A sample of moist but unsaturated air may become saturated by ? [ Revision flight ]

Question 137-1 : Expanding it adiabatically raising the temperature lowering the pressure keeping temperature constant compressing it adiabatically

exemple 237 Expanding it adiabatically. — Fabricet .don't get why an unsaturated air mass could become saturated by expanding it adiabatically by compressing it the relative humidity will increase until reaching the 100% of humidity making the air mass saturated . .if you compress it it will heat up and if you expand it will cool .during an adiabatic process heat is neither added nor lost air can hold a certain amount of water depending on it's temperature warmer air can hold more water vapour than colder air .thus by cooling the air it can hold less water vapour and the relative humidity increases how does air cool usually by increasing in height .so to get an unsaturated parcel of air with say 40% of relative humidity to 100% of relative humidity fully saturated a cloud then you must cool the parcel by lifting it to a higher level when it expands adiabatically it cools so relative humidity must increase Expanding it adiabatically.

The maximum amount of water vapour that the air can contain depends on the ?

Question 137-2 : Air temperature relative humidity stability of the air dewpoint

Admin .the most commonly used measure of humidity is relative humidity relative humidity can be simply defined as the amount of water in the air relative to the saturation amount the air can hold at a given temperature multiplied by 100 air with a relative humidity of 50% contains a half of the water vapor it could hold at a particular temperature . 501. concept of relative humidity .we can say that the amount of water vapour which air can hold largely depends on air temperature

Convective clouds are formed ?

Question 137-3 : In unstable atmosphere in stable atmosphere in summer during the day only in mid latitudes only

exemple 245 In unstable atmosphere. — In unstable atmosphere.

The most effective way to dissipate cloud is by ?

Question 137-4 : Subsidence convection a decrease in temperature a decrease in pressure

Areas of sinking air are generally cloudless because as air sinks it ?

Question 137-5 : Is heated by compression reaches warmer layers is heated by expansion loses water vapour

exemple 253 Is heated by compression. — Admin .as the air sinks to lower levels the pressure increases which compresses the air increasing density and temperature .as the air temperature increases its capacity to hold water vapour increases and relative humidity decreases Is heated by compression.

The main factor which contributes to the formation of very low clouds ahead of ?

Question 137-6 : Saturation of the cold air by rain falling into it and evaporating saturation of the warm air by rain falling into it and evaporating reduction of outgoing radiation due to clouds warm air moving over a cold surface

exemple 257 Saturation of the cold air by rain falling into it and evaporating. — Admin .clouds form in the front rain falls from them out of the warm sector into the cold sector . 559.latent heat is absorbed when going from liquid to gas vapour at low levels you will have stratus and nimbostratus clouds Saturation of the cold air by rain falling into it and evaporating.

In an unstable layer there are cumuliform clouds the vertical extent of these ?

Question 137-7 : Thickness of the unstable layer wind direction air pressure at the surface pressure at different levels

exemple 261 Thickness of the unstable layer — Thickness of the unstable layer

Which of the following phenomena are formed when a moist stable layer of air is ?

Question 137-8 : Stratified clouds inversions showers and thunderstorms areas of severe turbulence

exemple 265 Stratified clouds. — Admin .lifting moist stable layer of air produces stratus Stratified clouds.

The height of the lifting condensation level is determined by ?

Question 137-9 : Temperature and dewpoint at the surface temperature at surface and air pressure wind and dewpoint at the surface wet adiabatic lapse rate and dewpoint at the surface

exemple 269 Temperature and dewpoint at the surface. — Admin . 560.the height of a cloud base that results from lifting of near surface air can be estimated based on the surface values of temperature and dew point since the height at which a cloud will form is roughly the height at which the temperature and dew point would become equal due to expansion of the air as it rises to regions of lower pressure Temperature and dewpoint at the surface.

During an adiabatic process heat is ?

Question 137-10 : Neither added nor lost added lost added but the result is an overall loss

exemple 273 Neither added nor lost. — Neither added nor lost.

The decrease in temperature per 100 metres in an unsaturated rising parcel of ?

Question 137-11 : 1°c 2°c 0 65°c 0 5°c

exemple 277 1°c. — Admin .1°c/100 m or 3°c/1000 ft this is the dry adiabatic lapse rate 1°c.

The decrease in temperature per 100 metres in a saturated rising parcel of air ?

Question 137-12 : 0 6°c 1°c 1 5°c 0 35°c

exemple 281 0.6°c. — Admin .dry lapse rate = 3ºc/1000 ft or 1ºc/100 m.saturated lapse rate = 1ºc/1000 ft or 0 6ºc/100 m 0.6°c.

In unstable air ground visibility is most likely to be restricted by ?

Question 137-13 : Showers of rain or snow haze drizzle low stratus

exemple 285 Showers of rain or snow. — Showers of rain or snow.

A vertical temperature profile indicates the possibility of severe icing when ?

Question 137-14 : Intersects the 0°c isotherm twice coincides with a dry adiabatic lapse rate indicates temperatures below 40°c indicates temperatures above 3°c

exemple 289 Intersects the 0°c isotherm twice. — Admin .to intersect the 0ºc isotherm twice there must be warm air above cold air this occurs at a warm front and is where rain ice will be encountered Intersects the 0°c isotherm twice.

The rate of cooling of ascending saturated air is less than the rate of cooling ?

Question 137-15 : Heat is released during the condensation process moist air is heavier than dry air water vapour doesn't cool as rapidly as dry air water vapour absorbs the incoming heat from the sun

exemple 293 Heat is released during the condensation process. — Heat is released during the condensation process.

If the surface temperature is 15°c then the temperature at 10000 ft in a ?

Question 137-16 : 15°c 0°c 5°c 5°c

exemple 297 -15°c. — Admin . ascending unsaturated air means dry adiabatic lapse rate and we know that the environmental lapse rate elr is more than 3°c/1000ft for dry adiabatic lapse rate .15°c 3° x 10 = 15°c -15°c.

An inversion is ?

Question 137-17 : An increase of temperature with height an increase of pressure with height a decrease of pressure with height a decrease of temperature with height

exemple 301 An increase of temperature with height — An increase of temperature with height

In still air the temperature decreases at an average of 1 2°c per 100 m ?

Question 137-18 : Dry adiabatic lapse rate saturated adiabatic lapse rate environmental lapse rate normal lapse rate

exemple 305 Dry adiabatic lapse rate. — Admin .if the environmental lapse rate elr is more than 3°c/1000 ft dry adiabatic lapse rate the environment is unstable .if the environmental lapse rate elr is less than 1 8°c/1000 ft saturated adiabatic lapse rate the environment is stable .if the environmental lapse rate elr is more than 1 8°c/1000 ft but less than 3°c/1000 ft we have conditional stability . stable if air is dry .or. unstable if air is saturated .1 2°c per 100m is 3 6°c per 1000 ft .the environmental lapse rate elr is more than 3°c/1000 ft this temperature change is called 'dry adiabatic lapse rate' Dry adiabatic lapse rate.

From which of the following pieces of information can the stability of the ?

Question 137-19 : Environmental lapse rate dry adiabatic lapse rate surface temperature pressure at the surface

exemple 309 Environmental lapse rate. — Admin .if the environmental lapse rate elr is more than 3°c/1000ft dry adiabatic lapse rate the environment is unstable .if the environmental lapse rate elr is less than 1 8°c/1000ft saturated adiabatic lapse rate the environment is stable .if the environmental lapse rate elr is more than 1 8°c/1000ft but less than 3°c/1000ft we have conditional stability . stable if air is dry .or. unstable if air is saturated Environmental lapse rate.

A layer is absolutely unstable if the temperature decrease with height is ?

Question 137-20 : More than 1°c per 100m between 1°c per 100m and 0 65°c per 100m 0 65°c per 100m less than 0 65°c per 100m

exemple 313 More than 1°c per 100m. — Admin .if the environmental lapse rate elr is more than 3°c/1000 ft dry adiabatic lapse rate the environment is unstable .if the environmental lapse rate elr is less than 1 8°c/1000 ft saturated adiabatic lapse rate the environment is stable .if the environmental lapse rate elr is more than 1 8°c/1000 ft but less than 3°c/1000 ft we have conditional . stability if air is dry .or. unstability if air is saturated .the question states absolutely unstable it is more than 3°c/1000 ft .3°c/1000 ft = 1°c per 328 ft = 1°c for 100 m More than 1°c per 100m.

