ROLE OF PLANETARY WAVES, GRAVITY WAVES AND TIDES IN

THE DOWNWARD TRANSPORT OF NITROGEN OXIDES DURING

ELEVATED STRATOPAUSE EVENTS

Yvan J. Orsolini 1,2, Varavut Limpasuvan 3, Kristell Perot 5, Patrick Espy 4, Rob Hibbins 4, Donal Murtagh 5

1 Norwegian Institute for Atmospheric Research (NILU), Kjeller, No rway 2 Birkeland Centre for Space Science, University of Bergen, Norway

3 Coastal Carolina University, South Carolina, USA4 NTNU, Norway

5 Chalmers University of Technology, Gøteborg, Sweden

�Whole-Atmosphere Chemistry-Climate models still struggle to transport enough NOx down from MLT into stratosphere

�Downward transport from MLT is still subject of recent studies(Randall et al., JGR-2015; Meraner et al., JGR-2015; Siskind et al., JGR-2015)

�Large downward transport during Sudden Stratospheric Warmings with Elevated Stratopause (ESEs)

(Limpasuvan et al., JASTP-2012; Kvissel et al., JASTP-2012; Chandran et al., JGR-2013; Limpasuvan et al., JGR-2016)

� Case study of January 2013 ESE using WACCM� Detailed comparison with NO from satellite (Odin/SMR)� Role of planetary, gravity and tidal waves in forcing descent,

Outline

See Perot et al., ACP, 2014

70N-90N

ESE

From Bailey., et al., GRL 2014

(near 70N)

100

Strong descent of NO into stratosphere

Satellite Observations of Nitric Oxide (NO) during the ESE of 2012/13

SOFIE

Odin SMR (newest version V2.3)(about 4 obervation days per month)

Time/height axes slightly different

44

Climatological annual cycle

Satellite Observations of water vapour (H2O) during the ESE of 2012/13

See Orsolini et al., JGR 2010; Lossow et al., JGR 2009

70N-90N

� Strong mesospheric descent of dry air intostratosphere

� Started aloft in MLT

Odin SMR mesospheric H 2O

MLT descent

mesosphericdescent

5

� Whole-Atmosphere Community-Climate Model (ground to ~140 km),

developed at NCAR (Boulder, Colorado)

� Comprehensive chemistry-climate model with stratospheric chemistry,

gravity wave parametrization, some MLT processes

� SD-WACCM (Specified Dynamics) : Nudged winds and temperature with

NASA MERRA Re-Analyses up to 55 km

� Free-running above 60 km

� Re-runs for 2012/13 event :

� 3-hourly output

� Standard and enhanced vertical eddy diffusion in MLT

(halving Prandtl number, e.g. Garcia et al., 2014)

Whole-Atmosphere Chemistry-Climate model

WACCM with Specified Dynamics (SD-WACCM)

All Averaged [70N:90N]

MLS

SD-WACCM

[T]

[T]

[u]

w*

100km

0km

Elevated Stratopause

Event (ESE) in winter

2012/13Re-formation of elevated stratopause near 75 km (slightly lower than MLS)

Plunging of polar stratopause down to 35 km at onset

Strong mesosphericdescent

Key region Ascent and mesosphericcooling

All Averaged [40N:80N]

Resolved Waves(planetary waves, tides,

some gravity waves)

+

Total Forcing

GW drag(parametrized gravity

waves)

• Drastic changes in wave forcing

driving the mean meridional

circulation

• Strong westward forcing

– Other peak above 80 km

(westward, 5-12 days period)

– Peak near 50km

(quasi-stationary)

• GW dominant prior and after the

ESE, but reversal of GW drag in

MLT (red)

(mainly frontal GWs)

Mean flow forcing by resolved and gravitywaves

Key region

SD-WACCM

8[EP div]

[40N:80N]

0 +10 +20 +30 +40-10-20Days

[40N:80N]

[GWDorography + front]

• Strong PW westward forcing above

80km

• Reversal of total GW drag in MLT

Eastward forcingWestward forcing

100

80

60

40

20

0

Alt

itu

de

(k

m)

100

80

60

40

20

0

Alt

itu

de

(k

m)

Forcing by planetary and gravity waves

(Composite of 13 events)

Limpasuvan, V., Y. J. Orsolini, A. Chandran, R. R. Garcia, A.

K. Smith, On the Composite Response of the MLT to Major

Sudden Stratospheric Warming Events with Elevated

Stratopause, J. Geophys. Res. Atmos., 121,

doi:10.1002/2015JD024401.

