HR: 17:00h
AN: A54B-05 [Abstracts]
TI: Climate Response to Global Ozone Changes: Impacts of Tropospheric Ozone Increase and Stratospheric Ozone Decrease During the 20th Century
AU: * Sudo, K
EM: kengo@nagoya-u.jp
AF: Graduate School of Environmental Studies, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
AU: * Sudo, K
EM: kengo@nagoya-u.jp
AF: Frontier Research Center for Global Change, JAMSTEC, 3173-25, Showa-machi
Kanazawa-ku, Yokohama, 236-0001, Japan
AU: Akimoto, H
EM: akimoto@jamstec.go.jp
AF: Frontier Research Center for Global Change, JAMSTEC, 3173-25, Showa-machi
Kanazawa-ku, Yokohama, 236-0001, Japan
AB:
We study the climate response to changes in global tropospheric
and stratospheric ozone (O3) distributions from preindustrial
times (PI) to the present day (PD; ~2000) through a set of
model simulations. The climate response is evaluated by
conducting a pare of equilibrium climate simulations with the
CCSR/NIES/FRCGC climate model using PI vs. PD O3. We performed 5 distinct scenario
experiments (with 5 ensemble runs for each) to isolate the impacts
of (1) increases in long-lived GHGs (LLGHGs), (2) emission-induced
increase in tropospheric O3 (TOZ), and (3) halogen-induced
decrease in stratospheric O3 (SOZ). Climatologies of the
global O3 distributions in PI and PD for each of TOZ and SOZ
are generated using the chemistry climate model CHASER with PI and PD precursor emissions and halogen
loading.
In the simulation, tropospheric O3 burden increases by
~10 DU (0.41 W m-2 radiative forcing) up to the present
due to the emission increases (TOZ), but decreases by ~1 DU
due to the halogen-induced O3 depletion (SOZ); for SOZ, a
large O3 reduction (5-10 ppbv) is calculated in the upper
troposphere consistent with the O3 sonde observation in the
late 20th century.
As an equilibrium response, the TOZ increase causes a global and annual mean surface temperature increase
of 0.29 C° (NH:0.31 C°,SH:0.26 C°), equivalent to
13% of the estimated LLGHGs impact (2.27 C°). Responding
to TOZ, particularly large warming occurs in North America, Middle
East, and Asia, apparently reflecting the spatial distributions of
the radiative forcing from TOZ. However, our sensitivity
simulation with evenly distributed TOZ increase suggested that
such inhomogeneous warming response reflects the sensitivity of
our climate model rather than the forcing distributions. The SOZ
decrease, causing a decrease in tropospheric O3, leads to a
surface cooling of -0.04 C°. Both TOZ and SOZ cause
cooling in the lower to middle stratosphere (-0.5-1 C°).
LLGHGs similarly cool the upper stratosphere, but warm the lower
stratosphere due to the enhanced circulation.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0325 Evolution of the atmosphere (1610, 8125)
DE: 0365 Troposphere: composition and chemistry
DE: 1620 Climate dynamics (0429, 3309)
DE: 1626 Global climate models (3337, 4928)
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting