1. 4Monthly means for GHGs and halogens instead of annual means (past and future)
2. Update of forcings for the years 2001 to 2004 (Stephen Montzka) 4
3. For REF2 modeled SSTs of the Hadley scenario for the full time period (1980 to 2100) based on the A1B GHG scenario will be provided (UK Met Office) 
4. Data set to assimilate the future QBO in support of SCN2 (Marco Giorgetta)
   
5. Definition of Bromine sensitivity simulations (SCN1) (Ross Salawitch and Martyn Chipperfield) 
6. Description of heating rates or extinction coefficients in radiation scheme
7. A table of reaction rates based on JPL 2005 will be provided (A. Ravishankara)
8. Model recommendations concerning the model set-up and the variables that should be stored in order to allow sophisticated inter-comparisons of chemistry, transport, dynamics and radiation within the CCM. This includes e.g. a description how to calculate passive ozone tracer in a CCM, the proposed mean age of air tracer algorithm, etc.)

Some of the key questions that have been addressed by the WMO/UNEP Steering Committee are: (1) How well do we understand the past changes in stratospheric ozone (polar and extra-polar) over the past few decades in an environment where stratospheric constituents (including halogens, nitrogen oxides, water, and methane) were changing, as was the climate in this region? (2) What does our best understanding of the climate and halogens, as well as the changing stratospheric composition, portend for the future? (3) Given this understanding, what options do we have for influencing the future state of the stratospheric ozone layer?

In order to address question (1) and (2), we would propose the following two reference simulations:

REF 1: REPRODUCING THE PAST, Core time period 1980 to 2000

REF 1 is designed to reproduce the well-observed period of the last 25 years during which ozone depletion is well recorded, and allows a more detailed investigation of the role of natural variability and other atmospheric changes important for ozone balance and trends. This transient simulation includes all anthropogenic and natural forcings based on changes in trace gases, solar variability, volcanic eruptions, quasi-biennial oscillation (QBO), and sea surface temperatures (SSTs). SSTs in this run are based on observations. Depending on computer resources some model groups might be able to start earlier. We highly recommend reporting results for REF1 between 1960 and 2004 to examine model variability. Forcings for the simulation and a detailed description can be downloaded from the CCMVal website (http://www.pa.op.dlr.de/CCMVal/Forcings/CCMVal_Forcings.html). They are defined for the time period 1950 to 2004.

SSTs in REF1 are prescribed as monthly means following the global sea ice and sea surface temperature (HadISST1) data set provided by the UK Met Office Hadley Centre (Rayner et al., 2003). This data set is based on blended satellite and in situ observations.

Both chemical and direct radiative effects of enhanced stratospheric aerosol abundance from large volcanic eruptions are considered in REF1. The three major volcanic eruptions (Agung, 1963; El Chichon, 1982; Pinatubo, 1991) are taken into account, i.e., additional heating rates and sulfate aerosol densities are prescribed on the basis of model estimates and measurements, respectively. A climatology of sulfate surface area density (SAD) based on monthly zonal means derived from various satellite data sets between 1979 and 1999 has been provided by David Considine (NASA Langley Research Center, USA). Details on how to represent the sulfate SAD before 1979 are described on the CCMVal web site.

The QBO is generally described by zonal wind profiles measured at the equator. While the QBO is an internal mode of atmospheric variability and not a “forcing” in the usual sense, at the present time most models do not exhibit a QBO. This leads to an underestimation of ozone variability, and compromises the comparison with observations. While some of the models internally generate a QBO, for the others it has been agreed to assimilate observed tropical winds. Assimilation of the zonal wind in the QBO domain can add the QBO to the system, thus providing for example its effects on transport and chemistry. Radiosonde data from Canton Island (1953-1967), Gan/Maledives (1967-1975) and Singapore (1976-2000) have been used to develop a time series of measured monthly mean winds at the equator (Naujokat, 1986; Labitzke et al., 2002). This data set covers the lower stratosphere up to 10 hPa. Based on rocket wind measurements near 8 degree latitude, the QBO data set has been vertically extended to 3 hPa. The software package to assimilate the QBO by a linear relaxation method (also known as “nudging”) as well as the wind data sets have been provided by Marco Giorgetta (MPI Hamburg, Germany).

