Equilibrium level

In meteorology, the equilibrium level (EL), or level of neutral buoyancy (LNB), or limit of convection (LOC), is the height at which a rising parcel of air is at the same temperature as its environment.

Meteorology thermodynamic en
Diagram showing an air parcel path when raised along B-C-E compared to the surrounding air mass Temperature (T) and humidity (Tw)

This means that unstable air is now stable when it reaches the equilibrium level and convection stops. This level is often near the tropopause and can be indicated as near where the anvil of a thunderstorm because it is where the thunderstorm updraft is finally cut off, except in the case of overshooting tops where it continues rising to the maximum parcel level (MPL) due to momentum. More precisely, the cumulonimbus will stop rising around a few kilometres prior to reaching the level of neutral buoyancy and on average anvil glaciation occurs at a higher altitude over land than over sea (despite little difference in LNB from land to sea).[1]

See also


  1. ^ Takahashi, Hanii; Z. Luo (2012). "Where is the level of neutral buoyancy for deep convection?". Geophys. Res. Lett. 39 (L15809). Bibcode:2012GeoRL..3915809T. doi:10.1029/2012GL052638.

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Complex multiplier
This article deals with the concept in economics. For the multiplication of complex numbers, see Complex number#Multiplication and division.

The complex multiplier is the multiplier principle in Keynesian economics (formulated by John Maynard Keynes). The simplistic multiplier that is the reciprocal of the marginal propensity to save is a special case used for illustrative purposes only. The multiplier applies to any change in autonomous expenditure, in other words, an externally induced change in consumption, investment, government expenditure or net exports. Each of these operates to increase or reduce the equilibrium level of income in the economy.


The size of the multiplier should take account of all leakages from the circular flow of income and expenditure occurring in all sectors. The complex multiplier can be measured by the following formula:

where MPS= Marginal propensity to save, MRT= Marginal rate of taxation, MPM= marginal propensity to import. MPW = Marginal propensity to withdraw

Convective available potential energy

In meteorology, convective available potential energy (CAPE), is the amount of energy a clump of air (parcel) would have if lifted a certain distance vertically through the atmosphere. CAPE is effectively the positive buoyancy of an air parcel and is an indicator of atmospheric instability, which makes it very valuable in predicting severe weather. It is a form of fluid instability found in thermally stratified atmospheres in which a colder fluid overlies a warmer one. An air mass will rise if it is less dense than the surrounding air (its buoyant force is greater than its weight). This can create vertically developed clouds due to the rising motion, which could lead to thunderstorms. It could also be created by other phenomena, such as a cold front. Even if the air is cooler on the surface, there is still warmer air in the mid-levels, that can rise into the upper-levels. However, if there is not enough water vapor present, there is no ability for condensation, thus storms, clouds, and rain will not form.

Cumulonimbus cloud

Cumulonimbus (from Latin cumulus, "heaped" and nimbus, "rainstorm") is a dense, towering vertical cloud, forming from water vapor carried by powerful upward air currents. If observed during a storm, these clouds may be referred to as thunderheads. Cumulonimbus can form alone, in clusters, or along cold front squall lines. These clouds are capable of producing lightning and other dangerous severe weather, such as tornadoes. Cumulonimbus progress from overdeveloped cumulus congestus clouds and may further develop as part of a supercell. Cumulonimbus is abbreviated Cb.

Excess supply

In economics, an excess supply or economic surplus is a situation in which the quantity of a good or service supplied is more than the quantity demanded, and the price is above the equilibrium level determined by supply and demand. That is, the quantity of the product that producers wish to sell exceeds the quantity that potential buyers are willing to buy at the prevailing price. It is the opposite of an economic shortage (excess demand).

In cultural evolution, agricultural surplus in the Neolithic period is theorized to have produced a greater division of labor, resulting in social stratification and class.

Exchange rate

In finance, an exchange rate is the rate at which one currency will be exchanged for another. It is also regarded as the value of one country’s currency in relation to another currency. For example, an interbank exchange rate of 114 Japanese yen to the United States dollar means that ¥114 will be exchanged for each US$1 or that US$1 will be exchanged for each ¥114. In this case it is said that the price of a dollar in relation to yen is ¥114, or equivalently that the price of a yen in relation to dollars is $1/114.

