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Global Modeling and Assimilation Office
An overview of recent activities at the Global Modeling and Assimilation Office
with focus on the stratosphere K. Wargan, L. Coy, S. Pawson, A. Molod, R. Gelaro,
R. Todling, L. Takacs, C. Orbe, A. El Akkraoui, G. Partyka &
The GMAO team
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Outline
• Status of MERRA-2 validation • QBO ‘reboot’ in 2016 • Towards full stratospheric chemistry • Replay and downscaling experiments • AMIP simulations • Transition to 4D-EnVar!!! • Other ongoing developments
This talk focuses on the stratosphere. There is much more going on at GMAO: weather, tropospheric chemistry, land, ocean…
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Status of MERRA-2 validation: core publications
MERRA-2 overview paper Gelaro et al. 2016: The Modern-Era Retrospective Analysis for Research and Applications, Version-2 (MERRA-2); to be submitted to J. Clim. This week MERRA-2 ozone validation paper Wargan et al., 2016: Evaluation of the Ozone Fields in NASA's MERRA-2 Reanalysis, submitted to J. Clim. MERRA-2 QBO paper Coy et al., 2016: Structure and dynamics of the quasi-biennial oscillation as seen in MERRA-2, J. Clim Tech memos Bosilovich, M. G., et al. 2015: MERRA-2: Initial evaluation of the climate, NASA Tech. Rep. series on global modeling and data assimilation, NASA/TM-2015-104606, vol. 39, 136 pp., NASA. [Available at http://gmao.gsfc.nasa.gov/pubs/tm/docs/Bosilovich803.pdf.] McCarty et al. 2016: MERRA-2 Input Observations: Summary and Assessment, NASA/TM–2016-104606/Vol. 46 . Finished and ready for processing
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Status of MERRA-2 validation: the stratosphere & mesosphere
MERRA-2 Global Temperature Anomalies
1980 1985 1990 1995 2000 2005 2010 20151000
100
10
1
0.1
Pres
sure
(hPa
)
Averaging Period
-4.5 -4 -3.5 -3 -2.5 -2 -1.5 -1 -0.5 0.5 1 1.5 2 2.5 3 3.5 4 4.5}T (K) Gelaro et al., 2016
AMSU-‐A MLS
Pressure [h
Pa]
Some cooling, no obvious discontinuities in the lower stratosphere El Chichon and Mt. Pinatubo signal The largest impact of the observing system changes: in the upper stratosphere and mesosphere • Introduction of ATOVS AMSU-A • Introduction of MLS (p<5 hPa)
El Chichon Mt. Pinatubo
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Status of MERRA-2 validation: the stratosphere & mesosphere
Gelaro et al., 2016
Evolution of polar temperatures during the 2005-2006 Northern Hemisphere winter • Disappearance of the warm polar
stratopause during the major SSW • Reformation at a higher altitude and
slow descent These features are captured more realistically in MERRA-2 compared to MERRA that did not use MLS
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Status of MERRA-2 validation: the stratosphere & mesosphere
Globally averaged temperature at 10 hPa
MERRA-2 uses CRTM to assimilate SSU; cell pressure leaks are taken into account. The two reanalyses converge once more data become assimilated: AMSU, AIRS
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MEAN 30°N-‐60°N
DIFFERENCE St. Dev.
MIPAS MERRA MERRA-‐2
DJF MAM JJA SON
MIPAS - MERRA-2 correlations. Bold line: 0.7
MERRA did not assimilate Aura data Seasonal cycle at 40 hPa captured by both MERRA and MERRA-2 but MERRA-2 has smaller bias Large improvement in the MERRA-2 – MIPAS st. deviations during the Aura period
Aura period SBUV period
Status of MERRA-2 validation: ozone pp
mv
ppm
v
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MERRA-2 is in better agreement with the radiosondes at 50 hPa. Note that the sonde data are assimilated in both reanalyses
Sondes (gray shading) MERRA MERRA-‐2
Zonal wind at Singapore
Coy et al., 2016: J. Clim.
