HR: 1340h
AN: A43B-1146    [Abstracts]
TI: Ozone Radiative Feedback on the Quasi-Biennial Oscillation in the Tropical Stratosphere as Revealed in Chemistry-Climate Model Simulations
AU: * Shibata, K
EM: kshibata@mri-jma.go.jp
AF: Meteorological Research Institute, 1-1 Nagamine, Tsukuba, 305-0052, Japan
AU: Deushi, M
EM: mdeushi@mri-jma.go.jp
AF: Meteorological Research Institute, 1-1 Nagamine, Tsukuba, 305-0052, Japan
AB: Simulations on the recent past middle atmosphere were made with a chemistry-climate model (CCM) of Meteorological Research Institute (MRI). Three runs with different transport schemes for chemical species were performed for 25 years from 1980 to 2004. The three transport schemes are formally hybrid semi-Lagrangian type, which is of flux form in the vertical and, at once, of ordinary type in the horizontal, while they use different interpolation and/or approximation in calculating in-cell profiles from cell-average values, resulting in different properties in diffusiveness. The prototype scheme (Cubic3) uses a Lagrangian cubic interpolation of neighboring abundances in the horizontal and also uses it for overhead column abundances in the vertical. To the Cubic3 scheme, two improvements are successively incorporated: one is the piecewise rational-function method (PRM) in the vertical, and the other is a quintic Lagrangian interpolation in the horizontal, resulting in PRM3 (vertically PRM and horizontally cubic) and PRM5 (vertically PRM and horizontally quintic) schemes. The dynamics module of MRI-CCM is a spectral global model of T42 truncation with 68 layers extending from the surface to 0.01 hPa (about 80 km), wherein the vertical spacing is 500m in the stratosphere between 100 hPa and 10 hPa. Hines gravity wave (GW) drag is incorporated with an enhanced GW source in the tropics to spontaneously reproduce the QBO in zonal wind. The chemistry-transport module treats 36 long-lived species including 7 families, and 15 short-lived species with 80 gas phase reactions, 35 photochemical reactions and 9 heterogeneous reactions. MRI-CCM is integrated with observed forcings of SSTs, sea ice, volcanic aerosols, 11-year solar cycle, greenhouse gases, and halogens, the latter two of which are specified at the surface. It is found that PRM3 and PRM5 schemes substantially reduce the systematic positive bias in ozone, particularly in the tropical lower stratosphere and upper troposphere and that PRM5 reproduces most realistic ozone and other chemical species distributions with PRM3 being the next. For example, the ozone decrease amounts to about 40 % at 100hPa in PRM5 run. Along with these ozone reductions, the QBO period is also changed: it is about 27 months in Cubic3 run, while it is about 23 and 20 months for PRM3 and PRM5 runs. This shortening of the QBO period with the decrease in ozone abundance is compatible with authorsf previous simulations, in which switching on (off) of ozone radiative feedback prolongs (shortens) the QBO period by about 80 (35) %. In a less ozone condition in the lower stratosphere the ozone QBO amplitude also becomes smaller, so that the ozone radiative feedback weakens, resulting in a shorter QBO period.
DE: 0340 Middle atmosphere: composition and chemistry
DE: 0341 Middle atmosphere: constituent transport and chemistry (3334)
DE: 3300 ATMOSPHERIC PROCESSES
DE: 3334 Middle atmosphere dynamics (0341, 0342)
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting