Post on 25-Dec-2015
Influence of the sun variability Influence of the sun variability and other natural and and other natural and
anthropogenic forcings on the anthropogenic forcings on the climate with a global climate climate with a global climate
chemistry modelchemistry model
Martin SchranerMartin SchranerPolyproject meetingPolyproject meeting
26. October 200426. October 2004
26.10.2004 Martin Schraner
Overview
1. Model simulations
2. Preparations / Modifications of the model
3. Results
4. Outlook
26.10.2004 Martin Schraner
Aim
• Analysis of the influence of different forcing mechanisms (greenhouse gases, ODS, volcanoes, sun and QBO) on ozone, temperature and dynamics during 1975-2000 with transient model simulations
26.10.2004 Martin Schraner
SOCOL model (=Solar-Climate-Ozone Links)
• General circulation model MAECHAM4 coupled to chemistry-transport model MEZON
• Spectral model with T30 horizontal truncation• 39 levels, from surface to 0.01 hPa• Time step for dynamics and physics: 15 min; for
radiation and chemistry: 2 hours• Simulation of 41 chemical species• Reactions: 118 gas-phase, 33 photolysis and 16
heterogeneous reactions on/in sulfate aerosol • Coupling between chemistry and GCM by ozone
and water vapor
26.10.2004 Martin Schraner
Simulations Transient simulations with SOCOL for 1975-2000:
1. CONTROL: Control Run with constant, prescribed greenhouse gases and ODS concentrations of 1975 and a mean solar constant
2. GG: As 1., but with annually increasing greenhouse gases (CO2, CH4, N2O)
3. ODS: As 1., but with varying ODS4. GG+ODS: As 1., but with changing greenhouse gases and varying ODS5. GG+ODS+AER: As 4., but with volcanic aerosols6. GG+ODS+AER+SOL: As 5., but with varying solar forcings (varying solar
constant (-> radiation), varying photolysis rates)7. GG+ODS+AER+SOL+QBO: As 6., but with nudged QBO
In all simulations, continuously changing SST and SI (sea ice) are prescribed.Various ensembles of experiment 7. will be calculated.
26.10.2004 Martin Schraner
Modifications of SOCOL (1):Introduction of QBO
• Model cannot simulate QBO by itself (vertical resolution not fine enough), but it can be nudged
• QBO nudging by Marco Giorgetta adapted to ECHAM4 and introduced into the model
26.10.2004 Martin Schraner
Time series of mean zonal wind over equator 1976-1980
SOCOL without QBO
1976 1977 1978 1979
SOCOL with QBO
Observations (Canton Island, Gan/Maledives, Singapore)
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26.10.2004 Martin Schraner
Modifications of SOCOL (2):Extending the coupling of radiation
code with chemistry module
• Before: coupling of chemistry model with radiation module only for H2O and O3
• Now: coupling also for CH4, N2O and CFCs
-> 3d-concentrations calculated in the chemistry module at every time step are used in radiation part (instead of global constant concentrations)
26.10.2004 Martin Schraner
Modifications of SOCOL (3):Introduction of volcanic aerosols and
solar variability• Introduction of monthly and annually changing stratospheric aerosol
dataset GISS -> altitude, latitude, and time dependent stratospheric extinction coefficients (radiation part)-> altitude, latitude, and time dependent stratospheric surface densities and thus variable heterogeneous reaction rates (hydrolysis of N2O5!)
• Introduction of solar variability (combination of data from Margrit Habereiter with data from Lean) -> time dependent solar constant (radiation module)
-> time dependent photolysis rates (chemistry model)
26.10.2004 Martin Schraner
Time series of total ozone averaged over 65N-65S
26.10.2004 Martin Schraner
Stratospheric aerosol extinction coefficient [1/km] (550 nm) for July 1991 – Dec 1991
GISS SAGE 2 GISS / SAGE 2
Jul 91
Aug 91
Sep 91
Oct 91
Nov 91
Dec 91
26.10.2004 Martin Schraner
Ozone and temperature trend(trend over 1980-1997 per decade)
CONTROL
GG 2
ODS
GG+ODS
OBSERV
GG 1
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26.10.2004 Martin Schraner
Trend for water vapor for 1975-2000
CONTROL
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ODS
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26.10.2004 Martin Schraner
Results
• The obtained temperature and ozone trends for the run with changing greenhouse gases and changing ODS are closer to observations than the runs of experiment 1., 2. and 3.
• The model captures well the formation of the ozone hole over the southern high-latitudes, the ozone depletion in the upper stratosphere, the stratospheric cooling and tropospheric warming.
• The model simulates an increase of the stratospheric water mixing ratio of about 7%/decade in agreement with observations.
• However, the model underestimates the magnitude of ozone trends in the lower stratosphere at high latitudes
26.10.2004 Martin Schraner
Outlook (1)
• Introduction of new version of tropospheric aerosol data set (U. Lohmann)
• Introduction of new version of SAGE 2 retrieval (stratospheric aerosol data) into the model, incl. climatology for years without volcanoes
• Rerun of all simulations with updated model version (on the available PCs, all experiments can run together and take about 3 months)
26.10.2004 Martin Schraner
Outlook (2)• Analysis of simulations. Focus on the following questions:
– Does the model reproduce the observed trends in stratospheric ozone, temperature, and water vapor?
– Reasons for the increase of modelled water vapor. How does (dT/dt)cold point tropopause look like?
– GG reduce ozone destruction. This is understandable for the upper stratosphere (cooling by GG slows down ozone destroying reactions), but unclear for lower stratosphere (smaller ozone hole). Major warming? Dynamical effects?
– Influence of GG and ODS on stratospheric temperature: ≈1:1 at the stratopause and ≈2:1 in the lower stratosphere. More exactly quantification. Can the total temperature change be linearly combined from the single components?