A layer in which the temperature remains constant with height is ?

Question 137-21 : Absolutely stable unstable neutral conditionally unstable

exemple 317 Absolutely stable. — Admin .a layer in which the temperature remains constant or increases with height is absolutely stable .for example the layer just above the tropopause is absolutely stable from 12 km to 25 km the temperature does not vary with height it is an isothermal layer where we have absolute stability Absolutely stable.

A layer in which the temperature increases with height is ?

Question 137-22 : Absolutely stable absolutely unstable conditionally unstable neutral

exemple 321 Absolutely stable. — Admin .a layer in which the temperature remains constant or increases with height is absolutely stable .for example the layer just above the tropopause is absolutely stable from 12 km to 25 km the temperature does not vary with height it is an isothermal layer where we have absolute stability Absolutely stable.

A layer in which the temperature decreases with 1°c per 100 m increasing ?

Question 137-23 : Neutral for dry air absolutely stable absolutely unstable conditionally unstable

exemple 325 Neutral for dry air. — Admin .lapse rate is 1°c for 100 m 1° per 328 ft so 3°/1000 ft we have four possibilities .if the environmental lapse rate elr is more than 3°c/1000 ft dry adiabatic lapse rate the environment is unstable .if the environmental lapse rate elr is less than 1 8°c/1000 ft saturated adiabatic lapse rate the environment is stable .if the environmental lapse rate elr is more than 1 8°c/1000 ft but less than 3°c/1000 ft we have conditional . stability if air is dry .or. unstability if air is saturated .the question states 1°c per 100m it is not more or not less than 3°c/1000 ft it will be neutral for dry air Neutral for dry air.

If in a 100 m thick layer the temperature at the bottom of the layer is 10°c ?

Question 137-24 : Absolutely unstable absolutely stable conditionally unstable neutral

exemple 329 Absolutely unstable. — Admin .if the environmental lapse rate elr is more than 3°c/1000 ft dry adiabatic lapse rate the environment is unstable .if the environmental lapse rate elr is less than 1 8°c/1000 ft saturated adiabatic lapse rate the environment is stable .if the environmental lapse rate elr is more than 1 8°c/1000 ft but less than 3°c/1000 ft we have conditional stability . stable if air is dry .or. unstable if air is saturated .in our layer the environmental lapse rate is 2°c/300 ft or around 6°c/1000 ft which is absolutely unstable Absolutely unstable.

A wide body takes off on a clear night in dhahran saudi arabia shortly after ?

Question 137-25 : A very strong temperature inversion sand/dust in the engines very pronounced downdrafts low relative humidity

exemple 333 A very strong temperature inversion. — Admin .the question states 'clear night' we can exclude sand or dust in the engines . very pronounced downdrafts might be a acceptable answer but it means unstable air and clouds it can't be a clear night .humidity will not sufficiently affect lift and engine power to visually decrease the rate of climb .during the night radiation will cool the surface which then cools the air close to the surface the air temperature at 3 4000 ft the air is still very warm this is a very strong temperature inversion less density less lift and less power A very strong temperature inversion.

The value of the saturated adiabatic lapse rate is closest to that of the dry ?

Question 137-26 : Cirrus freezing fog stratus cumulonimbus

exemple 337 Cirrus. — Admin .if the environmental lapse rate elr is more than 3°c/1000 ft dry adiabatic lapse rate the environment is unstable .if the environmental lapse rate elr is less than 1 8°c/1000 ft saturated adiabatic lapse rate the environment is stable .if the environmental lapse rate elr is more than 1 8°c/1000 ft but less than 3°c/1000 ft we have conditional stability . stable if air is dry .or. unstable if air is saturated .as we go up in the atmosphere the air gets colder and the dry adiabatic lapse rate and the saturated adiabatic lapse rate become closer because the moisture varies the colder the air mass is the lesser moisture it can contain .cirrus clouds are located at high levels near the lowest temperatures of the troposphere Cirrus.

Dew point is defined as ?

