Adiabatic processes on a thermodynamic chart. Atms Sc 4310 / 7310 Lab 2 Anthony R. Lupo

Adiabatic processes on a thermodynamic chart.  1st law of thermodynamics in the form (imperfect form)  is a statement of the Conservation of energy (heat in = heat out)!

Adiabatic processes on a thermodynamic chart.  Left hand side (represents?):  Diabatic heating, which includes Latent Heat Release, Sensible Heating, and Radiational Heating.

Adiabatic processes on a thermodynamic chart.  Right hand side:  Term 1: Internal Energy (due to Temperature)  Term 2: “pressure work” term or work done by pressure by the environment on a parcel.  (expansion – heat added to system diabatically  contraction - heat removed diabatically)

Adiabatic processes on a thermodynamic chart.  Adiabatic process  dq/dt = 0 (no work done)!!  Thus, the internal energy equals the pressure work term. Also, now there are no diabatics so;

Adiabatic processes on a thermodynamic chart.  Expansion (lower pressure) cooling  work done on air parcel and energy lost to environment  Contraction (higher pressure) warming  work done by environment and energy gained at expense of environment

Adiabatic processes on a thermodynamic chart.  Constant Potential Temperature  Adiabatic system or flow follows lines of potential temperature.  Why? Let’s derive relationship for potential temperature

Adiabatic processes on a thermodynamic chart.  Derive…..start with 1 st law

Adiabatic processes on a thermodynamic chart.  And….

Adiabatic processes on a thermodynamic chart.  Some adiabatic processes  Adiabatic motion on the thermodynamic diagram: no work done, potential temperature is constant.  Use adiabatic motion as a first estimate of maximum temperature

Adiabatic processes on a thermodynamic chart.  LCL – lifting condensation level (air lifted adiabatically until saturation!)  LFC – level of free convection: rising parcel becomes warmer than environment, rises under it’s own power, or due to bouyant forces.  CCL – convective condensation level: Raise parcel along. Environmental sounding until saturation (intersect mixrat. And sounding)

Adiabatic processes on a thermodynamic chart.  Convective temperature -- take parcel down dry adiabatically to surface, that’s the temp we must get to to get convection.  Equilibruim level – where parcel becomes neutrally bouyant again.

Adiabatic processes on a thermodynamic chart. Convective available potential energy:  + value: parcels warmer than environment which gains energy from the air parcels  - value: parcels cooler than environment which must do work to lift parcels and loses energy.

Adiabatic processes on a thermodynamic chart.  Other buoyancy related indicies:  Lifted Index  Showalter Index  Energy Index

Adiabatic processes on a thermodynamic chart.  Questions?  Comments?  Criticisms?

Adiabatic processes on a thermodynamic chart.  The end!