ACCMIP simulations of Climate Change impacts on CO-tracer transport Ruth Doherty, Ian Mackenzie U....
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ACCMIP simulations of Climate Change impacts on CO-tracer transport Ruth Doherty, Ian Mackenzie U. Edinburgh Paul Young, Oliver Wild U. Lancaster Mieyun
ACCMIP simulations of Climate Change impacts on CO-tracer
transport Ruth Doherty, Ian Mackenzie U. Edinburgh Paul Young,
Oliver Wild U. Lancaster Mieyun Lin GFDL, Michael Prather UCI,
ACCMIP modellers ACITES York, Dec 2 nd 2013
Slide 2
Uses of a CO-Tracer What can a passive CO-tracer with a 50-day
lifetime tell us about transport in a CCM? What are its strengths
and weaknesses? Can we use this CO-tracer to create a metric of
vertical overturning in the troposphere? Focus on climate change
effects on transport
Slide 3
First CO tracer results from HTAP (TP1x)
Slide 4
CO tracer results from HTAP for Present and Future Climates
Implemented a CO tracer for a species with a 50 day lifetime
emitted as for CO over the NA, EU, EA and SA source region Two
chemistry-climate models STOC- HADAM3 and UM-CAM both driven by the
same SSTs from the HadAM3 GCM Results for 5-year (10-year) 2000s
and 2100s climates
Slide 5
CO-Tracer results from NA 5 year (10-year) annual-average
surface NA CO tracer concentrations for 2000 climate Difference in
5-year annual-average surface CO-tracer concentrations between the
2095 and 2000 climates In the future climate, less CO tracer from
NA remaining at the surface especially over the Great Plains region
but more over the E. and W. United States and outflow regions
Slide 6
And for other regions Similar results for the other three HTAP
regions Distinct patterns of adjacent areas of lower and higher
surface CO tracer concentrations Shift in circulation within all
the regions that extends across the regional boundaries between
present day and future But only one representation of climate
change. Full vertical picture
Slide 7
Atmospheric Chemistry & Climate Model Intercomparison
Project (ACCMIP) Another model intercomparison with a focus on
climate change Only CO-direct- a tracer with a 50-day lifetime
emitted form all CO emission sources across the globe Direct=
emissions from fossil and bio fuel combustion, biomass burning,
plant and soil release Present-day = ACChist= 2000s ~10 years (SST
climatology) Future = RCP 8.5 2100s ~10 years (SST climatology
Slide 8
Surface annual-mean CO tracer concentrations for 2000s Like CO
sources
Slide 9
Surface annual-mean CO_T: 2100s-2000s (2000s-1990s) Shifts in
surface patterns over major source regions Some model to model
similarities (eastern USA, S EU) and some differences some evidence
of reproducibility of shifts Signal larger than decadal variability
(as in CMAM) Causes?
