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 long-wave 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.

A heating degree day is defined as: 65°F - mean daily temp

Mean Annual Heating degree days over the U.S. in thousands