# Presentation: 124579

## Summary of Chlorine Session

**Summary of Chlorine Session**
**          ****Lucien Froidevaux**

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

##                             Wednesday, September 21, Morning 

-                             ***Wednesday, September 21, Morning ***
**                                              ****AGENDA                        **
-                 **Aura Validation: Chlorine Subgroup Session**
-                             Session chair: Lucien Froidevaux
-                      **Topic                                                                                  Presenter **
- >  MLS HCl vs HALOE, ACE, PAVE, AVE                              Lucien Froidevaux
- >  MLS ClO vs UARS/MLS, PAVE (ASUR), Odin/SMR          Michelle Santee
- >  MLS and ACE                                                                      Kaley Walker
- >  MLS ClO vs Odin/SMR ClO                                                 Brice Barret
- >  MLS HCl vs HALOE and models; MLS ClO vs models       Ross Salawitch
- >  MLS HOCl vs Balloon (FIRS-2) and model results              Lucien Froidevaux

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

## HCl: L. Froidevaux analyzed         1 year of HCl from 3 datasets.

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

**HCl: L. Froidevaux analyzed         1 year of HCl from 3 datasets.**
- -  As shown at previous meetings, MLS HCl > 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**

**MLS data**

***Plot by L. Froidevaux                             NOAA Cl surface data (S. Montzka)***

- O HALOE Sunrises                                       ●  HALOE Sunsets

- From surface chlorine* *       (4 or 6 yr lag)

-  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 < than curves shown).

-      **HCl variations at 50-60 km**

## MLS HCl vs PAVE / ASUR:

**MLS HCl vs PAVE / ASUR:**

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

**MLS HCl vs AVE / CIMS:**

- Average of profile comparisons for PAVE/ ASUR shows a bias between MLS and ASUR, with ASUR 20% > 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.

- - 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

## 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 CCl****y**** ?**

**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

## Odin/SMR versus MLS: B. Barret

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

**Odin/SMR versus MLS: B. Barret**
**Mean profiles:** Good agreement from 31 to 1 hPa
- MLS < SMR below 31 hPa  bias up to 0.4 ppbv
- SMR noisier than MLS
**Correlations**
- R > 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.

## MLS ClO: M. Santee

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

**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 > 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) < 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 P> 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.

##         > Newest ACE data to be put into AVDC
ACE-FTS v2.2 will be in very soon

> Continue assessing high altitude values versus MLS and HALOE 

>  Further comparisons underway/planned
ClONO2 vs. MIPAS
ClO vs. MLS
HOCl vs. MLS – need to take closer look
ClONO2 vs. HIRDLS?

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

- ACE (V1) and HALOE coincidences (avgs.)

**ACE update: K. Walker**

**Marty McHugh **

## > 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). 

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

**> ****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).**** **
**> First-order behavior seems of the right order for P < ~ 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 > 22 hPa.**
**>  Will check different retrieval methods. **
**  ****More modeling efforts, constrained by other MLS data.**

## Summary for chlorine species discussed at this session: HCl, ClO, and HOCl.

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

**Summary for chlorine species**** discussed at this session: HCl, ClO, and HOCl.**
**See MLS Data Quality Documentation for added data details/recommendations.**
**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 (< 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            P> 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 P< 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).