The lapse rate is defined as the negative of the rate of change in an atmospheric variable, usually temperature, with height observed while moving upwards through an atmosphere.^[1][2] While typically applied to Earth's atmosphere, the concept can be extended to any gravitationally supported ball of gas. For other uses, see Temperature (disambiguation). ... “Air” redirects here. ...

Definition

A formal, peer-reviewed definition from the Glossary of Meteorology^[3] is: Peer review (known as refereeing in some academic fields) is a scholarly process used in the publication of manuscripts and in the awarding of funding for research. ...

The decrease of an atmospheric variable with height, the variable being temperature, unless otherwise specified.

The term applies ambiguously to the environmental lapse rate and the process lapse rate, and the meaning must often by ascertained from the context.

Types of lapse rates

There are two types of lapse rate:

• Environmental lapse rate - which refers to the actual change of temperature with altitude for the stationary atmosphere (i.e. the temperature gradient)
• The adiabatic lapse rates - which refer to the change in temperature of a mass of air as it moves upwards. There are two adiabatic rates:^[4]
  • Dry adiabatic lapse rate
  • Moist adiabatic lapse rate

Environmental lapse rate

The environmental lapse rate (ELR), is the negative of the actual change of temperature with altitude of the stationary atmosphere at a specific time and specific location. The ELR at a given place varies from day to day and even during each day. As an average the International Civil Aviation Organization (ICAO) defines an international standard atmosphere with a temperature lapse rate of 6.4 °C/1000 m (3.5 °F/1000 ft) from sea level to 12 km. From 12 km up to 15 km (7 to 9 mi), the constant temperature is -55 °C (-67 °F), which is the lowest assumed temperature in ISA. It is important to remember that the standard atmosphere contains no moisture, and that the temperature of the atmosphere does not always fall steadily. For example there can be an inversion layer in which the temperature rises with increasing height. The International Civil Aviation Organization (ICAO), an agency of the United Nations, codifies the principles and techniques of international air navigation and fosters the planning and development of international air transport to ensure safe and orderly growth. ... The International Civil Aviation Organizintion (ICAO) Standard Atmosphere gives the average values for meteorological element at 40°N from mean sea level (MSL) to 80km (262,500 ft). ... Smoke rising in Lochcarron is stopped by an overlying layer of warmer air. ...

Dry adiabatic lapse rate

Emagram diagram showing variation of dry adiabats (bold lines) and moist adiabats (dash lines) according to pressure and temperature

The dry adiabatic lapse rate (DALR) is the negative of the rate at which a rising parcel of dry or unsaturated air changes temperature with increasing height, under adiabatic conditions. Unsaturated air has less than 100% relative humidity, i.e. its temperature is higher than its dew point. The term adiabatic means that no heat is gained or lost from outside the parcel. Air has low thermal conductivity, and the bodies of air involved are very large, so transfer of heat by conduction is negligibly small. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Wikipedia does not have an article with this exact name. ... In GIS or Tax talk a parcel is: a contiguous area of land described in a single description by a deed or other instrument or as one of a number of lots on a plat or plan, separately owned and capable of being separately conveyed. ... This does not adequately cite its references or sources. ... Dew on a spider web The dew point (or dewpoint) of a given parcel of air is the temperature to which the parcel must be cooled, at constant barometric pressure, for water vapor to condense into water, called dew. ... This article covers adiabatic processes in thermodynamics. ... In physics, thermal conductivity, k, is the intensive property of a material that indicates its ability to conduct heat. ... Heat conduction or thermal conduction is the spontaneous transfer of thermal energy through matter, from a region of higher temperature to a region of lower temperature, and hence acts to even out temperature differences. ...

Under these conditions, when the air is stirred (for instance, by convection), and a parcel of air rises, it expands, because the pressure is lower at higher altitudes. As the air parcel expands, it pushes on the air around it, doing work; since the parcel does work and gains no heat, it loses internal energy, and so its temperature decreases. (The reverse occurs for a sinking parcel of air.)^[5] Convection in the most general terms refers to the internal movement of currents within fluids (i. ... Look up work in Wiktionary, the free dictionary. ... In thermodynamics, the internal energy of a thermodynamic system, or a body with well-defined boundaries, denoted by U, or sometimes E, is the total of the kinetic energy due to the motion of molecules (translational, rotational, vibrational) and the potential energy associated with the vibrational and electric energy of...

