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I investigate the nightly mean emission height and width of the OH*(3-1)layer by comparing nightly mean temperatures measured by the ground-basedspectrometer GRIPS 9 and the Na lidar at ALOMAR. The data set contains 42coincident measurements between November 2010 and February 2014, when GRIPS 9was in operation at the ALOMAR observatory (69.3$^\circ$N, 16.0$^\circ$E) innorthern Norway. To closely resemble the mean temperature measured by GRIPS 9,I weight each nightly mean temperature profile measured by the lidar usingGaussian distributions with 40 different centre altitudes and 40 different fullwidths at half maximum. In principle, one can thus determine the altitude andwidth of an airglow layer by finding the minimum temperature difference betweenthe two instruments. On most nights, several combinations of centre altitudeand width yield a temperature difference of $\pm$2 K. The generally assumedaltitude of 87 km and width of 8 km is never an unambiguous, good solution forany of the measurements. Even for a fixed width of $\sim$8.4 km, one cansometimes find several centre altitudes that yield equally good temperatureagreement. Weighted temperatures measured by lidar are not suitable todetermine unambiguously the emission height and width of an airglow layer.However, when actual altitude and width data are lacking, a comparison withlidars can provide an estimate of how representative a measured rotationaltemperature is of an assumed altitude and width. I found the rotationaltemperature to represent the temperature at the commonly assumed altitude of87.4 km and width of 8.4 km to within $\pm$16 K, on average. This is not ameasurement uncertainty.

The airglow layer emission altitude cannot be determined unambiguously from temperature comparison with lidars