Earlier in the season I had some email correspodance with Cora Randall ( The PI of AIM), as part of this she suggested that NLC should be more frequent in the morning rather than the evening. To some extent that is supported by my observations. The theory comes from a paper by Stevens et al. (2010) (Tidally induced variations of polar mesospheric cloud altitudes and ice water content using a data assimilation system, J. Geophys. Res., 115, D18209, doi:10.1029/2009JD013225.). Available at (free to view) agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2009JD013225.
The theory is based on the output of a US Navy Weather Numerical Model.
While the model looks at the diurnal variation observations also depend on no clouds in the path bettween the obserever and the NLC (assuming you are observing from Earth not a satellite like AIM). I am unsure what the diurnal variation of clouds is - I know low cloud tends to lift and disappear under the influence of summer Sun.
I have now started to save the EUMETSAT cloud images for the nights (and mornings) that my NLC camera is running. More on how to do that automatically in a future post.