ATMS Phys

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Atmospheric Composition

Atmospheric Composition

78% Nitrogen, 21% Oxygen, 1% Argon and greenhouse gases

Hydrological Cycle

Vapor ←→ liquid (condensation, evaporation) 

Liquid ←→ solid (freezing, melting) 

Vapor ←→ solid (deposition, sublimation)

Layers of the Atmosphere

Troposphere, Tropopause, Stratosphere, Stratopause, Ozone Layer, Mesosphere, Mesopause, Thermosphere, Ionosphere 

Relationship between  pressure, temperature, density, and altitude

Temperature inversions at each -pause
Density decreases with height 
Pressure decreases with height 

Wet Bulb Temperature

Lowest temperature that can be reached by evaporating water

Dew Point Temperature

Temperature saturation would occur if moist air cooled isobarically

1st Law of Thermodynamics

Change in internal energy of closed system will be equal to the energy added to the system minus the work done by the system on its surroundings

1st Law of Thermodynamics Equation

 ΔU = Q + W

Entropy Equation

ΔS = Q/T

Isothermal Process

temperature is constant, changes in phase or state

Isobaric Process

pressure is constant, boiling water

Isochoric / Isovolumetric Process

volume is constant, otto cycle (how a car uses gasoline)

Adiabatic Process

a process where the parcel temperature changes due to an expansion or compression, no heat is added or taken away from the parcel, lightning strikes or thunderstorms

Wet Bulb Potential Temperature

Temperature an air parcel would have if cooled from its initial state to saturation and brought 1000 hPa in a moist adiabatic process

Potential Temperature

the temperature an air parcel of temperature T and pressure P would have if it were expanded or compressed under adiabatic conditions to some reference pressure

Lapse Rate

 the rate at which temperature changes with height

Dry Adiabatic Lapse Rate

Unsaturated parcels cool at a rate of 10°C km-1

Moist Adiabatic Lapse Rate

For a saturated parcel of air, then it cools at the rate of 6°C km-1

Why the moist adiabatic lapse rate less than the dry adiabatic lapse rate

as vapor condenses into water (or water freezes into ice) for a saturated parcel, latent heat is released into the parcel, mitigating the adiabatic cooling

Vapor Pressure

the pressure of a vapor in contact with its liquid substance

Saturation Vapor Pressure

is the vapor pressure which is in equilibrium with an open liquid surface

Mixing Ratio

the abundance of one component of a mixture relative to the total mixture

Saturation Mixing Ratio

the ratio of the mass of water vapor to the mass of dry air in a parcel of air at saturation

Relative Humidity

ratio of the amount of atmospheric moisture present relative to the amount that would be present if the air were saturated

Absolute Humidity

a measure of the actual amount of water vapor in the air, regardless of the air's temperature

Specific Humidity

 the weight of water vapor contained in a unit weight of air

Lifting Condensation Level

the level at which a parcel becomes saturated

Mixed Condensation Level

the lowest level at which condensation occurs (if at all) as a result of vertical mixing through a given layer

CAPE

Is the amount of energy available or required to develop a thunderstorm

Geopotential Height

work that must be done against the Earth’s gravitational field to raise a mass of 1 kg from sea level to a given point

Geopotential Height Equation

Φ(Z) = ∫ gdz or Z = Φ(Z)/g0 = (1/g0) ∫ gdz

Hydrostatic Equation Definition

balance between the gravity force and vertical component of the pressure gradient force

Hydrostatic Equation

dp/dz = -ρg

Geopotential Version of Hydrostatic Equation

gdz = dΦ = -RTdln(p)

Derivation of potential temperature equation from an adiabatic process

1. For adiabatic expansion potential temperature is conserved

2. Thus, θ = Ts=T(ps/p)^(R/Cp)

3. Substituting from ideal gas law, T = p/(ρR) gives: ps/ρs= (p/ρ)(ps/p)^(R/Cp)

4. Using Cv = Cp - R, we get ρ = ρs(p/ps)^(cv/cp)

Clausius-Clapeyron

Describes equilibrium condition for a thermo system w/ water and its vapor

Saturation Vapor Pressure Equation

e₂(r) = e₂(∞)exp[2σ/rRvρT]

Calculate sea level pressure from a station

Psl = P(293/(293-h*0.0065))

Atmospheric Instability Cases

Absolute stability: Γd > Γm > Γe
Absolute instability: Γe> Γd> Γm
Conditional instability: Γd> Γe> Γm

High Pressure Subsidence

High pressure promotes sinking air. As air sinks it warms adiabatically

Radiative Inversion

earth is cooled at night by longwave radiation emission to space

Frontal Inversion

when the air associated with the shallow air mass is colder than the air aloft, thus creating an inversion

Tropopause Inversion

created by the absorption of shortwave radiation by ozone

Richardson Number

used as a rough measure of expected turbulence

Relationship between CAPE and vertical velocity

Higher vertical velocities correlate with more severe thunderstorms thus higher velocities means more available energy to develop thunderstorms

Processes that affect atmospheric stability

Mixing - cooling the top layer and warming the bottom
Lifting due to surface heating - condensation due to rising thermals
Cold air flowing over warm body of water - creates increase in temperature with height

Radii of Cloud and Rain Droplets

Cloud drops: r<0.1mm
Drizzle drops: r ~ 0.1mm
Raindrops: r>0.1mm

Heterogeneous Nucleation

when water droplets form on nuclei from the vapor phase

Homogeneous Nucleation

when droplets form from the vapor phase in a pure environment (requires high supersaturations)

Haze Particles

tiny airborne particles (such as dust, smoke, or pollutants) that scatter light and reduce visibility in the atmosphere

Activated Droplet

a small water droplet that has grown to a size sufficient for cloud formation due to condensation or other processes

Homogeneous Freezing

the process by which a supercooled liquid drop freezes without the assistance of an ice nuclei; becomes statistically more likely as temperature decreases such that below -39°C all drops will freeze

Heterogeneous Freezing

the process by which a supercooled liquid drop freezes with the assistance of a solid aerosol particle which is able to act as an ice nuclei

Heterogeneous Deposition

the process by which water vapor is deposited onto an ice nuclei and takes on a crystalline form directly without first being in the liquid phase

Collision Efficiency

is equal to the fraction of those droplets with radius r in the path swept out by the collector drop that actually collide with it. Collision does not guarantee coalescence

Collection Efficiency

is the growth of a droplet by the collision-coalescence process. This is the product of collision efficiency and coalescence efficiency

Coalescence Efficiency

is the ratio of the number of coalescences to the number of collisions

Deposition Nucleation

a heterogeneous ice nucleation mechanism where water vapor molecules are deposited directly into the ice phase on an ice nucleating particle

Freezing Nucleation

the spontaneous freezing that occurs within supercooled liquid-water droplets as temperature decreases to near –40°C

Immersion Nucleation

induced by a particle immersed in the body of supercooled water

Contact Nucleation

occurs when an Ice Nucleating Particle comes into contact with the surface of a supercooled droplet and triggers the freezing

Two ways cloud particles can grow rapidly to precipitation

Collision and Coalescence

Liquid Water Content (LWC)

LWC = ρ

Critical Radius Equation