O3 MLS validation results: PAVE 2005 early look

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Summary of Chlorine Session Lucien
Froidevaux
Aura Validation Meeting, Greenbelt Chlorine
Session Summary / L. Froidevaux
Sep. 22, 2005

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Wednesday, September
21, Morning
AGENDA
Aura
Validation Chlorine Subgroup Session
Session chair Lucien
Froidevaux Topic

Presenter
gt MLS HCl vs HALOE, ACE, PAVE, AVE
Lucien Froidevaux gt MLS ClO vs
UARS/MLS, PAVE (ASUR), Odin/SMR Michelle
Santee gt MLS and ACE
Kaley
Walker gt MLS ClO vs Odin/SMR ClO
Brice Barret gt
MLS HCl vs HALOE and models MLS ClO vs models
Ross Salawitch gt MLS HOCl
vs Balloon (FIRS-2) and model results
Lucien Froidevaux

Aura Validation Meeting, Greenbelt
Chlorine Session Summary / L. Froidevaux
Sep.
22, 2005

3

• HCl L. Froidevaux analyzed 1 year of HCl
  from 3 datasets.
• - As shown at previous meetings, MLS HCl gt HALOE
  HCl by 10 -25 (some alt.
  dependence).
• MLS HCl matches ACE HCl better (most often
  within 5)
• - Behavior near 0.5 to 0.1 hPa needs further
  investigation. - Current
  recommendation for MLS vert. range 100 to 0.2
  hPa.

MLS HCl versus HCl from HALOE ACE

• Latitudinal variations are very similar among
  the 3 datasets (except for above offsets).
• Time variations for monthly mean differences are
  generally stable, sometimes within 1 (up
  high), but worse in lower stratosphere (higher
  variability).
• Time variation for monthly mean global MLS HCl
  at 50-60 km (see plot at right)
  shows good agreement with
  expectations from ground-based Cly data (x0.95
  shifted by 6 years), for slope and absolute
  values.
• Some discussion about amount of HCl that gets
  into the strat. (probably a bit lt than curves
  shown).

HCl variations at 50-60 km
MLS data
From surface chlorine (4 or 6 yr lag)
O HALOE Sunrises
? HALOE Sunsets
Plot by L. Froidevaux
NOAA Cl surface data (S. Montzka)
Aura Validation Meeting, Greenbelt
Chlorine Session Summary / L. Froidevaux
Sep.
22, 2005

4
MLS HCl vs PAVE / ASUR

Average of profile comparisons for PAVE/ ASUR
shows a bias between MLS and ASUR, with ASUR 20
gt MLS. This is similar as for O3 comparisons
probably an ASUR calibration issue (being looked
into). -
Also, slope of profiles (MLS vs ASUR) disagrees
significantly below 23 km.
MLS HCl vs AVE / CIMS

• - Agreement among AVE / CIMS HCl profiles and MLS
  HCl profiles shows agreement so far, for 100 hPa
  and lower pressures, but statistics and absolute
  errors do not allow for an easy quantification
  of any bias.
• Other methods such as correlation of HCl and O3
  are worth pursuing further.
• Tropical (CR-AVE) flights should confirm that
  MLS V1.5 HCl is high at 147 hPa (as seen in MLS
  vs HALOE).

Plot from CIMS team
Aura Validation Meeting, Greenbelt
Chlorine Session Summary / L. Froidevaux
Sep.
22, 2005

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Summary B
HCl R. Salawitch showed comparisons of HCl
temporal changes (HALOE, MLS) to various models
(AER, AER GSFC transport, photochemical
steady-state or PSS). Model HCl above 30 km
depends on age of air CCly time
series PSS model HCl agrees well with early
HALOE and Aura MLS HCl AER model /
AER transport agrees best with late HALOE
AER model / GSFC transport agrees with early
HALOE, lies between recent HALOE and MLS
but what exactly
was the level of peak CCly ?
MLS HCl versus HCl from various models.
Many other latitudes heights were shown.
Aura Validation Meeting, Greenbelt
Chlorine Session Summary / L. Froidevaux
Sep.
22, 2005

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Odin/SMR versus MLS B. Barret Mean profiles
Good agreement from 31 to 1 hPa MLS lt SMR below
31 hPa ? bias up to 0.4 ppbv SMR noisier than
MLS Correlations R gt 0.7 below and just above
the ClO minimum (14.7 hPa) Slope MLS/SMR 1 at
31.6 hPa where chlorine activation takes place.