Exchange rates are determined in the foreign exchange market, which is open to a wide range of different types of buyers and sellers, and where currency trading is continuous: 24 hours a day except weekends, i.e. trading from 20:15 GMT on Sunday until 22:00 GMT Friday. The spot exchange rate refers to the current exchange rate. The forward exchange rate refers to an exchange rate that is quoted and traded today but for delivery and payment on a specific future date.

In the retail currency exchange market, different buying and selling rates will be quoted by money dealers. Most trades are to or from the local currency. The buying rate is the rate at which money dealers will buy foreign currency, and the selling rate is the rate at which they will sell that currency. The quoted rates will incorporate an allowance for a dealer's margin (or profit) in trading, or else the margin may be recovered in the form of a commission or in some other way. Different rates may also be quoted for cash, a documentary form or electronically. The higher rate on documentary transactions has been justified as compensating for the additional time and cost of clearing the document. On the other hand, cash is available for resale immediately, but brings security, storage, and transportation costs, and the cost of tying up capital in a stock of banknotes ( bills )

Free convective layer

In atmospheric sciences, the free convective layer (FCL) is the layer of conditional or potential instability in the troposphere. It is a layer of positive buoyancy (PBE) and is the layer where deep, moist convection (DMC) can occur. On an atmospheric sounding, it is the layer between the level of free convection (LFC) and the equilibrium level (EL). The FCL is important to a variety of convective processes and to severe thunderstorm forecasting.

It is the layer of instability, the "positive area" on thermodynamic diagrams where an ascending air parcel is warmer than its environment. Integrating buoyant energy from the LFC to the EL gives the convective available potential energy (CAPE), an estimate of the maximum energy available to convection. The depth of the FCL is expressed by the formula:


FCL = PEL - PLFCDeep, moist convection is essentially a thunderstorm, it is cumulus congestus clouds or cumulonimbus clouds. An air parcel ascending from the near surface layer (mixed layer or boundary layer) must work through the stable layer of convective inhibition (CIN) when present. This work comes from increasing instability in the low levels by raising the temperature or dew point, or by mechanical lift. Without the aid of mechanical forcing, a parcel must reach its convective temperature (Tc) before moist convection (cloud) begins near the convective condensation level (CCL}, whereas with dynamic lift, cloud base begins near the lifted condensation level (LCL). This will remain as shallow, moist convection (small cumulus clouds) until breaking through the convective inhibition layer, after which DMC ensues as a parcel hits the LFC and enters the FCL, if thermal or mechanical forcing continues. At the level of neutral buoyancy (the EL), a parcel is cooler than the environment and is stable, so it slow down, eventually ceasing at the maximum parcel level (MPL).

Hamilton Project

The Hamilton Project is an economic research group and think tank within the Brookings Institution. It was originally launched in 2006 by Robert Rubin, toward the end of the George W. Bush presidency, by former Clinton administration economists. It went dormant after Barack Obama assumed office in 2009, because many of its members left to work for the White House, but in 2010, it was relaunched with Michael Greenstone as the new director.The Brookings Institution was mentioned as coming up with two proposals for the Hamilton Project that foresees reforms regarding public and corporate policies. These can serve as protection for workers against adverse effects of non-compete agreements or non-competing clause (NCC) as well as other labor market customs that are known as not supporting competition. Among these experts (authors) in this field are Matt Marx, a professor at Boston University, Eric Posner (law professor), and Alan Kreuger (economist).

The cause is attributed by these thinkers to “Monopsony Power” which occurs when employers control the labor market. It is cited as a monopoly in economics. This kind of employer has the capacity to keep wages under the equilibrium level. According to economic models, the monopsonist has the option of not reducing labor demand in answer to slight increase in price.

Heat burst

In meteorology, a heat burst is a rare atmospheric phenomenon characterized by gusty winds along with a rapid increase in temperature and decrease in dew point (moisture). Heat bursts typically occur during night-time and are associated with decaying thunderstorms.Although this phenomenon is not fully understood, it is theorized that the event is caused when rain evaporates (virga) into a parcel of cold, dry air high in the atmosphere- making the air denser than its surroundings. The parcel descends rapidly, warming due to compression, overshoots its equilibrium level and reaches the surface, similar to a downburst.Recorded temperatures during heat bursts have reached well above 40 °C (104 °F), sometimes rising by 10 °C (18 °F) or more within only a few minutes. More extreme events have also been documented, where temperatures have been reported to exceed 50 °C (122 °F). However, such extreme events have never been officially verified. Heat bursts are also characterized by extremely dry air and are sometimes associated with very strong, even damaging, winds.

