Atmospheric Ca and Ca+layers: Midlatitude observations and modeling

摘要: We report on a comprehensive set of observations the upper atmospheric Ca and + layers. The were obtained by ground-based lidars at Kuhlungsborn, Germany (54°N, 12°E), between December 1996 1998. During this period, 112 nights soundings 58 realized. layer has an average column abundance 2.1.10 7 cm -2 , centered around 90.3 km with mean peak density 22 -3 89.9 altitude. dominates total amount above 90 4.9.10 . Because vaporization cosmic dust is most probable source metals, densities metals within atmosphere are often compared in chondritic CI meteorites. show that severely depleted respect to other such as Na Fe, their relative abundances chondrites. present one-dimensional steady state chemistry model nighttime layers, based new laboratory studies CaO reaction kinetics. This able reproduce satisfactorily characteristic features annual layers provide possible explanation for unusual seasonal variation which exhibits pronounced summertime enhancement 87 km.