1	Geophysics Fluid Dynamics (ESS228)
2	Syllabus
3	What Are the Issues? The fundamental aim is to understand the circulations of the atmosphere and ocean and the observed distributions of physical quantities such as temperature. The temperature distribution can be viewed as the result of a "competition" between the sun, which tries to warm the tropics more than the poles (and so create horizontal contrasts), and gravity , which tries to remove horizontal contrasts and arrange for warmer fluid to overlie colder fluid. This "competition“ is complicated by such effects as the rotation of the earth, the variation of the angle between gravity and the rotation axis (the beta effect), and contrasts between the properties of air and water.
4	Radiation è Temperature gradient è Density gradient è Pressure gradient force è Motion è Equilibrium
5	Air Pressure and Air Density Weight = mass x gravity Density = mass / volume Pressure = force / area = weight / area
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9	Selective Absorption and Emission The atmosphere is not a perfect blackbody, it absorbs some wavelength of radiation and is transparent to others (such as solar radiation). è Greenhouse effect. Objective that selectively absorbs radiation usually selectively emit radiation at the same wavelength. For example, water vapor and CO2 are strong absorbers of infrared radiation and poor absorbers of visible solar radiation.
10	Vertical Distribution of Energy
11	What Are the Issues? The fundamental aim is to understand the circulations of the atmosphere and ocean and the observed distributions of physical quantities such as temperature. The temperature distribution can be viewed as the result of a "competition" between the sun, which tries to warm the tropics more than the poles (and so create horizontal contrasts), and gravity , which tries to remove horizontal contrasts and arrange for warmer fluid to overlie colder fluid. This " competition“ is complicated by such effects as the rotation of the earth, the variation of the angle between gravity and the rotation axis (the beta effect), and contrasts between the properties of air and water.
12	Effect of Convection
13	Potential Temperature (q) The potential temperature of an air parcel is defined as the the temperature the parcel would have if it were moved adiabatically from its existing pressure and temperature to a standard pressure P₀ (generally taken as 1000mb).
14	Dry and Moist Adiabatic Lapse Rates Dry adiabatic lapse rate is constant = 10ºC/km. Moist adiabatic lapse rate is NOT a constant. It depends on the temperature of saturated air parcel. The higher the air temperature, the smaller the moist adiabatic lapse rate. èWhen warm, saturated air cools, it causes more condensation (and more latent heat release) than for cold, saturated air.
15	Dry Adiabatic Lapse Rate
16	Moist Adiabatic Lapse Rate
17	Zenith Angle and Insolation The larger the solar zenith angle, the weaker the insolation, because the same amount of sunlight has to be spread over a larger area.
18	Latitudinal Variations of Net Energy Polarward heat flux is needed to transport radiation energy from the tropics to higher latitudes.
19	Polarward Energy Transport
20	Radiation è Temperature gradient è Density gradient è Pressure gradient force è Motion è Equilibrium
21	How Do Atmosphere and Ocean Transport Heat?
22	Geophs. Fluid Motion and Global Energy Balance Vertical temperature gradients Convection occurs that tries to reduce the vertical gradients Vertical variation of air density (i.e., stratification) Horizontal temperature gradients èFluid motion takes place to reduce the gradients èThe motion (i.e., the adjustment) takes place in a rotating and stratified system.