Revision > flight : A layer is absolutely unstable if the temperature decrease with height is ?

Question 133-1 : 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 233 more than 1°c per 100m. — .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 133-2 : Absolutely stable unstable neutral conditionally unstable

exemple 237 absolutely stable. — .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 133-3 : Absolutely stable absolutely unstable conditionally unstable neutral

.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

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

Question 133-4 : Neutral for dry air absolutely stable absolutely unstable conditionally unstable

exemple 245 neutral for dry air. — .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 133-5 : Absolutely unstable absolutely stable conditionally unstable neutral

.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

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

Question 133-6 : A very strong temperature inversion sand/dust in the engines very pronounced downdrafts low relative humidity

exemple 253 a very strong temperature inversion. — .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 133-7 : Cirrus freezing fog stratus cumulonimbus

exemple 257 cirrus. — .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 133-8 : 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 261 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 133-9 : Sublimation supercooling supersaturation radiation cooling

exemple 265 sublimation. — .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 133-10 : 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 269 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 133-11 : 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 273 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 133-12 : 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 277 decreases 1°c per 100 m. — . 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 133-13 : 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 281 greater than both saturated adiabatic lapse rate and dry adiabatic lapse rate — .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 133-14 : 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 285 environmental lapse rate is greater than both dry adiabatic lapse rate and saturated adiabatic lapse rate — .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 133-15 : Conditionally unstable stable unstable absolutely unstable

exemple 289 conditionally unstable. — .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 133-16 : 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 293 terrestrial radiation on a calm clear night. — .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 133-17 : 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 297 cloud-free nights in winter when the ground is dry. — .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 133-18 : 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 301 greater over the water surface. — .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 133-19 : 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 305 cold air in the lower part. — .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 133-20 : Stable conditionally unstable absolutely unstable unstable

exemple 309 stable. — .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 133-21 : Ground radiation convection convergence orographic lift

exemple 313 ground radiation. — .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.

Which of the following sets of conditions are most favourable to the ?

Question 133-22 : Environmental lapse rate greater than saturated adiabatic lapse rate through a great vertical extent high relative humidity and an initial lifting process extensive isothermal layer ice particles and water droplets must exist just below the freezing level and orographic lifting environmental lapse rate less than saturated adiabatic lapse rate with dew point below 0°c and considerable surface heating environmental lapse rate less than dry adiabatic lapse rate with freezing level below the cloud base high relative humidity and strong surface winds

exemple 317 environmental lapse rate greater than saturated adiabatic lapse rate through a great vertical extent, high relative humidity and an initial lifting process — environmental lapse rate greater than saturated adiabatic lapse rate through a great vertical extent, high relative humidity and an initial lifting process

Which of the following statements is correct ?

Question 133-23 : The bergeron findeisen process is mainly based on the difference of maximum vapour pressure over water and over ice of the same temperature the principle of the bergeron findeisen process is mainly based on the difference in size of the cloud elements at mid latitudes the coalescense process is usually the initial process in the formation of precipitation in the tropics stratiform precipitation does not occur

exemple 321 the bergeron-findeisen process is mainly based on the difference of maximum vapour pressure over water and over ice of the same temperature. — .the saturation vapour pressure is higher over water than over ice what that means that you will reach the frost point before you reach the dew point bergeron showed that in the mid latiudes because it is cold inside clouds precipitation is caused mainly by the coalence of water vapour onto ice crystals it does not explain everything and is just one of the theories of precipitation if there are no nuclei present you can raise the relative humidity to 460% before a drop will form spontaneously super saturation the bergeron-findeisen process is mainly based on the difference of maximum vapour pressure over water and over ice of the same temperature.

Which of the following statements is true of the dew point of an air mass ?

Question 133-24 : It can only be equal to or lower than the temperature of the air mass it can be higher than the temperature of the air mass it can be used together with the air pressure to estimate the air mass's relative humidity it can be used to estimate the air mass's relative humidity even if the air temperature is unknown

exemple 325 it can only be equal to, or lower, than the temperature of the air mass. — .the dewpoint temperature is the temperature at which the air can no longer hold all of its water vapor and some of the water vapor must condense into liquid water the dew point is always lower than or equal to the air temperature.if the air temperature cools to the dew point or if the dew point rises to equal the air temperature then dew fog or clouds begin to form .at this point where the dew point temperature equals the air temperature the relative humidity is 100% it can only be equal to, or lower, than the temperature of the air mass.

Which one of the following can provide the initial lifting leading to air mass ?

Question 133-25 : Advection of cold air over a warm sea mountain waves advection of warm air over a cold sea low level wind shear

exemple 329 advection of cold air over a warm sea. — .cold air over a warm surface gives convective lifting advection of cold air over a warm sea.

Which of the following quantities remains unchanged if unsaturated air is ?

Question 133-26 : Mixing ratio difference between temperature and dewpoint temperature maximum vapour pressure maximum mixing ratio

exemple 333 mixing ratio. — .if unsaturated air dry adiabatic lapse rate is lifted until it reaches the lifting condensation level the ratio of water vapour to air by mass called 'mass ratio' or 'mixing ratio' will remained unchanged .the mixing ratio of water vapor in air is used to describe humidity mixing ratio.

Which of the following processes will increase the stability of an air mass ?

Question 133-27 : Cooling by the underlying surface addition of water vapour in the lower layer warming of the air mass from below advection of colder air aloft

exemple 337 cooling by the underlying surface. — cooling by the underlying surface.

Which statement is correct for an absolutely unstable atmosphere ?

