1. NASA NPP OMPS Science Team meeting August 15, 2013
P. K. Bhartia, Zhong Chen, Rob Loughman, Leslie Moy, Steve Taylor

2. Evaluation of OMPS-LP radiances
- stray light - altitude registration
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3. Methodology Radiance Simulation Measured OMPS LP data
Higher accuracy RTM used for simulation
Still has scalar code & other issues
Bass & Paur cross-sections
ZM MLS O3, temp and GPH profiles
OMPS-NP reflectivity
NO2 from climatology, No aerosols
Measured OMPS LP data
Solar irradiances
Ungridded UV ( nm) radiances from long/short high gain, center slit images April 5 zonal means
Gridded UV 2012 Sept 14

4. Topic #1 : Estimation of additive errors (e. g
Topic #1 : Estimation of additive errors (e.g., straylight, dark current, air glow)
Pre launch values from Ball Aerospace
Radiance residuals
Ideal gas law approximation**

5. Ideal Gas Law approximation Technique used In the absence of absorption

6. _____K/km -34.16 T Red = 65S Green = 5N Blue = 45N Term 1 Term 2
dlnr/dz = dlnP/dz - dlnT/dz
-34.16 T
_____K/km
MLS has 4km vertical resolution
We are calculating slopes at 1km …

7. 45N 352nm 65S 5N 352 nm 352 nm Red = RTM dlnI/dz
Blue = Measured dlnI/dz
Green = /T + dlnT/dz
(first term in summation)
65S
352 nm 5N
352 nm

8. 45N 352nm 65S 5N 352 nm 352 nm Red = RTM dlnI/dz
Blue = Measured dlnI/dz
45N
352nm
65S
352 nm 5N
352 nm

9. 352 nm, 60 km
Red = RTM dlnI/dz
Blue = Measured dlnI/dz
352 nm, 50 km

10. Gridded Radiances April 14, 2012, 0-10 N
0 to 10N Lat Sept 14, 2012
No PreLaunch StrayLight Correction With Corrections
Gridded Radiances April 14, 2012, 0-10 N
NO stray light correction With stray light correction
density
density
measured
measured
Prelaunch stray light correction is ~working
Unrealistic RTM curvature at high altitudes probably due to boundary set at 80km
RTM
RTM

11. Topic 1: Conclusions to Stray Light analysis
No detectable stray light problem at 352nm below 50km
RTM error above 70km probably due to boundary set at 80km
Ideal gas law estimation is helpful but not a replacement for RTM calculations
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12. Topic #2 : Altitude Registration Errors two methods
305 nm radiance residuals - requires accurate radiance/irradiance, requires MLS, not affected by aerosols
“knee method” – compares the altitudes where the slope (dlnI/dz) is equal to zero (Janz et al., SPIE 1996)
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13. Alt Registration using 305 nm
305 nm not affected by reflectivity
No O3 abs
Strong sens to TH
strong O3 abs
weak sens to TH

14. 305 nm result 54.5 km Using SUSIM SI Using OMPS SI
Assuming MLS has 300m error, OMPS error is 0±200m

15. “Knee method”
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16. Altitude where slope = 0 shown here at 65deg South
300nm
305nm
RTM slope = Red,
Meas slope = Blue
315nm
310nm

17. Altitude where slope = 0 as a function of latitude bands
305nm
300nm
310nm
315nm

18. TH error as a function of latitude band
[300nm, 305nm, 310nm, 315nm]
MLS has +300m bias in GPH
and
Varies by latitude ~200m

19. Topic 2: Conclusions to Altitude Registration Errors
Both methods show a similar orbital dependence minima at poles, peak ~20°N, but the peak is larger using the “knee method” ~500m versus ~300m.
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20. Summary There are no show stoppers
No significant stray light error below ~50km at 352nm
TH errors vary ~500m pole to tropics

21. Recommendation
Keep normalization altitude at 68 km – no advantage to lowering
Increase RTM boundary from 80 to 100km
Begin study of aerosol using slopes of radiances
Work with Rob Loughman in improving the rxfer code
Change to vector code, fix other problems

23. MLS GPH uncertainties Z*
64 km
48 km
32 km
16 km
If we use MLS data to estimate TH error we have to consider error in MLS GPH.
NCEP/GMAO GPH may be better than MLS below 40 km, but probably not above.

24. Backup slide
ideal gas law: r = P/RT where r is rho (density)
take the first derivative with respect to z:
dr/dz= (1/RT) * dP/dz - (P/RT^2) * dT/dz
substitute dP/P = dlnP, dT/T = dlnT into above equation:
dr/dz = (P/RT) * (dlnP/dz) - (P/RT) * (dlnT/dz)
Substitude ideal gas law, r=(P/RT), dr/r=dlnr
dlnr/dz = dlnP/dz - dlnT/dz
R= Joules/(mol * K) (where Joule=kg*m^2/sec^2)
g=9.81 m/sec^2 (can vary with latitude)
molecular mass = kg/mol assuming dry air
dlnP/dz = molmass * gravity / R constant
= ( kg/mol) * (9.81 m/sec^2) / (8.314 kg*m^2/sec^2*mol*K)
so units cancel and you get
dlnP/dz = Kelvin / meter

27. April 5, N
dlnI(290nm)/dz, dlnI(352nm)/dz
dlnI(290nm)/dz - dlnI(352nm)/dz
RTM 290nm
Meas 290nm
Meas
RTM
RTM 352nm
Meas 352nm
In agreement
~52 km