# Presentation: 508357

## Chlorine Validation Session Summary  

**Chlorine Validation Session Summary****  **

##                                                                AGENDA

***                              ******Wednesday, September 13, 1:30 p.m. – 3:00 p.m.                                                                         ***
**                                                              ****Room 2503                                               **
**                                 ****Aura Validation : Chlorine Subgroup Session**
-                       Session chair: Lucien Froidevaux ( _[lucien@mls.jpl.nasa.gov](mailto:lucien@mls.jpl.nasa.gov)_)
-  1:30 - 1:35   Introduction
-  1:35 - 1:50   Global Measurements of Stratospheric Chlorine Dioxide from OMI                            Thomas Kurosu
-  1:50 - 1:55   **Discussion:** OMI-related (chlorine) planned validation papers & future needs/plans
-  1:55 - 2:10   Validation of the Aura MLS ClO Measurements                                                         Michelle Santee
-  2:10 - 2:25   HCl from EOS MLS on Aura: version 1.5 and preliminary version 2 data
-                         comparisons with satellite, balloon, and aircraft data                                            Lucien Froidevaux
-  2:25 - 2:40   HOCl from EOS MLS on Aura: version 1.5 and preliminary version 2 data
-                         comparisons with other measurements and models                                             Lucien Froidevaux
-  2:40 - 3:00   **Discussion:**  MLS-related (chlorine) planned validation papers
- 	                         Future needs/plans
-                                             Other topics?

##                      Status of OMI OClO Product      (T. Kurosu)

-   -  Current version: v0.9.50 (reprocessing is at ~1 July 2006)
**First ****comparison**** of current version ****with SCIAMACHY**** is encouraging**
**Morphology of OClO in vortex is similar                **
**OMI slant columns > SCIAMACHY slant columns**
- Fitting uncertainties: ~1x1014 mol/cm2 inside the vortex, ~0.4x1014 mol/cm2 outside
**The VERY limited datasets (grd-based, balloon) for validation will be looked into.**

-                      Status of OMI OClO Product      (T. Kurosu)

## Artifacts: pervasive negative bias of 0.4–0.5 ppbv in both day and night profiles below P~32 hPa; largely eliminated by taking day-night diffs. Somewhat worse than v1.5.

- ▪ **Validation paper planned                                            **▪ **Kiruna balloon flight (high ClO) should be useful**

**v2.1 MLS ClO**** ****similar to v1.5**
**Useful range: 100 to 1 hPa **but...
- Profiles slightly noisier
- Artifacts: pervasive negative bias of 0.4–0.5 ppbv in both day and night profiles below P~32 hPa; largely eliminated by taking day-night diffs. Somewhat worse than v1.5.
**Significant ClO changes are not expected for upcoming v2.2.**

**v1.51; Jan. 27, 05**

**v2.10; Jan. 27, 05**

**v1.51; Sep. 21, 05**

**v2.10; Sep. 21, 05**

-                        Validation of MLS ClO           (M. Santee)

## ●  Version 2.1 has some other changes 
     -  Spectroscopy: small linewidth changes to some O3 lines [near HCl line]
     -  Changes in treatment of retrievals for temperature and tangent pressure                                                         
     -  Changes in vertical smoothing constraint  better (~ 4 km) vertical 	resolution in upper stratosphere (but noisier); lower strat. ~ as before.

●  Changes in the retrieved standard HCl product (v2.1 versus v1.51)
     -  Precision (& observed scatter) are degraded [by ~factor of 2 in upper strat.]
     - Systematic changes: < ~5% for upper strat., ~10 % for lower strat.
     - MLS HCl at 147 hPa still not deemed reliable (e.g., negative biases) 

●  v2.2 HCl is not expected to change much from v2.1 (compared to above) 

-      -  Spectroscopy: small linewidth changes to some O3** **lines [near HCl line]
-      -  Changes in treatment of retrievals for temperature and tangent pressure
-      -  Changes in vertical smoothing constraint  better (~ 4 km) vertical 	resolution in upper stratosphere (but noisier); lower strat. ~ as before.
- ●  **Changes in the retrieved standard HCl product (v2.1 versus v1.51)**
-      -  Precision (& observed scatter) are degraded [by ~factor of 2 in upper strat.]
-      - Systematic changes: < ~5% for upper strat., ~10 % for lower strat.
-      - MLS HCl at 147 hPa still not deemed reliable (e.g., negative biases)
- ●  **v2.2 HCl is not expected to change much from v2.1 ****(compared to above)**** **

**O****3**

**37****HCl**

- ●  **Changes from version 1.51**
-      -  B13 off since Feb. 16 (degradation in counts)
-      -  HCl now comes from adjacent band (B14)  	covering most of 35HCl line and isotopic 	37HCl line   v1.52 has small systematic 	difference (a few % in upper strat.) vs v1.51
-             	+ somewhat poorer precision (by ~30%) 	and vertical resolution

**35****HCl**

**Spectra**

-                       Validation of MLS HCl       (L. Froidevaux)

##                       Validation of MLS HCl       (L. Froidevaux) 

- MLS vs ACE v1.51

- MLS vs ACE v2.10

- 17 days only

- 17 days only

-                       Validation of MLS HCl       (L. Froidevaux)

- HCl diffs. (global avg)  from v1.51    to v2.1 are consistent from day         to day

