def me2po(RE,Z):
    """
    me2po converts geometric altitude to geopotential altitude -- the US
    standard atmosphere works in geopotential altitudes, which approximates the
    altitude of a pressure surface above the mean sea level.
    
    The reasoning for this is as follows: A change in geometric altitude will
    create a change in gravitational potential energy per unit mass (as the 
    effects of gravity become smaller as two objects move away from each other)
    
    Inputs:
        RE: Earth radius
        Z: Geometric altitude
    Outputs:
        H: Geopotential altitude
    """
    H = RE*Z/(RE + Z)
    return H