Equivalent Potential Temperature Atms 4310 / 7310 Lab 6 Tony Lupo

Equivalent Potential Temperature  What is it?  Recall we said that the exponent is the ratio of the;  Latent Heating: Lw s / internal energy (CpT)  (Is the math speaking loud and clear?)

Equivalent Potential Temperature  Is it?

Equivalent Potential Temperature   We can also think of Equivalent Potential Temperature as the maximum possible temperature that could be attained if all the moisture were condensed or wrung out and the latent heat released into the air.   We can calculate this graphically also (graphically it will represent "squeezing the parcel dry"):

Equivalent Potential Temperature  Graphically (Find LCL first)

Equivalent Potential Temperature  Moist adiabatic process  temperature is conserved following a line of  e. The temperature conserved for moist or saturated parcels in a moist environment!  Isentropic: following lines potential temperatures. (dry adiabatic).

Equivalent Potential Temperature  Wet Bulb Temperature   Is the temperature to which air may be cooled by evaporating water into it at a constant pressure, or until saturated dm/dt = 0.   This process is not constant or conserved, there is an increase in mixing ratio and a concommittant decrease in T (and m s ).

Equivalent Potential Temperature   You can think of T w as a "compromise" temperature.   T w differs from dewpoint, which is the temperature air must cool to in order to be saturated. In this case NO moisture is added.  Then,  T d <= T w <= T

Equivalent Potential Temperature  Calculate graphically:

Equivalent Potential Temperature   Also can define  w (potential wet bulb temperature) from this process graphically.   Sometimes  w is used instead of  e.  T w  acts a "lower limit" to the afternoon max just as 850 hPa potential temperature is a maximum indicator. (more typically, winter, cloudy, rainy conditions)

Equivalent Potential Temperature  Equivalent temperature

Equivalent Potential Temperature  Air parcel stability: (Bryan and Fritsch, 2000, BAMS, Vol. 81 excellent review)  For extra credit: tell me about the paper? CRITIQUE it.  Stability  When parcels are lifted up or sink, there are bouyant forces and gravitational acting on these.

Equivalent Potential Temperature  Three possible outcomes:  buoyancy = gravity (neutral)  bouyancy > gravity (rising)  bouyancy < gravity (sinking)

Equivalent Potential Temperature  Bouyancy (B) can be defined as;  B = density of the parcel – density of the environment   becomes CAPE later this semester.

Equivalent Potential Temperature  Stability, determine qualitatively using thermodynamic diagrams. (KBIS)

Equivalent Potential Temperature  More examples (GRB and SGF):

Equivalent Potential Temperature  The end!

Equivalent Potential Temperature  Comments?  Criticisms?  Questions?