Status of MERRA-2 validation: the QBO
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Coy et al., 2016
Nairobi sondes MERRA MERRA-‐2
MERRA minus sondes MERRA-‐2 minus sondes
SBUV assimilated
MLS assimilated
SBUV period
Aura period
In the Aura period tropical ozone is • Consistent with the zonal wind • In agreement with ozonesondes Large vertical smoothing errors in SBUV obscure the phase propagation [Kramarova et al., 2013]
In the Aura period in MERRA-2 the QBO signal in ozone shows more realistic phase propagation
Status of MERRA-2 validation: the QBO
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MERRA-2a
-25
-25-15
-15
-15
-5
-5
-5
-5
5
5
5
5
5
15
100
10Pr
essu
re (h
Pa)
2015 2016
Compositeb
-25-25
-15
-15
-5
-5
-5
5
5
20
25
30
35
Pres
sure
Alti
tude
(km
)
-400 -200 0 200 400DaysAnomalyc
-15
-15-5
-5
-55
5
5 5
1525
100
10
Pres
sure
(hPa
)
2015 2016
Composite StDev x SQRT(2)d
5
15
15
20
25
30
35
Pres
sure
Alti
tude
(km
)
-400 -200 0 200 400Days
-50 -45 -40 -35 -30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 40 45 50}U (ms-1)
What Happened
Expected EvoluIon
Coy et al. submiLed to J. Climate
QBO ‘reboot’ of 2016 in MERRA-‐2
Out-of-phase easterlies disrupt the westerly phase in a broad layer centered around 40 hPa
Unprecedented Oddball Disrupted Unexpected Anomalous Rebooted Hiccup dip into the gravitational field of a black hole
Reported by Newman et al., 2016, GRL
Osprey et al., 2016, Science
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-60 -40 -20 0 20 40 60Latitude
1000
100
10
1
Pres
sure
(hPa
)
2016
-1 -1 -1-1
-1
-1
-1
-1
1
11
1
1 1
3
3 5 7
Februarymomentum flux
a
-60 -40 -20 0 20 40 60Latitude
1000
100
10
1
Pres
sure
(hPa
)
2014
-1 -1 -1
-1
-1
-1
-1-1
1 1
1
1
1
1Februarymomentum flux
b
-60 -40 -20 0 20 40 60Latitude
1000
100
10
1
Pres
sure
(hPa
)
2011
-1
-1
-1
1
11
1
1
1Februarymomentum flux
c
-60 -40 -20 0 20 40 60Latitude
1000
100
10
1
Pres
sure
(hPa
)
1998
-1
-1
-1
1
1
1
1
1
1Februarymomentum flux
d
Horizontal Momentum Flux (February)
Normalized by the Standard DeviaIon (mean removed)
Momentum Heat 2016
1998
2014
2011
40 Large (+9) 40 hPa and Large (+3) upper troposphere momentum flux.
Coy et al. submiLed to J. Climate
QBO ‘reboot’ of 2016 in MERRA-‐2
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2015 2016 2017 2018
a
-25
-25
-15
-15
-5
-5
-5
5
5
5
-25-25 -15-15
-5
-5
-5
5
5
100
10Pr
essu
re (h
Pa)
20
25
30
35
Pres
sure
Alti
tude
(km
)
2015 2016 2017 2018
b
-25
-25
-15
-15
-5
-5
-5
5
5
5
-25-15-15
-5
-5
5
100
10
Pres
sure
(hPa
)
20
25
30
35
Pres
sure
Alti
tude
(km
)
-50 -45 -40 -35 -30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 40 45 50
}U (ms-1)
Seasonal Forecasts Zonal Mean Zonal Wind 10oS-‐10oN
MERRA-‐2 1 Jul Fcst
2018 100
4
Forecast calls for descent of verIcal shear zones
Forecast erroneously called for descent of early Jan verIcal shear zones
Normal
Disrupted
2015 2016 2017
MERRA-‐2 1 Jan Fcst
(Low Horizontal ResoluIon)
QBO ‘reboot’ of 2016 in MERRA-‐2
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Adding the STRATCHEM chemistry model to GEOS-DAS; Research & Development stage
• STRATCHEM replaces a simplified parameterized chemistry scheme used in GMAO’s operational data assimilation experiments to date
• 34 transported and 17 derived species • 124 gas-phase and 39 photolysis reactions • Includes a PSC scheme and heterogeneous reactions • Reaction rates follow the recommendations in JPL 2010
We plan to assess its viability for use in future products
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STRATCHEM: Towards ozone forecasts
Ozone hole area Ozone hole area
Ozone mass deficit
Ozone mass deficit
With parameterized chem. With STRATCHEM
At present, the model is not suited for running ozone forecasts beyond a few hours With full chemistry we have a good ozone hole forecast skill out to at least 10 days
Analysis 5-day forecast 10-day forecast
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Chemical tendency
Sunlit fraction of the vortex Temperature at the pole Time-
integrated tendency
Chemical ozone loss • Late December to mid-March after the vortex broke apart • Maxima in early and late February correspond to vortex displacements (minor
and final warmings) exposing larger portions of the vortex to sunlight • Maximum cumulative loss of ~2.1 at 480 K (~18-20 km)
STRATCHEM: polar processing in 2015/2016
~20 km
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MERRA-2 AMIP simulations Ensemble of 10 model runs using the MERRA-2 GCM, at the same resolution, with the same boundary conditions and covering the same period. Purpose: Determine how the model climate compares with the reanalysis (and other atmospheric models), identify errors • For the stratosphere we will be interested in derived diagnostics, e.g. B-D circulation, age of air • Note that ozone and water vapor are constrained by climatologies – probably less interesting
than dynamics and transport • Currently in production; 5 ensemble members finished • The output will be made publicly available
This is work in progress. We haven’t looked at the stratosphere yet
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Replay and downscaling Assimilation
