CrIS SDR Product Review UMBC Validation Status · B(T) in K Number of Obs AIRS CrIS 160 180 200 220...

1

Intro ν Cal High-Res Mode CO High-Res ν Cal Rad. Cal.

CrIS SDR Product ReviewUMBC Validation Status

L. Larrabee Strow, H. Motteler, P. Schou, B. Imbiriba, P. Schou,S. Hannon

Physics Department andJoint Center for Earth Systems Technology

University of Maryland Baltimore County (UMBC)

October 23, 2012

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Overview

Frequency calibration

Short-wave high-resolution mode results

Radiometric validationInternal consistency (among FOVs)Relative to AIRS, IASI (SNOs)Relative to AIRS, IASI (Double Differences)

Main Results

Frequency calibration working very well

SDRs exhibit boxcar ringing inconsistencies: up to 1K

Hamming apodization reduces these problems significantly

Comparisons to AIRS, IASI within 0.2K or less

Evidence for a ∼0.2K systematic calibration error in far long-wave

High resolution works very well!

3


CrIS Frequency Calibration: Two Distinct Parts

Pseudo ν Cal: Alignment of detectors (Tobin)

Detector offsets from interferometer axis produces frequency shifts

Corrected with CMO operator, once 3x3 positions known

In-orbit 3x3 positions determined from relative frequency offsets

Original plan: Absolute shifts using B(T) Obs vs Calcs, gives both offsetsand Neon cal.

Relative approach more accurate (Tobin), < 1 ppm LW, MW, SW maybe 2-3ppm?

Absolute Calibration: Upwelling -→ Neon Lamp -→ Met Laser

Neon spectral calibration and alignment to interferometer axis needed.

ITT expected 1/month Neon calibration (so far not needed).

In-orbit Neon calibration done using LW window regions, sharp water lineson flat background. Limits one to very clear ocean scenes.

Unable to achieve similar accuracy with opaque channels in LW or MW.

SW hopeless for Neon calibration with 0.2 cm OPD.

4


Present Focal Plane Positions and Neon Calibration

The Neon lamp calibration was determined using data fromFeb. 25 LW window region observations.

Errors in treatment of FOV5 in IDPS SDR code forced us to“fudge” the positions of the remaining 8 detectors in the LWand MW arrays.

These adjustment were small, LW=1.4 and MW=2.2 ppm. Notsufficient information to modify SW.

Formal monthly Neon calibrations are presently not beingdone. Only offline at UMBC.

Has production of new CMO operator happened? Maybe soon?

5


ν Calibration Overview

CrIS In-orbit Neon Cal unchanged from TVAC!

Examine time series of Neon calibration using (a) Long-waveand (b) Mid-wave bands.

Calibration done daily using clear ocean tropical subsets

650 700 750 800 850 900 950 1000 1050 11000.5

0.4

0.3

0.2

0.1

0

0.1

0.2

0.3

0.4

0.5

Wavenumber (cm 1)

FOV3

F

OV8

in K

Spectral Cal Difference between 2 Detectors with existing LUTs

7.5 ppm Cal Error

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Metrology Laser Wavelength vs Time

Left: Metrology laser λ (and temperature) versus time a/c to Neonlamp, Right: Zoom showing daily variation.

Feb Mar Apr May Jun Jul Aug Sep Oct

−1.5

−1

−0.5

0

0.5

1

1.5

2

2.5

3

3.5

Time

∆ ν

(pp

m)

Met Laser νLaser Temp

07/27 07/28 07/29 07/30 07/31 08/01 08/02 08/03 08/04

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

Time∆

ν (

ppm

)

Linear drift starting in mid-September when temperature offsetoccurred?

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CrIS Frequency Calibration vis Upwelling RadiancesUsing Long-wave Band

Left: All fovs, Right: Mean and Std (over FOVs)

Apr May Jun Jul Aug Sep Oct Nov−2.5

−2

−1.5

−1

−0.5

0

0.5

ν E

rror

(pp

m)

123456789

Apr May Jun Jul Aug Sep Oct Nov0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

ν E

rror

(pp

m)

−1 x Mean band1 ν calStd over Fovs

Upwelling frequency calibration mirrors the Neon calibration of the metrologylaser. If the CMO has not been updated (waits for a 2 ppm change), this meansthe metrology laser has indeed drifted. If the Neon was drifting, we would notsee the same shift in the upwelling spectra (again assuming the CMO operatorremains unchanged). Slight differences among FOVs.

