Meteorology - Understanding Temperature

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Questions and Answers

The measurement of surface temperature is made:

at approximately 4 feet above ground level (correct)

at ground level

at approximately 10 metres from ground level

at approximately 4 metres above ground level

The purpose of a "Stevenson screen" is to:

maintain a moist atmosphere so that the wet bulb thermometer can function correctly

prevent the mercury freezing in the low winter temperatures

keep the wet and dry bulb thermometers away from surface extremes of temperature (correct)

protect the thermometer from wind, weather and from direct sunshine

If temperature remains constant with an increase in altitude there is:

an isothermal layer (correct)

uniform lapse rate

an inversion aloft

an inversion

The surface of the earth is heated by:

short wave solar radiation Signup and view all the answers

Cloud cover will reduce diurnal variation of temperature because:

incoming solar radiation is reflected back to space and outgoing terrestrial radiation is re-radiated from the cloud layer back to the surface Signup and view all the answers

Diurnal variation of the surface temperature will:

increase as wind speed increases Signup and view all the answers

Which of the following surfaces is likely to produce a higher than average diurnal variation of temperature?:

rock or concrete Signup and view all the answers

Most accurate temperatures above ground level are obtained by:

radiosonde Signup and view all the answers

The method by which energy is transferred from one body to another by contact is called:

conduction Signup and view all the answers

The diurnal variation of temperature is:

reduced anywhere by the presence of cloud Signup and view all the answers

The troposphere is heated largely by:

conduction from the surface, convection and the release of latent heat Signup and view all the answers

An inversion is one in which:

there is an increase of temperature as height increases Signup and view all the answers

The sun gives out amount of energy with wavelengths. The earth gives out relatively amounts of energy with relatively wavelengths.

large, short, small, long Signup and view all the answers

With a clear night sky, the temperature change with height by early morning is most likely to show:

an inversion from near the surface and a 2°C per 1000 ft lapse rate above Signup and view all the answers

Over continents and oceans, the relative temperature conditions are:

colder in winter over land, warmer in winter over sea Signup and view all the answers

Study Notes

Meteorology - Temperature

Meteorology is the study of the atmosphere and its phenomena.
Temperature is a key element in meteorology.

Objectives

Temperature measurements
Heating of the atmosphere
Surface temperature variations

Unit of Measurements

Fahrenheit scale: +32 to +212 degrees
Celsius (or Centigrade) scale: 0 to +100 degrees
Kelvin (or Absolute) scale: +273 to +373 degrees
Conversion factors for Celsius, Fahrenheit, and Kelvin are available on CRP 5.

Latent Heat

Changes of state (solid, liquid, gas) involve absorbing or releasing latent heat.
Specific examples of latent heat transfer are shown in a diagram.

Stevenson Screen & Thermograph

Thermograph records temperature changes on a rotating drum.
Stevenson Screen houses instruments like the thermograph. (Shown in an image)

Radiosonde

Measures temperature, pressure, humidity, winds
Tracking is done optically/radio theodolite or radar.
It is used for high altitude measurements.
It is attached to a balloon with a radar reflector and a ground-based radar to track its height.

Heating of the Atmosphere - Solar Radiation

Solar radiation, a shortwave high-intensity radiation, heats the earth's surface.
This process is called insolation.
Some of the heat is reflected back into the atmosphere.

Heating of the Atmosphere - Terrestrial Radiation

The Earth re-radiates heat energy back to the atmosphere as a long wave length.
The atmosphere absorbs some of the heat. The air reduces in temperature with an increase in height.
The lapse rate (the rate at which temperature drops with height) is typically 1.98°C per 1,000 feet or 0.65°C per 100 meters.

Heating of the Atmosphere - Greenhouse Effect

Water vapor and CO2 in the atmosphere absorb heat and re-radiate it back to the Earth.
This effect maintains the Earth's warmth.
Water vapor is responsible for 36% to 70% of the greenhouse effect, or even more depending on the region.

Heating of the Atmosphere - Conduction

Heating of the atmosphere (surface) through direct contact.
Shown diagrammatically with an image illustrating a temperature profile during the day.

Heating of the Atmosphere - Convection

Re-radiated heat rises to higher altitudes, creating thermal or convection currents.
The movement of air in response to differences in temperature.
Illustrated in an image.

Heating of the Atmosphere - Condensation

Water vapor turns into a solid state and releases latent heat.
The heat released warms the surrounding air. This process is important.

Heating of the Atmosphere - Advection

The movement of air masses horizontally, resulting in temperature changes.
For example, polar air moving to lower latitudes leads to cooler air.

All Heating Processes

A diagram summarising all the different heat transfer processes within the atmosphere.

Temperature Variation with Height - Lapse Rate

The rate at which temperature decreases with increasing height in a stable atmosphere.
1.98°C per 1000ft or 0.65°C per 100m is the standard.
The actual rate varies due to seasons, time of day, and location.

Temperature Variation with Height - Isothermal Layer

A layer of air with constant temperature with increasing altitude.
Typical values between 11 to 20 kilometers altitude
May be at lower altitudes, for instance above ground.

Temperature Variation with Height - Inversions

Layers of air where temperature increases with height.
Examples of these inversions are radiation inversions, turbulence inversions, and subsidence inversions,
They can form at night, and can be found at low altitudes to significantly higher up.

Surface temperature - Angular Elevation of the Sun

Latitude affects surface temperature due to the angle of sunlight.
Higher latitudes receive less direct sunlight, resulting in lower temperatures.
Lower latitudes receive more direct sunlight, concentrating the heat in a smaller area which causes higher temperatures.

Surface Temperature - Effect of Seasons

Seasonal changes in the Earth's tilt affect the angle of sunlight at different latitudes, causing variations in temperature. (Illustrated with diagrams)

Surface Temperature - Variations Between Land and Sea

Land heats and cools more quickly than water.
This difference in heating rate leads to different temperatures between land and sea, particularly during the day and night.

Surface Temperature - Diurnal Variation

The temperature changes during a 24-hour period.
Highest temperature usually occurs several hours after the sun reaches its highest point.
Lowest temperatures typically occur shortly after sunrise on a clear night.

Surface Temperature - Cloud Cover By Day and Night

Cloud cover reduces diurnal temperature range during both day and night.
During the day, clouds reflect incoming solar radiation, resulting in reduced temperatures.
During the night, clouds absorb outgoing terrestrial radiation, leading to higher temperatures / less diurnal change / warmer temperatures

Surface Temperature - Effect of Wind

Wind speeds can affect the diurnal temperature range by mixing air, reducing temperature differences between land and sea.

Surface Temperature - Location

The topography also affects temperatures.
The presence of valleys or mountains can enhance or impede heat movement.
Fog will typically be found in valleys in the early morning.

Surface Temperature - Variations of Land & Sea in Temperate Climate

In summer, temperatures over land are higher than over water.
In winter, temperatures over land are lower than over water.

Surface Temperature - Origin/Source of Air Supply

Diagrams showing origin and source of air supply of different tempuratures. (Blue for cool air, red for warm air).

Average Temperature

Global average temperatures are visualized on a map.
Diagrams illustrating the variations across geography.

Summary / Consolidation

A summary of the different topics covered.

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Description

Explore the fascinating aspects of temperature in meteorology through this quiz. Learn about temperature measurements, the different temperature scales like Celsius and Fahrenheit, and the role of latent heat in atmospheric processes. Test your knowledge on essential tools such as thermographs and radiosondes.