Chapter 5 -- Notes

Question 1

How much water is cycled through the atmosphere in a year?

Answer 1

380,000 cubic km (91,000 cubic miles).

Question 2

Define latent heat.

Answer 2

The energy absorbed or released during a change of state.

Question 3

Define latent heat of condensation.

Answer 3

The energy released when water vapor changes to the liquid state. The amount of energy released is equivalent the amount absorbed during evaporation.

Question 4

Define latent heat of vaporization.

Answer 4

The energy absorbed by water molecules during evaporation. It varies from about 600 calories per gram for water at 0°C to 540 calories per gram at 100°C.

Question 5

Define Sublimination and Deposition

Answer 5

Sublimination is a conversion of a solid to gas, and Deposition is the opposite.

Question 6

What is the most important gas in the atmosphere when it comes to understanding atmospheric processes

Answer 6

Water vapor

Question 7

Name the five methods Meteorologists to express the water-vapor content.

Answer 7

Absolute humidity Mixing ratio Vapor pressure Relative humidity Dew point

Question 8

Define Absolute humidity

Answer 8

The mass of water vapor in a given volume of air (usually as grams per cubic meter). A.H. = ^{M. of W.V.(g)}/_{Volume of Air (m²)}

Question 9

Define Mixing ratio.

Answer 9

The mass of water vapor in a unit of air compared to the remaining mass of dry air. M.R. = ^{M. of W.V.(g)}/_{M. of Dry Air.(kg)}

Question 10

Define…

Answer 10

This is showing that for example if its 5 °C (at sea level) the the saturation mixing ratio is 5 g/kg which means that the air is saturated when it contains 5g of water vapor per kg of air.

(P.S. every 10°C increase, the amount of of w.v. needed for saturaion doubles)

Question 11

Define saturation and saturation vapor pressure.

Answer 11

The maximum possible quantity of water vapor that the air can hold at any given temperature and pressure.

The vapor pressure, at a given temperature, wherin the water vapor is in equilibrium with a surface of pure water or ice.

Question 12

Define Vapor Pressure

Answer 12

That part of the total atmospheric pressure attributable to its water-vapor content.

Question 13

Define *net evaporation *and net condensation.

And which is more common?

Answer 13

When more water is evaporating than is condensating and vice versa.

Net evaporation.

Question 14

What causes fog?

Answer 14

Net evaporation

Question 15

What determines whether the rate of evaporation exceeds the rate of condesation or vice versa?

Answer 15

1. Temperature of the surface water. (net evaporation is greater when temperatures are high)
2. Vapor pressure in the air around the liquid. (net evaporation is greater when the air is dry)

Question 16

What is Relative Humidity**?

Answer 16

The ratio of the air’s actual water-vapor content compared with the amount of water vapor required for saturation at that temperature (and pressure).

Question 17

How can Relative Humidity be changed?

Answer 17

1. By the addition or removal of water vapor
2. By changing the temperature

Question 18

Wher does most the moisture in the air come from?

Answer 18

evaporation from the oceans

Question 19

Define Dew Point.

Answer 19

The temperature to which air has to be cooled in order to reach saturtation.

Unlike *Relative Humidity *Dew-Point temperature is a meausure of the actual moisture content of a parcel of air.

Low indicates dry air. High indicates moist air.

Question 20

Name the three **Natural **changes in Relative Humidity?

Answer 20

1. Daily changes in temperatures (daylight versus nighttime temperatures).
2. Temperature changes that result as air moves horizontally from one location to another.
3. Temperature changes caused as air moves vertically in the atmosphere.

Question 21

What instrument’s are used to measure Relative Humidity?

Answer 21

Hygrometers

The most accurate one is the psychrometer.

Question 22

How does a psychrometer work?

Answer 22

It has two thermometers next to each other one has a cloth wick tied around the bottom that soaked in water. Then they wave the psychrometer back and forth and the thermometer with the wick will lose heat due to the evaporation of the water and how much heat it loses corrolates to how much humidity is in the air.

Question 23

Define Adiabatic Temperature Changes.

Answer 23

The cooling or warming of air caused when air is allowed to expand or is compressed, not because heat is added or subtracted.

Question 24

How much does a parcel of unsaturated air adiabatically cool (heat) while rising (descending)?

What is this rate called?

Answer 24

10°C for every 1000 meters (5.5°F per 1000 feet).

The Dry Adiabatic Rate

Question 25

What is the Lifting Condensation Level?

Answer 25

The height at which rising air that is cooling at the dry adiabatic rate becomes saturated and condesation begins.

Question 26

What is the *Wet Adiabatic Rate? *

Answer 26

The rate of adiabatic temperature change in *saturated *air. The rate of temperature change is variable, but is always less than the dry adiabatic rate.

Question 27

During what season is the **Dew Point **at its highest?

Answer 27

Summer