Aura Validation Meeting, Greenbelt
Chlorine Session Summary / L. Froidevaux
Sep.
22, 2005

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MLS ClO M. Santee vs UARS/MLS Seasonal
variations and lat. distributions of enhanced
wintertime ClO match
climatological variations from UARS MLS
- Low bias of 0.2-0.3 ppbv for P
gt or equal to 46 hPa can be
eliminated by doing
Day-Night ClO (averages). vs SLIMCAT 3-D Model
consistency test activation/deactivation.
More
details being looked into (research) vs
PAVE/ASUR Overall good tracking of enhanced
regions as go into vortex
MLS values (smoothed to ASUR resolution) lt
ASUR ClO by 0.1 to 0.4
ppbv for 15-30 km region, appears consistent
with low known bias in
MLS (mentioned above). vs Odin/SMR
Good latitudinal tracking of these data (mid-Aug
mid-Sep 04) low
MLS bias (0.3 ppbv) shows up here also. Apart
from persistent negative bias (0.3 ppbv) at Pgt
45 hPa, agreement with other datasets is
within10-30 so far. Future plans Address the
low bias issue and continue comparisons, also
with MIPAS and ACE products
ground-based datasets.

Aura Validation Meeting, Greenbelt
Chlorine Session Summary / L. Froidevaux
Sep.
22, 2005

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ACE update K. Walker
ACE (V1) and HALOE coincidences (avgs.)

• gt Newest ACE data to be put into AVDC
• ACE-FTS v2.2 will be in very soon
• gt Continue assessing high altitude values versus
  MLS and HALOE
• gt Further comparisons underway/planned
• ClONO2 vs. MIPAS
• ClO vs. MLS
• HOCl vs. MLS need to take closer look
• ClONO2 vs. HIRDLS?

Marty McHugh
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• gt HOCl MLS product has lines in the 640 GHz
  region. It is a weak signal, needing many days
  of zonal mean averages for useful retrieval (1
  to 2 weeks).
• gt First-order behavior seems of the right order
  for P lt 22 hPa.
  - Retrieve 50-150 pptv, often with
  more during the day than at night. Some
  day-night changes from month to month seem to be
  (crudely) reflected in SLIMCAT model, but current
  SLIMCAT values are low vs data (MLS balloons).
• Balloon comparisons give very rough
  agreement, but would like to do better.
• MLS HOCl not recommended for P gt 22
  hPa.
• gt Will check different retrieval methods.
• More modeling efforts, constrained by other MLS
  data.

Aura Validation Meeting, Greenbelt
Chlorine Session Summary / L. Froidevaux
Sep.
22, 2005

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Summary for chlorine species discussed at this
session HCl, ClO, and HOCl. See MLS Data Quality
Documentation for added data details/recommendatio
ns. HCl Status Very good tracking vs lat.
(and overall vs time of year) in comparisons with
HALOE and ACE, except for 10-20 high MLS bias
vs HALOE little bias (lt 5) between MLS ACE,
but 0.5 to 0.1 hPa behavior needs further
investigation (mainly for ACE). Reasons for
possible HALOE low bias ( any time dependence?)
are TBD. Future plans MLS team to address
small negative bias in wintertime lower strat.
(see MLS Data Quality Document) and continue
assessing error bars for MLS data.
Others should investigate ACE/ATMOS data
continuity (w/same retrievals/spectroscopy).
ClO Status Apart from persistent negative MLS
bias (0.3 ppbv), mainly for Pgt 45
hPa, agreement with other datasets is within
10-30 so far. Future plans MLS team to address
the low bias issue and continue comparisons,
also with MIPAS and ACE products
ground-based datasets.
HOCl Status Noisy/provisional MLS product is
difficult to validate, but first-order
reasonableness is apparent for Plt 22 hPa.
Current SLIMCAT results appear too low. Future
plans MLS team to investigate improved
retrievals. Future validation needs for above
products Nothing critical beyond what is
currently planned. High latitude 2006 winter
balloon campaign will hopefully add useful
comparisons under perturbed winter vortex
conditions, especially for HCl ClO. In situ
tropical aircraft data can confirm high known
bias for MLS HCl at P 147 hPa (not a currently
recommended pressure for use of MLS data).

Aura Validation Meeting, Greenbelt
Chlorine Session Summary / L. Froidevaux
Sep.
22, 2005