Question 133-28 : Visibility is good between showers the environmental lapse rate is less than 1°c / 100 m clouds are mainly of the stratiform type the dry adiabatic lapse rate is more than 1°c / 100 m

exemple 341 visibility is good between showers. — .if the environmental lapse rate elr is more than 3°c/1000 ft dry adiabatic lapse rate the environment is unstable .stable air will produce stratiform cloud .unstable air mass produces showers under cumulonimbus clouds outside showers visibilty is good visibility is good between showers.

Relative humidity ?

Question 133-29 : Increases if the air is cooled whilst maintaining the vapour pressure constant is higher in warm air than in cool air is higher in cool air than in warm air decreases if the air is cooled whilst maintaining the vapour pressure constant

exemple 345 increases if the air is cooled whilst maintaining the vapour pressure constant. — .the air contracts therefore takes less volume .the water quantity does not change maintaining the vapour pressure constant' thus relative humidity increases increases if the air is cooled whilst maintaining the vapour pressure constant.

What is true for the water vapour distribution in the layer between the surface ?

Question 133-30 : The lower part is relatively moist and the upper part is relatively dry the whole layer is relatively dry the whole layer is relatively moist the lower part is relatively dry and the upper part is relatively moist

exemple 349 the lower part is relatively moist and the upper part is relatively dry. — .500 hpa = fl 180.se trade winds and ne trade winds converge at the itcz intertropical convergence zone they occur only in the lower part of the troposphere and are more pronounced over the oceans in the trade winds there is a maximum of humidity as a result of the trade winds long sea passage .in the upper part the air originates from the sub tropical high pressure belt is sinking warming adiabatically if temperature increases relative humidity will decrease the upper part is relatively dry the lower part is relatively moist and the upper part is relatively dry.

What is the dry adiabatic lapse rate ?

Question 133-31 : 3 0°c/1000 ft 2 0°c/1000 ft 1 5°c/1000 ft 3 5°c/1000 ft

exemple 353 3.0°c/1000 ft — .the dry adiabatic lapse rate has a constant fixed value of 1°c/100 m 3°c/1000 ft 3.0°c/1000 ft

What is a characteristic of stable air ?

Question 133-32 : Stratiform clouds unlimited visibility fair weather cumulus clouds temperature decreases rapidly

exemple 357 stratiform clouds. — stratiform clouds.

What is a characteristic phenomenon for a stable atmosphere ?

Question 133-33 : Stratified clouds weak wind no precipitation many vertical currents

exemple 361 stratified clouds. — .the words to distinguish between clouds produced by instability and other clouds are stratiform/stratified for clouds forming in a stable layer and convective clouds for clouds developing in an unstable environment stratiform clouds are basically flat and layered . stable clouds include cirrostratus altostratus nimbostratus and stratus .convective clouds have vertical development and often extend through a significant depth of the troposphere .convective clouds include cumulonimbus cumulus cirrus and altocumulus stratified clouds.

In an unsaturated layer in the friction layer the air is well mixed by ?

Question 133-34 : Correspond to the dry adiabatic lapse rate at first coincide with the average dry adiabat and then coincide with the average wet adiabat always change toward a more stable position coincide with the average wet adiabat in the layer

exemple 365 correspond to the dry adiabatic lapse rate. — .if the layer remains unsatured we have a conditional stability depending on dry or satured air but mixing the temperature in the turbulence layer will change the vertical temperature profile by increasing the vertical rate of temperature change it will correspond to the dry adiabatic lapse rate correspond to the dry adiabatic lapse rate.

Good visibility in the lower levels may be expected when ?

Question 133-35 : Cool dry air is moving over a warmer surface warm air is moving over a cold surface the atmospheric pressure is low the air temperature is low

exemple 369 cool dry air is moving over a warmer surface. — .good visibility is associated with unstable air a cool dry air moving over a warm surface will become unstable cool dry air is moving over a warmer surface.

A layer of stratus is most likely to be dispersed by ?

Question 133-36 : Insolation resulting in the lifting of the condensation level absorption of longwaved solar radiation in the stratus layer the release of latent heat due to precipitation adiabatic cooling due to subsidence

exemple 373 insolation resulting in the lifting of the condensation level. — insolation resulting in the lifting of the condensation level.

After a clear night cumuliform clouds are formed in the morning why can the ?

Question 133-37 : Because the surface temperature increases the wind speed is increasing because the cold air mass changes into a warm air mass because the stability increases because the difference between the temperature and the dewpoint temperature at the initial condensation level becomes smaller

exemple 377 because the surface temperature increases. — because the surface temperature increases.

Air masses which are being cooled from below are often characterized by ?

Question 133-38 : Fog poor visibility and layered clouds strong winds cumulus clouds good visibility uniform temperature good visibility continuous rain and freezing temperatures

exemple 381 fog, poor visibility and layered clouds. — fog, poor visibility and layered clouds.

An inversion is ?

Question 133-39 : An absolutely stable layer a conditionally unstable layer an unstable layer a layer that can be either stable or unstable

exemple 385 an absolutely stable layer — an absolutely stable layer

An unstable air mass is forced to ascend a mountain slope what type of clouds ?

Question 133-40 : Clouds with considerable vertical development and associated turbulence stratiform clouds with considerable turbulence layer like clouds with little vertical development stratiform clouds with a temperature inversion

exemple 389 clouds with considerable vertical development and associated turbulence. — .unstable air = cumulus.stable air = stratus.this question has been seen at the exam with this wording a conditionally unstable air mass is forced to ascend a mountain slope what type of clouds can be expected .right answer remains unchanged clouds with considerable vertical development and associated turbulence.

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