METEOR 4100 - Global Circulation
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Course Title: METEOR 4100 Tropical Meteorology (Global Circulation)Instructor: Jophet D. Flores
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Chapter 3 Overview
General Principles of Atmospheric Motion
General Circulation of the Atmosphere
Ocean Circulation
Response to Equatorial Heating
Monsoons
Tropical Circulation and Precipitation Distribution
Role of Tropics in General Circulation
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General Principles of Atmospheric Motion
Simplifications for Large-scale Motions
Large-scale Vertical Structure
Large-scale Atmospheric Structures
Scale Analysis of the Tropics
Natural Coordinate System
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Useful Simplifications of Force Balances
Motion is evaluated using Newtonian principles: force = mass × acceleration.
Focus on the acceleration of an air parcel, resulting in the Navier-Stokes equations applicable to both air and water.
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Useful Simplifications of Force Balances
Pressure Gradient Force: Moves fluid from high to low pressure.
Acceleration expression:
Acceleration = pressure gradient + Coriolis + effective gravity + friction.Coriolis Parameter: Defined as
f = 2Ω sin(Φ)(Ω = Earth’s rotation rate).
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Motion Dynamics
Acceleration due to Coriolis Effect is perpendicular to velocity; frictional forces oppose motion.
Local rate of change in motion expressed with
D/Dt = (local change + advection terms).
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Balance Above Friction Layer
Above the friction layer, balance exists between pressure gradient and Coriolis forces.
Geostrophic Wind: Approximated as
Vg = k × (1), blows parallel to isobars.
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Surface Wind Dynamics
At the surface, friction increases and winds are not parallel to the pressure field but angled toward lower pressure.
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Wind Around High/Low Pressure Areas
Winds flow parallel to isobars in balance with pressure gradient and Coriolis forces, changing near circulation centers.
Calculated wind from balance is termed gradient wind.
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Vertical Motion Equations
Vertical motion defined as:
Acceleration = pressure gradient + gravity.Pressure decreases with height leading to positive acceleration in lower pressure zones.
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Conservation Principles in Meteorology
Conservation of quantities in meteorology (mass, energy, angular momentum) except for external influences.
Focus on continuity equation for mass conservation.
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Air Transport Rates
Analyzing the transport rate of air utilizing density, area, and velocity.
Equation for total flux rate:
Flux Rate = density × velocity.
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Continuity Equation Derivation
Net rate of mass inflow expressed by
df/dt + ∇·(flux rate) = 0.
Represents conservation where no mass is created or destroyed.
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Continuity Equation Forms
Flux Form:
+ ∇ · (ρ*V) = 0.Advective Form:
(∂ρ/∂t) + ∇ · (ρ veterans) = 0.
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Utility of Continuity Equation
Acts as a tool for forecasting, linking density changes of air parcels to velocity divergence.
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Understanding Divergence and Convergence
Application to tropical atmosphere:
Convergence leads to rising air (low pressure, clouds) while divergence results in sinking air (high pressure, dryness).
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Hydrostatic Balance
In large-scale circulations, negligible vertical scales lead to hydrostatic balance:
P = -ρg (pressure gradient balanced by weight).
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Ideal Gas Law
Relationship among pressure, density, and temperature:
P = ρRT.
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Geopotential and Hydrostatic Equation
Hydrostatic equation can be rewritten to show geopotential as a function of pressure and temperature.
Geopotential: Indicates height relative to atmospheric pressure.
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Hypsometric Equation
Relates layer thickness between pressure surfaces to temperature, showing more rapid pressure decrease in colder air columns.
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Temperature Gradient and Geostrophic Wind
The pressure gradient relates to the geostrophic wind across layers, affecting wind speeds and directions in large-scale systems.
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Conservation of Energy
Thermodynamic principles account for energy added vs. temperature change, establishing balancing rules.
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Thermodynamics and Potential Temperature
Detailed relationships explored via the thermodynamic energy equation and ideal gas law when conditions are adiabatic.
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Dry Adiabatic Lapse Rate
Determined from thermodynamic principles leading to temperature change with altitude for dry air.
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Large-scale Structures in the Atmosphere
Dynamics indicate air flows about low/high pressure formations, leading to large-scale patterns.
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Large-scale Pressure Dynamics
Air convergence into low pressure and divergence away from high pressure supports mass continuity.
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Temperature Impacts on Motion
Vertical motions in pressure areas infer typical cloudiness and precipitation generated by air movements.
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Vorticity Overview
Measures of local flow rotation significant within meteorology.
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Relative Vorticity Definition
Defined by wind components as it applies to midlatitude flows.
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Vorticity Calculation
Relative vorticity and its units measured; implications for cyclone genesis in specific conditions.
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Earth Vorticity and Coriolis Parameter
Rotation effects on horizontal winds within the Earth’s sphere.
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Absolute Vorticity
Combination of relative and Earth vorticity introduces corrections for vertical components influencing air parcels.
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Potential Vorticity Definitions
Potential vorticity terms and conservation in adiabatic flows underlies complex interactions in atmospheric movements.
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Analyzing Atmospheric Dynamics
Critical to chart airflow indicating underlying pressure dynamics, particularly in tropical regions.
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Scale Analysis in Tropics
Importance of evaluating forces based on lengths, mass, time, and temperature metrics to prioritize factors.
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General Vorticity Dynamics
Evaluation of relative vorticity importance under various atmospheric conditions dependent on flow stability.
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Scale Analysis Illustrated
Visual display of various atmospheric processes categorized by their lengths and time scales.
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Coriolis and Geostrophic Balance
Analysis in equatorial regions demonstrating unique wind response in absence of general balance.
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Rossby Number Consideration
A dimensionless assessment of inertial and Coriolis forces to validate geostrophic assumptions.
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Static Stability Considerations
The Brunt-Väisälä frequency defines the dynamics of fluid stability in various conditions across hydrospheres.
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Rossby Radius of Deformation
Impacts of gravity and rotational forces on horizontal scales producing feedback loops in circulation.
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Scaling Ocean Dynamics
Open evaluations of ocean dynamics correlate with fluid dynamic principles outlining motions moving vertically.
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Tropical Ocean Clarity
Interaction effects between ocean circulation, temperature variations, and associated atmospheric changes.
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Thermohaline Dynamics
Overview of ocean dynamics implying the interactions between temperature, salinity, and overall distribution.
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Ocean Effect on Climate
Noting the effects of causative factors underlying ocean and climate interplay into larger shifts.
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Equatorial Heating Response
Tropical dynamics originating from heating gradients fuel variations impacting precipitation and global circulation.
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Monsoon Characterization
The societal implications derived from monsoon systems shaping regional weather patterns and climatic variability.
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