SPARC Report on the Evaluation of Chemistry-Climate ... - WMO

STRATOSPHERIC PROCESSES
AND THEIR ROLE IN CLIMATE
<strong>SPARC</strong>
A project of the WMO/ICSU/IOC World Climate Research Programme
<strong>SPARC</strong> <strong>Report</strong> on the Evaluation of
Chemistry-Climate Models
June 2010
Prepared by the <strong>SPARC</strong> Chemistry-Climate Model Validation Activity Group
under the auspices of the <strong>SPARC</strong> Scientific Steering Group
Edited by V. Eyring, T. G. Shepherd and D. W. Waugh
WCRP - 132
WMO/TD - No. 1526
<strong>SPARC</strong> <strong>Report</strong> No. 5

Editing: Diane Pendlebury
Design and Layout: Diane Pendlebury and Victoria De Luca
Citation, <strong>SPARC</strong> CCMVal (2010):
<strong>SPARC</strong> CCMVal (2010), <strong>SPARC</strong> <strong>Report</strong> on the Evaluation of Chemistry-Climate Models, V.
Eyring, T. G. Shepherd, D. W. Waugh (Eds.), <strong>SPARC</strong> <strong>Report</strong> No. 5, WCRP-132, WMO/TD-No.
1526.
Available at http://www.atmosp.physics.utoronto.ca/<strong>SPARC</strong>
We acknowledge the British Atmospheric Data Centre (BADC) for collecting and archiving the
CCMVal model output, which is available in the CCMVal-2 project directory at the BADC.

Contents
List of Figures
List of Tables
Lists of Authors, Reviewers and Modelling Groups
xi
xxiii
xxvii
Executive Summary
Preface............................................................................................................................... xxxi
Overall Key Findings..........................................................................................................xxxii
Overall Recommendations................................................................................................xxxiii
Key Findings by Chapter...................................................................................................xxxiv
Recommendations by Chapter............................................................................................... xl
Chapter 1: Introduction 1
1.1 Rationale...........................................................................................................................1
1.2 CCMVal concept for model evaluation and analysis.........................................................3
1.3 Quantitative performance metrics.....................................................................................4
1.4 Progress beyond the state-of-the-art................................................................................8
1.5 <strong>Report</strong> Structure................................................................................................................9
References............................................................................................................................10
Chapter 2: Chemistry Climate Models and Scenarios 17
2.1 Introduction.....................................................................................................................18
2.2 Climate change in CCMVal-2..........................................................................................18
2.3 Major components of chemistry climate models and their coupling by transport and
radiation................................................................................................................................19
2.3.1 Dynamics...............................................................................................................19
2.3.1.1 Dynamical cores and model grids...............................................................19
2.3.1.2 Horizontal diffusion......................................................................................23
2.3.1.3 The Quasi-Biennial Oscillation....................................................................24
2.3.1.4 Gravity wave drag.......................................................................................25
2.3.2 Radiation..............................................................................................................27
2.3.3 Chemistry and composition...................................................................................27
2.3.3.1 Stratospheric chemistry...............................................................................27
2.3.3.2 Tropospheric chemistry...............................................................................27
2.3.3.3 Mesospheric and upper atmospheric chemistry and physics......................30
iii
xxxi

