Ozone Layer in the 21st CenturySwagath Navin Manohar

Framework for evaluating changes in ozone1. Stages in evolution of the ozone layer2. Ozone changes in the Near and Long term3. Milestones in evolution of ozone layer4. Significance of statistical tools

Factors affecting the increase of ozone - Non ODS s1. Atmospheric Chemical Composition2. Stratospheric Temperature

Statistical Methods1. Change in Linear Trend2. CUSUM

Attribution of recent behavior of ozone1. Upper Stratosphere2. Lower Stratosphere3. Polar Ozone

Stages in evolution• Slowing of ozone decline (near term)

• Turnaround of ozone (near term)

• Full recovery (long term)

Milestones• Milestones 1─Weakening of

negative trend• Milestones 2─Reversal of

trend• Milestones 3─EESC back to

pre-1980s value• Milestones 4─Parameter

reaching pre 1980s value

Statistical Analyses─Principal tool─Could be used to derive trends

in changes in the ozone─Defines the uncertainty─More complex models are

required to represent the atmospheric processes sufficiently

Factors Affecting the Detection, Attribution and Timing of Milestones

1. Stratospheric Halogen Loading

2. Atmospheric Chemical Composition

3. Stratospheric Temperature

4. Atmospheric Transport

5. Solar Cycle

6. Volcanic Eruptions

Stratospheric Halogen Loading

1. Important factor impacting the ozone level

2. Estimation could lead to observing changes in the levels

3. Could mislead to wrong milestone time scales

Atmospheric Chemical Composition1. Changes in levels of other gases and their effects2. Compositional change of ozone depleting gas-Example

Stratospheric Temperature1. Changes in temperature could have large influence on ozone2. Important factor in future predictions3. Major source of uncertainty4. Dependence on various factors5. Greenhouse Effect

Atmospheric Transport1. Major factor contributing to stratospheric ozone variability2. Detection of recovery milestones3. Signal-noise ratio4. Experimental discussion

Solar Cycle

1. Solar maximum

2. Variation with altitude and latitude

Volcanic Eruptions

1. Large impact on stratospheric ozone

2. Future projections

3. Eruption of Mt. Pinatubo

4. High chlorine conditions

5. Low chlorine conditions

Statistical Methods for Detection of Milestones

1. Significance of statistics

2. Multiple linear regression Fits

3. Types of statistical method used

Change in Trend

CUSUM

Attribution of Recent Behavior of Ozone

• Deals with scientific assessment

• Difficulty• Applications in

different regionsUpper Stratospheric

ozone

Lower and total column ozone

Polar ozone

Lower Stratospheric Ozone

1. Slowing of ozone decline in lower stratospheric ozone and in total ozone column

2. Role of atmospheric transport

3. Region dominated by Dynamical and transport processes

4. Changes in transport makes a major contribution to ozone column

Polar Ozone1. Severity of ozone

depletion discontinued

2. Anomalous stratospheric temperature and reduced frequency of PSC

3. Polar EESC decreasing 0.6% per year

4. Could be linked with that of future recovery in the long term

Danke!!!!!!!