SPARC/IGACO-O3/IOC Initiative on

Understanding Past Changes in the Vertical Distribution of Ozone

includingDo we need another assessment? Or what?

Neil Harris

SPARC / IGACO-O3 / IOC Workshop on Past Changes in the Vertical Distribution of Ozone

Geneva January 25th-27th 2011

Outline

• 1998 SPARC/IOC/GAW Ozone Profile Assessment• Motivation and lessons learnt

• Where do we stand now, 15 years on?• Are the measurements good enough? And, for what?

• Workshop• What are ther new issues?• What can be done about them?

• Possible next steps

SPARC/IOC/GAWAssessment of Trends in the Vertical Distribution of OzoneMay 1998 Edited by N. Harris, R. Hudson and C. Phillips

SPARC Report No. 1, andWMO Ozone Research and Monitoring Project Report No. 43

MotivationDifficulties to derive consistent (global) profile ozone trends, esp. ≤ 20 kmDisagreements between satellite series SAGE (I and II) and SBUVLarge uncertainties, variable coverage

Assessment of Trends in Vertical Distribution of Ozone (1998)

Profile information available for 1998 Ozone Profile Assessment

Ground-based largely northern mid-lats satellite largely global & higher alt

1970 199019801960

Trends in differences vs SAGE IIFigure 1 from 1998 summary Key results:

Drifts were pretty large - up to 10% per decade.

What is needed for ozone-climate studies? 1 %/ decade (as for column)? 3 %/ decade? 10 %/ decade?

Is it helpful to have a target?Or should we just do what we can?

Key results:Combined estimate of the mean trend in vertical distribution of ozone over northern mid-latitudes from 1980-1996 (heavy solid line) calculated using the trends derived from SAGE I/II, ozonesondes, SBUV and Umkehr measurements. Combined uncertainties are shown as 1 (light solid lines) and 2 (dashed lines).

The combined trends and uncertainties are extended down to 10 km as shown by the light dotted lines. The results below 15 km are a mixture of stratospheric and tropospheric trends and the exact numbers should be viewed with caution.

Combined trends have not been extended lower into the troposphere because there are concerns regarding the representativeness of any mean trends derived from the small sample of sonde stations.

But much, much more in there…..

Figure 2 from 1998 summary

Lessons learnt (nearly all positive)

Committed team of authors and contributors• mix of neutrals and experts (latter on instrument teams)• wanting to improve overall understanding of measurements• not overly concerned with ‘defending’ their own instruments• able to commit real time and effort• supported by agencies or institutions

Assessment provided (for the first time) • the chance to spend enough combined time to sort the problem out• the appropriate expert forum• a tangible end product (an assessment produced in time for the 1998 UNEP/WMO

Assessment)

Assessment of Trends in Vertical Distribution of Ozone (1998)

Where do we stand now?How does the ozone profile recover as ODS decrease?

Recent measurements of the vertical ozone distribution did not say much at all about

• ODS recovery • Effect of climate change

Why?No consistent global view of ozone profile measurements after 2005• SAGE (workhorse for 1984-2005) turned

off; as was HALOE (1991-2005)• Many satellites making profile

measurements since 2005, but they have not been well enough assessed to know what has been happening to trends in ozone profile

McLinden

a

Changes in distribution of ozone as climate changes

Seidel et al., Nat. Geo., 2008

Change in location of maximum total ozone gradient in sub-tropics

Total ozone is stable to 1% / decade

Vertical-latitudinal cross-sections of past values (1960–1970, black contours) and long-term changes (differences between 1960–1970 and 2090–2100, colour shading) for (a) annual mean vertical residual velocity; and (b) ozone using an ensemble mean of three simulations from the CMAM. For ozone, the past values are in units of ppmv and the long-term changes as relative changes.

a

Hegglin and Shepherd, Nat. Geo., 2010

Changes in distribution of ozone as climate changes

Ozone

Vertical-latitudinal cross-sections of past values (1960–1970, black contours) and long-term changes (differences between 1960–1970 and 2090–2100, colour shading) for (a) annual mean vertical residual velocity; and (b) ozone using an ensemble mean of three simulations from the CMAM. For ozone, the past values are in units of ppmv and the long-term changes as relative changes.

a

Hegglin and Shepherd, Nat. Geo., 2010

Changes in distribution of ozone as climate changes

% change over 130 yrs

Ozone

Vertical-latitudinal cross-sections of past values (1960–1970, black contours) and long-term changes (differences between 1960–1970 and 2090–2100, colour shading) for (a) annual mean vertical residual velocity; and (b) ozone using an ensemble mean of three simulations from the CMAM. For ozone, the past values are in units of ppmv and the long-term changes as relative changes.

a

Hegglin and Shepherd, Nat. Geo., 2010

Changes in distribution of ozone as climate changes

% change over 130 yrs

What stability / precision /accuracy is needed?What is achievable?

