Transcript Heat, Temperature & Circulation

Heat, Temperature and
Atmospheric Circulation
Temperature and Heat
• Temperature
– Proportional to average kinetic energy of
atoms/molecules of substance
• Heat
– Energy in transit, if two objects are at different
temperatures, energy is transferred
Temperature Scales
• Celsius (oC)-1742
– 100-degree
– Boiling (100o) & freezing (0o) point of pure water at
sea level
• Fahrenheit (oF) -1714
– Also based on phase changes on water
– Boiling (212oF); Freezing (32oF)
• Kelvin (K)
– 0 K, Absolute zero -273.15oC
– Freezing point of water 273.15K; boiling point
373.15K
Conversion Formulas
•
•
•
•
oF
= 9/5 oC + 32o
oC = 5/9 (oF – 32o)
K = 5/9 (oF + 459.67)
K = oC + 273.15
Measuring Air Temperature
• Thermoscope- Galileo 1592
• Thermometer
– Alcohol
– Mercury
• Thermograph
– Bimetallic sensing element
– Brass-iron
– Pointer calibrated to read in oC oF
– Continuous trace of temperature with time
Conduction & Convection
• Convection is the transfer of heat by the
actual movement of the warmed matter
(fluids-liquids and gases)
• Conduction is the transfer of energy
through matter from particle to particle
(collision of particles)
• Radiation is BOTH a form of energy and a
means of energy transfer (it can travel
through a vacuum)
Phase Changes of Water
• Heat is ABSORBED from the environment
during: Melting, Evaporation, Sublimation
• Heat is RELEASED to the environment
during: condensation and precipitation
Bowen Ratio
• A Bowen ratio is the ratio of energy fluxes
from one medium to another by sensible
and latent heating respectively.
• It is calculated by the equation
• where Qh is sensible heating and Qe is
latent heating.
• Global Bowen ratio is 0.3
Comparison of
incoming solar
radiation
outgoing and
outgoing longwave radiation
with latitude.
Energy transfer
is required to
maintain a
balance
Thermohaline Circulation
• The thermohaline circulation is the global
density-driven circulation of the oceans
• Wind-driven surface currents (such as the
Gulf Stream) head polewards from the
equatorial Atlantic, cooling all the while
and eventually sinking at high latitudes
• This dense water then flows into the
Ocean Basins
Satellite image
of warm and
cold eddies
spinning of
the Gulf
Stream
Cold & Warm Air Advection
• Cold/Warm air advection is the process in which
the wind blows from a region of cold/warm air to
a region of warmer/cooler air
• Winds are blowing from a region of cooler/warm
air to a region of warmer/colder air, which results
in a cooling/warming of the warmer/colder
region.
• As the colder/warm advection persists,
temperatures in the warmer/colder region will
begin to decrease/increase as the
colder/warmer air moves into the region of
warmer/colder air.
Heating degree day
• Heating degree day (HDD) and cooling
degree day (CDD) are quantitative indices
designed to reflect the demand for energy
needed to heat or cool a home or business.
• These indices are derived from daily
temperature observations, and the heating (or
cooling) requirements for a given structure at a
specific location are considered to be directly
proportional to the number of heating degree
days at that location.
Mean Annual Heating degree days over the U.S. in thousands
A heating degree day is defined as: 65°F - mean daily temp