For an ideal gas, the equation relating temperature T and pressure p for an adiabatic process is^[6]

p(z)^{γ − 1} / T(z)^γ = constant

where γ is the heat capacity ratio (γ=7/5, for air) and z is the altitude. A second relation between the pressure and temperature is the equation of hydrostatic equilibrium:^[7] The heat capacity ratio is simply the ratio of the heat capacity at constant pressure to that at constant volume It should be noted that chemical engineers and many others commonly refer to the heat capacity ratio as rather than . ... Hydrostatic equilibrium occurs when compression due to gravity is balanced by a pressure gradient which creates a pressure gradient force in the opposite direction. ...

where g is the standard gravity, R the gas constant, and m the molar mass. Combining these two equations to eliminate the pressure, one arrives at the result for the DALR,^[8] g (also gee, g-force or g-load) is a non-SI unit of acceleration defined as exactly 9. ... The gas constant (also known as the universal or ideal gas constant, usually denoted by symbol R) is a physical constant used in equations of state to relate various groups of state functions to one another. ... This article does not cite any references or sources. ...

.

Saturated adiabatic lapse rate

When the air is saturated with water vapour (at its dew point), the moist adiabatic lapse rate (MALR) or saturated adiabatic lapse rate (SALR) applies. It varies strongly with the moisture content,^[4] which depends on temperature, and lightly with pressure from 3 (high temperature near surface) to + 9.78°C/km (very low temperature) as one can see in the diagram. However, at temperatures above freezing it is usually near + 4.9 °C/km (+ 2.7 °F/1000 ft or + 1.51°C/1000 ft). The reason for the difference is that latent heat is released when water condenses. Even though there are no more than 10 grams of water in a kilogram of air at 15 degrees Celsius, water's high heat of vaporization creates a significant release of the energy when it condenses (and is an important source of energy in the development of thunderstorms). Until the moisture starts condensing, the parcel of air cools at the DALR so any air that is unsaturated can be assumed to be 'dry'. In chemistry, saturation has four different meanings: In physical chemistry, saturation is the point at which a solution of a substance can dissolve no more of that substance and additional amounts of that substance will appear as a precipitate. ... Boundaries: Phase, Pressure, Temperature Evaporation/Sublimation Whenever a water molecule leaves a surface, it is said to have evaporated. ... Dew on a spider web The dew point (or dewpoint) of a given parcel of air is the temperature to which the parcel must be cooled, at constant barometric pressure, for water vapor to condense into water, called dew. ... In thermochemistry, latent heat is the amount of energy in the form of heat released or absorbed by a substance during evaporation. ... The heat of vaporization is a physical property of substances. ...

Significance in meteorology

The varying environmental lapse rates throughout the earth's atmosphere are of critical importance in meteorology, particularly within the troposphere. They are used to determine if the parcel of rising air will rise high enough for its water to condense to form clouds, and, having formed clouds, whether the air will continue to rise and form bigger shower clouds, and whether these clouds will get even bigger and form cumulonimbus clouds (thunder clouds). // Meteorology (from Greek: μετέωρον, meteoron, high in the sky; and λόγος, logos, knowledge) is the interdisciplinary scientific study of the atmosphere that focuses on weather processes and forecasting. ... Atmosphere diagram showing the mesosphere and other layers. ... An air parcel is an imaginary chunk of air in the atmosphere. ... hello--~~~~fake <gallery> poos[[kill]] </gallery> For other uses, see Cloud (disambiguation). ... Cumulonimbus (Cb) is a type of cloud that is tall, dense, and involved in thunderstorms and other intense weather. ...

