HR: 09:15h
AN: GC11A-06    [Abstracts]
TI: Evolution of water vapor and age of air in coupled chemistry-climate model simulations of the stratosphere
AU: * Austin, J
EM: john.austin@noaa.gov
AF: Geophysical Fluid Dynamics Lab., PO Box 308, Princeton, NJ 08540-0308 United States
AU: Wilson, R J
EM: john.wilson@noaa.gov
AF: Geophysical Fluid Dynamics Lab., PO Box 308, Princeton, NJ 08540-0308 United States
AU: Li, F
EM: feng.li@noaa.gov
AF: Geophysical Fluid Dynamics Lab., PO Box 308, Princeton, NJ 08540-0308 United States
AB: Stratospheric water vapor concentrations and age of air are investigated in an ensemble of coupled chemistry-climate model simulations covering the period 1960 to 2005. Observed greenhouse gas concentrations, halogen concentrations, aerosol amounts and sea surface temperatures are all specified in the model as time varying fields. The results are compared with two timeslice experiments for the years 1960 and 2000, in which the sea surface temperatures are set to the same climatological values, aerosol concentrations are fixed at background levels, while greenhouse gas and halogen concentrations are set to the values for the relevant years. The timeslice runs indicate an increase in stratospheric water vapor from 1960 to 2000 due primarily to methane oxidation. The age of air is found to be significantly less in the year 2000 run than the 1960 run. The transient runs from 1960 to 2005 indicate broadly similar results: an increase in water vapor and a decrease in age of air. However, the results do not change gradually. The age of air decreases significantly only after about 1975, probably due to the reduction of ozone. The changes in age of air are related to changes in tropical upwelling which changes the transport of methane into the stratosphere. Oxidation of the increased methane results in enhanced water vapor amounts. A similar increase also occurs periodically due to the three volcanic eruptions during the period. It is suggested that the observed rapid stratospheric water vapor increase during the period 1980 to 2000 arose from a combination of the effect of volcanic eruptions and probably unrelated increased tropical upwelling.
UR: http://www.gfdl.noaa.gov/~jaa/Results3.html
DE: 0340 Middle atmosphere: composition and chemistry
DE: 0341 Middle atmosphere: constituent transport and chemistry (3334)
DE: 0370 Volcanic effects (8409)
SC: Global Climate Change [GC]
MN: Fall Meeting 2005