Keynesian cross

The Keynesian cross diagram is a formulation of the central ideas in Keynes' General Theory. It first appeared as a central component of macroeconomic theory as it was taught by Samuelson in his textbook, Economics: An Introductory Analysis. The Keynesian Cross plots aggregate income (labelled as Y on the horizontal axis) and planned total spending or aggregate expenditure (labelled as AD on the vertical axis).

Level of free convection

The level of free convection (LFC) is the altitude in the atmosphere where the temperature of the environment decreases faster than the moist adiabatic lapse rate of a saturated air parcel at the same level.

The usual way of finding the LFC is to lift a parcel from a lower level along the dry adiabatic lapse rate until it crosses the mixing ratio line of the parcel: this is the lifted condensation level (LCL). From there on, follow the moist adiabatic lapse rate until the temperature of the parcel reaches the air mass temperature, at the equilibrium level (EL). If the temperature of the parcel along the moist adiabat is warmer than the environment on further lift, one has found the LFC.

Since the volume of the parcel is larger than the surrounding air after LFC by the ideal gas law (PV = nRT), it is less dense and becomes buoyant rising until its temperature (at E) equals the surrounding airmass. If the airmass has one or many LFC, it is potentially unstable and may lead to convective clouds like cumulus and thunderstorms.

Maximum parcel level

The maximum parcel level (MPL) is the highest level in the atmosphere that a moist convectively rising air parcel will reach after ascending from the level of free convection (LFC) through the free convective layer (FCL) and reaching the equilibrium level (EL), near the tropopause. As the parcel rises through the FCL it expands adiabatically causing its temperature to drop, often below the temperature of its surroundings, and eventually lose buoyancy. Because of this, the EL is approximately the region where the distinct flat tops (called anvil clouds), often observed around the upper portions of cumulonimbus clouds. If the air parcel ascended quickly enough then it retains momentum after it has cooled and continues rising past the EL, ceasing at the MPL (visually represented by the overshooting top, above the anvil).Dynamic processes within and between convective cells, such as updraft merging and cloud base areal size, factor into the actual ultimate cloud top height, in addition to atmospheric thermodynamics of the MPL. Updraft merging can lead to higher cloud tops thus an implication is that organized convection can be taller convection.

Overshooting model

The overshooting model, or the exchange rate overshooting hypothesis, first developed by economist Rudi Dornbusch, is a theoretical explanation for high levels of exchange rate volatility. The key features of the model include the assumptions that goods' prices are sticky, or slow to change, in the short run, but the prices of currencies are flexible, that arbitrage in asset markets holds, via the uncovered interest parity equation, and that expectations of exchange rate changes are "consistent": that is, rational. The most important insight of the model is that adjustment lags in some parts of the economy can induce compensating volatility in others; specifically, when an exogenous variable changes, the short-term effect on the exchange rate can be greater than the long-run effect, so in the short term, the exchange rate overshoots its new equilibrium long-term value.

Dornbusch developed this model back when many economists held the view that ideal markets should reach equilibrium and stay there. Volatility in a market, from this perspective, could only be a consequence of imperfect or asymmetric information or adjustment obstacles in that market. Rejecting this view, Dornbusch argued that volatility is in fact a far more fundamental property than that.

According to the model, when a change in monetary policy occurs (e.g., an unanticipated permanent increase in the money supply), the market will adjust to a new equilibrium between prices and quantities. Initially, because of the "stickiness" of prices of goods, the new short run equilibrium level will first be achieved through shifts in financial market prices. Then, gradually, as prices of goods "unstick" and shift to the new equilibrium, the foreign exchange market continuously reprices, approaching its new long-term equilibrium level. Only after this process has run its course will a new long-run equilibrium be attained in the domestic money market, the currency exchange market, and the goods market.

As a result, the foreign exchange market will initially overreact to a monetary change, achieving a new short run equilibrium. Over time, goods prices will eventually respond, allowing the foreign exchange market to dissipate its overreaction, and the economy to reach the new long run equilibrium in all markets.

Overshooting top

An overshooting top (or penetrating top) is a dome-like protrusion shooting out of the top of the anvil of a thunderstorm. When an overshooting top is present for 10 minutes or longer, it's a strong indication the storm is severe.

