SORCE meeting 2011, Sedona, AZ
Modeling of the 11-year Solar Cycle Response
in Upper Atmospheric Hydroxyl Radicals
King-Fai Lia,b, Shuhui Wangc, Thomas J. Pongettic,
Stanley P. Sanderc, Yuk L. Yunga, Jerald W. Harderd,
Marty Snowd, Franklin P. Millsb, Tao Lie, Thierry
LeBlancc, I. Stuart McDermidc
a
California Institute of Technology; b Australian National University, c Jet
Propulsion Laboratory; d Laboratory for Atmospheric and Space Physics,
University of Colorado; e University of Science & Technology of China
Correspondence: King-Fai Li (kfl@gps.caltech.edu)

a.
1
0
-1
-2
-3
1/1/1960
0
OH Column Variability (%)
The solar-cycle modulation recently reported by Shuhui Wang
4 a. %
et al. (2011) OH column shows 10±3
2
 Modeled OH column response using
previous solar model
predicts 3.7 % only
0
 Recent satellite UV measurements
show unexpectedly large
-2
Modeled 11-year
FTUVS OH total
column
solar-cycle
variability -4
Modeled MLS OH partial column
OH Column Variability (%)
2
6
1/1/1970
3
1/1/1980
1/1/1990
Year of Solar Cycle
6
9
b.
1/1/2000
2
0
-2
NRL Flux
-4
Modeled variability x 3
-6
1/1/1999
1/1/2002
1/1/2005
FTUVS total column
1/1/1960
1/1/1970
0
3
12
FTUVS OH
MLS OH
4
1/1/1996
1/1/2010
1/1/2008
OH Column Variability (%)
OH Column Variability (%)
Motivation
1/1/1980
MLS partial column
1/1/1990
6YEAR
9
6
1/1/2000
1/1/2010
12
FTUVS OH
MLS OH
4
2
0
-2
-4
-6
1/1/2011 1/1/1996
SORCE Flux
Modeled variability x1.3
1/1/1999
1/1/2002
1/1/2005
1/1/2008
1/1/2011
An “Error Estimation”

Error estimates are as
important as the
measured means

Spectral uncertainty
should also propagate
in the models

Very very conservative
uncertainty limits will
be tested
(Conservative)
5% SOLSTICE
2% SIM
Backward Extrapolation

Extrapolate to the solar
max in Jan 2002 using
Mg-II index

Uncertainty = regression
error + instrument
uncertainty
OH Photochemistry
B
B
A
A: H2O photolysis
B: OH + O(3P) → H + O2
O(3P) comes from
photolysis of O2 and O3.
A
C. H2O + O(1D) → OH + O2
C
C
D
O(1D) comes from the
photolysis of
O3 + h → O2 + O(1D).
D. Shielding effect due to
the increased overhead
O3 opacity
Modeled Response (1D)
(Blue) Solar-cycle modulation
using the extrapolated UV changes
(Shade) Uncertainty related to
extrapolation
(Black) Simulation using Lean’s
spectrum
(Orange) Canty and Minschwaner
(2007).
OH column = 6.4 ± 2.5 %
versus obs 10 ± 3%
Modeled Response (3D)
Summary

Simulated solar response of the mid-latitude
OH column abundance is much closer to
observations when the latest satellite solar UV
measurements are used.

Nevertheless, the observed solar response is
still slightly greater than the simulated value.

Future OH measurements through the next
solar maximum (expected in 2013) will be
extremely valuable for investigating these
differences further.
How about O3?
 Merkel
et al. examined
the effect in the lower
mesosphere
 Stratosphere
Daytime
???
 Continuous satellite
measurements too
short
Merkel et al. (2011)
Ground-based measurements

LIDAR O3 measurement
over Mauna Loa, Hawaii
(MLO)
 MLO agrees with 1D/2D
photochemical models
 Max level of WACCM is
wrong
 WACCM zero level too low
O3 chemistry is much simpler