Does it depend on altitude?What spatial resolution is required?

Ozone

Available O3 profile measurements

Do not want to enter into “debate” on funding future instruments other than to say

they are needed!!!

Available O3 profile measurements

ENVISAT & AURA with multiple instrumentsSCISAT, ODIN with ≥ 1 instrument

Available O3 profile measurements

SBUV record 1978-now, but different instruments - low vertical resolution below 25 kmA number of other UV-Vis instruments (GOME, SCIAMACHY, OSIRIS...)

Is there an occultation record that can extend SAGE?Series of microwave limb-sounders (MLS, ODIN, A-MLS, SMILES)What to use for validation? What for their own trends?Much better geographical spread of ground-based networks in last 10 years

SBUV GOME UmkehrSondesMicrowave LidarAircraft

Goal of new Ozone profile activityOverall goal: reliable knowledge of longterm (stratospheric) ozone profile evolution:

involvesa) satellite data retrieval, quality and records b) ground-based measurements (ozonesonde, lidars, Umkehr ...) retrieval, quality and recordsc) procedures for homogenizing existing vertically resolved ozone measurements from

different sourcesd) creating databases in different coordinate systems (for different users)

Should be used as input for UNEP/WMO O3 Assessment in 2014, i.e. ready in 2013

How best to proceed? Another assessment? Or is a different mechanism better?

More instruments, more peopleWill need rigour and diplomacy

Can electronic means be used more (vs meetings)?

First step: Workshop in Geneva: Jan 25-27 2011

AimsDefine issues

Discuss (a) what is being done and (b) what could be done*(c) how best to coordinate globally?

includingwill there be a core measurement again? is it best to have multiple core measurements?what should be used for validation, what for trends?what are good ways to merge time series?how can this be assessed?

Decide how this initiative should be organisedleaders, work plan, communication, end product

* ESA, NASA, CSA, SSC already have relevant programmes / projects and other groups working on it

ProgrammeSatellite• How good are the records?• How can the recent records be best used to make multi-decadal records?• Are measurements by different techniques compatible?• Can SAGE be extended? Can we do better?• What work is on-going?• Chairs: Claus Zehner & Larry Flynn

Ground-based• How good are the records?• Which are suitable for multi-decadal analyses on their own? (Global?)• How best to use for validation?• What work is on-going?• Chairs: Mike Kurylo & Wolfgang Steinbrecht

First step: Workshop in Geneva: Jan 25-27 2011

ProgrammeIntegrated data sets• What is there?• Instrumentally-based vs combined data sets?• Role for full data assimilation? Does using met. data help or hinder?• Chair: Bill Randel

All chairs have been asked (a) to keep to the timetable (i.e. be brutal and ruthless) and (b) lead the discussion.

Posters

Will then have ~ 1 day for discussionsMixture of break-out groups and plenaryNeed to produce a plan of action for next two yearsWill be looking for interest and commitmentIdentify topics, leaders, needsPlan will be discussed next week at SPARC Steering Group

First step: Workshop in Geneva: Jan 25-27 2011

Possible outcomes

1. Assessment 2. Series of papers / focussed reports adding up

could lead to virtual assessment3. Agree workplan (work and poss. papers) leading to another workshop in a year

then decide re assessment / papers4 Do nothing special

In all cases, need to define• Issues• Studies• Sub-groups• Leadership• Timetable• Level of commitment

Need to avoid undue ownership (and defence) of instruments ?

1998 Assessment Structure

Chapter 1. Characteristics of Ozone Data Sources Used for Trend IdentificationLead Authors : David Hofmann, Clive Rodgers

Chapter 2. Ozone Data Quality Lead Authors : James M. Russell III, Herman G. J. Smit

Chapter 3. Ozone Change as a Function of Altitude Lead Authors : Richard Stolarski, William Randel

Possible outcomes

1. Assessment 2. Series of papers / focussed reports adding up

could lead to virtual assessment3. Agree workplan (work and poss. papers) leading to another workshop in a year

then decide re assessment / papers4 Do nothing special

In all cases, need to define• Issues• Studies• Sub-groups• Leadership• Timetable• Level of commitment

Thank you