As unsaturated air rises, its temperature drops at the dry adiabatic rate. The dew point also drops, but much more slowly, typically about - 2 °C per 1000 m. If unsaturated air rises far enough, eventually its temperature will reach its dew point, and condensation will begin to form. This altitude is known as the lifting condensation level (LCL) when mechanical lift is present and the convective condensation level (CCL) absent mechanical lift, in which case, the parcel must be heated from below to its convective temperature. The cloud base will be somewhere within the layer bounded by these parameters. The lifted condensation level or lifting condensation level (LCL), represents the height at which an air parcel being lifted dry adiabatically will become saturated because of adiabatic cooling (caused by expansion) and condense into cloud. ... The convective condensation layer (CCL) represents the height where an air parcel becomes saturated when lifted adiabatically to achieve buoyant ascent. ... The convective temperature (CT or Tc) is the approximate temperature that air near the surface much reach for cloud formation without mechanical lift. ... This article refers to meterology, for the airborne base of Captain Scarlet see Cloudbase. ...

The difference between the dry adiabatic lapse rate and the rate at which the dew point drops is around 8 °C per 1000 m. Given a difference in temperature and dew point readings on the ground, one can easily find the LCL by multiplying the difference by 125 m/°C.

If the environmental lapse rate is less than the moist adiabatic lapse rate, the air is absolutely stable — rising air will cool faster than the surrounding air and lose buoyancy. This often happens in the early morning, when the air near the ground has cooled overnight. Cloud formation in stable air is unlikely. In physics, buoyancy is the upward force on an object produced by the surrounding fluid (i. ...

If the environmental lapse rate is between the moist and dry adiabatic lapse rates, the air is conditionally unstable — an unsaturated parcel of air does not have sufficient buoyancy to rise to the LCL or CCL, and it is stable to weak vertical displacements in either direction. If the parcel is saturated it is unstable and will rise to the LCL or CCL, and either be halted due to an inversion layer of convective inhibition, or if lifting continues, deep, moist convection (DMC) may ensue, as a parcel rises to the level of free convection (LFC), after which it enters the free convective layer (FCL) and usually rises to the equilibrium level (EL). A temperature inversion is a meteorological phenomenon where air temperature increases with height. ... Convective inhibition (CIN or CINH) is a meteorlogic parameter that measures the amount of energy that will prevent an air parcel from rising from the surface to the level of free convection. ... The level of free convection (LFC) is any point 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 free convective layer (FCL) is the layer of conditional or potential instability in the troposphere. ... In meteorology, the equilibrium level (EL), or level of neutral buoyancy (LNB), is the height at which a rising parcel of air is at a temperature of equal warmth to it. ...

If the environmental lapse rate is larger than the dry adiabatic lapse rate, it has a superadiabatic lapse rate, the air is absolutely unstable — a parcel of air will gain buoyancy as it rises both below and above the lifting condensation level or convective condensation level. This often happens in the afternoon over many land masses. In these conditions, the likelihood of cumulus clouds, showers or even thunderstorms is increased. This article or section does not adequately cite its references or sources. ... This article is about clouds in meteorology. ... A thunderstorm, also called an electrical storm or lightning storm, is a form of weather characterized by the presence of lightning and its attendant thunder produced from a cumulonimbus cloud. ...

Meteorologists use radiosondes to measure the environmental lapse rate and compare it to the predicted adiabatic lapse rate to forecast the likelihood that air will rise. Charts of the environmental lapse rate are known as thermodynamic diagrams, examples of which being Skew-T log-P diagrams and tephigrams. (See also Thermals). radiosonde with measuring instruments A radiosonde (Sonde is German for probe) is a unit for use in weather balloons that measures various atmospheric parameters and transmits them to a fixed receiver. ... Thermodynamic diagrams are diagrams used by scientists and engineers to represent the thermodynamic states of a material (typically fluid) and the consequences of manipulating this material. ... Black and White Skew-T log-P Color Skew-T log-P diagram, SVG/ PDF format A Skew-T Log-P diagram is one of four thermodynamic diagrams commonly used in weather analysis and forecasting. ... A tephigram is one of four thermodynamic diagrams commonly used in weather analysis and forecasting. ... This article is about the atmospheric phenomenon. ...