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CrIS Frequency Calibration vis Upwelling RadiancesUsing Mid-wave Band

Left: All fovs, Right: Mean and Std

Apr May Jun Jul Aug Sep Oct Nov−4

−3.5

−3

−2.5

−2

−1.5

−1

−0.5

0

0.5

1

ν E

rror

(pp

m)

123456789


0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

ν E

rror

(pp

m)

−1 x Mean band2 ν calStd over Fovs

The mid-wave frequency calibration shows a frequency drift very similar tolong-wave. I do not know why the mid-wave frequency calibration varies by up to3.5 ppm among FOVs. We saw this in the Feb. 25 data. D. Tobin’s relativecalibration indicates this is incorrect.

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Neon vs Upwelling ν Calibration


0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

ν E

rror

(pp

m)

−1 × Mean band1 ν calStd over FovsNeon ν cal +1.3 ppm

SDR algorithm waits for a 2 ppm Neon shift to re-compute new CMOPresumably that has not yet happened, so cannot testThus, upwelling calibration roughly follows NeonDifferences may be upwelling algorithm issues?

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CrIS High Resolution Mode

UMBC has processed all the CrIS high-resolution mode datafrom Feb. 23, 2012 into calibrated radiances using CCAST

Liens on these radiances:Non-linear correction not applied (no effect on shortwave)Nominal geolocation (good enough for most purposes)Not in SDR formatUses our best-effort CMO apodization removal operators fromthe July time-frame.These data recorded with the old FIR decimation filter

We have computed clear-sky observed radiances for everyobservation

For a single southern ocean granule we have compared thesedata to IASI data in the same region, suitably degraded to CrIS0.8 OPD resolution.

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Example High-Resolution Spectra

800 1000 1200 1400 1600 1800 2000 2200 2400

180

200

220

240

260

280

Wavenumber (cm−1)

B(T)

in K

Normal ModeHigh−Res Mode −50K

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Example Spectra: Shortwave Only

2150 2200 2250 2300 2350 2400 2450 2500 2550

180

200

220

240

260

280

300

Wavenumber (cm−1)

B(T

) in

K

Normal ModeHigh−Res Mode

Not Noise!

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High-Resolution CMO Operator

UMBC developed a high-resolution CMO operator

Matrix inversion to derive CMO operator condition numbergoes from 1 for center FOV to 106 for corner FOVs.

With careful filtering, high condition number can be handled

Note below: large relative ν offset of off-axis spectra; Left:Normal Mode, Right: High-resolution Mode

2354 2356 2358 2360 2362 2364

−0.2

0

0.2

0.4

0.6

0.8

1

Wavenumber (cm−1)

Impu

lse

Res

pons

e

CornerSideCenter

2354 2356 2358 2360 2362 2364

−0.2

0

0.2

0.4

0.6

0.8

1

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Relative Error in CMO Corrections

Plot shows single uniform 3x3 spectraDifference curves (from FOV5) are uniform in frequencyCorrection errors close to radiances values for cold observations.

2150 2200 2250 2300 2350 2400 2450 2500 2550−0.5

0

0.5

1

1.5

2

2.5

3

3.5

4

Wavenumber (cm−1)

Rad

ianc

e

FOV1FOV2FOV3FOV4FOV5FOV6FOV7FOV8FOV9

2150 2200 2250 2300 2350 2400 2450 2500−0.15

−0.1

−0.05

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

Wavenumber (cm−1)

Rad

ianc

e

FOV1FOV2FOV3FOV4FOV5FOV6FOV7FOV8FOV9

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CMO Correction Errors Reduced with HammingApodization

Same data as in previous slide, but Hamming apodized

2150 2200 2250 2300 2350 2400 2450 2500 2550−0.5

0

0.5

1

1.5

2

2.5

3

3.5

Wavenumber (cm−1)

Rad

ianc

e

FOV1FOV2FOV3FOV4FOV5FOV6FOV7FOV8FOV9FOV corner − FOV5FOV side − FOV5

2200 2250 2300 2350 2400 2450 2500 2550

−0.05

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

Wavenumber (cm−1)

Rad

ianc

e

FOV1FOV2FOV3FOV4FOV5FOV6FOV7FOV8FOV9FOV corner − FOV5FOV side − FOV5

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CMO Correction Errors in Brightness Temperature:Hamming

FOVn-FOV5 differences multiplied by 5X and offset by 260K

2150 2200 2250 2300 2350 2400 2450 2500 2550220

230

240

250

260

270

280

290

300

Wavenumber (cm−1)

B(T

) in

K

FOV1

FOV2FOV3

FOV4

FOV5

FOV6

FOV7FOV8

FOV9

+−1K (FOVn−FOV5)

2160 2180 2200 2220 2240

245

250

255

260

265

270

275

280

285

290

295

Wavenumber (cm−1)

B(T

) in

K

FOV1

FOV2

FOV3

FOV4

FOV5FOV6

FOV7

FOV8

FOV9+−1K (FOVn−FOV5)

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High-Resolution Validation: CrIS vs IASI B(T)

2200 2250 2300 2350 2400 2450 2500

230

240

250

260

270

280

Wavenumber (cm−1)

B(T

) in

K

IASICrIS

(a) CrIS/IASI Obs, Hamming Apodized.