Population momentum

Population momentum is a typical consequence of the demographic transition. Even if a high-fertility, high-growth population experiences an immediate drop in fertility to replacement rate, that population will continue to grow for several decades. Eventually, because the new fertility rate is replacement, the population achieves equilibrium at some new level. Population momentum is defined as the ratio of the size of the population at that new equilibrium level to the size of the initial population. Population momentum usually occurs in populations that are growing.

Price support

In economics, a price support may be either a subsidy or a price control, both with the intended effect of keeping the market price of a good higher than the competitive equilibrium level.

In the case of a price control, a price support is the minimum legal price a seller may charge, typically placed above equilibrium. It is the support of certain price levels at or above market values by the government.

A price support scheme can also be an agreement set in order by the government, where the government agrees to purchase the surplus of at a minimum price. For example, if a price floor were set in place for agricultural wheat commodities, the government would be forced to purchase the resulting surplus from the wheat farmers (thereby subsidizing the farmers) and store or otherwise dispose of it.

Startup neutron source

Startup neutron source is a neutron source used for stable and reliable initiation of nuclear chain reaction in nuclear reactors, when they are loaded with fresh nuclear fuel, whose neutron flux from spontaneous fission is insufficient for a reliable startup, or after prolonged shutdown periods. Neutron sources ensure a constant minimal population of neutrons in the reactor core, sufficient for a smooth startup. Without them, the reactor could suffer fast power excursions during startup from state with too few self-generated neutrons (new core or after extended shutdown).

The startup sources are typically inserted in regularly spaced positions inside the reactor core, in place of some of the fuel rods.

The sources are important for safe reactor startup. The spontaneous fission and cosmic rays serve as weak neutron sources, but these are too weak for the reactor instrumentation to detect; relying on them could lead to a "blind" start, which is an unsafe condition. The sources are therefore positioned so the neutron flux they produce is always detectable by the reactor monitoring instruments. When the reactor is in shutdown state, the neutron sources serve to provide signals for neutron detectors monitoring the reactor, to ensure they are operable. The equilibrium level of neutron flux in a subcritical reactor is dependent on the neutron source strength; a certain minimum level of source activity therefore has to be ensured in order to maintain control over the reactor when in strongly subcritical state, namely during startups.The sources can be of two types:

Primary sources, used for startup of a fresh reactor core; conventional neutron sources are used. The primary sources are removed from the reactor after the first fuel campaign, usually after few months, as neutron capture resulting from the thermal neutron flux in an operating reactor changes the composition of the isotopes used, and thus reduces their useful lifetime as neutron sources.

Californium-252 (spontaneous fission)

Plutonium-238 & beryllium, (α,n) reaction

americium-241 & beryllium, (α,n) reaction

polonium-210 & beryllium, (α,n) reaction

radium-226 & beryllium, (α,n) reactionWhen plutonium-238/beryllium primary sources are utilized, they can be either affixed to control rods which are removed from the reactor when it is powered, or clad in a cadmium alloy, which is opaque to thermal neutrons (reducing transmutation of the plutonium-238 by neutron capture) but transparent to fast neutrons produced by the source.

Secondary sources, originally inert, become radioactive and neutron-producing only after neutron activation in the reactor. Due to this, they tend to be less expensive. Exposure to thermal neutrons also serves to maintain the source activity (the radioactive isotopes are both burned and generated in neutron flux).

Sb-Be photoneutron source; antimony becomes radioactive in the reactor and its strong gamma emissions (1.7 MeV for 124Sb) interact with beryllium-9 by an (γ,n) reaction and provide photoneutrons. In a PWR reactor one neutron source rod contains 160 grams of antimony, and stay in the reactor for 5–7 years. The sources are often constructed as an antimony rod surrounded by beryllium layer and clad in stainless steel. Antimony-beryllium alloy can be also used.The chain reaction in the first critical reactor, CP-1, was initiated by a radium-beryllium neutron source. Similarly, in modern reactors (after startup), delayed neutron emission from fission products suffices to sustain the amplification reaction while yielding controllable growth times. In comparison, a bomb is based on immediate neutrons and grows exponentially in nanoseconds.


Surplus may refer to:

Economic surplus, one of various supplementary values

Excess supply, a situation in which the quantity of a good or service supplied is more than the quantity demanded, and the price is above the equilibrium level determined by supply and demand

Government budget surplus

Military surplus, obsolete or obsolescent military goods usually offered for sale

Surplus: Terrorized into Being Consumers, a documentary film

Surplus value, surplus labour, surplus product in Marxian economics

"The Surplus", a 2008 episode of The Office

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