How and why humidity and vapour pressure change as a parcel of air with an unchanging amount of water vapor rises, expands, and cools

Asked by: Christopher Washington

How does the relative humidity change for an air parcel of constant water content as it is lifted into the atmosphere?

As a rising parcel cools, its relative humidity increases. Once the relative humidity reaches 100% (determined when the parcel temperature cools down to its original dew point temperature), further lifting (and cooling) results in net condensation, forming a cloud.

How can the relative humidity of a parcel of air be changed?

We can thus change the relative humidity of a air parcel by either increasing or decreasing the amount of water vapor in the parcel (this changes the mixing ratio of the air mass) OR by raising or lowering the temperature of the air mass (this changes the capacity of the air mass).

What happens to the relative humidity of a rising air parcel?

The air parcel expands as it rises and this expansion, or work, causes the temperature of the air parcel to decrease. As the parcel rises, its humidity increases until it reaches 100%.

Why does the temperature within a parcel of air decrease when the parcel rises?

As a parcel of air in the earth’s atmosphere rises through the atmosphere, it experiences decreasing pressure and thus expands. This expansion lowers the temperature of the air parcel, and therefore the air cools as it rises.

What would cause the air parcel to expand as it rises?

A rising parcel of air expands because the air pressure falls with elevation. This expansion causes the air to cool. A falling parcel of air contracts because the air pressure increases. The contraction causes the air to warm.

Why does an air parcel become saturated as it rises?

As a rising parcel cools, its relative humidity increases. Once the relative humidity reaches 100% (determined when the parcel temperature cools down to its original dew point temperature), further lifting (and cooling) results in net condensation, forming a cloud.

How and why might the relative humidity of an air parcel change as it moves up a mountain What are the consequences of these changes for precipitation?

As the air moves up the windward side of a mountain, it cools, and the volume decreases. As a result, humidity increases and orographic clouds and precipitation can develop. When the air descends the leeward side, it warms and is drier because the moisture in the air was wrung out during the ascent.

How might the relative humidity of a parcel of air change as it moves up the side of a mountain Why?

As a rising parcel cools, its relative humidity increases. Once the relative humidity reaches 100% (determined when the parcel temperature cools down to its original dew point temperature), further lifting (and cooling) results in net condensation, forming a cloud.

What happens to the relative humidity of an unsaturated air parcel when its temperature increases Why?

The relative humidity of a rising unsaturated air parcel increases. This is because the temperature and dewpoint values are converging towards each other (the temperature is cooling more than the dewpoint thus as they approach each other the relative humidity increases).

Why do moist parcels cool at a slower rate than dry parcels as they rise?

Any saturated parcel (parcel with 100% relative humidity) cools at a slower rate. This is because the process of water vapor condensing into a liquid releases heat. The released heat that is added to the atmosphere slows the rate of cooling.

When a parcel of air rises does it become warmer cooler or remain the same temperature?

Rising air experiences a drop in temperature, even though no heat is lost to the outside. The drop in temperature is a result of the decrease in atmospheric pressure at higher altitudes. If the pressure of the surrounding air is reduced, then the rising air parcel will expand.

When a parcel rises How does its pressure volume and temperature change?

Pressure decreases when a parcel is lifted. From the gas law, the (density x temperature) must also decrease. Both number density and temperature decrease when a parcel expands.

Why do rising air parcels cool at a slower rate once they become saturated?

As saturated air rises, expands, and cools, condensation releases latent heat inside the parcel. The latent heat energy offsets and reduces the cooling due to expansion. There isn’t enough latent heat energy to cause the rising parcel to warm.

Why does air expand as it moves upward through the atmosphere quizlet?

why does air expand as it moves upward through the atmosphere? As air moves upward through the atmosphere the pressure gradually decreases due to gas and internal energy decreases, in which the air expands and cools adiabatically.

What happens to an air parcel as it rises through the atmosphere quizlet?

In the atmosphere, a rising air parcel will expand. An air parcel will cool at the dry adiabatic lapse if it is lifted, remains unsaturated, and does not exchange energy or mass with its environment during lifting.

What happens to the parcel of air as it descends?

→ The temperature of the air parcel (or balloon) decreases with elevation. The lost energy is used to increase the potential energy of air molecular. Similarly when the air parcel descends, the potential energy of air molecular is converted back to kinetic energy. → Air temperature rises.

Which of the following will increase in a rising parcel of air?

Solution(By Examveda Team) Relative humidity will increase in a rising parcel of air.

Which type of fog is produced when air is lifted over a topographic barrier?

Which type of fog is produced when air is lifted over a topographic barrier? Upslope fog.

Which air parcel will have more rainfall and why?

If an air parcel is warmer than the surrounding air it will rise. As an air parcel rises, energy transfers from the warm air parcel to the cold surrounding air until their temperatures become equal. When an air parcel starts with a higher temperature, it will rise higher and lose more energy, causing more rainfall.

Why do moist parcels cool at a slower rate than dry parcels as they rise?

Any saturated parcel (parcel with 100% relative humidity) cools at a slower rate. This is because the process of water vapor condensing into a liquid releases heat. The released heat that is added to the atmosphere slows the rate of cooling.

When a parcel of air rises does it become warmer cooler or remain the same temperature?

Rising air experiences a drop in temperature, even though no heat is lost to the outside. The drop in temperature is a result of the decrease in atmospheric pressure at higher altitudes. If the pressure of the surrounding air is reduced, then the rising air parcel will expand.