Influence of the sun variability and other natural and anthropogenic forcings on the climate with a global climate chemistry model Martin Schraner Polyproject

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


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


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


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.


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


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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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)


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)


Time series of total ozone averaged over 65N-65S


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


Ozone and temperature trend(trend over 1980-1997 per decade)

CONTROL

GG 2

ODS

GG+ODS

OBSERV

GG 1

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Trend for water vapor for 1975-2000

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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


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)


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?

Documents

Influence of the sun variability and other natural and anthropogenic forcings on the climate with a global climate chemistry model Martin Schraner Polyproject