chapter 3: air temperature Flashcards
Temperature can be described as
the degree of hotness or coldness of a specific body.
The temperature of a body is the condition which determines its ability
to
transfer heat to other bodies or to receive heat from them.
The temperature of a body is the condition which determines its ability to transfer heat to other bodies or to receive heat from them. In a system of two bodies, the one which loses heat to the other is said to be at
a higher temperature.
Practical temperature scales are based on
fixed points
Practical temperature scales are based on fixed points. These are
constant and easily reproducible
Two internationally-agreed fixed points are the
melting point and the boiling point
The melting point is
the temperature at which pure ice melts under an external pressure of one standard atmosphere.
The melting point is the temperature at which pure ice melts under an external pressure of one standard atmosphere. This point is also called the
freezing point
The boiling point is
the temperature at which pure water boils under the one atmospheric pressure.
The main common temperature scales are:
Celsius (or the centigrade), Fahrenheit and Kelvin.
melting point of celsius
0
the boiling point for celcius
100
the melting point of fehrenheit
32
the boiling point of fahrenheit
212
the melting point of kelvin
273.15
the boiling point of kelvin
373.15
To convert temperature from Celsius value to the corresponding Fahrenheit value we can use the following formula:
F = 9/5 ( C)+32
To convert temperature from Fahrenheit to Celsius scale used the following formula:
C = 5/9 (F-32 )
The Celsius scale and Kelvin scale are related by the following formula:
K = C+ 273.15
Air temperature varies from
day to night
Air temperature varies from day to night, by the reason of
reason of the earth’s rotation around itself.
Air temperature varies from day to night, by the reason of the earth’s
rotation around itself.
Because of the continuous cooling during night by the
loose of the earth’s (terrestrial) radiation into the atmosphere minimum temperature is observed early morning (about one hour after sunrise).
Because of the continuous cooling during night by the loose of the earth’s (terrestrial) radiation into the atmosphere minimum temperature is observed early morning (about one hour after sunrise). Maximum temperature occurs at
about two hours after noon
Maximum temperature occurs at about two hours after noon. This is because
the atmosphere is heated from the earth’s surface.
Also air temperature varies seasonally. This is due to
the earth’s revolution in its orbit around the sun with a tilt of 23.5
In addition the air temperature varies with latitude due to
the spherical form of our planet and varies with height by the reason that the atmosphere is not heated directly from the sun (the sun rays are short-wave radiations).
In addition the air temperature varies with latitude due to the spherical
form of our planet and varies with height by the reason that the atmosphere is
not heated directly from the sun (the sun rays are short-wave radiations). It is heated from
earth’s surface by the terrestrial radiation (terrestrial radiations are long-wave radiations)
In addition the air temperature varies with latitude due to the spherical form of our planet and varies with height by the reason that the atmosphere is not heated directly from the sun (the sun rays are short-wave radiations). It is heated from the earth’s surface by the terrestrial radiation (terrestrial radiations are long-wave radiations) another reason for decreasing temperature is the
decreasing pressure with height. As the pressure decreases the air expands and cools.
Also there are a temperature variations from place to place such as the differences between the heating of the air above water and land. These variations are caused by
heating properties of various surfaces
Also there are a temperature variations from place to place such as the
differences between the heating of the air above water and land. These
variations are caused by heating properties of various surfaces. Land is heated
more rapidly and for higher temperatures than water, and it is cooled more rapidly and for lower temperatures than water.
These variations are caused by heating properties of various surfaces. Land is heated more rapidly and for higher temperatures than water, and it is cooled more rapidly and for lower temperatures than water. Variations in air temperatures, therefore, are much greater over
land than over water
An important reason for temperature variations over water
(rising and falling much more slowly than surface temperatures on land) is that water is highly mobile
An important reason for temperature variations over water (rising and falling much more slowly than surface temperatures on land) is that water is highly mobile. As water is heated,
turbulence distributes the heat through a considerably larger mass.
An important reason for temperature variations over water (rising and
falling much more slowly than surface temperatures on land) is that water is
highly mobile. As water is heated, turbulence distributes the heat through a
considerably larger mass. On a daily basis, temperature changes occur to
depths of
6 meters or more below the surface,
An important reason for temperature variations over water (rising and
falling much more slowly than surface temperatures on land) is that water is
highly mobile. As water is heated, turbulence distributes the heat through a
considerably larger mass. On a daily basis, temperature changes occur to
depths of 6 meters or more below the surface, and on a yearly basis , o ceans
and deep lakes are subject to temperature variations through a layer between
200 to 600 meters thick.
In contrast, heat does not penetrate deeply into
soil or rock
In contrast, heat does not penetrate deeply into soil or rock; it remains in a
thin surface layer.
In contrast, heat does not penetrate deeply into soil or rock; it remains in a
thin surface layer. Here there is no
turbulence transfer of h eat, there is only a slow process of conduction.
Once pollutants enter the atmosphere their concentration
decreases as
they mix with clean air.