The difference in moist adiabatic lapse rate and the dry rate is the cause of Föhn winds phenomenon (also known as "Chinook winds" in parts of North America). A föhn wind or foehn wind occurs when a deep layer of prevailing wind is forced over a mountain range (Orographic lifting). ... Image:Shitnook wind. ...

Mathematical definition

In general, a lapse rate is expressed as the negative ratio of the temperature change and the altitude change, thus:

where γ is the adiabatic lapse rate given in units of temperature divided by units of altitude, T = temperature, and z = altitude, and points 1 and 2 are measurements at two different altitudes. The definition, agreement and practical use of units of measurement have played a crucial role in human endeavour from early ages up to this day. ...

Note: In some cases, Γ or α can be used to represent the adiabatic lapse rate in order to avoid confusion with other terms symbolized by γ, such as the specific heat ratio^[9] or the psychometric constant^[10]. The heat capacity ratio is simply the ratio of the heat capacity at constant pressure to that at constant volume It should be noted that chemical engineers and many others commonly refer to the heat capacity ratio as rather than . ...

See also

• Adiabatic process
• Atmospheric thermodynamics
• Fluid mechanics
  • Fluid dynamics
• Föhn wind

In thermodynamics, an adiabatic process or an isocaloric process is a thermodynamic process in which no heat is transferred to or from the working fluid. ... In the physical sciences, atmospheric thermodynamics is the study of heat and energy transformations in the earth’s atmospheric system. ... Fluid mechanics is the subdiscipline of continuum mechanics that studies fluids, that is, liquids and gases. ... Fluid dynamics is the sub-discipline of fluid mechanics dealing with fluids (liquids and gases) in motion. ... A föhn wind or foehn wind occurs when a deep layer of prevailing wind is forced over a mountain range (Orographic lifting). ...

External links

• National Science Digital Library - Lapse Rate
• National Science Digital Library - Environmental lapse rate
• National Science Digital Library - Absolute stable air
• A good introduction article on lapse rate calculation from first principles

Additional reading

• Beychok, Milton R. (2005). Fundamentals Of Stack Gas Dispersion, Fourth Edition, author-published. ISBN 0-9644588-0-2.  www.air-dispersion.com
• M K Yau and R.R. Rogers (1989). Short Course in Cloud Physics, Third Edition, Butterworth-Heinemann. ISBN 0-7506-3215-1. 

Fundamentals Of Stack Gas Dispersion is a book devoted to the basic fundamentals of air pollution dispersion modeling of continuous, buoyant pollution plumes from stationary point sources. ...

References

1. ^ Mark Zachary Jacobson (2005). Fundamentals of Atmospheric Modeling, 2nd Edition, Cambridge University Press. ISBN 0-521-83970-X. 
2. ^ C. Donald Ahrens (2006). Meteorology Taday, 8th Edition, Brooks/Cole Publishing. ISBN 0-495-01162-2. 
3. ^ Todd S. Glickman (June 2000). Glossary of Meteorology, 2nd Edition, American Meteorological Society, Boston. ISBN 1-878220-34-9.  (Glossary of Meteorolgy)
4. ^ ^{a b} Adiabatic Lapse Rate, IUPAC Goldbook
5. ^ Danielson, Levin, and Abrams, Meteorology, McGraw Hill, 2003
6. ^ Landau and Lifshitz, Statistical Physics Part 1, Pergamon, 1980
7. ^ Landau and Lifshitz, Fluid Mechanics, Pergamon, 1979
8. ^ Kittel and Kroemer, Thermal Physics, Freeman, 1980; chapter 6, problem 11
9. ^ Salomons, Erik M. (2001). Computational Atmospheric Acoustics, First Edition, Kluwer Academic Publishers. ISBN 1-4020-0390-0. 
10. ^ Stull, Roland B. (2001). An Introduction to Boundary Layer Meteorology, First Edition, Kluwer Academic Publishers. ISBN 90-277-2769-4.