Question 137-27 : The temperature to which moist air must be cooled to become saturated at a given pressure the lowest temperature at which evaporation will occur for a given pressure the lowest temperature to which air must be cooled in order to reduce the relative humidity the temperature below which the change of state in a given volume of air will result in the absorption of latent heat

exemple 341 The temperature to which moist air must be cooled to become saturated at a given pressure — The temperature to which moist air must be cooled to become saturated at a given pressure

The process by which water vapour is transformed directly into ice is known as ?

Question 137-28 : Sublimation supercooling supersaturation radiation cooling

exemple 345 Sublimation. — Admin .the answer should be 'deposition' .sublimation ice to water vapour .deposition water vapour to ice.but the expression 'sublimation' may be be used for both processes Sublimation.

A foehn wind occurs on the ?

Question 137-29 : Leeward side of a mountain range and is caused by significant moisture loss by precipitation from cloud windward side of a mountain range and is caused by surface heating windward side of a mountain range and is caused by surface cooling and reverse air flow leeward side of a mountain range and is caused by the condensation level being lower on the leeward side than on the windward side

exemple 349 Leeward side of a mountain range and is caused by significant moisture loss by precipitation from cloud — Leeward side of a mountain range and is caused by significant moisture loss by precipitation from cloud

Relative humidity at a given temperature is the relation between ?

Question 137-30 : Actual water vapour content and saturated water vapour content water vapour weight and dry air weight water vapour weight and humid air volume dew point and air temperature

exemple 353 Actual water vapour content and saturated water vapour content — Actual water vapour content and saturated water vapour content

A parcel of unsaturated air is forced to rise through an isothermal layer so ?

Question 137-31 : Decreases 1°c per 100 m remains constant decreases 0 65°c per 100 m becomes equal to the temperature of the isothermal layer

exemple 357 Decreases 1°c per 100 m. — Admin . unsaturated air and forced to rise ascending mean dry adiabatic lapse rate and we know that the environmental lapse rate elr is more than 3°c/1000ft for dry adiabatic lapse rate 1°c par 100 m Decreases 1°c per 100 m.

Absolute instability in the atmosphere will occur when the environmental lapse ?

Question 137-32 : Greater than both saturated adiabatic lapse rate and dry adiabatic lapse rate less than saturated adiabatic lapse rate less than both saturated adiabatic lapse rate and dry adiabatic lapse rate greater than saturated adiabatic lapse rate but less than dry adiabatic lapse rate

exemple 361 Greater than both saturated adiabatic lapse rate and dry adiabatic lapse rate — Admin .if the environmental lapse rate elr is more than 3°c/1000 ft dry adiabatic lapse rate the environment is unstable .if the environmental lapse rate elr is less than 1 8°c/1000 ft saturated adiabatic lapse rate the environment is stable .but .if the environmental lapse rate elr is more than 1 8°c/1000 ft but less than 3°c/1000 ft we have conditional stability . stable if air is dry unsaturated .or. unstable if air is saturated Greater than both saturated adiabatic lapse rate and dry adiabatic lapse rate

For both saturated and unsaturated air instability will occur when the ?

Question 137-33 : Environmental lapse rate is greater than both dry adiabatic lapse rate and saturated adiabatic lapse rate environmental lapse rate is greater than saturated adiabatic lapse rate but less than dry adiabatic lapse rate environmental lapse rate is less than both dry adiabatic lapse rate and saturated adiabatic lapse rate dry adiabatic lapse rate is less than saturated adiabatic lapse rate but greater than environmental lapse rate

exemple 365 Environmental lapse rate is greater than both dry adiabatic lapse rate and saturated adiabatic lapse rate — Admin .if the environmental lapse rate elr is more than 3°c/1000 ft dry adiabatic lapse rate the environment is unstable .if the environmental lapse rate elr is less than 1 8°c/1000 ft saturated adiabatic lapse rate the environment is stable .but .if the environmental lapse rate elr is more than 1 8°c/1000 ft but less than 3°c/1000 ft we have conditional stability . stable if air is dry unsaturated .or. unstable if air is saturated Environmental lapse rate is greater than both dry adiabatic lapse rate and saturated adiabatic lapse rate

In the lower levels of the atmosphere when the environmental lapse rate is ?

