Shuhui Wang

Observing OH Response to the Solar Cycle

Over 5-year Aura MLS OH Measurements in Combination With the 13-year Ground-based FTUVS OH Measurement

Shuhui WangStanley P. Sander, Thomas J. Pongetti, Nathaniel J. Livesey, and Michelle L. Santee

Jet Propulsion Laboratory, Caltech

King-Fai Li and Yuk L. YungDivision of Geological and Planetary Sciences, Caltech

MLS OH —[Pickett et al., 2008; Wang et al., 2008]FTUVS OH — [Cageao et al., 2001; Cheung et al., 2008]

• OH (together with HO2) plays a key role in the HOx catalytic reaction cycle leading to O3 destruction in the

middle atmosphere.

• Primary sources of OH

Stratosphere O3 + h O(1D) + O2

O(1D) + H2O 2 OH

Mesosphere

H2O + h OH + H

• OH variability

Diurnal variation

Seasonal variation

Solar cycles

―11-year cycle (sunspot)

― 27-day cycle (rotation)

FTUVS summer OH Column (1013cm-2)

Introduction - OH

MLS OH Density at [29.5N, 39.5N]

Pres

sure

(hPa

)

05 06 07 08 09

Aura Science Team Meeting 2010 (Boulder, CO)Aura Science Team Meeting 2010 (Boulder, CO) OH Response to the OH Response to the Solar CycleSolar Cycle

1978 1983 1988 1993 1998 2003 20080.260

0.265

0.270

0.275

0.280

0.285

0.290

0.295

So

lar

Mg

II

Daily MgII Annual mean MgII

Solar Mg II Index from NOAA

• Mg II core-to-wing ratio (~280nm) is a robust measure of chromospheric activity and a very reliable indicator of solar UV variability.

• OH, produced through photolysis, is expected to show variability during the solar cycle.FTUVS OH dataFTUVS OH data

MLS OH MLS OH


Introduction – Solar Cycle• The 11-year solar cycle is also known as the “sunspot cycle”.

• The Sun has just came out of an extended solar minimum and entered the solar cycle 24 (max predicted to be in 2013).

Sep, 2010

Hint of Solar Signal in MLS OH Climatology (2005)


Hint of Solar Signal in MLS OH Climatology (2009)


2004 2005 2006 2007 2008 20090.92

0.94

0.96

0.98

1.00

1.02

1.04

jan feb mar apr may jun jul aug sep oct nov dec

No

rma

lize

d to

th

e 2

00

5 v

alu

e

2004 2005 2006 2007 2008 20091.2

1.4

1.6

1.8

2.0

2.2

2.4

OH

Den

sity

(10

7cm

-3)

MLS Monthly Mean at ~2 hPa at ~34ºN

• MLS OH Climatology generally shows a clear decreasing trend during 2004-2009.

• Exceptions are seen in Feb-May, 2008.

• On average, OH decreases ~1.5% per year.


Hint of Solar Signal in MLS OH Climatology

Vertical Stratification of Solar Cycle Signal


7/1/2004 7/1/2005 7/1/2006 7/1/2007 7/1/2008 7/1/20093

4

5

6

7

8

Annual mean

MLS

OH

col

umn

(10

13cm

-2)

Daily measurement at TMF [29.5N, 39.5N]

7/1/2004 7/1/2005 7/1/2006 7/1/2007 7/1/2008 7/1/20095.0

5.2

5.4

5.6

5.8

6.0

Annual mean

MLS

OH

col

umn

(1013

cm-2)

7/1/2004 7/1/2005 7/1/2006 7/1/2007 7/1/2008 7/1/2009-6

-4

-2

0

2

4

6

Var

iabi

lity

(%) Variability of annual mean from the first year mean (Oct 2004 - Oct 2005)

Solar Cycle Signal in 5-year MLS OH Partial Column at TMF

• The solar cycle response (column OH) from annual mean MLS data at TMF is ~ 4% decrease from 2004 to 2009.


1/1/1997 1/1/1999 1/1/2001 1/1/2003 1/1/2005 1/1/2007 1/1/2009 1/1/2011

3

4

5

6

7

8

9

19

20

21

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24

Daily max

OH

col

umn

daily

max

(10

13cm

-2)

1/1/1997 1/1/1999 1/1/2001 1/1/2003 1/1/2005 1/1/2007 1/1/2009 1/1/2011

3

4

5

6

7

8

9

1-year FFT smoothing 2-year FFT smoothing

OH

col

umn

daily

max

(10

13cm

-2)

Interpolated daily max Monthly mean of daily max

1/1/1997 1/1/1999 1/1/2001 1/1/2003 1/1/2005 1/1/2007 1/1/2009 1/1/2011-8-6-4-202468

1-year FFT smoothing 2-year FFT smoothing

Diff

eren

ce fr

om

all-t

ime

mea

n (%

)

MLS OH column variability

UT


Solar Cycle Signal in 13-year FTUVS OH Column Data at TMF

http://www.pmodwrc.ch/pmod.php?topic=tsi/composite/SolarConstant


Total Solar Irradiance (TSI) Records from Multiple Satellites

[Fröhlich, 2006]


Total Solar Irradiance (TSI) Records from Multiple Satellites

• The comparison of the three composites with a reconstruction of TSI (based on Kitt-Peak magnetograms [Wenzler, 2005]) shows that PMOD is the most reliable TSI composite.




Observed OH Variation is in Phase with the Solar Cycle (TSI)

NOAA Solar Magnesium II Index from multiple Satellite


Observed OH Variation is in Phase with the Solar Cycle (Mg II)

Summary• The 5-year MLS global OH observations and the 13-year OH column data from FTUVS at TMF provide a great opportunity to study the hydrogen chemistry variation in the middle atmosphere, in particular, the response to the solar 11-year cycle.

• MLS OH climatology shows a clear decreasing trend during 2004-2009. The vertical profiles of such variability show two peaks at the two density peaks of OH. The integrated MLS OH columns show a decrease of ~4-5%.

• The FTUVS OH columns show a variability of ~10% (peak to valley) due to the solar 11-year cycle.

• The comparison of observed OH variability and with the TSI and Mg II records confirms that the 10% variability in OH column is associated with the solar cycle.

• Ongoing work – Modeling the OH response to solar cycle: Detailed modeling studies are required to fully understand the mechanisms through which solar variability governs the middle atmospheric chemistry. One of the largest uncertainties in such modeling work is the solar output variability. AGU GC29


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