module 3
surface temperature
determined by energy balance at the surface
sensible heat may move from one surface to another by conduction
may be transferred by the mixing of fluid (such as the atmosphere) by convection
latent heat transfer: exchange of heat during evaporation (cooling) or condensation (warming)
factors affecting air temperature
insolation: daily and seasonal variations
latitude: also daily and seasonal variations and energy deficit
surface type: albedo of surface as well as surface moisture
coastal vs. interior location: temperature range is lower at coasts
elevation: thinner atmosphere means less greenhouse effect
temperature
thermometers describe energy (temp is not the same as heat)
temperature declines with height in the troposhere
warm air is less dense than cold air
warm air rises, cold air sinks
daily insolation: mid-latitude
varies with time of day and season
early or late in the day there is a deficit
the length of time for a surplus also changes seasonally
daily maxima and minima
positive net radiation leads to an increase in temperature, but there is a time lag
temperatures
rural areas
transpiration from leaves colls the surface
evaporation from moist soils plus transpiration from plants = evapotranspiration
urban areas
water is channeled so surfaces tend to be dry
surfaces are often dark (asphalt)
building materials store heat, and heat is released from buildings
the urban heat island
the heat island tends to persist over night
parks can reduce the heating
desert urban areas often do not exhibit heat islands, where irrigated vegetation may make the city cooler
elevation and temperature
generally temperatures drop with altitude
daily temperature range also increases due to decreased greenhouse gases
normally temp decreases with height, but sometimes upper air is warmer than lower air = tem inversion
occurs if the ground cools overnight
cold air may flow into an area
net radiation and temp
low latitudes have greater amounts and longer periods of surplus energy
high latitudes experience large and long periods of deficit
maritime and continental climates
land heats and cools quickly while water heats and cools slowly
during a year an ocean surface has a smaller annual range of temperature (maritime climates)
a land surface has a larger annual range (continental climates)
the annual cycle of air temp: land and water contrasts
world patterns of air temp
distribution of air temps shown on a map uses isotherms
reveals centers of low or high temps and temp gradients
temps decreases from the equator to the poles
large landmasses located in the subarctic and artic zones develop centers of extremely low temps in winter
temps in equatorial regions change little from jan to july
isotherms make a large north-south shift from jan to july over continents in the mid-latitude and subarctic zones
highlands are always colder than surrounding lowlands
areas of perpetual ice and snow are always intensely cold