Question 137-34 : Conditionally unstable stable unstable absolutely unstable

exemple 369 Conditionally unstable. — Admin .if the environmental lapse rate elr is more than 3°c/1000 ft dry adiabatic lapse rate the environment is unstable .if the environmental lapse rate elr is less than 1 8°c/1000 ft saturated adiabatic lapse rate the environment is stable .but .if the environmental lapse rate elr is more than 1 8°c/1000 ft but less than 3°c/1000 ft we have conditional stability . stable if air is dry unsaturated .or. unstable if air is saturated Conditionally unstable.

Surface temperature inversions are frequently generated by ?

Question 137-35 : Terrestrial radiation on a calm clear night an unstable air mass causing convection currents and mixing of the atmosphere at lower levels gusting winds increasing surface friction during the day with consequent mixing at the lower levels compression causing the release of latent heat in a layer of stratiform cloud

exemple 373 Terrestrial radiation on a calm clear night. — Admin .the cooling of land after sunset by thermal radiation in calm conditions with clear sky will generate ground inversions Terrestrial radiation on a calm clear night.

Surface based temperature inversions are common during ?

Question 137-36 : Cloud free nights in winter when the ground is dry cloud free days in summer when the ground is dry cloudy days in summer when the ground is wet cloudy days in winter when the ground is wet

exemple 377 Cloud-free nights in winter when the ground is dry. — Admin .a temperature inversion is a thin layer of the atmosphere where the normal decrease in temperature with height switches to the temperature increasing with height a long clear winter night will lead to surface temperature inversion radiation inversion between surface up to 500 ft Cloud-free nights in winter when the ground is dry.

The maximum vapour pressure over a flat supercooled water surface and the ?

Question 137-37 : Greater over the water surface smaller over the water surface equal over both surfaces the same over both surfaces if the air pressure is the same

exemple 381 Greater over the water surface. — Admin .the maximum vapour pressure is greater over the water surface because it is easier for the flat supercooled liquid water to change state into vapour the flat ice surface has to sublimate into vapour there will be more molecules of water vapour in the atmosphere over the supercooled water than over the ice pressure will be greater Greater over the water surface.

The stability in a layer increases by advection of ?

Question 137-38 : Cold air in the lower part warm air in the lower part dry air in the upper part moist air in the lower part

exemple 385 Cold air in the lower part. — Admin .the stability of the atmosphere depends on its ability to resist vertical motion .there are 2 things to have a look at moisture advection and temperature advection .a moisture advection .since water vapour is lighter than air moisture decreases air density causing it to rise since moist air cools at a slower rate it is generally less stable than dry air since the moist air must rise higher before its temperature cools to that of the surrounding air the dry adiabatic lapse rate unsaturated air is 3°c per 1000 feet the moist adiabatic lapse rate varies from 1 8°c to 3°c per 1000 feet .it's not answer moist air in the lower part .dry air is heavier and will want to sink therefore dry air aloft decreases stability as less dry air below will tend to rise and replace it .it's not answer dry air in the upper part .b temperature advection .advecting warm air in the lower parts of the troposphere will make the parcel warmer than its surrounding therefore it'll keep rising .it's not answer warm air in the lower part .conclusion .the combination of moisture and temperature determine the stability of the air cool dry air is very stable and resists vertical movement the greatest instability occurs when the air is moist and warm as it is in the tropical regions in the summer .correct answer is cold air in the lower part Cold air in the lower part.

The temperature at the surface is given as +15°c and at 4000 ft it is +9°c ?

Question 137-39 : Stable conditionally unstable absolutely unstable unstable

exemple 389 Stable. — Admin .between surface and 4000 ft the temperature drops by 6°c or 1 5°c per 1000 ft .if the environmental lapse rate elr is more than 3°c/1000 ft dry adiabatic lapse rate the environment is unstable .if the environmental lapse rate elr is less than 1 8°c/1000 ft saturated adiabatic lapse rate the environment is stable .if the environmental lapse rate elr is more than 1 8°c/1000 ft but less than 3°c/1000 ft we have conditional stability . stable if air is dry .or. unstable if air is saturated Stable.

Which of the following phenomena is least likely to lead to the formation of a ?

Question 137-40 : Ground radiation convection convergence orographic lift

exemple 393 Ground radiation. — Admin .convection convergence and orographic lift can all lead to the formation of a cumulonimbus with thunderstorm ground radiation will dissipate clouds or generate a convective activity and may sometimes create cumulus clouds Ground radiation.

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