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Question 160-1 : A layer can be ? [ Formation assignment ]
Stable for unsaturated air and unstable for saturated air.
.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.
Question 160-2 : In a layer of air the decrease in temperature per 100 metres increase in height is more than 1°c. this layer can be described as being ?
Absolutely unstable.
.more than 1°c/100 m = more than 3°c/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 unsaturated..or. unstable if air is saturated.
Question 160-3 : Which statement is true for a conditionally unstable layer ?
The environmental lapse rate is less than 1°c/100 m.
.more than 1°c/100 m = more than 3°c/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 unsaturated..or. unstable if air is saturated.
Question 160-4 : The stability in a layer is increasing if ?
Warm air is advected in the upper part and cold air in the lower part.
.it is similar to an inversion..if a parcel of air is forced to rise, it will be colder than the air it is rising into, so the moment the trigger stops lifting it, it will sink back to the level it started from, because it is more dense. the layer is stable.
Question 160-5 : Which of the following statements concerning the lifting of a parcel of air is correct ?
Unsaturated parcels cool more rapidly than saturated parcels.
.there is less moisture in an unsaturated parcels to retain heat.
Question 160-6 : When in the upper part of a layer warm air is advected the ?
Stability increases in the layer.
.it is similar to an inversion..if a parcel of air is forced to rise, it will be colder than the air it is rising into, so the moment the trigger stops lifting it, it will sink back to the level it started from, because it is more dense. the stability increases in the layer.
Question 160-7 : The dew point temperature ?
Can be equal to the air temperature.
Question 160-8 : Relative humidity depends on ?
Moisture content and temperature of the air
Question 160-9 : When water evaporates into unsaturated air ?
Heat is absorbed.
.a known phenomena when water evaporates into unsaturated air is that the air is cooled. the water transitioning from a liquid state to a gaseous state is transitioning from a lower energy state to a higher energy state. the energy required for this transition to take place is provided to the water in the form of heat that is taken out of the surrounding air. this latent heat of vaporization leaving the air causes a temperature of the air to be reduced.
Question 160-10 : A moist but unsaturated parcel of air becomes saturated by ?
Lifting the parcel to a higher level.
.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.
Question 160-11 : A sample of moist but unsaturated air may become saturated by ?
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.
Question 160-12 : The maximum amount of water vapour that the air can contain depends on the ?
Air temperature.
.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.
Question 160-13 : Convective clouds are formed ?
In unstable atmosphere.
Question 160-14 : The most effective way to dissipate cloud is by ?
Subsidence.
Question 160-15 : Areas of sinking air are generally cloudless because as air sinks it ?
Is heated by compression.
.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.
Question 160-16 : The main factor which contributes to the formation of very low clouds ahead of a warm front is the ?
Saturation of the cold air by rain falling into it and evaporating.
.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.
Question 160-17 : In an unstable layer there are cumuliform clouds. the vertical extent of these clouds depends on the ?
Thickness of the unstable layer
Question 160-18 : Which of the following phenomena are formed when a moist, stable layer of air is forced to rise against a mountain range ?
Stratified clouds.
.lifting moist, stable layer of air produces stratus.
Question 160-19 : The height of the lifting condensation level is determined by ?
Temperature and dewpoint at the surface.
. 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.
Question 160-20 : During an adiabatic process heat is ?
Neither added nor lost.
Question 160-21 : The decrease in temperature, per 100 metres, in an unsaturated rising parcel of air is ?
1°c.
.1°c/100 m or 3°c/1000 ft this is the dry adiabatic lapse rate.
Question 160-22 : The decrease in temperature, per 100 metres, in a saturated rising parcel of air at lower level of the atmosphere is approximately ?
0.6°c.
.dry lapse rate = 3ºc/1000 ft or 1ºc/100 m.saturated lapse rate = 1ºc/1000 ft or 0.6ºc/100 m.
Question 160-23 : In unstable air, ground visibility is most likely to be restricted by ?
Showers of rain or snow.
Question 160-24 : A vertical temperature profile indicates the possibility of severe icing when the temperature profile ?
Intersects the 0°c isotherm twice.
.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.
Question 160-25 : The rate of cooling of ascending saturated air is less than the rate of cooling of ascending unsaturated air because ?
Heat is released during the condensation process.
Question 160-26 : If the surface temperature is 15°c, then the temperature at 10000 ft in a current of ascending unsaturated air is ?
15°c.
. 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.
Question 160-27 : An inversion is ?
An increase of temperature with height
Question 160-28 : In still air the temperature decreases at an average of 1.2°c per 100 m increase in altitude. this temperature change is called ?
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...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'.
Question 160-29 : From which of the following pieces of information can the stability of the atmosphere be derived ?
Environmental lapse rate.
.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.
Question 160-30 : A layer is absolutely unstable if the temperature decrease with height is ?
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.
Question 160-31 : A layer in which the temperature remains constant with height is ?
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.
Question 160-32 : A layer in which the temperature increases with height is ?
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.
Question 160-33 : A layer in which the temperature decreases with 1°c per 100 m increasing altitude is ?
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.
Question 160-34 : If in a 100 m thick layer the temperature at the bottom of the layer is 10°c and at the top of the layer is 8°c then this layer is ?
Absolutely 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...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.
Question 160-35 : A wide body takes off on a clear night in dhahran, saudi arabia. shortly after take off the aircraft's rate of climb drops to zero. this can be due to ?
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.
Question 160-36 : The value of the saturated adiabatic lapse rate is closest to that of the dry adiabatic lapse rate in ?
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.
Question 160-37 : Dew point is defined as ?
The temperature to which moist air must be cooled to become saturated at a given pressure
Question 160-38 : The process by which water vapour is transformed directly into ice is known as ?
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.
Question 160-39 : A foehn wind occurs on the ?
Leeward side of a mountain range and is caused by significant moisture loss by precipitation from cloud
Question 160-40 : Relative humidity at a given temperature is the relation between ?
Actual water vapour content and saturated water vapour content
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