HDO in the mesosphere: Observation and modeling of novel isotopic variability

摘要: [1] First measurements of [HDO]/[H2O] ratios in the lower mesosphere (50–70 km) are described. HDO and H2O abundances were obtained over period 1992–2002, by ground-based observation microwave (λ ∼ 1.4 mm) spectral emission lines. Measured depletions highly variable, with δD values ranging from −58% ± 3% to −3% 9% (58% less deuterium than standard mean ocean water). Mesospheric decrease increasing abundance. This is contrary stratospheric increase abundance, indicating that physical mechanisms controlling mesospheric depletion fundamentally different mechanism (conversion methane water) known control depletion. A photochemical model used show observed behavior consistent slower photolysis H2O. The difference rates follows a cross sections two isotopomers at wavelengths >175 nm. Water this region important only mesosphere. Therefore for isotopic separation does not conflict results accepted studies.