Introduction to ALOHA‐90: The airborne lidar and observations of the Hawaiian Airglow Campaign

The middle atmosphere is a region of complex photochemical and dynamic interactions. Stretching from roughly 30 to 100 km altitude, this is the transition region between the stratosphere and thermosphere and is perhaps the least understood region of the earth's atmosphere. A variety of interesting and important structures are found in this region including the ozone layer, noctilucent clouds, the airglow layers, the meteoric metal layers and the recently discovered sporadic Na and Fe layer phenomena.