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).