The influence of the 11-year solar cycle on photolysis rates is parameterized according to the intensity of the 10.7 cm radiation of the sun (which is a proxy to the phase of the given solar cycle). The spectral distribution of changes in the observed extra-terrestrial flux is based on investigations presented by Lean et al. (1997) (see http://www.drao.nrc.ca/icarus/www/sol_home.shtml for details).

Recommendation: We recommend reporting results for REF1 between 1960 and 2004 to examine model variability. We will be conducting detailed model evaluation with data between 1980 and 2004 (i.e., during the satellite measurement period). Please check the list of model recommendations that is specified under (D). We encourage groups to run ensembles.

REF 2: MAKING PREDICTIONS, Core time period 1980 to 2025

REF 2 is an internally consistent simulation from the past into the future. The proposed transient simulation uses the IPCC SRES scenario A1B(medium) (IPCC, 2000). REF 2 only includes anthropogenic forcings; natural forcings such as solar variability are not considered, and the QBO is not externally forced (neither in the past, nor in the future). Sulfate surface area density is consistent with REF1 through 1999. Sulfate surface area densities beyond 1999 will be fixed at 1999 conditions (volcanically clean conditions). Changes in halogens will be prescribed following the Ab scenario (WMO, 2003; Table 4B-2). SSTs in this run are based on coupled atmosphere-ocean model-derived SSTs. Depending on computer resources some model groups might be able to run longer and/or start earlier. We recommend reporting results for REF2 until 2050. The forcings on the website are defined through 2100.

Fully coupled atmosphere-ocean CCMs that extend to the middle atmosphere and include coupled chemistry, will use their internally calculated SSTs. CCMs driven by SSTs and sea ice distributions from the underlying IPCC coupled-ocean model simulation could use the model consistent SSTs. One constraint is to make the SST dataset consistent with the SRES greenhouse gas (GHG) scenario A1B(medium). All other CCM groups will run with the same SSTs, provided by a single IPCC coupled-ocean model simulation. These simulations have good spatial resolution, so the data-sets should be suitable for all the CCMs participating in the WMO/UNEP assessment.

Recommendation: We encourage groups to run ensembles.

Scenarios for sensitivity experiments to address question (3) will be defined later. Possible sensitivity experiments could be:

SCN 1 (REF 1 with enhanced BrO_Y): An additional simulation is being developed to represent the known lower stratospheric deficit in modeled inorganic bromine abundance. This simulation will be identical to REF 1, with the exception of including source gases abundances that will increase the burden of BrO_Y. Details of this simulation will be made available shortly.

SCN 2 (REF 2 with natural forcings): A sensitivity simulation defined similar to REF1, with the inclusion of solar variability, volcanic activity, and the QBO in the past. Future forcings will include a repeating solar cycle and QBO, under volcanic clean aerosol conditions. SSTs will be based on REF2.

GHG used for WMO/UNEP 2002 runs. Extended until 2004

Table 2.  Main features of current coupled chemistry-climate models (CCMs). CCMs are listed alphabetically. The horizontal resolution is given in either degrees latitude x longitude (grid point models), or as T21, T30, etc., which are the resolutions in spectral models corresponding to triangular truncation of the spectral domain with 21, 30, etc., wave numbers, respectively. All CCMs have a comprehensive range of chemical reactions except the UMUCAM model, which has parameterized ozone chemistry. The coupling between chemistry and dynamics is represented in all models, but to different degrees. All models include orographic gravity wave drag schemes (O-GWD); most models additionally include non-orographic gravity wave drag schemes (NonO-GWD).

GEOS CCM

M.P. Chipperfield, W. Tian

GHG used for WMO/UNEP 2002 runs. The file gives surface volume mixing ratios of CH4 (ppbv), N2O (ppbv) and CO2 (ppmv)

The influence of the 11-year solar cycle on photolysis rates is parameterized according to the intensity of the 10.7 cm radiation of the sun (data available at: http://www.drao.nrc.ca/icarus/www/daily.html).  The spectral distribution of changes in extra-terrestrial flux is based on investigations presented by Lean et al. (1997).

