module 3

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