  Starting from basic physical principles, we present a novel derivation
linking the global wind power to measurable atmospheric parameters. The
resulting expression distinguishes three components of the atmospheric power
(the kinetic power associated with horizontal and vertical motion and the
gravitational power of precipitation) and highlights problems with previous
approaches. Focusing on Lalibert\'e et al. (2015), we show how inappropriate
treatment of material derivatives in the presence of phase transitions leads to
significant errors in wind power analyses. We discuss the physical constraints
on global wind power and the opportunities provided by considering the dynamic
effects of water vapor condensation.