DOWNLOAD --->  Data Set for transient model simulations (maver_1951-2000.dat) (25.2 kB).   (Contact for questions: Christoph Brühl)

Recommendation: Use observed flux (column 3 in maver_1951-2000.dat)

10,7 cm solar flux from http://www.drao.nrc.ca/icarus/www/maver.txt
More explanation see http://www.drao.nrc.ca/icarus/www/sol_home.shtml

B5.   Assimilated Quasi-Biennial Oscillation (QBO)

The QBO has been assimilated in several studies with the aim to study QBO effects on the dynamics and/or chemistry. Often the assimilation procedures assume a certain idealistic meridional structure of the QBO jets and force the model to follow the externally given vertical zonal wind structure within the QBO domain. Even simple relaxation methods (see for example Giorgetta et al., 1999) can provide fairly realistic QBO structures, and the GCM will generate the secondary meridional circulation of the QBO and the related temperature signal. This can provide a significant improvement for certain experiments. The method implies nearly no costs compared to the costs of the GCM integration.

The QBO is described by zonal wind profiles measured at the equator.

QBO data sets provided by Marco Giorgetta (Contact for questions: Marco Giorgetta )

* Surface Area Density data (SAD)  WMO2002 SAD dataset put together by David Considine, LaRC. This data set is based on SAGE and SAM data.  
Monthly zonal mean surface area density climatology derived from various satellite data.

DOWNLOAD ---> SAD data set 1979 to 1999 (1.8 MB) provided by David Considine (Contact for questions: David Considine)

B7.   Other issues

(a) Impact of new HCFCs (141B, 142B, 123) (Contact for questions: Rolando Garcia and Doug Kinnison)

e.g. instead of including HCFCs explicitly, we could instead use MCF, HCFC22 and CH3Cl as "surrogates", as follows:
    MCF --> MCF + 2/3 * HCFC141B
    HCFC22 --> HCFC22 + 1.0 * HCFC142B
    CH3Cl --> CH3CL + 2.0 * HCFC123
This approach was used in the WMO1998 2D model assessment. These surrogates have similar tropospheric and stratospheric lifetimes as the omitted HCFCs.

AGREEMENT ON SCENARIO needed. So far proposed:  Scenario Ab (best guess scenario), Scenario B2 (Table 4B-2 of WMO2003, page 4.90)

UNEP/WMO Scientific Assessment of Ozone Depletion: 2002
Chapter 1: Controlled substances and other trace gases
Scenarios from Archie McCulloch (Marbury Techn. Cons.), John Daniel (NOAA/AL), Steve Montzka (NOAA/CMDL), and Guus Velders (RIVM/LLO), September 21, 2001 (Version 3)

For the model simulation, please use scenario  -> B2

So far proposed:
The focus of the future simulation is NOT a model-model intercomparison. Rather we would like to make the best shot at predicting the future. REF 2 is a simulation that focuses on consistency and that follows the  IPCC simulations. Essentially we are asking the modeling groups to make their best prediction. Therefore, having consistent SST in future(and past of the making prediction simulation) is not necessary.
In any case one constrait is to make the SST data set consitstent with the GHG scenario.

Proposal:

a.       Fully coupled atmosphere ocean CCMs with the atmosphere extending to the middle atmosphere, with coupled chemistry, use their internally calculated SSTs (probably beyond the possibilities for most groups).

b.      CCMs driven by SST and sea ice of the underlying IPCC coupled-ocean model simulation could use the model consistent SSTs. One constraint is to make the SST data set consistent with the GHG scenario. However, if preferred, they could also decide to use the SSTs defined under (5c).

c.       All other CCM groups might wish to run with equal SSTs: We propose to use the modeled SSTs of the Hadley scenario for the full time period (1980 to 2025 or longer) based on the chosen GHG scenario.

                                                               i.      Do you agree? If not, why?

The QBO is described by zonal wind profiles measured at the equator.

QBO data sets for the future are provided by Marco Giorgetta (Contact for questions: Marco Giorgetta )