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Question 146-1 : How does relative humidity and the dewpoint in an unsaturated air mass change with varying temperature ? [ Certification weather ]

When temperature increases the relative humidity decreases and the dewpoint remains constant

Admin .relative humidity is a percentage based on how much moisture is in the air versus how much moisture the air can hold .relative humidity will change if moisture is added to or taken from the air mass or if the temperature changes .if temperature increases relative humidity decreases and if temperature decreases relative humidity increases .the dewpoint is the temperature that the atmosphere must reach for a parcel of air to become fully saturated in an unsaturated air mass the dewpoint will remains constant if the temperature changes exemple 246 When temperature increases, the relative humidity decreases, and the dewpoint remains constant.

Question 146-2 : When a given mass of air descends what effect will it have on relative humidity ?

It decreases

Admin .when air descends its temperature increases if temperature increases relative humidity will decrease . 501 exemple 250 It decreases.

Question 146-3 : During the late afternoon an air temperature of +12°c and a dew point of +5°c were measured what temperature change must at least occur during the night in order to induce saturation ?

It must decrease to +5°c

Admin .if air temperature decreases by 5°c air temperature will not be saturated 12°c 5°c = 7°c .so air temperature must decrease to +5°c to become saturated air temperature and dew point must be equal exemple 254 It must decrease to +5°c.

Question 146-4 : Which of the following changes of state is known as sublimation in meteorology ?

Solid direct to vapour

Admin .sublimation is the process in which a material changes from a frozen solid to a gas without passing through the intermediate liquid state exemple 258 Solid direct to vapour.

Question 146-5 : A parcel of moist but not saturated air rises due to adiabatic effects which of the following changes ?

Relative humidity

Admin .the absolute humidity is a measure of mass of water vapour per unit volume of air grams per cubic metre and mixing ration is a measure of mass of water vapour per unit mass of air grams per kilogram these will not change as temperature changes .the relative humidity is a measure of the percentage degree of saturation and this will change as temperature changes . 501 exemple 262 Relative humidity.

Question 146-6 : In which of the following changes of state is latent heat released ?

Gas to liquid

Admin .latent heat is absorbed when going from liquid to gas solid to liquid solid to gas .latent heat is released when going from gas to liquid liquid to solid gas to solid exemple 266 Gas to liquid.

Question 146-7 : How are high level condensation trails formed that are to be found occasionally behind jet aircraft ?

Through water vapour released during fuel combustion

Admin .it is the water vapour produced when hydrocarbon fuels are burnt exemple 270 Through water vapour released during fuel combustion.

Question 146-8 : In an air mass with no clouds the surface temperature is 15°c and the temperature at 1000 m/agl is 13°c this layer of air is ?

Stable

Admin .lapse rate is 2°c for 1000 m 3000 ft so 0 6°c for 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 exemple 274 Stable.

Question 146-9 : If a saturated air mass descends down a slope its temperature increases at ?

A lower rate than in dry air as evaporation absorbs heat

Admin .relative humidity will change if moisture is added to or taken from the air mass or if the temperature changes .if temperature increases relative humidity decreases and if temperature decreases relative humidity increases exemple 278 A lower rate than in dry air, as evaporation absorbs heat.

Question 146-10 : Continuous freezing rain is observed at an airfield which of the four diagrams is most likely to reflect temperatures above the airfield concerned . 297 ?

Diagram 4

Admin .there are a few basic elements that need to be in place for freezing rain to occur there must be a thick layer of warm air in the mid layers of the atmosphere there also must be a very narrow layer of below freezing temperatures at the surface . 545.the rain is falling into air with a temperature below 0°c exemple 282 Diagram 4.

Question 146-11 : An isothermal layer is a layer of air in which the temperature ?

Remains constant with height

exemple 286 Remains constant with height.

Question 146-12 : An inversion is a layer of air which is ?

Absolutely stable

exemple 290 Absolutely stable.

Question 146-13 : The environmental lapse rate in an actual atmosphere ?

Varies with time

exemple 294 Varies with time.

Question 146-14 : The dry adiabatic lapse rate has a value of ?

1°c/100 m

Admin .the dry adiabatic lapse rate has a constant fixed value of 1°c/100 m 3°c/1000 ft exemple 298 1°c/100 m.

