Long Term Variability in the Midlatitude Lower Stratosphere

Wednesday, 17 December 2014
Anne R Douglass, NASA Goddard SFC, Greenbelt, MD, United States, Susan Elaine Strahan, NASA Goddard Space Flight Ctr, Greenbelt, MD, United States and Luke Oman, NASA/GSFC, Greenbelt, MD, United States
The on-going records of ground based column measurements of HCl made at NDACC stations begin as early as the late 1980s. These column measurements are complemented by satellite observations of long-lived trace gases, including the Upper Atmosphere Research Satellite Halogen Occultation Experiment (1992-2005) the Aura Microwave Limb Sounder (2004 – ongoing). The Global Modeling Initiative Chemistry and Transport Model driven by meteorological fields from the Goddard Earth Observing System Modern Era Retrospective Analysis for Research and Applications (MERRA) was used to produce a simulation for 1979 – 2012 that is useful for interpretation of these observations. The tracer measurements from both sensors are well represented by the simulation, supporting the use of simulated lower stratospheric mean age to interpret the column observations. There are several periods of at least 3-5 years during which the growth or decline in HCl column is smaller than expected given the upper stratospheric change in inorganic chlorine. During the early 1990s when the chlorine source gases are increasing rapidly these periods of slow growth are associated with periods of greater than average mean age.