# Presentation: 502368

## Continued Analysis of Measured and Modeled HOx: Validation and Analysis of Satellite, Balloon and Ground-based Observations

**Sept. 20, 2005**
**Retrieval v2.1**
- HO2: 2 day avg. lat =[–60,60]

**Continued Analysis of Measured and Modeled HO****x****: Validation and Analysis of Satellite, Balloon and Ground-based Observations**
**T. Canty****1****, H. M. Pickett****2****, R.J. Salawitch****2****, K. W. Jucks****3****, B. J. Drouin****2****, S. Sander****2****, R.P. Cageao****2****, K. Minschwaner****4****, L.J. Kovalenko****2****, W. A. Traub****2****, N. J. Livesey****2****, W. G. Read****2****, and J. W. Waters****2**
- 1Santa Barbara Applied Research, Pasadena, California, USA
- 2Jet Propulsion Laboratory, Calif. Inst. of Tech., Pasadena, California, USA
- 3Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts** **
- 4 New Mexico Inst. of Mining & Technology, Socorro, NM, USA

**Diurnal Variation of OH column**

**AM/PM asymmetry: **A recent paper by *Li et al,* *GRL*,
- 2005 reported an AM/PM asymmetry in the OH column measured
- by the FTUVS instrument at Table Mtn., CA. They determined that
- the average summer OH column peaks  ~26 minutes after solar transit.
- Our model OH column, constrained by MLS H2O and O3 profiles, for Sept. 23, 2004 peaks at ~ 12:24 LST. It should be noted that the OH column record from PEPSIOS indicates a seasonal variation in asymmetry not observed by FTUVS.

- Model OH column peaks at ~12:24 LST.
- Measured OH column, FTUVS, peaks at ~12:26 LST.

- Over 50% of the modeled daytime OH column can be attributed to the OH profile between 40-60 km.   The partial column from 60-80 km exhibits a steady increase throughout the day due to the longer lifetime of HOx species at these altitudes.  This build up of HOx most influences the total column near midday as the % of total column from 40-60 km is at minimum and the sun is still high (i.e. before the total column decreases from decreasing photolytic processes).

- Ground based instruments have been regularly measuring total OH column since  the late 1970s.
- 	• PEPSIOS (**Poly Etalon Pressure-Scanned Interferometric Optical Spectrometer )**
- 		Socorro, NM (34.5oN, 107oW)
- 		Differential absorption measurement using Fabry-Perot interferometers** **
**	**** **• FTUVS (**Fourier-Transform Ultraviolet Spectrometer) **
- 		Table Mountain, CA (34.4oN, 117.7oW)
**	****	**Compares Doppler-shifted East/West solar limb spectra
- 	 • 2004 Validation campaign: OH measured by 1 satellite, 2 balloon, and 2 ground based 	instruments

**Noontime Dip: ****Top left:** No anomalous signal from ground based  ultraviolet radiometer observations at  305 and 320 nm from Socorro, NM.  **Top right:** Global observations from EP/TOMS indicate a total ozone column of ~275 D.U. for the southwestern U.S. (i.e. lower stratospheric O3 not likely cause).  **Right: **WVMS H2O measurements indicate small decrease in H2O at time of “dip” but not larger enough to account for OH variations (based on our model constrained by WVMS H2O; not shown). **Bottom Right:** OMI observations of global reflectivity indicate clear skies in southwest U.S. during validation campaign.  **Bottom Left:** Low aerosol index also observed for this region.  From these results, there were no unusual conditions on Sept. 23, 2004 that may have caused the “dip”.

**OH**
- • Previous OH retrievals (left) have sparse coverage in the mesosphere leading to large variations in  the profiles.  Version 2.1 retrievals (right) have better coverage leading to better obs./model agreement .
- • Mdl_C yields best over all agreement at
- all altitudes.  No indication of a HOx dilemma
- (see below).
- • Dotted FIRS-2 curve (above 40 km) indicates
- observed column fitted to assumed profile shape.

**HO****2**
- • Oscillations in the MLS HO2 profiles below 60 km (left) are removed by averaging over a
- larger latitude bin (–60, 60) (right).  Good
- agreement with FIRS-2
- • Model over-predicts both MLS and FIRS-2
- below 40 km, but lies within uncertainties
- • Above ~62 km, MLS HO2 is strongly influence
- by the a-priori profile.

- • 2r  calculated for ~20-60 km (altitude range where HO2 is not strongly affected by a priori profiles)
- • 2r  has been reduced through the use of the
- V2.1 profiles (2r =3.5 for V1.5 profiles, 2r =1.2 for
- V2.1 profiles for Mdl_C).
- • While Mdl S&S yields good agreement between
- measured and modeled OH, overall best agreement is found for Mdl_C.

**Sept. 23, 2004**
**Retrieval v1.5**
- 15 day zonal avg, 34  10°N

**Sept. 23, 2004**
**Retrieval v2.1**
- HO2: 2 day avg. lat =[–60,60]

**OH**
- • As was the case for Sept. 2004,
- Mdl_C yields best over all agreement at all altitudes for the Sept 2005 profiles.
- • No indication of a HOx dilemma (see below).
- •  Balloon profiles higher than MLS near 40 km.

- • Again, use of the Smith & Stewart, 1994
-  rate constant reduces the 2r for OH
- compared to standard kinetics.
- • Overall best agreement for Mdl C
- (2r =1.5).

**HO****2****/OH**
- • HO2/OH for older MLS retrievals is strongly
- influenced by the HO2 oscillations.
- • Oscillations largely removed for newer  retrievals (below 62 km).
- • FIRS-2 indicates a higher partitioning ratio than
- MLS from 40-60 km.

**HO****x**
- • Even with the oscillations in HO2, the
- overall HOx profile is consistent with the profile
- from FIRS-2 (left).
- • Smoother HOx profiles for new MLS retrievals (right).
- • Standard chemistry over-predicts total HOx
- from 40-65 km.  Mdl_C within measurement
- uncertainty.

**HO****2**
- • The 2005 MLS HO2 profile shows good agreement with FIRS-2 throughout the stratosphere (as before, the HO2 profile is a 2-day zonal average from –60° to 60° latitude).

**HO****2****/OH**
- • The model partitioning of HO2 to OH for 2005 is in good agreement with observations below 40 km.
- • MLS and FIRS-2 now agree!

**HO****x**
- • Modeled HOx profiles are consistent
- with observations above 45 km. Below
- this, model results lie between MLS and
- FIRS-2

- National Aeronautics and Space Administration

**National Aeronautics and Space Administration**
**Jet Propulsion Laboratory**
- California Institute of Technology
- Pasadena, California
**www.nasa.gov**

**Conclusions**

-  V2.1 MLS retrievals show better agreement with balloon observations of HO2
-  Model using JPL02 kinetics, a 25% faster rate for O+OH, and 20% increase in OH+HO2 is in good agreement with OH, HO2, HO2/OH, and HOx from 20-60 km.
-   Diurnal variation in observed column OH (peak at 12.26 LST) is reproduced by model constrained by MLS observations.
-   “Dip” in OH column observed by ground based and balloon instruments poorly understood at this time (no correlations to UV irradiance, O3, H2O, aerosols, and reflectivity)

**V1.5 vs.V2.1**
**2004**

**2005**

**For more information**