I am wondering about the gravity wave (as well as the acoustic wave) calculation in atmospheric model. I know that the non-hydrostatic model should take the internal gravity wave and acoustic wave into account, but how are both internal and external gravity wave represented in a hydrostatic model? What does the gravity wave drag parameterization do?

I am new to atmospheric numerical model, and thanks in advance for answering the question!

I am wondering the representation of the internal / external gravity wave and acoustic wave in both hydrostatic and non-hydrostatic model. Thank you!