Once pollutants enter the atmosphere their concentration decreases as
they mix with clean air. The rate of dilution depends on
atmospheric conditions
Once pollutants enter the atmosphere their concentration decreases as
they mix with clean air. The rate of dilution depends on atmospheric
conditions, such as
wind speed and atmospheric stability
The way atmospheric stability plays a role is the following: solar radiation
is refle cted and absorbed by the surface of the Earth; the absorbed radiation heats the surface, which in turn heats the air near the surface; normally (under atmospheric unstable situations) warm air from near the surface moves upward and is replaced by cold air from above (convection)
The fact that the temperature in the troposphere decreases with altitude allows …………… to happen
convection
in the case of surface inversion ………………………… is high
the rate of dilution of pollutants
temperature inversion
The temperature in the troposphere does not always decrease with altitude
In the presence of a temperature inversion, the
air near the surface is
trapped and cannot move upward
In the presence of a temperature inversion, the
air near the surface is trapped and cannot move upward. In this case
gases emitted at the surface do not dilute, and the concentration of pollutants increases.
Temperature inversions happen in cities that are in
valleys.
Temperature inversions happen in cities that are in valleys. In this
case the inversion happens because of
radiative cooling from the surface.
In this
case the inversion happens because of radiative cooling from the surface. At
night the surface cools by
emission of infrared radiation
In this
case the inversion happens because of radiative cooling from the surface. At
night the surface cools by emission of infrared radiation, so that
the coldest air is adjacent to the Earth’s surface and the air temperature increases with altitude.
In this case the inversion happens because of radiative cooling from the surface. At night the surface cools by emission of infrared radiation, so that the coldestair is adjacent to the Earth’s surface and the air temperature increases with altitude. This inversion generally persists until
the surface is warmed again the next morning by absorption of sunlight
Thermal inversions are also common in areas near
mountain ranges such as in southern California
Thermal inversions are also common in areas near mountain ranges such as in southern California. In this case, the temperature
increases because of air that warms up as it descends down the mountain slope
The temperature normally decreases with
increasing altitude throughout the troposphere.
The temperature normally decreases with increasing altitude throughout
the troposphere. This decrease of temperature with altitude is defined as the
lapse rate of temperature
The average lapse rate is
6.5 c/km
lapse rate for dry air
10 c/km
lapse rate for moist air is
5 c/km
inversion.
the temperature increases with height
Sometimes, the temperature increases with height. This process is called the
inversion. The inversion is
the negative lapse rate
Sometimes, the temperature increases with height. This process is called the
inversion. The inversion is the negative lapse rate. There are main two types of
inversions:
surface inversion and inversion aloft
Surface inversion forms by the reason of
continuous cooling at calm and clear nights
Inversion aloft occurs when
a warm air mass moves over a cold air mass
The variation of temperature measures by
thermometers.
There are many types of thermometers. The most common of them are:
1- Liquid-in-glass thermometer. This is a simple instrument that provides relatively accurate readings over a wide temperature range. When temperature rises the fluid expands. In liquid-in-glass thermometers used either mercury or ethyl alcohol. Mercury can only be used down to about -36 C, which is just above its freezing point. For Lower temperatures, absolute ethyl alcohol is generally suitable.
2- Liquid-in-metal thermometer. The indicating unit of these thermometers is really a pressure gauge calibrated to read temper ature. It is widely used in motor car engines as a temperature gauge. This principle is also used in some thermographs. A pen is fitted to the tip of the pointer and the nib moves across a chart placed on a rotating cylindrical drum.
3- Thermograph. It is a self-recording thermometer which makes a continuous record of temperature measurements.
If the Earth was a homogeneous body without the present land/ocean
distribution, its temperature distribution would be
strictly latitudinal
If the Earth was a homogeneous body without the present land/ocean
distribution, its temperature distribution would be strictly latitudinal (Figure
3.5). However, the Earth is more complex than this being composed of a
mosaic of land and water.
If the Earth was a homogeneous body without the present land/ocean
distribution, its temperature distribution would be strictly latitudinal (Figure
3.5). However, the Earth is more complex than this being composed of a
mosaic of land and water. This mosaic causes
latitudinal zonation of temperature to be disrupted spatially.
The following two factors are important in influencing the distribution of temperature on the Earth’s surface:
- The latitude of the location determines how much solar radiation is received.
- Surface properties
The latitude of the location determines how much solar radiation is received. Latitude influences
the angle of incidence and duration of daylength.
Surface properties - surfaces with high albedo absorb
less incident radiation
Surface properties - surfaces with high albedo absorb less incident radiation. In general, land absorbs less
insolation that water because of its lighter color.
Surface properties - surfaces with high albedo absorb less
incident radiation. In general, land absorbs less insolation that
water because of its lighter color. Also, even if two surfaces
have the same albedo, a surface’s
specific heat determines the amount of heat energy required for a specific rise in temperature per unit mass.
In general, land absorbs less insolation that
water because of its lighter color. Also, even if two surfaces
have the same albedo, a surface’s specific heat determines the
amount of heat energy required for a specific rise in
temperature per unit mass. The specific heat of water is some
five times greater than that of
rock and the land surface
The specific heat of water is some
five times greater than that of rock and the land surface
As a result, water requires
the input of large amounts of energy to cause a rise in its temperature.
specific heat of water
1
specific heat of air
0.24
specific heat of granite
0.19
specific heat of sand
0.19
specific heat of iron
0.11
Mainly because of specific heat, land surfaces behave quite differently from
water surfaces. In general, the surface of any extensive deep body of water
heats more
slowly and cools more slowly than the surface of a large land body.
Other factors influencing the way land and water surfaces heat and cool include:
- Solar radiation warms an extensive layer in water, on land just the immediate surface is heated.
- Water is easily mixed by the process of convection.
- Evaporation of water removes energy from water’s surface.
