# Presentation: 412035

## Sea surface temperature measured by the MODerate resolution Imaging Spectroradiometer (MODIS).

**R. H. Evans, E. J. Kearns, P. J. Minnett, O. B. Brown, **
**&**
**Warner Baringer, Jim Brown, Kay Kilpatrick, Sue Walsh.**
**Meteorology and Physical Oceanography**
**Rosenstiel School of Marine and Atmospheric Science**
**University of Miami**

- MODIS Team Meeting
- 23 July 2002

## SST Status

- Focus areas -
- L1b versions -> calibration, validation
- Terra Reprocessing - Version 3 L1b
- Collection 4 coefficients, validated
- Terra Forward processing -Version 4.0.5 L1b
- Collection 4 coefficients, validation comparison in progress
- Aqua Forward processing - prelaunch LUT - V3
- Collection 3 preliminary coefficients
- Aqua Forward processing - first on-orbit LUT - V4
- Repeat calculations based on LUT (should be available this week)

## Approach

- Radiative transfer based pre-launch SST retrieval equation derivation
- Regression based (AVHRR) based operational retrieval equation derivation
- Validation based on comparison to contemporaneous, co-located (MAERI) radiometric SST
- Auxiliary validation provided by buoy observations to extend space, time, in situ conditions

## Aqua, Terra L2 track and scan SST, SST4

- Along scan

- Along track

- SST-Terra
- SST4-Terra
- SST-Aqua
- SST4-Aqua

- Aqua, Terra tracks not co-registered
- Pixel-pixel noise ~0.03C along scan
- Along track order 2x along scan

## MODIS SST comparison to AVHRR Pathfinder

## Aqua-Terra SST comparison

- Increase in A-T for day due to diurnal warming, day field SST merge difficult

- Curvature in A-T likely due to use of pre-launch LUT
- where a0, a2=0

## Time-series of M-AERI measurements on Explorer of the Seas

- The *Explorer of the Seas* is a Royal Caribbean Cruise Liner, operating a bi-weekly schedule out of Miami. It is outfitted as an oceanographic and atmospheric research vessel, very suitable for satellite validation. For more details see http://www.rsmas.miami.edu/rccl/

## M-AERI data from Explorer of the Seas

## Validation of MODIS SSTs

- M-AERI cruises:
- ‘Hand-picked’ manually processed clear sky conditions for four cruises
- Routine processing, January-May 2002
- Buoy matchups:
- Routine processing, January-May 2002

## MODIS : M-AERI MatchupsHand-picked set – Pathfinder derived coefficientsBlue = Mediterranean – April 2000; Red = Pacific – March, April 2001; Pink = Pacific – March, April 2001; Green = Atlantic - Explorer of the Seas.

_***All data***_
**M = 0.20K std= 0.26K **
**N  = 242**

_***Explorer of the Seas***_
**M = 0.15K **
**std= 0.21K **
**N  = 50**

## Explorer of the Seas MODIS : M-AERI Matchups, Jan-May 2002

## MODIS : Buoy Matchups, Jan-May 2002.

## Near surface temperature gradients – reality

**Profile measured at 12:51 local time on **
**4 October 1999.  Off Baja California, **
**R/V *****Melville***** MOCE-5 cruise.**
**Blue line = SkinDeEP* profile**
**Blue circle = M-AERI skin temp.**
**Red cross = Float bulk SST at ~0.05m**
**Green star = Ship thermosalinograph at ~3m**

- From  Ward, B. and P. J. Minnett, 2001. An autonomous profiler for near surface temperature measurements. *Gas Transfer at Water Surfaces.* M. A. Donelan, W.M. Drennan, E.S. Saltzmann and R. Wanninkhof (Eds.) *American Geophysical Union Monograph 127.* 167 - 172.

## Time evolution of near-surface thermal gradients 

**SkinDeEP profiles on 12 October 1999.** **Off Baja California,  R/V *****Melville*****.**
- From  Ward, B. and P. J. Minnett, 2001. An autonomous profiler for near surface temperature measurements. *Gas Transfer at Water Surfaces.* M. A. Donelan, W.M. Drennan, E.S. Saltzmann and R. Wanninkhof (Eds.) *American Geophysical Union Monograph 127.* 167 - 172.

## The need for validation

- The **infrared bands** of MODIS form **self-calibrating radiometers.** The retrieved SST fields are validated to confirm the procedures used to generate them from the radiometer data are performing as believed, *i.e*. it is the **atmospheric correction algorithm that is being validated**.
- This requires **instrumental imperfections** to be **known**** **and the data **corrected**.
- The validation exercise provides a determination of the **accuracy characteristics of the derived fields. **

## Wind speed dependence of the skin effect

- Note collapse of envelope at moderate to high wind speeds.

## Wind speed dependence of diurnal & skin effects

- Terra and Aqua overpass times.

