Inclass Exercise #4: The Importance of Temperature Advection

Advection is one way in which temperatures at a stationary observation site may be changed. Temperature advection is one term in a concept equation that will help you understand how temperatures at a location change.  The equation that we will be using is called the Temperature Tendency Equation.

 

In algebraic form, the Temperature Tendency Equation can be written:

 Term A

 =

 Term B

 +

 Term C

 =

 

 +

 

(Equation 1)

where T= temperature, t= time, V= mean wind speed along the portion of a streamline, s, along which the advection is to be evaluated and the subscript air  parcel means with respect to the air parcel.

 

 Question 1: What are the units of each of the terms in equation (1)? (Filled in in class discussion)

Term A ___[Temp] [time]-1

Term B _______[Temp] [time]-1

Term C ____[dist] [time]-1 [Temp] [dist]-1=_______[Temp]  [time]-1

 

Term A estimates the temperature changes experienced by a thermometer at a station at a fixed location (sometimes called the "temperature tendency.")

Term B estimates the temperature changes experienced by air parcels as they move along (for example, due to conductional heating or cooling, latent heat release, compressional warming due to sinking etc.)

Term C estimates the temperature changes at the local station caused by horizontal motion (advection) of colder or warmer air to the station (thus, replacing the air there formerly and causing a temperature change).

In a trivial example, on a calm, clear day in the mid summer, during which great conductional warming occurs, Term A would equal Term B, since Term C would be zero.

Alernatively, there are situations in which the advection term is huge, and Term B can be dropped on an order of magnitude basis. In which case, Term A = Term C (all of the local temperature change will be due to advection).