Proposal Science Issues

• How will ozone recover over the next few decades in a changing climate?

• How has past ozone change affected the changing climate and how will future chemistry changes modify climate?

Basic Philosophy

•Get to fully interactive chemistry/dynamics through step-by-step simulations

•Key is ability to use model(s) in experiment mode.

– Get an idea from analysis – Formulate experiment– Run experiment, analyze results

•Requires computer throughput

Runs completed or now running

CTM• 50-year 1973-2022 with

Halogens, volcanic aerosols, solar cycle

• 20-year 1979-1999 without volcanic aerosols

• 9-year 1973-1981 with Pinatubo aerosols in 1975

GCM• 50-year 1949-1998 with

varying SST• 50-year 1949-1998 with

AMIP repeating SST• 50-year 1949-1998 with

mean repeating SST• 20-year with 1979 ozone

in radiation code• 20-year with 1999 ozone

in radiation code

50-year CTM IntegrationTotal Column Ozone from Model

Model run includeschlorine variationvolcanic aerosols,solar cycle, and dynamic variability.

We can deduce theimpact of each by statistical trend analysis, althoughthis is imperfect.

But with a model we can do the experiment!

Runs completed or now running

CTM• 50-year 1973-2022 with

Halogens, volcanic aerosols, solar cycle

• 20-year 1979-1999 without volcanic aerosols

• 9-year 1973-1981 with Pinatubo aerosols in 1975

GCM• 50-year 1949-1998 with

varying SST• 50-year 1949-1998 with

AMIP repeating SST• 50-year 1949-1998 with

mean repeating SST• 20-year with 1979 ozone

in radiation code• 20-year with 1999 ozone

in radiation code

CTM run Without Volcanic AerosolsDifference from basic 50-year simulation

averaged over the entire year of 1992

The model difference can be further examined for changes inchemical catalytic cycles.

NOx conversion toHNO3 decreasesozone loss

NOx conversion toHNO3 decreasesInterference withChlorine and thusIncreases ozone loss

Runs completed or now running

CTM• 50-year 1973-2022 with

Halogens, volcanic aerosols, solar cycle

• 20-year 1979-1999 without volcanic aerosols

• 9-year 1973-1981 with Pinatubo aerosols in 1975

GCM• 50-year 1949-1998 with

varying SST• 50-year 1949-1998 with

AMIP repeating SST• 50-year 1949-1998 with

mean repeating SST• 20-year with 1979 ozone

in radiation code• 20-year with 1999 ozone

in radiation code

What if Pinatubo erupted into a low-chlorine stratosphere?

Low chlorine meansthat volcanic aerosolsmostly reduce NOx loss while there isless chlorine loss to be interfered with.

Runs completed or now running

CTM• 50-year 1973-2022 with

Halogens, volcanic aerosols, solar cycle

• 20-year 1979-1999 without volcanic aerosols

• 9-year 1973-1981 with Pinatubo aerosols in 1975

GCM• 50-year 1949-1998 with

varying SST• 50-year 1949-1998 with

AMIP repeating SST• 50-year 1949-1998 with

mean repeating SST• 20-year with 1979 ozone

in radiation code• 20-year with 1999 ozone

in radiation code

SST constant in both runs

Increases in yellowto red, decreases inblue to purple.

Maximum increase and decrease about0.8K

20-year Average of Surface Temperature Difference at Each model point between

simulations for 1979 ozone and 1999 ozone

Test of Significance of Surface Temperature Changes

At each point calculatethe standard deviationdivided by the squareroot of 12 months times20 years to get standarderror of mean.

At left is ratio of meandifference at each pointdivided by the standarderror of the mean.

Yellow to red indicatesgreater than 2 standard errors of signficance

Probability Distribution of Surface Temperature Differences between GCM Runs with 1999 ozone

vs 1979 ozone in radiation code

4.9% > 2 sigma

32% > 1 sigma

i.e. Random-if there is an effectthe run is not long enough todemonstrate it.

Difference x 108-8 0

On-line chemistry• 1-year using

stratospheric integrator

• Testing strat-trop integrator

Runs completed or now running

Coupled Chemistry• None yet

Runs we would like to (should) do

CTM• Time-slice with more chlorine (~5-7 ppbv)

– Test cycle interaction at larger chlorine– Also evaluates what could have been

• Chlorine change without solar cycle– Clearly separates solar cycle– Basis for tests of possible solar cycle in circulation

• Hindcast with cold NH winter (GMI)– Gives envelope for ozone recovery

• Hindcast with warm NH winter (GMI)– Gives other side of envelope for ozone recovery

• Extend ozone recovery of 50-year run beyond 2022 to maybe 2050– Go to “complete” recovery

Runs we would like to (should) doGCM

• Redo 20-year delta ozone runs with interactive SST

– Surface temperature changes are dampened in constant SST runs– Gives full response to test radiative forcing

• Extend 20-year delta ozone runs for increased significance of changes

– Only significant difference so far is delay of Antarctic vortex breakup and a change in residual circulation

• 20-year run with PV-theta ozone climatology– Test the importance of having ozone heating correlate with wave

structures for radiative damping

• Time slice run (20+ years) preindustrial vs present tropospheric ozone

– Test impact of changes in tropospheric ozone from 1900 to present on surface temperature and meteorology

Runs we would like to (should) do

On-line chemistry

• 5-year test with stratospheric integrator– On-line/off-line test– Preparation for coupled stratospheric chemistry

• Few-month test with strat-trop integrator– Test timing to see how much speed up is necessary for useful

experiments

• Speed up options tests with strat-trop integrator

– Evaluate various methods that are suggested

Runs we would like to (should) do

Coupled Chemistry• Ozone hole recovery test

– Chemistry simulation with interactive vortex

• 50-year stratospheric hindcast/forecast run– Extend hindcast to model with all connections that we know– Does it reproduce data better?

• Time slice preindustrial trop-strat chemistry– Preparation for long simulation run

• Time slice present trop-strat chemistry– Get statistics of present chemical situation rather than just the

meteorology of a single year

• Time slice future (2100) trop-strat chemistry– Statistics of where we think we are going

• THINK BIG - 250 year trop strat run 1850-2100– The ultimate simulation

What should be scope of proposal?

• Preliminary experiments to understand feedbacks

• Online chemistry

• Fully-coupled stratosphere

• Fully-coupled strat-trop chemistry

• Tropospheri chemistry experiments

Interactions

• What is relationship with GMI?

• How do we relate to GMAO?

• How does GISS figure in this?

• What about WACCM?

Fully interactive model

Dynamical Coreheating,

surface stress

RadiationTa, Ts, solar,

LandQ, solar

ChemistrySource gases, solar, T,wind

OceanQ, solar

Tests:1979 ozone1999 ozone

Tests:Varying SSTFixed SST

Model variables for time slice experiments (current model)

• Chemical source gases • Green house gas levels (pre-industrial to doubled CO2)• Volcanic aerosol levels (background or Pinatubo)• Solar (max/min or mean)• Sea surface temperatures (max/min or mean)

Extreme chemistry - use that to test radiative impact (1-7 ppb Cly)

Extreme radiative forcing - use that to test chemistry (250 ppm - 680 ppm CO2)

Extreme surface conditions - test radiative & dynamical changes (warm year vs. cold year)

CTM/FVGCM: Run FVGCM run CTM re-run FVGCM with CTM O3 compare runs

Tests between chemistry and radiation (non-interactive)

High ozone

Cly = 1 ppb

Low ozone

Cly = 5 ppb

Low CO2

CO2=250 ppm

Pre-industrial

High CO2

CO2=680 ppm

2050 Future avoided