Zonal-mean CO-tracer decadal mean 2000s (top) Diff CO-tracer
decadal mean 2100s-2000s (bottom) Reasonable agreement Surface
general decreases strongest at Equator (up to 5-10 ppb), increases
10N & 30N (up to 2-5 ppb) UT- tropics reductions of 1-2ppb (up
to 5 ppbv) weaker Hadley circulation signal? UT- extra-tropics esp
NH- enhanced STE /higher tropopause (Fang et al. 2011 JGR)
Slide 12
Co-tracer decadal mean 2000s 1000-900hPa average (top) and
400-200 hPa average (bottom) Fairly similar patterns across
models
Slide 13
Gradient co-tracer (1000-900)-(400-200) hPa 2000s (ppb)
Positive values over emission source regions and nearby outflow
Negative values for outflow especially S. Hemisphere Similarish
picture in 2100s (not shown)
Slide 14
Difference 2100s-2000s co-tracer (1000-900) hPa (top) and
400-200 hPa (bottom) At 1000-900 hpa: mixed signal N and S of
equator (global mean decreases but with N. Africa and Asia
increases) At 400-200 hPa: tropical signal more uniform across
hemispheres (large decreases) and large increases at N. poles (STE,
higher tropopause)
Slide 15
Difference 2100s-2000s co-tracer gradient (1000-900)-(400-200)
hPa gradient increases over tropical land but decreases elsewhere
especially northern polar latitudes Tropics: co-tracer gradient
strengthens over emission regions (Fang et al. suggest reduced
convective mass flux)
Conclusions Shifts in circulation patterns of surface CO-tracer
around major emission source regions Largest CO-tracer decreases in
tropics -weaker Hadley circulation but confined areas of increased
CO-tracer at the Equator also (convection scheme?) Large uniform
increases in northern mid-latitudes upper troposphere and reduced
LT-UT gradient Mixed gradient changes over tropics- increases over
N. tropical land Contributions from changes in tropopause
height/STE and from changes in upwelling
Slide 18
Seasonal (MAM and JJA CO-T changes: 2100s-2000s (2000s-1990s)
UM-CAM, GISS similar between seasons, more increases in tropics in
JJA CAM 3.5 very different in tropics
Slide 19
Fang et al. (2011) JGR 20 year average zonal mean distribution
of CO tracer (unit: ppbv) during 19812000 (black solid contour) and
the changes of that tracer from 19812000 to 20812100 (color shaded)
Blue dashed and dotted lines show the tropopause location during
19812000 and 20812100, respectively Only changes significant at the
95% confidence level are shown
Slide 20
Vertical overturning Model nameUM-CAMGISS NCAR- CAM3.5 CMAM
STOC- HadAM3 Michaels suggestion 1. emiss_co 4 *area: total over
all grid boxes (kg s-1) 18819.8 19622. 4 19344.519307.019327.1 2.
emiss_aco / Mass air (normalised to a 125m cell height) ratio
Mair/MCO: mean (ppb day-1) 2000s/2100s 23.54 24.05 24.44 24.75
23.48 23.76 23.94 24.36 24.27 24.72 3. diff (925-325 hpa) 2
co-tracer: mean of all grid cells (ppb) 2000s/2100s 3.68 3.64 4.60
4.41 3.23 2.83 4.47 4.85 4.02 4.07 4. mean grad co- tracer (ppb)
/mean(emiss co in ppb day- 1)**(days) 0.157 0.151 0.188 0.178 0.137
0.119 0.187 0.199 0.165 0.173 5. diff fut-pres of 11.(day) and (%)
-0.005 (-3.2%) -0.010 (- 5.4%) -0.018 (- 13.2%) +0.012 (+12.4 %)
+0.007 (+4.3%) 6. Fang et al. relative change in the COt gradient
change but between 925hPa and 325hPa and (2 nd left term)***
-2.7%-4.3%-12.5%+8.9%+2.4% Results from ACCMIP monthly data:
italics = rcp 8.5, nonitalics = acchist 2000 10 years Notes: 1 cmam
and stoc-hadam3 are very slightly different. 2 nearest model layer
to 925 and 325 hpa (not much divergence between models)- need to
interpolate **~3ppb/~24 ppb/day=0.14-0.19 days- 3.x hours seems not
sensible. Not sure that this division tells us truly about
transport between the two levels- would lifetime (50days) not come
in? (checked emission field in ppb looks sensible) *** Fang et al.
use lifetime and a 2 box model for the LT and FT. Ive calculated
the same relative change in the COt gradient change but between 925
- 325 hPa. (They calculate FT-LT ) Message: Both methods give a
similar idea about global mean changes LT-UT of (range -13% to
+10/2%) but these are the combined result of different responses in
tropics and high latitudes (be nice to separate tropics especially
land tropics but not sure of validity) Fang Y., A. M. Fiore, L. W.
Horowitz, A. Gnanadesikan, I. Held, G. Chen, G. Vechhi, H. Levy
(2011) Impacts of changing transport and precipitation on pollutant
distribution in a future climate, J. Geophys. Res.>,
doi:10.1029/2011JD016105.