter-Tropical Convergence Zone is usually readily seen as **a line of cumulus clouds in the tropics**. This is the location where northeast winds in the Northern Hemisphere converge with the southeast winds from the Southern Hemisphere.

### What is speed divergence speed convergence? ›

Directional divergence occurs when air streams are flowing apart. divergence in the upper atmosphere should indicate areas of rising air. leads to decreased vorticity. the net inflow of air to a region. speed convergence **occurs when winds are slowing down along the direction of flow**.

### How does convergence form clouds? ›

Large scale convergence lifts a layer of air (sometimes hundreds of kilometers across), the air cooling as it rises. **If the rising air cools to its saturation point, the water vapor will condense out to form cloud droplets**.

### How do you solve convergence and divergence? ›

Convergence and Divergence - Introduction to Series - YouTube

### How do you find convergence and divergence of a series? ›

Strategy to test series

**If a series is a p-series, with terms 1np, we know it converges if p>1 and diverges otherwise**. If a series is a geometric series, with terms arn, we know it converges if |r|<1 and diverges otherwise. In addition, if it converges and the series starts with n=0 we know its value is a1−r.

### Which is better convergence or divergence? ›

In technical analysis, **divergence is given greater preference** as the 'divergence behaviour' may reflect a change in a price trend or sentiment. Convergence is a phenomenon when two components move in the same direction.

### What do divergence and convergence in atmospheric flow do in terms of velocity? ›

**Horizontal divergence gives a decrease in vertical velocity with height.** **Horizontal convergence gives an increase in vertical velocity with height.**

### Does diverging or converging air produce hurricanes? ›

Waves that occur within the dominant easterly winds over the tropical Atlantic cause areas of converging and diverging winds. **The convergence forces air to rise, triggering numerous thunderstorms that can go on to become hurricanes**.

### What is divergent flow? ›

Divergence **measures the change in density of a fluid flowing according to a given vector field**.

### What is an example of divergence? ›

Divergence is defined as separating, changing into something different, or having a difference of opinion. An example of divergence is **when a couple split up and move away from one another**. An example of divergence is when a teenager becomes an adult.

### Why do you think convergence is important? ›

The simple concept of convergence **allows multiple tasks to be performed on a single device, which effectively conserves space and power**. For example, rather than carrying separate devices – like a cell phone, camera and digital organizer – each technology converges on a single device, or smartphone.

### What is convergence in geography? ›

**A BROAD AREA WHERE two tectonic plates are colliding** is a zone of convergence. An area where plates are moving apart is a zone of divergence. Convection in Earth's mantle drives the two motions. Convergence occurs above descending limbs of convective cells, whereas divergence takes place above cells' rising limbs.

### How do you detect divergence? ›

Divergence only exists **if the SLOPE of the line connecting the indicator tops/bottoms DIFFERS from the SLOPE of the line connection price tops/bottoms**. The slope must either be: Ascending (rising) Descending (falling) Flat (flat).

### What is the unit of divergence? ›

The divergence and curl take spatial derivatives of the vector field, so their units are **1/length**. If the velocity vector field has units of m/s, the the curl or divergence of the velocity vector field has units of 1/s.

### What is convergence and its types? ›

Media convergence is an umbrella term that can be defined in the context of technological, industrial, social, textual, and political terms. The three main types of Media Convergence are: **Technological Convergence**. **Economic Convergence**. **Cultural Convergence**.

### Which of the following is an example of convergence? ›

**Concentration of a beam of light using a curved reflector** is an example of convergence of light as the beam of light is focused at a point.

### What is another word for convergence? ›

In this page you can discover 33 synonyms, antonyms, idiomatic expressions, and related words for convergence, like: **confluent, meet, meeting, joining, concentration, concourse, disembogue, connect, coherence, union and merging**.

### When speed divergence occurs in the upper atmosphere? ›

When speed divergence occurs in the upper atmosphere, what effect does it have on cyclogenesis? **It greatly enhances cyclogenesis by increasing convergence on the surface below**.

### What causes upper level convergence? ›

**A strengthening high-pressure system (sea-level pressure increasing with time)** has upper-level convergence in the column that exceeds low-level divergence, resulting in weight gain in the central air columns.

### What is the other name for convergence rainfall? ›

ZIMSEC O Level Geography Notes: Frontal/ Cyclonic/Convergence Rainfall. This is also know as **frontal or cyclonic or depression rainfall**. Cyclonic rainfall occurs in the temperate latitudes and is closely associated with winds called the Westerlies.

### Why do convergent winds form? ›

The Intertropical Convergence Zone (ITCZ) lies in the equatorial trough, a permanent low-pressure feature where **surface trade winds, laden with heat and moisture**, converge to form a zone of increased convection, cloudiness, and precipitation.

### What is Convectional rainfall short answer? ›

Convectional rainfall **occurs when the heated air from the earth's surface rises upwards along with the water vapour and gets condensed when it reaches a higher altitude**. Here the clouds carrying the water vapour are not carried away by the wind and hence, it rains in the same place.

### What is mass convergence? ›

Mass convergence is **found in areas where winds come together**. As winds come together, mass builds up and therefore causes air to rise, creating an updraft. Convergence may occur due to topography or daytime heating, and can be especially strong along fronts and dry lines.

### How does speed divergence lead to storms strengthening? ›

How does speed divergence lead to storms strengthening? **The increased divergence aloft allows for more convergence at the surface, and increases uplift**. A weather front is: A narrow boundary between colliding air masses, usually resulting in stormy weather.

### What is convergence in meteorology? ›

Convergence. **A contraction of a vector field; the opposite of divergence**. Convergence in a horizontal wind field indicates that more air is entering a given area than is leaving at that level.

### What is the divergence definition? ›

Definition of divergence

1a : **a drawing apart (as of lines extending from a common center)** b : difference, disagreement.

### What is convergence of air? ›

Convergence is **an atmospheric condition that exists when there is a horizontal net inflow of air into a region**. When air converges along the earth's surface, it is forced to rise since it cannot go downward.

### What is meant by the term convergence? ›

Definition of convergence

1 : **the act of converging and especially moving toward union or uniformity** the convergence of the three rivers especially : coordinated movement of the two eyes so that the image of a single point is formed on corresponding retinal areas. 2 : the state or property of being convergent.