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Question 147-1 : The decrease in temperature per 100 metres in a saturated rising parcel of air at lower level of the atmosphere is approximately ? [ Certification weather ]

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 exemple 247 0.6°c.

Question 147-2 : In unstable air ground visibility is most likely to be restricted by ?

Showers of rain or snow

exemple 251 Showers of rain or snow.

Question 147-3 : A vertical temperature profile indicates the possibility of severe icing when the temperature profile ?

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 exemple 255 Intersects the 0°c isotherm twice.

Question 147-4 : 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

exemple 259 Heat is released during the condensation process.

Question 147-5 : If the surface temperature is 15°c then the temperature at 10000 ft in a current of ascending unsaturated air is ?

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 exemple 263 -15°c.

Question 147-6 : An inversion is ?

An increase of temperature with height

exemple 267 An increase of temperature with height

Question 147-7 : 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

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' exemple 271 Dry adiabatic lapse rate.

Question 147-8 : From which of the following pieces of information can the stability of the atmosphere be derived ?

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 exemple 275 Environmental lapse rate.

Question 147-9 : A layer is absolutely unstable if the temperature decrease with height is ?

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 exemple 279 More than 1°c per 100m.

Question 147-10 : A layer in which the temperature remains constant with height is ?

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 exemple 283 Absolutely stable.

Question 147-11 : A layer in which the temperature increases with height is ?

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 exemple 287 Absolutely stable.

Question 147-12 : A layer in which the temperature decreases with 1°c per 100 m increasing altitude is ?

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 exemple 291 Neutral for dry air.

Question 147-13 : 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

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 exemple 295 Absolutely unstable.

Question 147-14 : 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

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 exemple 299 A very strong temperature inversion.

Question 147-15 : The value of the saturated adiabatic lapse rate is closest to that of the dry adiabatic lapse rate in ?

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 exemple 303 Cirrus.

Question 147-16 : Dew point is defined as ?

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

exemple 307 The temperature to which moist air must be cooled to become saturated at a given pressure

Question 147-17 : The process by which water vapour is transformed directly into ice is known as ?

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 exemple 311 Sublimation.

Question 147-18 : A foehn wind occurs on the ?

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

exemple 315 Leeward side of a mountain range and is caused by significant moisture loss by precipitation from cloud

Question 147-19 : Relative humidity at a given temperature is the relation between ?

Actual water vapour content and saturated water vapour content

exemple 319 Actual water vapour content and saturated water vapour content

Question 147-20 : A parcel of unsaturated air is forced to rise through an isothermal layer so long as it remains unsaturated the temperature of the parcel ?

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 exemple 323 Decreases 1°c per 100 m.

Question 147-21 : Absolute instability in the atmosphere will occur when the environmental lapse rate is ?

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 exemple 327 Greater than both saturated adiabatic lapse rate and dry adiabatic lapse rate

Question 147-22 : For both saturated and unsaturated air instability will occur when the ?

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 exemple 331 Environmental lapse rate is greater than both dry adiabatic lapse rate and saturated adiabatic lapse rate

Question 147-23 : In the lower levels of the atmosphere when the environmental lapse rate is greater than saturated adiabatic lapse rate but less than dry adiabatic lapse rate the air mass is described as being ?

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 exemple 335 Conditionally unstable.

Question 147-24 : Surface temperature inversions are frequently generated by ?

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 exemple 339 Terrestrial radiation on a calm clear night.

Question 147-25 : Surface based temperature inversions are common during ?

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 exemple 343 Cloud-free nights in winter when the ground is dry.

Question 147-26 : The maximum vapour pressure over a flat supercooled water surface and the maximum vapour pressure over a flat ice surface of the same temperature are compared .the maximum vapour pressure is ?

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 exemple 347 Greater over the water surface.

Question 147-27 : The stability in a layer increases by advection of ?

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 exemple 351 Cold air in the lower part.

Question 147-28 : The temperature at the surface is given as +15°c and at 4000 ft it is +9°c the state of this layer is said to be ?

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 exemple 355 Stable.

Question 147-29 : Which of the following phenomena is least likely to lead to the formation of a cumulonimbus with thunderstorm ?

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 exemple 359 Ground radiation.

Question 147-30 : Which of the following sets of conditions are most favourable to the development of thunderstorms ?

Environmental lapse rate greater than saturated adiabatic lapse rate through a great vertical extent high relative humidity and an initial lifting process

exemple 363 Environmental lapse rate greater than saturated adiabatic lapse rate through a great vertical extent, high relative humidity and an initial lifting process

Question 147-31 : Which of the following statements is correct ?

The bergeron findeisen process is mainly based on the difference of maximum vapour pressure over water and over ice of the same temperature

Admin .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 exemple 367 The bergeron-findeisen process is mainly based on the difference of maximum vapour pressure over water and over ice of the same temperature.

Question 147-32 : Which of the following statements is true of the dew point of an air mass ?

It can only be equal to or lower than the temperature of the air mass

Admin .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% exemple 371 It can only be equal to, or lower, than the temperature of the air mass.

Question 147-33 : Which one of the following can provide the initial lifting leading to air mass thunderstorms ?

Advection of cold air over a warm sea

Admin .cold air over a warm surface gives convective lifting exemple 375 Advection of cold air over a warm sea.

Question 147-34 : Which of the following quantities remains unchanged if unsaturated air is lifted until it reaches the lifting condensation level ?

Mixing ratio

Admin .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 exemple 379 Mixing ratio.

Question 147-35 : Which of the following processes will increase the stability of an air mass ?

Cooling by the underlying surface

exemple 383 Cooling by the underlying surface.

Question 147-36 : Which statement is correct for an absolutely unstable atmosphere ?

Visibility is good between showers

Admin .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 exemple 387 Visibility is good between showers.

Question 147-37 : Relative humidity ?

Increases if the air is cooled whilst maintaining the vapour pressure constant

Admin .the air contracts therefore takes less volume .the water quantity does not change maintaining the vapour pressure constant' thus relative humidity increases exemple 391 Increases if the air is cooled whilst maintaining the vapour pressure constant.

Question 147-38 : What is true for the water vapour distribution in the layer between the surface and the 500 hpa pressure surface in the tradewind belt ?

The lower part is relatively moist and the upper part is relatively dry

Admin .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 exemple 395 The lower part is relatively moist and the upper part is relatively dry.

Question 147-39 : What is the dry adiabatic lapse rate ?

3 0°c/1000 ft

Admin .the dry adiabatic lapse rate has a constant fixed value of 1°c/100 m 3°c/1000 ft exemple 399 3.0°c/1000 ft

Question 147-40 : What is a characteristic of stable air ?

Stratiform clouds

exemple 403 Stratiform clouds.


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