iv
Contents
2.3.3.4 Time-integration of chemical kinetics..........................................................30
2.3.3.5 Photolysis....................................................................................................31
2.3.3.6 Heterogeneous reactions and PSC microphysics.......................................31
2.3.3.7 Boundary conditions, emissions and surface sinks.....................................33
2.3.4 Transport...............................................................................................................35
2.3.4.1 Advection.....................................................................................................35
2.3.4.2 Convective transport and turbulent mixing of chemical species..................37
2.4 CCMVal-2 models and development since CCMVal-1....................................................37
2.4.1 AMTRAC3 (known as AMTRAC in CCMVal-1)......................................................37
2.4.2 CAM3.5.................................................................................................................39
2.4.3 CCSRNIES............................................................................................................39
2.4.4 CMAM...................................................................................................................40
2.4.5 CNRM-ACM..........................................................................................................40
2.4.6 E39CA (known as E39C in CCMVal-1).................................................................40
2.4.7 EMAC....................................................................................................................41
2.4.8 GEOSCCM ...........................................................................................................41
2.4.9 LMDZrepro............................................................................................................41
2.4.10 MRI......................................................................................................................41
2.4.11 SOCOL and NiwaSOCOL....................................................................................41
2.4.12 ULAQ...................................................................................................................42
2.4.13 UMETRAC...........................................................................................................42
2.4.14 UMSLIMCAT ......................................................................................................42
2.4.15 UMUKCA-METO and UMUKCA-UCAM..............................................................42
2.4.16 WACCM..............................................................................................................43
2.5 Definitions of simulations and external forcings..............................................................43
2.5.1 Internal and external modelling uncertainties.......................................................45
2.5.2 CCMVal-2 simulations...........................................................................................45
2.5.2.1. REF-B0: Year 2000 time-slice simulation...................................................45
2.5.2.2. REF-B1: Reproducing the past..................................................................45
2.5.2.3. REF-B2: Making Predictions......................................................................46
2.5.3 External forcings....................................................................................................47
2.5.3.1 SSTs and sea ice.........................................................................................47
2.5.3.2 Long-lived greenhouse gases and ozone-depleting substances................47
2.5.3.3 Ozone precursors........................................................................................48
2.5.3.4 Stratospheric aerosol surface area densities and direct aerosol-related
heating.....................................................................................................................48
2.5.3.5 QBO time series..........................................................................................50
2.5.3.6 Solar irradiance...........................................................................................50
2.5.4 Deviations from simulation definitions...................................................................50
2.6 Diagnostic output requested for CCMVal-2.....................................................................55
Acknowledgements...............................................................................................................56
References............................................................................................................................56

Contents
v
Chapter 3: Radiation 71
3.1 Introduction.....................................................................................................................72
3.1.1 Radiative based diagnostics..................................................................................72
3.2 Radiative Transfer Parameterisation...............................................................................72
3.3 Global mean temperature and temperature trends in CCMs..........................................75
3.3.1 Global mean temperature climatology...................................................................75
3.3.2 Global mean temperature trends: Past.................................................................78
3.3.3 Global mean temperature trends: Future..............................................................80
3.4 Evaluation of the CCM radiation codes performance......................................................81
3.4.1 Experimental set-up..............................................................................................82
3.4.2 Fluxes: Control experiment...................................................................................83
3.4.3 Fluxes: Sensitivity experiments.............................................................................85
3.4.4 Heating/Cooling rates: Control experiment...........................................................89
3.4.5 Heating/Cooling rates: Sensitivity experiments.....................................................93
3.4.6 Radiation scheme errors and model temperature biases .....................................96
3.5 Solar signal in CCMs.......................................................................................................97
3.5.1 Experimental Setup...............................................................................................98
3.5.2 Sensitivity of the solar signal to spectral resolution...............................................98
3.6 Summary.......................................................................................................................100
3.6.1 Summary by model.............................................................................................102
3.6.2 Overall summary.................................................................................................106
References..........................................................................................................................106
Chapter 4: Stratospheric Dynamics 109
4.1 Introduction...................................................................................................................109
4.2 Evaluation data sets and analyses................................................................................112
4.3 Mean climatology..........................................................................................................113
4.3.1 Zonal-mean temperatures and eastward wind....................................................113
4.3.2 Stationary waves / zonal asymmetries................................................................116
4.3.3 Brewer-Dobson circulation / tropical upwelling....................................................119
4.3.4 Heat flux / heat flux-temperature correlations.....................................................124
4.3.5 Polar stratospheric cloud threshold temperatures...............................................126
4.4 Variability.......................................................................................................................129
4.4.1 Extra-tropical variability of the zonal-mean zonal wind.......................................129
4.4.2 Tropical variability of the zonal-mean zonal wind................................................132
4.4.3 Frequency of major stratospheric sudden warmings...........................................134
4.4.4 Timing of final warmings / winter-summer transition...........................................136
4.5 Conclusions...................................................................................................................138
4.5.1 Multi-model summary..........................................................................................138
4.5.2 Summary by model.............................................................................................139
4.5.3 Quantitative assessment / metrics......................................................................142
4.5.4 Future projections................................................................................................144
Acknowledgements.............................................................................................................144

