lecture 5 air temperature Flashcards
transpiration process of vegetation
water is taken up by plant roots and moved to the leaves, where it is lost to the atmosphere (cools the leaf surfaces). Water also evaporates directly from the soil, again cooling the surface and moderating air temperature
evapotranspiration.
Because evaporation and transpiration have similar effects, these processes are frequently referred to collectively as evapotranspiration
urban heat island
Waste heat generated in large cities can increase air temperatures in the central region of a city several degrees above the surrounding suburbs and countryside, an effect known as an urban heat island
lapse rate
The atmosphere is mainly warmed from the surface below, so temperatures can be expected to decrease with altitude.
normal temperature lapse rate
rate measures an average drop in temperature in stationary air for the entire Earth over a long period.
On average, temperature drops with altitude at a rate of 6.4
°C per 1,000 m (6.4 °C 1,000 m-1).
environmental temperature lapse rate
indicates the actual change in temperature with altitude at a specific time and specific location.
altitudes
thermosphere mesopause mesosphere stratopause stratosphere tropopause troposphere
Troposphere
Being the lowest layer of the atmosphere, the troposphere holds about 80 percent of its total mass (and almost all the water vapour in the atmosphere)
The equatorial and tropical troposphere is the thickest (~16 km) and the troposphere around the poles (~6 km) is the thinnest - (due to the rotation of the Earth on its axis and thermal expansion in the warmer zones).
The troposphere gives way to the stratosphere at the
tropopause.
stratosphere
The stratosphere in which the air becomes slightly warmer as altitude increases is just above the tropopause,
The stratosphere extends to an altitude of roughly 50 km above the Earth’s surface.
Strong, persistent winds—the jet streams—are found in the lower stratosphere; they are linked to the formation and movement of weather systems in the troposphere.
The ozone layer that is only present in stratosphere, shields organisms by absorbing the intense UV radiation emitted by the sun.
The stratospheric ozone layer contains over 90 percent of the Earth’s ozone and is responsible for absorbing 97 to 99 percent of the UV light emitted by the sun.
The warming of the stratosphere with altitude is mainly caused by the absorption of solar energy by ozone molecules.
mesosphere
In the mesosphere, temperature falls with altitude.
This layer begins at the stratopause and ends at the mesopause, where it gives way to the thermosphere, a layer in which, theoretically, temperature increases.
temprerature inversion
Radiating long-wave energy to the atmosphere by the ground surface during the night, causes negative net radiation and thus the surface cools; this in turn cools the overlying air.
Under clear, calm conditions, cool, dense air will accumulate at the ground surface to produce a temperature inversion.
Additionally, the horizontal transport of air by advection can bring a layer of warm air into a region at any height in the atmosphere, interrupting the normal temperature lapse.
Land and Water Contrasts
Insolation penetrates deeper into water than into ground surfaces which therefore heat more intensely.
Water has a higher specific heat than soil and rocks (it takes 5 times as much heat to raise the temperature of water 1 ºC than for soil and rock).
Some energy is dissipated through the continuous evaporation of water.
Warm surface water can mix with cooler water below and maintain a lower temperature.
isotherms
shows the distribution of air temperatures on a map where lines drawn to connect locations having the same temperature.
They are constructed by drawing smooth lines through and between the points of known temperature (usually at intervals of 5 or 10-degree differences).
Isothermal maps depict broad temperature patterns from which temperature gradients — directions along which temperatures change — can be derived.
Three main factors — latitude, marine-continental location, and altitude
— determine the patterns of isotherms at the global scale.
These combine to produce:
1) A temperature decrease from the equator to the poles,
2) Extremely low winter temperatures for large subarctic and Arctic land masses,
3) Equatorial region temperatures that change little over the course of the year,
4) Large north – south isotherm shifts from January to July over midlatitude and subarctic zone continents,
5) Highlands that are colder than their surrounding lowlands,
6) Areas of perpetual ice and snow which are always intensely cold,
7) Isothermal patterns which are associated with ocean currents.
Five characteristic patterns are evident when comparing the differences between January and July global isothermal maps:
The annual range increases with latitude, especially over northern hemisphere continents.
The largest ranges occur in the subarctic and arctic zones of Asia and North America.
The annual range is moderately large on land areas near the Tropics of Cancer and Capricorn.
The annual range over oceans is less than over land at the same latitude.
The annual range is very small over oceans in the tropical zone
