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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