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Contents
References..........................................................................................................................144
Chapter 5: Transport 149
5.1 Introduction...................................................................................................................149
5.2 Transport Diagnostics for the Tropics............................................................................150
5.2.1 Ascent..................................................................................................................151
5.2.1.1 Tape Recorder Phase Speed....................................................................151
5.2.1.2 Ascent from Mean Age Gradients..............................................................155
5.2.1.3 Comparison of Vertical Velocities..............................................................157
5.2.2. Tropical-Mid-latitude Mixing................................................................................159
5.2.2.1 Tape Recorder Amplitude..........................................................................159
5.2.2.2 Tropical CH 4
Vertical Gradient...................................................................160
5.2.2.3 Tropical Mean Age.....................................................................................162
5.2.2.4 Tropical-Midlatitude N 2
O PDFs..................................................................163
5.3 Transport Diagnostics for the Extra-tropics...................................................................165
5.3.1 Integrated processes affecting extra-tropical composition..................................166
5.3.1.1 Mid-latitude Mean Age...............................................................................166
5.3.1.2 Fractional Release of Cl y.................................................................................................... 166
5.3.1.3 Northern mid-latitude Cl y time series.........................................................167
5.3.1.4 N 2
O annual cycle in the LS........................................................................169
5.3.1.5 Mean age at 60°N/S..................................................................................169
5.3.2 Polar processes...................................................................................................172
5.3.2.1 Antarctic Spring CH 4
PDFs .......................................................................172
5.3.2.2 Antarctic September N 2
O profiles..............................................................174
5.3.2.3 Antarctic spring Cl y time series ................................................................175
5.4 Stratospheric transport changes in the 21 st Century.....................................................176
5.5 Summary ......................................................................................................................177
5.5.1 Transport Summaries by Model..........................................................................177
5.5.2 Overall CCMVal-2 Model Transport Summary....................................................184
5.5.3 Summary of 21 st century transport changes........................................................187
5.5.4 Comparison to CCMVal-1 model transport..........................................................187
5.5.5 Requirements for transport credibility..................................................................188
References..........................................................................................................................188
Chapter 6: Stratospheric Chemistry 191
6.1 Introduction...................................................................................................................192
6.2 Formulation of Chemical Schemes...............................................................................192
6.3 Evaluation of CCMs......................................................................................................192
6.3.1 Evaluation of Photolysis Rates............................................................................194
6.3.1.1 Introduction to PhotoComp........................................................................194
6.3.1.2 PhotoComp 2008 experiments..................................................................195
6.3.1.3 PhotoComp 2008 results and discussion..................................................197
6.3.1.4 PhotoComp 2008 grading.........................................................................202

Contents
vii
6.3.2 Evaluation of Radical (Fast) Chemistry (Non Polar Region)...............................202
6.3.2.1 Background to photochemical steady state model comparisons..............203
6.3.2.2 Photochemical steady state model results................................................205
6.3.3 Evaluation of Reservoir and Long- Lived Chemistry...........................................213
6.3.3.1 Tracer-tracer correlations..........................................................................213
6.3.3.2 Comparison with satellite climatologies.....................................................217
6.3.3.3 Long-term variations..................................................................................218
6.3.4 Evaluation of Polar Chemistry.............................................................................227
6.3.4.1 Evolution of gas-phase HNO 3
, H 2
O, and HCl............................................227
6.3.4.2 Surface area density of PSCs...................................................................231
6.3.4.3 Chemical ozone depletion in the polar vortices ........................................233
6.3.4.4.1 Meteorological conditions in the polar vortex.........................................238
6.3.4.4.2 Evolution of Chemical Ozone Loss in the Polar Vortex..........................239
6.3.4.4.3. Polar Chemical Ozone Depletion vs. PACl and ClO x
............................242
6.4 Summary.......................................................................................................................243
6.4.1 Summary by model......................................................................................243
6.4.2 Overall Summary ......................................................................................................247
References..........................................................................................................................247
Chapter 7: Upper Troposphere and Lower Stratosphere 253
7.1 Introduction...................................................................................................................253
7.2 Description of observational data sets used for CCM validation...................................254
7.2.1 Balloon data........................................................................................................256
7.2.2 Aircraft data.........................................................................................................256
7.2.3 Satellite data........................................................................................................256
7.2.4 Meteorological Analyses......................................................................................258
7.3 Metrics and Grading......................................................................................................258
7.3.1 Grading of Mean and Correlative Quantities.......................................................258
7.3.2 Taylor Diagram ...................................................................................................259
7.4 Results: The Tropical UTLS..........................................................................................260
7.4.1 Cold Point Tropopause Temperature...................................................................261
7.4.2 Lapse Rate Tropopause Pressure ......................................................................262
7.4.3 Transport in the TTL............................................................................................263
7.4.4 Ozone .................................................................................................................265
7.4.5 Water Vapour ......................................................................................................266
7.4.6 Intra-seasonal Variability/ Waves........................................................................268
7.4.7 Vertical Thermal Structure...................................................................................271
7.5 The Extra-tropical UTLS................................................................................................273
7.5.1 Dynamical Structure of the Extra-tropical UTLS..................................................274
7.5.1.1 Zonal mean wind.......................................................................................274
7.5.1.2 Mass of the Lowermost Stratosphere........................................................275
7.5.1.3 Extra-tropical Tropopause pressure..........................................................276
7.5.1.4 Extra-tropical Tropopause Inversion Layer ...............................................277

