IS CHEMICAL HEATING A MAJOR CAUSE OF THE MESOSPHERE INVERSION LAYER

A region of thermal enhancement of the mesosphere has been detected on numerous occasions by in situ measurements, remote sensing from space , and lidar techniques. The source of these ''temperature inversion la yers'' has been attributed in the literature to the dissipation relati ng to dynamical forcing by gravity wave or tidal activity, However, th e conclusion that the dynamics of the mesopause region is the principa l source for such anomalies is open to question. While it is certain t hat the dynamics of gravity wave breaking plays an important role in p roviding the source of momentum flux required to drive the diabatic ci rculation, evidence that gravity wave breaking can produce the inversi on layer with amplitude as large as that observed in lidar measurement s has been limited to results of numerical modeling. We note that an a lternative source exists for the production of the thermal inversion l ayer in the mesosphere, i.e., the direct deposition of heat by exother mic chemical reactions, Two-dimensional modeling combining a comprehen sive model of the mesosphere photochemistry with the dynamical transpo rt of long-lived species shows that the region from 80 to 95 km may be heated as much as 3 to 10 K/d during the night and half this rate dur ing the day, Given the uncertainties in our understanding of the dynam ics and chemistry for the mesopause region, separating the two sources by passive observations of the mesosphere thermal structure looks to be difficult. Therefore we have considered an active means for produci ng a mesopause thermal layer, namely the release of ozone into the upp er mesosphere from a rocket payload. The induced effects would include artificial enhancements of the OH and Na airglow intensities as well as the mesopause thermal structure, The advantage of the rocket releas e of ozone is that detection of these effects by ground-based imaging, radar, and lidar systems and comparison of these effects with model p redictions would help quantify the partition of the artificial inversi on layer production into sources of dynamical and chemical forcing,