**Sep. 23/24: remote**      (MkIV & FIRS-2)                **Sep. 17: in situ** **(ALIAS)**

- -  Ft. Sumner balloon HCl versus MLS HCl for 2004 shows agreement to within 10 -15% with v2.1 data for 32 to 4.6 hPa, and larger variations at higher pressures.
- -  Preliminary comparisons were also shown/done for Sep. 2005                            (still needs some work, but looks reasonably good)

- (dashed avg. is                           for v1.5 data)

**v2.1 MLS data**

**Avg.** **% dif.**

-  MLS/ACE     comparisons                               -  Now seem to obtain better agreement with ACE profiles in lower mes. (up to 0.3 hPa)                                                                                                                                                  -  More days/statistics  will give more robust results + can check  differences vs latitude
- -  MLS v2.1 still 10-15% high versus HALOE (was shown in breakout session)

##                       Validation of MLS HCl       (L. Froidevaux) 

**> Validation needs?**
- -  Campaigns: check winter balloon data (Kiruna 2007) for different conditions in the (depleted LS HCl), although ‘one snapshot’ may not provide a stringent constraint
**> Longer-term planning (mostly)**
- -  Continue to look at MLS upper stratospheric data versus expected decreases
- -  Continue consistency checks between MLS & ACE-FTS + more balloon data (08, 09?)
-   Add comparisons to column FTIR data (HCl+ClONO**2**) [for > 2-3 yrs of MLS V2 data]                    	and possibly check versus ground-based microwave ClO data

- -  Can add V1.52 monthly means cautiously to pre-Feb. 2006 data, after adjustment for small (but non-negligible vs yearly decrease) shifts between v1.51 and v1.52 data.
-   Global decrease in HCl (ClTOT) continues.
- -  **Note:**  **Will need to reprocess the whole MLS mission (since Aug. 2004) to get best/consistent time series for analyses across Feb. 2006 time period.**

- V1.52 data

- V1.52 data with adjustement for                   mid-Feb. 2006 shift between MLS data versions  ~ 2% drop in 2 years

- V1.51 data

- Slope of                   expected decrease

**0.5 hPa monthly mean HCl ****(60S-60N)**

-                       Validation of MLS HCl       (L. Froidevaux)

## Summary: HOCl data and comparisons require more work
         -     Changes in new MLS data (v2.1) yield a decrease (~ 10-40%) in upper stratospheric HOCl
        -   Can cautiously use MLS HOCl data (V1.5 and V2) for continued evaluations at pressures from                                    	10 hPa to 2 hPa (revised vertical range).                                                                                                                                                                                        -   Note: MLS HOCl requires ~ 15 days of zonal means (10° or 20°-wide bins) for < ~10 pptv precision 

	-  MLS day and night HOCl data (averages) show qualitative similarities with balloon data and with models           
                > night profiles peak at higher altitude 
                > smaller daytime abundances than at night  

        -  MLS HOCl values are lower (by ~ 30-50%) than FIRS-2 data (and seem lower than MIPAS data).

           -    However, more work is needed on local time matching or corrections (diurnal effects are important) for all the profiles obtained (SLS, MkIV, FIRS-2)  + need model studies (see L. Kovalenko poster).

          -   Uncertainties in rate of formation for HOCl affect the model results significantly                  
           > the lower k (ClO+HO2) values (recommended, JPL 2006) appear to agree better with HOCl from               
              MLS than with FIRS-2 (PSS model from Kovalenko/Salawitch... and also simple daytime equilibrium  	model constrained with MLS data)

       -   Need to also keep working on sorting out / explaining differences in the various balloon measurements;                  some differences may be local time issues (some may not be).

      -  Main MLS issue: improve the lower stratospheric MLS HOCl data quality 
             > However, this has lower priority than other potential improvements for MLS  

Validation paper?                                                                                                                                                    Probably better after MLS product improves, e.g., possibly via retrievals on radiance averages.

**         **-     Changes in new MLS data (v2.1) yield a decrease (~ 10-40%) in upper stratospheric HOCl
-         -   Can _cautiously _use MLS HOCl data (V1.5 and V2) for continued evaluations at pressures from                                    	10 hPa to 2 hPa (revised vertical range).                                                                                                                                                                                        -   Note: MLS HOCl requires ~ 15 days of zonal means (10° or 20°-wide bins) for < ~10 pptv precision
- 	-  MLS day and night HOCl data (averages) show qualitative similarities with balloon data and with models
-                 > night profiles peak at higher altitude
-                 > smaller daytime abundances than at night
-         -  MLS HOCl values are lower (by ~ 30-50%) than FIRS-2 data (and seem lower than MIPAS data).
-            -    However, more work is needed on local time matching or corrections (diurnal effects are important) for all the profiles obtained (SLS, MkIV, FIRS-2)  + need model studies *(see L. Kovalenko poster).*
-           -   Uncertainties in rate of formation for HOCl affect the model results significantly
-            > the lower k (ClO+HO2) values (recommended, JPL 2006) appear to agree better with HOCl from
-               MLS than with FIRS-2 (PSS model from Kovalenko/Salawitch... and also simple daytime equilibrium  	model constrained with MLS data)
-        -   Need to also keep working on sorting out / explaining differences in the various balloon measurements;                  some differences may be local time issues (some may not be).
-       -  Main MLS issue: improve the lower stratospheric MLS HOCl data quality
-              > However, this has lower priority than other potential improvements for MLS
**Validation paper?****                                                                                                                                                    **Probably better after MLS product improves, e.g., possibly via retrievals on radiance averages.

-                     Validation of MLS HOCl       (L. Froidevaux)