Meteorology - Understanding Temperature

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.

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.