\deqn{r = \mathrm{the\: linear\: correlation\: coefficient\: between\:} Q_{sim}\: \mathrm{and\:} Q_{obs}}{r = the linear correlation coefficient between Q[sim] and Q[obs]}
\deqn{r = \mathrm{the\: linear\: correlation\: coefficient\: between\:} sim\: \mathrm{and\:} obs}{r = the linear correlation coefficient between Q[sim] and Q[obs]}
\deqn{r = \mathrm{the\: linear\ correlation\: coefficient\: between\:} Q_{sim}\: \mathrm{and\:} Q_{obs}}{r = is the linear correlation coefficient between Q[sim] and Q[obs]}
\deqn{r = \mathrm{the\: linear\ correlation\: coefficient\: between\:} sim\: \mathrm{and\:} obs}{r = is the linear correlation coefficient between Q[sim] and Q[obs]}