OH AX in Mesospheric Limb Spectra

1
OH A-X in Mesospheric Limb Spectra
Databases OSIRIS OH A-X ACE-FTS H2O HALOE
H2O SORCE Lyman a MSIS, ECMWF Presented at
the LIMB Workshop Montreal, April 2006
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OH A-X Initiatives

• Derive OH Densities
• Diurnal and Seasonal
• Latitude and Longitude
• OH as H2O Proxy in Upper Mesosphere
• OSIRIS Data from November, 2001 to Present
• OH in PMCs (?)

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OSIRIS Limb Spectra

• OH 0-0 Band at 308 nm
• OH 1-1 Band at 314 nm

• Background Subtracted
• Band Shape Comparisons OK

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OH Limb Radiance to OH Density

• OH Forward Model Iterative Approximation
• Collisional Deactivation, Self Extinction
• MAHRSI g Factors
• Noise Estimates

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Error Sources

• Electron Noise in Rayleigh Plus OH
• Electron Noise in Rayleigh Reference
• Error in Baseline Fitting at Anchor Points
• Anchors on Either Side of Target Band
• 3 or More Pixels in Each Anchor Region
• Errors Combined as Root Sum Square
• Does NOT Include Systematic Errors (lt15)
• Note
• Correct for NO Bands
• Avoid PMCs
• Avoid N2 Second Positive Auroral Signature at
  317 nm

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Derived OH Profiles

• April 20-21 2005
• 70º North Latitude
• HALOE H2O Input
• Photochemical Model

Average of 15 Profiles
0805 SLT
1645 SLT
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Model OH Diurnal Variation at 80 km
HOX Removed at Night. Recovers Slowly in
Morning Major Source is Solar Lyman a on
H2O Results Below for Early June at 60º
North Range of H2O Mixing Ratios
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Extended OSIRIS Limb Spectra
4 June 2005 59º N 183º E 68º SZA
1740 LT (Late Afternoon)
OH 1-0 at 282 nm
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OSIRIS Limb Minus Rayleigh Background
4 June 2005 59º N 183º E 68º SZA
1740 LT (Late Afternoon)
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OSIRIS OH Density Profiles Late Spring
High H2O Mixing Ratio at 80 km
4 June 2005 59º N 183º E 68º SZA
1740 LT (Late Afternoon)
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Select Bright OH Scans

• To Improve Band Ratio Measurements
• Detected Bright Early Morning OH Scan
• Profile Not Typical
• Source ??

Truncated
Typical
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(ACE-FTS H2O Model) vs (OSIRIS OH)
ACE-FTS H2O Model vs OSIRIS OH
ACE-FTS H2O
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OSIRIS OH vs Model OH

• Validate OSIRIS OH
• Use ACE-FTS H2O with Model
• Latitude within 2º
• Local Time within 30 minutes

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OSIRIS OH and PMCs

• Compare OH X Density Maps with PMC Maps
• OH as Proxy for Water Vapour via Lyman a
• May, June, July, August 2005
• Both for 83 km (OH X Horizontal Slice)
• Correlation ? Anti-correlation ?
• Also July 2002, 2003

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PMC Index Definition

• Wavelength for PMC Index is 312 nm, Clear of OH
• Checked OK for 290 nm and 300 nm
• PMC Index is Loge Backscatter Ratio (BSR)
• Index gt 0.3 is Definitive PMC Signature
• Maximum Index Clipped at 3.0 to Enhance Faint
  Events
• Note Maximum Observed PMC BSR 30
• BSR Reference 76 km and 90 km, Underestimates

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OH Spring Summer 2005 PM 83 km
24 Mar 2005
27 May 2005
29 Apr 2005
06 Aug 2005
02 Jul 2005
12 Sep 2005
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PMCs North 2005 PM 83 km
04 June 2005
02 July 2005
27 May 2005
15 Aug. 2005
28 July 2005
03 Sept. 2005
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OH and PMCs 2005 PM
23 June 2005 PM
02 July 2005 PM
OH
PMC
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OH and PMCs 23 June 2005 PM

• OH and PMCs Anti-correlated ??
• Sanity Check on OH !! Spectra OK ??
• Considerable Background Noise Increase
• Extinction lt 3 (at 300 nm, 100/cc, 50 nm
  Radius, Mie, BSR 30)

Faint PMC 77N 130E
Bright PMC 76N 037E
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OH and PMCs 02 July 2005 PM
Bright PMC 79N 015E
Faint PMC 77N 092E
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OH and PMCs 2005 AM
02 July 2005 AM
23 June 2005 AM
OH
PMC
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OH and PMCs 2002 2003 PM
02 July 2002 PM
01 July 2003 PM
OH
PMC
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OH and PMCs 2002 2003 AM
02 July 2002 AM
01 July 2003 AM
OH
PMC
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Infer Total H2O from OH PMC

• OH ? (H2O)0.5 from Photochemical Model (Figure
  Below)
• HALOE Maximum H2O 4 ppmv from PMC Ice (Hervig
  et al.)
• HALOE Latitude Range 65ºN to 70ºN
• OSIRIS PMC Index 70ºN to 82ºN gt 2 x (Index 65ºN
  to 70ºN)
• Assume Maximum H2O 8 ppmv from PMC Ice

H2O Ice (PMC)
H2O Vapour (OH)
H2O
OH
H2O Total
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Total H2O 23 June 2005

• 83 km
• Afternoon
• OH ? (H2O)0.5
• Ice Max. 8 ppmv

H2O Vapour (OH)
H2O Ice (PMC)
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Total H2O 02 July 2005

• 83 km
• Afternoon
• OH ? (H2O)0.5
• Ice Max. 8 ppmv

H2O Vapour (OH)
H2O Ice (PMC)
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Total H2O 02 July 2002

• 83 km
• Afternoon
• OH ? (H2O)0.5
• Ice Max. 8 ppmv

H2O Vapour (OH)
H2O Ice (PMC)
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Total H2O 01 July 2003

• 83 km
• Afternoon
• OH ? (H2O)0.5
• Ice Max. 8 ppmv

H2O Vapour (OH)
H2O Ice (PMC)
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PMC Tentative Conclusions

• OSIRIS Bright OH and Strong PMC Signals
  Anti-correlated
• Considerable Spatial Variability in Total H2O
  (Sum of Two Sources)
• Tests vs PMC Models Essential Require
  Colocated T(K)

The End