Five Important Factors Influencing Air Temperature Are

Chapter 3 Air Temperature

This chapter focuses on the temperature of the air above the Earth’s surface. It examines air temperature, its measurement, and the factors that cause it to vary through time and space. This chapter also considers the topic of global warming.  Five important factors influencing air temperature are:  insolation  latitude  surface type  coastal versus interior location  elevation  Temperature is a measure of the sensible heat of a substance which changes as energy flows across its surface.  When the net radiation of a surface – the balance between incoming shortwave and outgoing longwave radiation – is positive, the surface temperature rises, and when net radiation is negative, the surface temperature falls.  Heat energy can be transferred by conduction, by latent heat transfer, and by convection.  The daily cycles of insolation and net radiation peak at solar noon, while the daily cycle of air temperature peaks in the mid-afternoon.  Air temperature measured above an urban surface is usually higher than that over a nearby rural surface.  The troposphere is the lower part of the atmosphere in which temperature declines with altitude.  The environmental temperature lapse rate – the rate of temperature change with altitude – averages 6.4° C per 1000 meters in the troposphere.  The troposphere is the zone in which most every-day weather phenomena (i.e. clouds, storms, rainfall, snowfall) occur.  The top of the troposphere is known as the tropopause and is found about six kilometers above the surface at the poles and sixteen kilometers above the surface at the equator.  In the stratosphere, the absorption of ultraviolet radiation causes the temperature to increase with altitude.  Daily air temperature cycles tend to be more pronounced in high elevation environments.  In a temperature inversion, the normal situation of air cooling with altitude is reversed and air warms with altitude.  Yearly temperature range is greater in high latitude and continental locations and less at equatorial and coastal locations.  The world patterns of isotherms are largely explained by latitude, coastal-interior contrasts, and elevation.  Six important points about temperature patterns are:  Temperatures decrease from the equator to the poles.  Large landmasses in the subarctic and arctic develop centers of extremely low temperatures in winter.  Temperatures in equatorial regions change little from January to July.  Isotherms make a large north-south shift from January to July over continents in the midlatitude and subarctic zones.  Highlands are colder than surrounding lowlands.  Areas of perpetual ice and snow are intensely cold.  Five important points about temperature range are:  The annual temperature range increases with latitude.  The greatest ranges are in the subarctic and arctic zones of Asia and North America.  Annual range is moderately large on land in the tropical zone.  Annual range in coastal areas is less than the range inland at the same latitude.  Small temperature ranges are found near oceans in the tropical zone.  Factors affecting global warming and cooling include:  greenhouse gases  tropospheric aerosols  cloud changes  land cover changes  changes in solar output  aerosols from volcanic activity  The warming effect of the greenhouse gases (carbon dioxide, methane, nitrous oxides, ozone, and chloroflourocarbons) has exceeded the cooling effect of other factors since about 1850.  Observations show both substantial annual variations in the average temperature of the lower atmosphere and a pronounced trend toward warmer temperatures in recent years.  Most scientists agree that the observed atmospheric warming trend is the result of greenhouse gas emissions from human activities and that the warming trend will continue into the future.