Thermodynamics Flashcards
What is thermodynamics?
Study of laws that govern: conversion of energy from one form to another, direction heat will flow, availability of energy to do work
Molecular Mass
Mass of a molecule
Ideal Gas Law
Relates pressure, density, and temperature
Gas Constant
Constant relating variables in ideal gas law; depends on the molar mass
Ways to quantify the concentration of an atmospheric gas
Mass mixing ratio, volume mixing ratio, number density
Mass Mixing Ratio
Percentage of a particular gas in the total composition of a sample of gas
Partial Pressure
Pressure that would be exerted by the molecules of a particular gas from a sample if they were alone in the volume at a certain temperature
Partial Volume
The volume that would be occupied by the molecules of a gas from a sample if they were alone at a pressure and temperature
What is Dalton’s Law?
In a mixture of non-reacting gases, the total pressure and volume is the sum of the partial pressures/volumes
Volume Mixing Ratio
The relative amount of a particular gas in a gas sample
Number density
The number of molecules of a gas per unit volume
Most significant contributors to composition of gases in the atmosphere?
Nitrogen (78%), Oxygen (21%), Argon (1%)
What is hydrostatic balance?
The equilibrium between the gravitational force and pressure force on an air parcel. Relates pressure and altitude
Lapse Rate
Rate of decrease of temperature with height
Hypsometric equation
Gives the thickness of an atmospheric layer bound by two pressure levels with constant temperature (or mean temperature)
First law of thermodynamics
dU=dQ+dW, conservation of energy
Work
Force exerting over a distance (positive when force does work ON a system - internal energy increases)
Entropy
Measure of disorder of system S = kblnW
Second law of thermodynamics
Irreversible processes (one direction) involve an increase in entropy in an isolated system
Reversible process
If you make very small changes in a system, a process can be reversed, total entropy change of system and surroundings = 0
Enthalpy
Measure of the total heat content of a thermodynamic system
Heat capacity
amount of heat required to raise the temperature of a body by 1K. May be at constant pressure or volume
Adiabatic heating
Temperature change of a parcel due to a change in air pressure caused by volume expansion related to vertical displacement (no change in heat, reversible process, no change in entropy)
Diabatic heating
Temperature change not related to adiabatic heating (phase changes of water, radiation)
Potential temperature
The temperature a parcel would have if brought adiabatically to the surface, constant when the parcel moves adiabatically
Air parcel
Small air of mass, affected by environment, but doesn’t affect environment, pressure equals pressure of environment, but temperature, density and composition may differ from environment
Adiabatic lapse rate
Rate of decrease of temperature with height following an adiabatic parcel as it rises
Environmental lapse rate
Differs from adiabatic lapse rate
Statically stable
Adiabatic lapse rate > environmental lapse rate, parcel heavier than surroundings and sinks, potential temperature increases with height
Statically unstable
Adiabatic lapse rate < environmental lapse rate, parcel lighter than surroundings and rises, potential temperature decreases with height
Neutral stability
Adiabatic lapse rate = environmental lapse rate
Buoyancy force
Difference in forces of mass of air displaced and mass of the parcel
Buoyancy frequency
Determines the motion of an air parcel in the atmosphere due to the buoyancy force. Depends on the if the atmosphere is statically stable (oscillatory motion), or unstable (exponential solution)
Total potential temperature
Sum of potential energy and internal energy
Available potential energy
The potential energy in the atmosphere available for conversion to kinetic energy, slopes in isobars
Why is water important for the climate system
Precipitation, radiative effects, stratospheric ozone
Saturation vapor pressure
Pressure and temperature at which the rate of evaporation = rate of condensation (determined by Clausius Clapeyron equation)
Gibbs free energy
Difference between enthalpy and entropic energy, measure of a system’s ability to do work
Gibbs free energy of a system in equilibrium
Total specific G of system is sum of G’s of each phase and the specific G in each phase is the same
Clausius-Clapeyron equation
Relationship between the change in pressure with temperature, which are related by the latent heat of a phase change, temperature and change in volume associated with the phase change
Relative humidity
Measure of moisture, ratio of water vapor compared to saturation vapor pressure
What happens to vapor pressure as a parcel rises?
The temperature decreases as a parcel rises, and the vapor pressure decreases, but also the saturation vapor pressure decreases, so the parcel may reach saturation
Dew point
Temperature air must be cooled at constant pressure for it to be saturated
Saturated adiabatic lapse rate
At saturation, latent heat is released, modifies the dry adiabatic lapse rate (lapse rate decreases)
Conditional instability
A saturated parcel is conditionally stable if the lapse rate is < saturated adiabatic lapse rate
Equivalent potential temperature
Potential temperature a parcel would have if all its moisture were condensed and the latent heat was used to heat the parcel
Ways the temperature of a parcel can be brought to equivalent potential?
Raise parcel to top of atmosphere to condense moisture and release heat, bring parcel adiabaticaly back to surface
Tephigram
Thermodynamic diagram used to interpret the temperature and humidity structure of the atmosphere
What affects the formation of clouds?
Curvature of water droplets (larger radius = less curvature = more cloud formation), T and P
How does droplet radius affect vapor pressure?
Vapor pressure required to reach saturation vapor pressure is much greater over curved surfaces (supersaturation to reach equilibrium)
What can reduce the RH necessary for cloud formation?
Having a cloud condensation nucleus (solute), occupy surface sites otherwise occupied by water molecules, reduces evaporation rate
Raoult’s Law
Partial vapor pressure of each component of an ideal mixture of liquids is equal to the vapor pressure of the pure component multiplied by its mole fraction in the mixture
Kohler Curve
Shows the supersaturation at which a cloud droplet is in equilibrium with the environment over a range of droplet diameters