Question 146-15 : The dry adiabatic lapse rate ?

Has a constant fixed value

Admin .the dry adiabatic lapse rate has a constant fixed value of 1°c/100 m 3°c/1000 ft exemple 302 Has a constant fixed value.

Question 146-16 : An air mass is called stable when ?

The vertical motion of rising air tends to become weaker and disappears

exemple 306 The vertical motion of rising air tends to become weaker and disappears

Question 146-17 : Advection is ?

Horizontal motion of air

Admin .advection is horizontal motion of air .subsidence is vertically downwards motion of air .convection is vertically upwards motion of air exemple 310 Horizontal motion of air.

Question 146-18 : Subsidence is ?

Vertically downwards motion of air

Admin .advection is horizontal motion of air .subsidence is vertically downwards motion of air .convection is vertically upwards motion of air exemple 314 Vertically downwards motion of air.

Question 146-19 : Rising air cools because ?

It expands

exemple 318 It expands.

Question 146-20 : A layer can be ?

Stable for unsaturated air and unstable for saturated air

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 exemple 322 Stable for unsaturated air and unstable for saturated air.

Question 146-21 : 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

Admin .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 exemple 326 Absolutely unstable.

Question 146-22 : Which statement is true for a conditionally unstable layer ?

The environmental lapse rate is less than 1°c/100 m

Admin .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 exemple 330 The environmental lapse rate is less than 1°c/100 m.

Question 146-23 : The stability in a layer is increasing if ?

Warm air is advected in the upper part and cold air in the lower part

Admin .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 exemple 334 Warm air is advected in the upper part and cold air in the lower part.

Question 146-24 : Which of the following statements concerning the lifting of a parcel of air is correct ?

Unsaturated parcels cool more rapidly than saturated parcels

Admin .there is less moisture in an unsaturated parcels to retain heat exemple 338 Unsaturated parcels cool more rapidly than saturated parcels.

Question 146-25 : When in the upper part of a layer warm air is advected the ?

Stability increases in the layer

Admin .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 exemple 342 Stability increases in the layer.

Question 146-26 : The dew point temperature ?

Can be equal to the air temperature

exemple 346 Can be equal to the air temperature.

Question 146-27 : Relative humidity depends on ?

Moisture content and temperature of the air

exemple 350 Moisture content and temperature of the air

Question 146-28 : When water evaporates into unsaturated air ?

Heat is absorbed

Admin .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 exemple 354 Heat is absorbed.

Question 146-29 : A moist but unsaturated parcel of air becomes saturated by ?

Lifting the parcel to a higher level

Admin .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 exemple 358 Lifting the parcel to a higher level.

Question 146-30 : 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 exemple 362 Expanding it adiabatically.

Question 146-31 : The maximum amount of water vapour that the air can contain depends on the ?

Air temperature

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 exemple 366 Air temperature.

Question 146-32 : Convective clouds are formed ?

In unstable atmosphere

exemple 370 In unstable atmosphere.

Question 146-33 : The most effective way to dissipate cloud is by ?

Subsidence

exemple 374 Subsidence.

Question 146-34 : Areas of sinking air are generally cloudless because as air sinks it ?

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 exemple 378 Is heated by compression.

Question 146-35 : 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

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 exemple 382 Saturation of the cold air by rain falling into it and evaporating.

Question 146-36 : In an unstable layer there are cumuliform clouds the vertical extent of these clouds depends on the ?

Thickness of the unstable layer

exemple 386 Thickness of the unstable layer

Question 146-37 : Which of the following phenomena are formed when a moist stable layer of air is forced to rise against a mountain range ?

Stratified clouds

Admin .lifting moist stable layer of air produces stratus exemple 390 Stratified clouds.

Question 146-38 : The height of the lifting condensation level is determined by ?

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 exemple 394 Temperature and dewpoint at the surface.

Question 146-39 : During an adiabatic process heat is ?

Neither added nor lost

exemple 398 Neither added nor lost.

Question 146-40 : The decrease in temperature per 100 metres in an unsaturated rising parcel of air is ?

1°c

Admin .1°c/100 m or 3°c/1000 ft this is the dry adiabatic lapse rate exemple 402 1°c.


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