Top panel: NH₃ (3,3) main line peak intensities against elevation of repeated observations toward the reference position of W33 Main (see Table 1). The standard deviations of the mean of the flux density is about 4.4%. Bottom panel: NH₃ (3,3) main line peak intensities against the epoch of the observation, also toward the W33 Main peak position. The gray dotted line connects the average T_mb (3,3) values of each day.