Temperature distribution

Hi,

I need to simulate one aspect of a species of gas from the tropopause
to the thermosphere. Atmospheric science is not my field of expertise,
so I am unfamilar with the temperature distribution for input into my
model. My questions are as follows:
1) What is the best source for data concerning the temperature
gradient?
2) Is there a model to which there is a good fit to the data?
3) Is it true that the temperature is only a function of height?


TIA,

Juno