An overview of recent activities at the Global Modeling and - - PowerPoint PPT Presentation

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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 2015 1000 100 10 1 0.1 Pressure (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 ¡[hPa] ¡

Some cooling, no obvious discontinuities in the lower stratosphere El Chichon and Mt. Pinatubo signal The largest impact of the

• bserving 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

ppmv ppmv

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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-2

a

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5

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5

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5 5 5 5 5 15

100 10 Pressure (hPa) 2015 2016

Composite

b

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20 25 30 35 Pressure Altitude (km)

• 400
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200 400 Days

Anomaly

c

Composite StDev x SQRT(2)

d

• 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 Unp Unprecedent nted 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
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20 40 60 Latitude 1000 100 10 1 Pressure (hPa)

2016

• 1
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1 1 1 1 1 1 3 3 5 7 February momentum flux

a

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20 40 60 Latitude 1000 100 10 1 Pressure (hPa)

2014

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1 1 1 1 1 1 February momentum flux

b

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20 40 60 Latitude 1000 100 10 1 Pressure (hPa)

2011

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1 1 1 1 1 1 February momentum flux

c

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20 40 60 Latitude 1000 100 10 1 Pressure (hPa)

1998

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1 1 1 1 1 1 February momentum 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

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5

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5 5 5

• 2

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100 10 Pressure (hPa) 20 25 30 35 Pressure Altitude (km) 2015 2016 2017 2018

b

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5

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5 5 5

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100 10 Pressure (hPa) 20 25 30 35 Pressure Altitude (km)

• 50
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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 ¡

• zone ¡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

• ther 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 ¡[hPa] ¡ 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

• n 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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20 40 60 80 100 120 140

Analysis times

0.5 1 1.5 2 2.5 3

MLS global statistics for March 2016

MERRA-2 O-F STRATCHEM O-F MERRA-2 O-A STRATCHEM O-A

Penalty ¡func[on ¡

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 ¡[hPa] ¡ Pressure ¡[hPa] ¡ 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