2170 2180 2190 2200 2210 2220245

250

255

260

265

270

275

280

285

Wavenumber (cm−1)

B(T

) in

K

IASICrIS

CO Lines

(b) CrIS/IASI Obs, Hamming Apodized:Zoom.

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High-Resolution Validation: CrIS vs IASI BiasesBiases with respect to ECMWF

2200 2250 2300 2350 2400 2450 2500 2550

−1.5

−1

−0.5

0

0.5

1

1.5

Wavenumber (cm−1)

Bia

s in

K

IASICrIS

(c) CrIS/IASI Bias, Hamming Apodized.

2170 2180 2190 2200 2210 2220−1

−0.5

0

0.5

Wavenumber (cm−1)

Bia

s in

K

IASICrIS

Window Channels

Atmospheric CO Lines

(d) CrIS/IASI Obs, Hamming Apodized:Zoom.

Note in (c,d) above, one expects IASI and CrIS window channels to differby 0.1K due to diurnal variation in the SST. Here we use a constantdiurnally averaged SST. Thus, the bias difference between CrIS and IASI isabout 0.1K less than shown here for window channels!

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CO Retrievals from High-Resolution Mode SpectraLeft: CrIS, Right: AIRS Color Scale in K

“Retrieval” is just bias between Obs and Calc radiances for a single CO channel.Calc radiances use ECMWF.Remove scenes where window radiance bias > 5K (Clouds).

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CO Retrievals from High-Resolution Mode SpectaLeft: CrIS, Right: MOPPIT

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CO Retrievals from High-Resolution Mode Specta

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Frequency Calibration Using High-ResolutionShort-Wave

High-resolution data used to calibration Neon, 1 day’s worth

High-resolution brings out very stable features with spectralcontrast

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High-Resolution SW Calibration of Neon

2200 2250 2300 2350 2400 2450 2500

220

225

230

235

240

245

250

255

260

265

270

Wavenumber (cm−1)

B(T

) in

K

All ChannelsNeon Cal Channels

Existing Neon calibration limited to non-polar clear ocean scenes (morebelow).

As previously stated, unable to achieve high Neon calibration accuracy withopaque LW, MW channels, which would allow calibration over the entireorbit.

High-resolution in the SW allows us to use the very high-peaking lines in the2350 cm−1 region, indicated by green circles above.

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LW Opaque Channel Calibration of Neon

660 680 700 720 740 760

220

225

230

235

240

245

250

255

260

265

270

Wavenumber (cm−1)

B(T

) in

K

All ChannelsNeon Cal Channels

(e) LW opaque Neon cal channels.

0.01 0.02 0.03 0.04 0.05

50

100

150

200

250

300

350

Kernel Function

Pre

ssur

e in

mba

r

LWSW

(f) LW vs SW cal channel kernels.

Opaque LW channels include emission from 200 mbar. Leads to inaccurateNWP calculations (clouds, polar) with poor performance in the polar night.

Moreover, LW opaque channel frequency calibration not accurate;presumably due to NWP radiance calculation errors.

With high-resolution, can use extremely high-peaking CO2 channel (5-10mbar, 30+ km) with very good performance.

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Final Results: Neon Frequency Calibration

−80 −60 −40 −20 0 20 40 60 80−20

−15

−10

−5

0

5

10

15

20

25

Latitude

Neo

n O

ffset

in p

pm

LW High−AltitudeSW High−AltitudeLW Operational

Each circle represents a 360 second

period that allowed an accurate

calibration.

Present operational Neon: black circles, LW window, ± 40 degrees latitude.

LW opaque channels provide more observations (blue circles). But, apparent5 ppm offset, and very poor performance in the polar night.

SW opaque using CrIS high-spectral resolution mode gives extremely goodperformance, low noise, well into the polar night portion of the orbit.

SW high-resolution agrees very well with LW window region Neoncalibration, maybe 1 ppm.

IASI (METOP-A/B) uses these channels for all metrology laser calibration forall three bands.

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Radiance Intercomparisons

Following slides are a small sample of radiometricintercomparisons between CrIS and AIRS/IASI.

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CrIS and IASI Double-Difference

800 1000 1200 1400 1600 1800 2000 2200 2400 2600−0.2

−0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

Wavenumber (cm−1)

CrI

S −

IAS

I in

K

SST Diurnal Correction

CrIS Bias vs IASI Bias (relative to ECMWF), tropics, ocean only

Very good agreement. But SST in calcs off by 0.1K! (maybe)

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CrIS and IASI SNOs + DDs: SNOs for May 2012 (LW)SNOs from JPL Sounder PEATE: 10 min, 8 km windows, S. Hemis: -73 deg S.

