I Fought the Law
Work It
I Have Potential
Moisture
Potpourri
100
In words, describe the 1st law of thermodynamics
change in internal energy is equal to heating minus work done (conservation of energy)
100
What specific type of work have we focused when discussing atmospheric processes?
pressure-volume work
100
What is the potential temperature of the air at 300 mb?
50 C
100
If the vapor pressure is less than the saturation vapor pressure, the air is
unsaturated (RH < 100%)
100
What is the numeric value of c_p
1004 J kg-1 K-1
200
What is the 2nd law of thermodynamics?
entropy of the universe cannot decrease
200
During adiabatic expansion of an air parcel, is work positive, negative, or zero?
positive (parcel does work on the surroundings)
200
What is the name of a potential temperature contour?
isentrope
200
Saturation vapor pressure (of a plane surface of pure liquid water) is only a function of what state variable?
Temperature
200
What is the value of the dry adiabatic lapse rate?
9.77 C / km
300
What term in the 1st law of thermodynamics is zero during an adiabatic process?
heating (\delta q)
300
In an isochoric process, is the work done is positive, negative, or zero?
zero
300
On a skew-T diagram, what is the lapse rate along a line of constant potential temperature?
9.77 C / km (dry adiabatic lapse rate)
300
What is the definition of dew point?
temperature air would have if it were cooled at constant pressure and constant moisture content to its saturation point.
300
What is sensible heating?
-heating that produces a change in internal energy (temperature) without a change in pressure
-heating that results in a change in enthalpy
400
In a reversible process, does entropy increase, decrease, or stay the same?
stay the same
400
What atmospheric process would produce negative work?
Compression (environment does work on the air parcel)
400
An air parcel with a temperature of 280 K originating at 1000 mb undergoes dry adiabatic ascent to 500 mb. What is it’s potential temperature?
280 K
400
What two processes can increase relative humidity
-increase in moisture content (increase in vapor pressure)
-decrease in temperature (decrease in saturation vapor pressure)
400
How do you identify rising motion on an isentropic surface?
Areas where wind is directed from higher pressures towards lower pressures
500
In an isobaric process, a change in enthalpy is directly related to
heating
\delta q = dh - \alpha dp
(if isobaric, dp=0)
500
Why is the specific heat of air at constant pressure (cp) greater than the specific heat of air at constant volume (cv)?
At constant pressure, some internal energy must be converted to work to expand the parcel against the pressure of the environment.
500
What two environmental characteristics determine the maximum potential intensity of a hurricane?
Temperature of outflow at cloud top
Temperature difference between the underlying ocean and near-surface air
500
Explain the difference between dew point and relative humidity.
dew point is a measure of how much water vapor is in the air. Relative humidity is a measure of how close the air is to being saturated.
500
What is the difference between a reversible and irreversible process?
-entropy must increase for an irreversible process but for a reversible process it stays the same
-irreversible process modifies the environment in some way