1 Flashcards
Everything radiates as a
black body
Latent heat
Heat released/absorbed during change in phase
Sensible heat
The heat we feel…Transferred by rising and mixing of warm air
Vapour pressure (e) =
Actual amount of vapour in the air at any given time
Saturated vapour pressure (es) =
Maximum amount of water vapour a parcel of air can possibly hold
How is temperature rested to saturated vapour pressure?
The higher the temp = The higher saturated vapour pressure (es)
Water will continue to evaporate into a parcel of air until
e = es….vapour pressure = saturated vapour pressure
Unsaturated air =
Dry air
Relative Humidity (RH) =
e/es x 100%……Ratio of actual moisture to maximum moisture content
Mass Mixing Ratio =
Weight of moisture per kg of dry air….g/Kg
When does condensation occur?
When air is saturated…i.e. e = es and RH = 100%
The temperature at which condensation occurs is
Dew Point Temperature (Td)
How can condensation occur?
By cooling at constant pressure, cooling by lifting (adiabatic) or by adding more moisture to the air parcel eg. subtropical oceans
Dry Adiabatic Lapse Rate (DALR) =
The rate at which dry (unsaturated) air cools with height…9.8degreesC/Km
Environmental Lapse Rate =
The actual rate at which the atmosphere cools (static)
The atmosphere is stable if…
DALR > ELR…Stable…The parcel is cooling more quickly than the air around it
The atmosphere is unstable if…
DALR < ERL…Unstable…The parcel if cooling less quickly than the air around it
Air can become unstable if it is…
Heated from below
Air can become stable if it is…
Cooled from below
1st Law Thermodynamics in relation to adiabatic cooling
du + dw = 0….So it must cool
Free convection
Convection due to density differences
Forced convection
Uplift by mechanical forces eg. orographic barrier (mountain), frontal uplift
Supersaturation
Air cooled below its dew point
Hygroscopic Nucleir are what?
Particles which attract water e.g. aerosols, dust…Condensation occurs onto hygroscopic nuclei
Cumuloform signifies
Free convection…….heaped clouds
Stratiform signifies
Forced convection…..flat, sheet-like clouds, mass ascent
Pressure gradient equation =
Change in pressure / Change in distance
What is an adiabatic process
Occurs without exchange of heat between a system and its surroundings.
Cooling by lifting…Air parcel rises, where pressure is lower, so it expands.
As it expands, it does work on its surroundings
This extracts heat energy
The parcel cools
Vapour pressure, e remains the same
Saturated vapour pressure, es decreases with decreasing heat
Until e = es, and condensation occurs (RH = 100%)
Coriolis =
Apparent deflection of moving objects (air masses) to right in N and left in S hemisphere, as earth rotates
What is geostrophic wind?
Balanced flow between Pgf and Co, observed above the friction layer in the atmosphere (above 500m)
- Must have straight parallel isobars - Wind blows at right angles to the pressure gradient
- Pgf = Co
How does friction affect V?
Friction reduces V, therefore Coriolis reduces
How does friction affect wind direction?
Causes convergence of air into low pressure
Convergence
Air moves toward areas of low pressure (due to friction)…Due to deceleration … Leads to clouds/rain
Divergence
Air moves outward away from an area of high pressure…Due to acceleration
Surface convergence leads to
Upward motion…Ascent
Surface divergence leads to
Downward motion…Descent
Vorticity =
The spin in the system (of moving body)
Positive vorticity when
When vorticity if in the same sense of the Earth: “Cyclonic”
Negative Vorticity when
When vorticity is in the opposite sense of the Earth: “Anticyclonic”
Absolute vorticity =
Total spin in the system … Remains a constant
Define jet streams
Narrow Bands of very strong winds in the upper troposphere (Associated with intense horizontal temperature gradients)