650 700 750 800 850 900 950 1000 1050

−0.1

−0.05

0

0.05

0.1

0.15

0.2

0.25

Wavenumber (cm−1)

CrI

S−

IAS

I in

K

IDPS Box:SNOIDPS Hamming:SNOStd Err:SNOIDPS−CCAST HammingCrIS−IASI:DD

CrIS-IASI boxcar apodization has large ringing. Uncertain to cause, used all 4 IASIFOVs, all 9 CrIS FOVs for now.

Significant (for climate) offset in the longwave!

Red curve is CrIS from CCAST (UW/UMBC Matlab SDR testbed algorithm). CCASTmuch closer to IASI, but more work needed.

CrIS-IASI DD is bias double-difference from ECMWF

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650 700 750 800 850 900 950 1000 1050

−0.1

−0.05

0

0.05

0.1

0.15

0.2

0.25

Wavenumber (cm−1)

CrI

S−

IAS

I in

K






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650 700 750 800 850 900 950 1000 1050

−0.1

−0.05

0

0.05

0.1

0.15

0.2

0.25

Wavenumber (cm−1)

CrI

S−

IAS

I in

K






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650 700 750 800 850 900 950 1000 1050

−0.1

−0.05

0

0.05

0.1

0.15

0.2

0.25

Wavenumber (cm−1)

CrI

S−

IAS

I in

K






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CrIS and IASI SNOs: Data for May 2012 (MW)

1300 1400 1500 1600 1700

−0.2

−0.15

−0.1

−0.05

0

0.05

0.1

0.15

0.2

NH (day)

Wavenumber (cm−1)

CrI

S−

IAS

I in

K

IDPS BoxcarIDPS HammingStd. Err

CrIS-IASI boxcar apodization again has ringing.

Very good agreement. Can we determine interconsistency below 0.05K?

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CrIS-AIRS SNOs LocationsWith 10-min,8 km window obtain full latitude range!

−100 −50 0 50 1000

1000

2000

3000

4000

5000

6000

7000

Latitude

SN

Os

per

Mon

th

Unlike IASI-AIRS or IASI-CrIS, wide latitude range of SNO’s.

This allows very detailed inter-comparisons as a function of scene type. Here we

examine SNO differences with scene temperature for one channel.

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2552 cm−1 SNOs for AIRS, CrIS

160 180 200 220 240 260 280 300 3200

2000

4000

6000

8000

10000

12000

14000

16000

B(T) in K

Num

ber

of O

bs

AIRSCrIS

160 180 200 220 240 260 280 300 320180

200

220

240

260

280

300

320

AIRS B(T) in K

CrI

S B

(T)

in K

2552 cm−1

Good number of SNOs over a large range of B(T)’s

CrIS hits a B(T) floor around 200K.

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SNO AIRS-CrIS: LongwaveEarly Global SNO Comparisons Using AIRS-to-CrIS Conversion

700 750 800 850 900 950 1000 1050−1

−0.8

−0.6

−0.4

−0.2

0

0.2

0.4

0.6

0.8

1

AIR

S−

CrI

S in

K

1200 1250 1300 1350 1400 1450 1500 1550 1600−1

−0.8

−0.6

−0.4

−0.2

0

0.2

0.4

0.6

0.8

1

Wavenumber (cm−1)

AIR

S−

CrI

S in

K

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CCAST vs IDPS: Avg Radiometric Differences

Longwave

650 700 750 800 850 900 950 1000 1050

−0.4

−0.3

−0.2

−0.1

0

0.1

0.2

Wavenumber (cm−1)

∆ B

(T)

in K

Midwave: 0.006K

1300 1400 1500 1600 1700

−1

−0.5

0

0.5

1

Wavenumber (cm−1)

∆ B

(T)

in K

Shortwave: 0.03K

2150 2200 2250 2300 2350 2400 2450 2500 2550

−1

−0.5

0

0.5

1

Wavenumber (cm−1)

∆ B

(T)

in K

Longwave: FOVs 1-3,4-6

Midwave: FOVs 1,6,9

Averaged over all FOVs forshortwave (no non-linear)

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Possible Errors for High Temperature ScenesReal part of 860 cm−1 vs Imaginary Part

Color scale is number of observations

CrIS SDR Product Review UMBC Validation Status · B(T) in K Number of Obs AIRS CrIS 160 180 200 220...

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Transcript of CrIS SDR Product Review UMBC Validation Status · B(T) in K Number of Obs AIRS CrIS 160 180 200 220...