What is air temperature?
Air temperature is a measure of the heat (or kinetic energy) in the atmosphere. It is expressed as degrees Celsius (°C) or degrees Fahrenheit (°F). Air temperature varies with latitude, elevation, season and position over land or water. Air temperature is generally warmer near the equator than the poles. However, wind and weather patterns move air to moderate these temperature differences: cooler air flows towards the equator and warmer air flows poleward.
Gulf of Maine air temperature
Heat is continually exchanged between earth's surface and the atmosphere above it. However, the rate of heat exchange is quite different over water bodies and landmasses; this is because water has a much higher heat capacity than soil. As many New Englanders know, Gulf of Maine coasts have more moderate climates (i.e., cooler in the summer, warmer in the winter) than inland areas. This type of variation is also evident in the graph below: the annual range of average monthly air temperatures in Concord, New Hampshire (NH) is 28.2°C (50.9°F) but only 17.8°C (32.0°F) at a buoy located off the NH coast. Another interesting fact to note is, at that buoy, the annual range of monthly surface water temperature is only 14.0°C (25.2°F).
GoMOOS buoys measure air temperature (°C and °F) at 1 meter above sea level every hour.
In addition to determining whether or not we use heat or air conditioning, air temperature has a major influence on our weather patterns, including wind and precipitation. Like water, the temperature of air regulates its density: cold air sinks and warm air rises. Weather forecasts often refer to convection cells. These are bodies of air that move up and down in response to temperature-related changes in density. High-pressure areas occur where air cools and sinks towards Earth’s surface. Low-pressure areas occur where air is heated and rises. Pressure, along with the Coriolis force and other forces acting on the air, direct the intensity and direction of winds.
Air temperature also effects condensation and evaporation of water. When air temperature increases, it may be easier for water molecules to evaporate. The opposite can be true when the air temperature decreases: it may be easier for water vapor molecules to condense. Depending on the moisture content of the air, these temperature changes can affect humidity, cloud formation, and precipitation.
Beyond the Gulf: Why and how much does air temperature vary?
The amount of solar energy received by Earth varies with latitude, so the temperature of the air varies with latitude too. In the tropics, the sun’s rays hit Earth's surface directly. At higher latitudes these rays hit Earth's surface at an angle, so they spread over a relatively larger area, and more of the energy is reflected back to the atmosphere. This, coupled with seasonal variation in day length at higher latitudes, results in warmer air temperatures at the equator than at the poles.
Compared to water temperature, air temperatures can vary significantly on a global scale. The highest recorded air temperature was 58°C (136.4°F) in northern Africa during the summer of 1922. Antarctica holds the record for the lowest recorded air temperature at –89°C (-128.2°F)!
- Lalli, C.M. and T.R. Parsons. (1993). Biological Oceanography – An Introduction. Butterworth Heinemann.
- NOAA / National Data Buoy Center. (2002). Station 44005 - Gulf of Maine. URL: http://www.ndbc.noaa.gov/station_page.phtml?$station=44005
- NOAA / National Weather Service. (2002). Gray / Portland Climate Data - Past weather and normals. URL: http://www.erh.noaa.gov/er/gyx/climate.shtml
- Open University Course Team. (1989). Ocean Circulation. Pergamon Press.
- Thurman, H.V. (1994). Introductory Oceanography Ð 7th Edition. Macmillan Publishing Company.