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Contents
7.5.2 Transport and mixing ..........................................................................................278
7.5.2.1 Tracer seasonal cycles in the ‘background’ Lowermost Stratosphere.......278
7.5.2.2 Meridional Tracer Gradients .....................................................................282
7.5.2.3 Normalised Vertical Profiles of CO in Tropopause Coordinates................282
7.5.2.4 Vertical profiles of O 3
, H 2
O and CO relative to the tropopause height.......284
7.5.2.5. Structure of the ExTL................................................................................286
7.5.3 Variability in UTLS ozone....................................................................................287
7.6 Trends in the UTLS.......................................................................................................289
7.6.1 Tropical Tropopause Trends ...............................................................................289
7.6.2 Extra-tropical Tropopause Trends.......................................................................292
7.7 Summary and Conclusions...........................................................................................293
7.7.1 Quantitative metrics ............................................................................................293
7.7.2 Qualitative Diagnostics Discussion.....................................................................293
Tropical Diagnostics..............................................................................................293
Extra-tropical Diagnostics......................................................................................294
7.7.3 Qualitative Model Discussion..............................................................................294
7.7.4 Overall Summary ................................................................................................296
References .........................................................................................................................297
Chapter 8: Natural Variability of Stratospheric Ozone 305
8.1 Introduction...................................................................................................................306
8.2 Data and Methodology..................................................................................................306
8.2.1 Data.....................................................................................................................306
8.2.2 Multiple Linear Regression Analysis....................................................................308
8.3 Annual Cycle in Ozone..................................................................................................309
8.3.1 Annual cycle at selected locations in the stratosphere........................................310
8.3.2 Springtime ozone values.....................................................................................312
8.3.3 Annual cycle metrics............................................................................................312
8.4 Interannual Polar Ozone Variability...............................................................................314
8.4.1 Heat flux and column ozone................................................................................316
8.4.2 Temperature and column ozone..........................................................................318
8.4.3 Stratospheric annular mode and column ozone..................................................319
8.5 Solar Cycle....................................................................................................................321
8.5.1 Vertical structure of temperature and ozone signal in the tropics........................322
8.5.2 Latitudinal structure of the solar signal in temperature and ozone......................324
8.6 QBO in Ozone...............................................................................................................326
8.6.1 Equatorial Variability and the QBO signal in the stratosphere.............................326
8.6.2 QBO signal in column ozone...............................................................................329
8.7 ENSO Signal in Ozone..................................................................................................330
8.8 Volcanic Aerosols..........................................................................................................332
8.8.1 Global mean temperature response....................................................................333
8.8.2 Vertical temperature response............................................................................334
8.8.3 Ozone response..................................................................................................334

