Atmosphere, Ocean and Climate Dynamics Fall 2008

Transcription

1 MIT OpenCourseWare Atmosphere, Ocean and Climate Dynamics Fall 2008 For information about citing these materials or our Terms of Use, visit:

2 Contents 0.1 Preface Natural fluid dynamics Rotating fluid dynamics Holicism I The Atmosphere 19 1 Characteristics of the atmosphere Geometry Chemical composition of the atmosphere Physical properties of air Moist air The global energy balance Effective planetary temperature (emission temperature) The atmospheric absorption spectrum The greenhouse effect A simple greenhouse model A leaky greenhouse A more opaque greenhouse The vertical structure of the atmosphere Vertical distribution of temperature and Greenhouse gases Typical temperature profile Atmospheric layers The relationship between pressure and density: hydrostatic balance Vertical structure of pressure and density

3 4 CONTENTS Isothermal atmosphere Non-isothermal atmosphere Density Convection The nature of convection Convection in a shallow fluid Instability Convection in water (an almost-incompressible fluid) Buoyancy Stability Energetics GFD Lab II: convection Dry convection in a compressible atmosphere The adiabatic lapse rate Potential temperature The atmosphere under stable conditions Gravity waves Temperature inversions Moist convection Humidity Saturated adiabatic lapse rate Radiative-convective equilibrium Convection in the atmosphere Convective clouds Occurrence and depth of convection Where does convection occur? The Meridional Structure of the Atmosphere Temperature Latitudinal dependence of incoming radiation Latitudinal dependence of outgoing radiation Meridional structure of temperature The energy balance of the atmosphere Pressure and geopotential height The height of pressure surfaces Geopotential surfaces Moisture... 90

4 CONTENTS Winds Distribution of winds The equations of fluid motion Differentiation following the motion Equation of motion for a nonrotating fluid Forces on a fluid parcel The equation of motion Hydrostatic balance The continuity equation Incompressible flow Compressible flow Equation of motion for a rotating fluid GFD Lab III: radial inflow Transformation into rotating coordinates The rotating equation of motion Experiments with Coriolis forces on a parabolic rotat- ing table Geostrophic motion The Taylor-Proudman Theorem The thermal wind equation Subgeostrophic flow: the Ekman layer Putting things on the sphere GFD Lab X: An experiment on the Earth s rotation The centrifugal force, modified hydrostatic balance and geopotential surfaces on the sphere Components of the Coriolis force on the sphere: the Coriolis parameter Geostrophic balance on the sphere Small Rossby number flow Thermal wind in pressure coordinates Thermal wind expressed in terms of potential temper- ature The general circulation of the atmosphere The tropical Hadley circulation The midlatitude circulation Energy stored in the thermal wind

5 6 CONTENTS Available potential energy Baroclinic instability GFD Lab XI: baroclinic instability of the thermal wind The big picture of the atmospheric heat (and momentum) budget Energy requirements, as deduced from observations Incorporating eddy transfer in to our general circula- tion theory II The Ocean The ocean and its circulation Physical characteristics of the ocean Properties of seawater; equation of state Temperature and salinity structure The mixed layer and thermocline The observed circulation Inferences from geostrophic and hydrostatic balance Ocean surface structure and geostrophic flow Deep geostrophic flow The wind-driven circulation The wind stress and Ekman layers Balance of forces in the Ekman layer Wind-driven Ekman pumping Response of the interior ocean to Ekman pumping Interior balances Taylor-Proudman on the sphere GFD Lab XIII: Wind-driven ocean gyres The wind-driven gyres and western boundary currents The depth-integrated circulation Mass transport of gyres: western boundary current speeds Effects of inhomogeneity Taylor-Proudman in a layered ocean Ocean eddies Observations of ocean eddies...236

6 CONTENTS Baroclinic instability in the ocean The thermohaline circulation of the ocean Sources of deep water Time scales and intensity of thermohaline circulation Abyssal circulation schematic deduced from Taylor-Proudman Observations of the abyssal circulation GFD Lab XIV: The thermohaline circulation Why western boundary currents? GFD Lab XV: Source sink flow in a rotating basin The ocean s role in climate Ocean Heat storage Ocean heat transport Mechanisms of ocean heat transport