Figure 6

Dependence of NLC presence/absence on mesospheric conditions. Results of the summer temperature and humidity measurements in 2007 and 2008 by the MLS/Aura instrument at 60°N and baric height of 0.46 Pa. The longitude and time are taken as closest to a single event at each of the sites of the Northern hemisphere network for noctilucent clouds observation: namely, either for absence of NLC under clear weather (red dots) or NLC occurrence of small brightness (green triangles) or occurrence of bright NLC (blue circles).