Generate the analysis state, ANA INCREMENT = ANA-BKG
Force the GCM with INCREMENT Run GCM, generate new BKG
Replay Use ANA from an existing analysis
INCREMENT = ANA-BKG Force the GCM with INCREMENT
Run GCM, generate new BKG
• Faster (the analysis step is already done) • Can be run with a different model and/or at different resolution • Analysis increments can be applied selectively
GMAO has produced a 12.5 km resolution replay of MERRA-2 (2000-2015) • Weather: tropical cyclones better resolved, differences in
precipitation • Stratosphere: gravity waves resolved better than in MERRA-2
Omega [Pa/s]
MERRA-‐2
12.5 km replay
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Transport in the model, analysis and replay There exist systematic differences in transport between analysis, CTM, and replay: The use of instantaneous analysis fields leads to systematic errors in transport
These issues are being investigated
Replay minus analysis N2O at 480 K, 1 March 2015
%
Realistic age of air in MERA-2 driven CTM Too young in replay Improved with time-averaged analysis forcing
Replay produces faster descent inside the polar vortex leading to lower N2O mixing ratio
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Transition to 4D-EnVar
• A version of 4D data assimilation in which – Ensemble forecasts are used to estimate
background error covariances – The ensemble eliminates the need for a
tangent linear and adjoint model integration
• In this implementation the background error covariance matrix is a combination of a static and an ensemble component
• 32 ensemble members • Incremental analysis update • Now run in parallel to the operational forward
processing; it will become the next operational stream
Pressure [h
Pa]
StaIc B Ensemble B
Ensemble & static component weights
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Other ongoing developments
• Vertical resolution: 72 layers à 132 layers; ~0.5 km in the stratosphere • Seasonal forecasts (contributing to the North American Multi-Model
Ensemble): upgrade to a more recent model configuration in progress • Tropospheric chemistry: inclusion of a new tropospheric chemistry model
(GEOS-Chem), carbon data assimilation, work towards multispecies data assimilation
Plans for new reanalyses • MERRA-2 based full chemistry reanalysis (in replay mode) • Coupled atmosphere-ocean-land-ice 1980 onwards • High resolution atmospheric reanalysis 2000s
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Summary of GMAO developments • GMAO validation of MERRA-2 and research
– Stratosphere: a section in Gelaro et al., QBO paper (Coy et al. 2016a); anomalous 2016 QBO: Newman et al., 2016, Coy et al. 2016b; polar TIL and SSWs (Wargan & Coy 2016)
– Ozone: Wargan et al., ozone validation paper submitted to J. Clim. • Introduction of full stratospheric chemistry • MERRA-2 AMIP and downscaling experiments • Ongoing research on stratospheric transport in analyses, models
and replay • Transition to 4D-EnVAR • Lots and lots of work on the troposphere, land and ocean…
Note: production of MERRA was discontinued; final date: 29 February 2016
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Technical note: Incremental Analysis Update; ‘ANA’ vs. ‘ASM’ output
Each predictor step, e.g. 15 min: xi+1 = xi+Δx(xi) In the corrector step: xi+1 = xi+Δx(xi)+ΔANA
Nonlinearity sits here: the tendency depends on state, which depends on the analysis increment
‘ANA’ = background state + analysis increment
‘ANA’ : the analyzed states, the closest to the observations, 6-hourly, only assimilated fields ‘ASM’: the IAU state, consistency between fields and tendencies (dynamical, radiative,…), 3-hourly, larger set of fields (e.g. EPV). Use ‘ASM’ for most applications
Diagram by Bill Putman ASM
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backup
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Wargan et al., 2016
Tropopause – 50 hPa
MERRA MERRA-‐2
Difference St. Dev.
Improvement.
Correla[ons
Lower stratospheric ozone between 30°N and 60°N in ozonesondes, MERRA and MERRA-2 • Error standard deviation 11.2% (8.1 % in the
Aura period) • Very high correlation MERRA-2 performs significantly better than MERRA when Aura data are assimilated
Status of MERRA-2 validation: ozone
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0 20 40 60 80 100 120 140Analysis times
0
0.5
1
1.5
2
2.5
3MLS global statistics for March 2016
MERRA-2 O-FSTRATCHEM O-FMERRA-2 O-ASTRATCHEM O-A
Pena
lty fu
nc[o
n STRATCHEM: Impact on the GEOS-DAS
performance
Large reduction in the MLS ozone term of the penalty function indicates much better agreement between the model and MLS and a healthier data assimilation system.
MERRA-2 GEOS- STRATCHEM
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Note on MLS ozone data versions
We replaced MLS v2.2 with v4.2 on 1 June 2015 We turned off the 261 hPa level on 1 May 2016 because of high bias
Pressure [h
Pa]
Pressure [h
Pa]
Version 2.2
Version 4.2
V 2.2 Oct 2004-May 2015
V4.4 w/ 261 hPa level June 2015 – May 2016
V4.4, 261 hPa turned off Since June 2016
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