Temperaturenear 91 kmat 52N

PW-1 burst

Observed Planetary Waves in MLT during ESEs of 2012/13

SABER SD-WACCM

Composite of ES-SSW during 2000-2008

MERRA [u] (~50 km)SuperDARN V (~95 km)

SuperDARN radar wind (97km)

Stray, N., Y. Orsolini, P. Espy, V. Limpasuvan, and R. Hibbins, 2015: Observations of Planetary Waves in the

Mesosphere-Lower Thermosphere during Stratospheric Warming Events, Atmospheric Chemistry & Physics,

doi:10.5194/acp-15-4997-2015.

Lon Lon

Tim

e �

All averaged [70N:90N]

Pr = 2

Enhanced diffusion

Relative NO Difference in %

(Pr = 4 – Pr = 2) / Pr = 2

Pr = 4

Standard

SD-WACCM NO during

ESE of 2012/13

• Enhanced diffusion increases

NO, up to 100%, in descending

tongue

• Sporadic differences occur in

lower and mid mesosphere

� NOT in upper mesosphere

� NOT improving MLT

descent

• white contour: resolved wave

forcing (from previous slide) Key region

1111

(SD-WACCM minus SMR ) / SMR ref

� relative difference to a pre-winter background profile

� WACCM sampled as SMR (geolocation)

� Model NO deficit persists withenhanced diffusion

� Discrepancy starts in the MLT «key region»

SD-WACCM / Odin-SMR

comparison of NO during ESE of

2012/13

Key region

Pr = 2

Enhanced diffusion

SW2 RMS

AMPL

� Evidence for large tidal amplification (migrating SW2 tide) following

the SSW of Jan 2013

� Good coincidence with observations, but simulated tides are too

weak (e.g. Smith 2012)

Semi-diurnal tide amplification: SD-WACCM vs. radar observations during ESE of 2012/13

Model Vertical scale is different

SD-WACCM

Trondheim meteor radar(data courtesy of Hibbins & Espy)

Radar

Trondheim

(63 N)

U V

13

100

80

60

40

20

0

Alt

itu

de

(k

m)

80S 60S 40S 20S EQ 20N 40N 60N 80N 80S 60S 40S 20S EQ 20N 40N 60N 80N

80S 60S 40S 20S EQ 20N 40N 60N 80N

100

80

60

40

20

0

Alt

itu

de

(k

m)

V SW2 RMS Amplitude Anomaly

[Onset: Day +10]

[Onset: Day +10] [Onset: Day +10]

[T] Anomaly [Ozone] Anomaly

80S 60S 40S 20S EQ 20N 40N 60N 80N

[Onset: Day +10]

SW2 EP Flux

Semidiurnal Migrating Tide

Tide composite (13 ESEs)

TIDE AMPLIFICATION AND FORCING OF RESIDUAL CIRCULATION

• Tide Amplification � Ozone increase at low latitudes and/or changes in wind structure (tidal

waveguide)

• However, the tidal forcing of W* (as a component of resolved wave forcing) is small and lags the

descent

SD-WACCM

Averaged [40N:80N] [90-130km]Migrating diurnal tide (DW1)

Migrating semidiurnal tide (SW2)

(e.g. Goncharenko et al., 2012; +others)

CONCLUSIONS

� Elevated stratopause event (ESE) 2012/13 well-captured by WACCM_SD

� SD_WACCM still remain defficient in representing downward transport of

NO from MLT into the stratosphere:

� Weaker than observed by SMR, despite increased MLT diffusion

� Weaker MLT descent at the time of stratopause reformation, when

planetary wave forcing dominates

�Better constraint on dynamics, e.g. use of data assimilation with DART (?)

Limpasuvan, V., Y. J. Orsolini, A. Chandran, R. R. Garcia, A. K. Smith, On the Composite Response of the MLT to Major Sudden Stratospheric Warming

Events with Elevated Stratopause, J. Geophys. Res. Atmos., 121, doi:10.1002/2015JD024401.

Orsolini Y.J., V. Limpasuvan, K. Pérot, P. Espy, R. Hibbins, S. Lossow, K. Raaholt Larsson, D. Murtagh, Modelling the descent of nitric oxide during the

Elevated Stratopause Event of January 2013, to be submitted to JASTP, September 2016

RESERVE SLIDES

1818SD-WACCM and SMR NO during ESE of 2012/13

� Clear descending

NO-rich tongue in

SMR, weak in

WACCM

� Negative bias in

WACCM below 10-3

hPa, incl. prior to the

event

(but not above)

SD-WACCM : dashed linessampled as SMR (geolocation)

SMR : full lines

1919

(SD-WACCM minus SMR ) / SMR ref

relative difference to a pre-winter background profile

WACCM sampled as SMR (geolocation)

� Negative bias (NO deficit) persists with enhanceddiffusion

� Discrepancy starts in the MLT «key region»

SD-WACCM / Odin-SMR

comparison of NO during ESE of

2012/13

Key region

Pr = 4

standard