Contents
ix
8.9 Conclusions...................................................................................................................335
8.9.1 Summary by process...........................................................................................336
8.9.2 Model by model summary...................................................................................339
References..........................................................................................................................342
Chapter 9: Long-term projections of stratospheric ozone 347
9.1 Introduction...................................................................................................................347
9.2 Analysis methods..........................................................................................................349
9.2.1 Multi-Model Time Series Analysis........................................................................349
9.2.2 Multi-linear regression analysis...........................................................................349
9.3 Tropical Ozone..............................................................................................................350
9.3.1 From the 2006 WMO assessment:......................................................................350
9.3.2 Further analysis of the CCMVal-1 runs...............................................................350
9.3.3 Tropical TSAM analysis.......................................................................................351
9.3.4 Multiple linear regression analysis......................................................................354
9.3.5 The effect of upwelling on ozone.........................................................................356
9.3.6 Brief summary.....................................................................................................356
9.4 Mid-Latitude Ozone.......................................................................................................356
9.4.1 From the 2006 WMO assessment:......................................................................356
9.4.2 Further analysis of the CCMVal-1 runs...............................................................356
9.4.3 Mid-Latitude TSAM analysis................................................................................358
9.4.4 Multiple linear regression analysis......................................................................359
9.4.5 Brief Summary.....................................................................................................359
9.5 Polar Ozone..................................................................................................................359
9.5.1 From the 2006 WMO assessment: .....................................................................359
9.5.2 Further analysis of the CCMVal-1 runs...............................................................359
9.5.3 Polar TSAM analysis...........................................................................................360
9.5.4 Antarctic ozone hole diagnostics.........................................................................362
9.5.5 Brief Summary.....................................................................................................365
9.6 Ozone recovery.............................................................................................................366
9.6.1 From the 2006 WMO assessment:......................................................................366
9.6.2 Further analysis of the CCMVal-1 runs...............................................................366
9.6.3 Recovery based on TSAM analysis....................................................................367
9.6.4 The relationship between O 3 and Cl y return dates..............................................369
9.6.5 Ozone recovery as a function of latitude and reference year.............................370
9.6.6 The Role of transport in mid-latitude ozone recovery..........................................371
9.6.7 Brief Summary.....................................................................................................372
9.7 Summary.......................................................................................................................373
9.7.1 Summary by Model.............................................................................................373
9.7.2 Overall Summary.................................................................................................375
References..........................................................................................................................375

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Contents
Chapter 10: Effects of the stratosphere on the troposphere 379
10.1 Introduction ................................................................................................................379
10.2 Validation of tropospheric and stratospheric climate..................................................382
10.2.1 Multi-model mean comparison .........................................................................383
10.2.2 CCMVal-2 performance.....................................................................................385
10.2.3 CCMVal-2 vs. CCMVal-1...................................................................................387
10.2.4 CCMVal-2 vs. CMIP3........................................................................................387
10.3 Evaluation of Stratosphere-Troposphere Coupling in Models.....................................388
10.3.1 Downward propagation of Annular Mode anomalies.........................................388
10.3.2 Annular mode time scales and predictability.....................................................391
10.4 Simulations of stratospheric influence on the troposphere in the past and future.......395
10.4.1 Dynamical effects..............................................................................................395
10.4.1.1 Southern Hemisphere.............................................................................395
10.4.1.2 Northern Hemisphere..............................................................................398
10.4.2 Radiative effects................................................................................................398
10.4.2.1 The response of surface UV radiation to stratospheric ozone changes..399
10.4.2.2 Radiative forcing due to stratospheric ozone changes............................401
10.4.3 Chemical effects................................................................................................402
10.4.3.1 Stratosphere-to-troposphere ozone fluxes..............................................402
10.5 Summary.....................................................................................................................405
10.5.1 Summary by Model...........................................................................................405
10.5.2 Overall Summary...............................................................................................407
References ........................................................................................................................408
Appendix A: Major Acronyms and Abbreviations 413
Appendix B: Time Series Additive-Model Analysis 419
B.1 Multi-Model Ensemble Analysis....................................................................................418
B.2 Nonparametric estimation of the individual model trends.............................................419
B.3 Baseline-adjustment of the trend estimates..................................................................420
B.4 Multi-model trend estimates..........................................................................................421
References..........................................................................................................................424
Appendix C: List of WCRP <strong>Report</strong>s 425