Question 1

Condensation occurs primarily when air is cooled, because as temperature drops the speed of the water molecules increases.

Accepted Answer

Condensation occurs primarily when air is cooled, but this cooling causes the speed of the water molecules to decrease, not increase, making the air less able to hold moisture, which can then condense into liquid form.

Question 2

The specific humidity and mixing ratio of an air parcel remain constant as long as water vapor is not added to or removed from the parcel.

Accepted Answer

Specific humidity and mixing ratio both describe the amount of water vapor in a parcel of air relative to the mass of dry air, and they remain constant as long as there is no addition or removal of water vapor, even if the parcel expands or contracts.

Question 3

In the United States, the lowest dew point, and hence the driest air, is found in the Southwest, with the lowest values found in Arizona.

Accepted Answer

False

Question 4

If the amount of water vapor in a descending atmospheric air parcel remains constant, the specific humidity also remains constant.

Accepted Answer

Specific humidity is defined as the mass of water vapor per unit mass of air, so if the amount of water vapor remains constant as the air parcel descends, the specific humidity also remains constant.

Question 5

The relative humidity is often near 100 percent in polar regions.

Accepted Answer

Polar regions are characterized by cold temperatures and high levels of moisture in the air. The cold temperatures cause the air to hold less moisture, resulting in high relative humidity levels, often near 100 percent.

Question 6

Comparing the three phases of water, molecules in the solid phase (ice)have the slowest vibrational speed, and molecules in the gaseous phase (water vapor)have the highest vibrational speeds.

Accepted Answer

In the solid phase, molecules are closely packed in a fixed position and can only vibrate around their fixed points, leading to slower vibrational speeds. In the gaseous phase, molecules are far apart and move freely at high speeds, resulting in the highest vibrational speeds.

Question 7

When the air temperature increases, the saturation vapor pressure decreases.

Accepted Answer

When the air temperature increases, the saturation vapor pressure increases because warmer air can hold more water vapor.

Question 8

Condensation differs from precipitation, because during precipitation water vapor is removed from the atmosphere, whereas during condensation solid or liquid water is removed from the atmosphere.

Accepted Answer

Condensation is the process where water vapor becomes liquid water, and it often precedes precipitation, which is when any form of water (liquid or solid) falls from the atmosphere to the surface. Condensation itself does not remove water from the atmosphere but transforms its state, while precipitation is the actual removal of water from the atmosphere.

Question 9

During the winter, high relative humidity can irritate the mucus membranes in the nose and throat.

Accepted Answer

Low relative humidity during the winter can irritate the mucus membranes in the nose and throat because dry air can lead to dehydration of these tissues.

Question 10

Nighttime temperatures rarely drop below the dew point temperature because at saturation, latent heat of condensation is released into the air.

Accepted Answer

When the air temperature drops to the dew point temperature, saturation occurs, leading to condensation. This process releases latent heat into the air, which can help prevent the temperature from falling further, thus making it rare for nighttime temperatures to drop below the dew point.

Question 11

Water in a glass will evaporate more quickly on a windy, warm, dry summer day than on a calm, cold, dry winter day.

Accepted Answer

Evaporation rates increase with higher temperatures, lower humidity, and greater air movement, all of which are more characteristic of a windy, warm, dry summer day compared to a calm, cold, dry winter day.

Question 12

When the dew point is determined with respect to a flat surface of ice, it is called the ice point.

Accepted Answer

When the dew point is determined with respect to a flat surface of ice, it is called the frost point, not the ice point. The dew point refers to the temperature at which air becomes saturated with moisture when cooling, leading to dew formation on surfaces. The frost point specifically refers to the temperature at which moisture in the air will freeze upon surfaces, forming frost, when the reference surface is ice.

Question 13

Saturation is more likely to occur in cool air than in warm air.

Accepted Answer

Cool air can hold less moisture than warm air, so it reaches saturation more quickly as moisture is added.

Question 14

A region can have a high specific humidity and low relative humidity because large amounts of water vapor in the air and very high air temperatures will cause the specific humidity to be high, but the relative humidity to be low.

Accepted Answer

Specific humidity is a measure of the actual amount of water vapor in the air, regardless of temperature, while relative humidity is a measure of the current amount of water vapor in the air relative to the maximum amount of water vapor the air can hold at that temperature. High temperatures increase the air's capacity to hold water vapor, so even if there is a lot of water vapor, the relative humidity can be low if the air's capacity to hold water vapor is not fully utilized.

Question 15

The air's moisture content can be described by measuring the pressure exerted by the water vapor in the air.

Accepted Answer

The moisture content of the air is often described by the partial pressure of water vapor present, which is the pressure exerted by just the water vapor in the air.

Question 16

Saturation vapor pressure primarily depends upon air temperature.

Accepted Answer

Saturation vapor pressure increases with an increase in air temperature because warmer air can hold more water vapor before condensation occurs.

Question 17

A sling psychrometer directly measures the relative humidity.

Accepted Answer

A sling psychrometer measures the dry bulb and wet bulb temperatures, which are then used to calculate the relative humidity, not directly measure it.

Question 18

Under saturated conditions, for every molecule that evaporates, one must condense, and no net loss of liquid or vapor molecules results.

Accepted Answer

Under saturated conditions, the rate of evaporation equals the rate of condensation, meaning for every molecule that evaporates, one molecule condenses, resulting in no net change in the amount of liquid or vapor.

Question 19

Plants give up moisture by a process called perspiration.

Accepted Answer

Plants give up moisture through a process called transpiration, not perspiration.

Question 20

A strand of human hair is known to increase by 2.5 percent as the relative humidity increases from 0 to 100 percent.

Accepted Answer

Human hair hygrometer readings are based on the principle that a strand of human hair increases in length by about 2.5 percent with a relative humidity change from 0 to 100 percent, making it a natural and sensitive measure for humidity changes.

Quiz 4: Atmospheric Humidity