## 25-Jun-02 SST night

- Aqua

- Terra

## Merged Terra-Aqua SST night 25jun02

## Merged T-A North Atlantic 25jun02 SST4

## Conclusions

- Collection 4, Version 3L1b (Reprocessing) validated
- MAERI radiometric comparison, better than 0.25C
- Buoy comparison supports MAERI validation, extends to wider range of space, time, in situ conditions
- Collection 4, Version 4.0.5 (Forward Processing) validation in progress
- Aqua pre-launch equation coefficient test completed, night Terra-Aqua merged image provides near complete global coverage (not counting persistent cloud presence)
- Collection x, Aqua waiting for delivery of on-orbit LUT
- Outstanding Aqua issues: verify brightness temperatures, non-linear behavior for bands 31,32
- Manuscript with complete details near completion

## Conclusions

- M-AERI provides a critical validation tool for MODIS SST
- Buoys provide a valuable secondary validation, numbers allow sampling a wider selection of environmental variability
- Preliminary SST validation shows *Terra *MODIS comparable to best AVHRR
- Need to establish lack of seasonal and regional biases
- Need to validate experimental SST4 fields
- Look forward to *Aqua* MODIS data.

## Slide 24

## Ocean Color Radiances measured by the MODerate resolution Imaging Spectroradiometer (MODIS).

**R. H. Evans, E. J. Kearns, H. R. Gordon**
**K. Voss, D. Clark **
**&**
**Warner Baringer, Jim Brown, Kay Kilpatrick, Sue Walsh.**
**Meteorology and Physical Oceanography**
**Rosenstiel School of Marine and Atmospheric Science**
**University of Miami**

- MODIS Team Meeting
- 23 July, 2002

## Ocean Color Status

- Focus areas -
- L1b versions -> calibration, validation
- Terra Reprocessing - Version 3 L1b
- Collection 4 coefficients, validation announcement this week
- Terra Forward processing -Version 4.0.5 L1b
- Collection 4 coefficients, validation comparison in progress
- Aqua Forward processing - prelaunch LUT - V3
- Collection ‘x’ preliminary coefficients
- Aqua Forward processing - first on-orbit LUT -V4
- Repeat calculations based on LUT (should be available this week)

## Calibration Approach

- Use at surface nLw, atmospheric and surface reflectance corrected
- Validation site for in situ reference is MOBY @ Hawaii, more extensive validation for other regions will require completion of reprocessing (use of SIMBIOS reference data)
- Cross-scan: Referenced to pixel 500, minimum of sun glint
- Detector Balance: Referenced to detector 5, low noise, center of detector array
- Mirror side Balance: reference to side 1
- Remove time trends: Compare modal peak for area surrounding MOBY to MOBY, high temporal density, not dependent on cloud free conditions
- Calibration: Adjust MOBY-MODIS single pixel match-ups to remove bias

## Terra Mirror Side Cross-scan vs time gain, no cal

- 412 nm

## Terra Mirror Side Cross-scan vs time gain, corrected

- 551 nm

## nLw412 Modal Terra-Moby Time Series

- Reprocessing
- Col 4, V3 L1b

- New Forward
- Col 4, V4 L1b

- Moby
- Terra

- Overall bias must be removed with MOBY matchups

## nLw551 Modal Terra-Moby Time Series

- Moby
- Terra

- New Forward
- Col 4, V4 L1b

- Reprocessing
- Col 4, V3 L1b

- Overall bias must be removed with MOBY matchups

## MODIS - MOBY nLw 412nm Calibration Matchups

- Reprocessing
- Col 4, V3 L1b

- New Forward
- Col 4, V4 L1b

## MODIS - MOBY nLw 551nm Calibration Matchups

- Reprocessing
- Col 4, V3 L1b

- New Forward
- Col 4, V4 L1b

## Cross-scan MODIS-Moby Comparison

- 412 nm

- 551 nm

- Reprocessing
- Calibration
- Coll 4, V3L1b

- proportion

- prop

## Cross-scan MODIS-Moby Comparison

- 412 nm

- 551 nm

- New Forward
- Calibration
- Coll 4, V4L1b

- proportion

- prop

## 412 nm Detector gain variation time-scan

- Reprocessing,  Coll4, V3 L1b

- Time

- Scan

## 551 nm Detector gain variation time-scan

- Reprocessing,  Coll4, V3 L1b

- Time

- Scan

## 412 nm Detector gain variation time-scan

- New Forward,  Coll4, V4 L1b

- Time

- Scan

## 551 nm Detector gain variation time-scan

- New Forward,  Coll4, V4 L1b

- Time

- Scan

## Calibration Statistics

| Wavelength | Reprocessing |  | New Forward |  |
| --- | --- | --- | --- | --- |
|  | Bias | Std. Dev. | Bias | Std. Dev. |
| 412 | 1.008 | 0.105 | 0.995 | 0.112 |
| 443 | 1.001 | 0.075 | 1.003 | 0.089 |
| 488 | 1.001 | 0.045 | 1.010 | 0.069 |
| 531 | 1.004 | 0.067 | 1.010 | 0.095 |
| 551 | 1.004 | 0.073 | 1.005 | 0.108 |
| 667* | 1.115 | 1.904 | 1.301 | 0.301 |
| 678* | 1.312 | 0.450 | 1.440 | 0.310 |

- V3 L1b                      V4.0.5 L1b

- * MOBY measurements marginal at these wavelengths

## 25jun02 Chlmod Terra-up, Aqua down

## 25jun02 ChlMod Merge Terra-AquaPre-launch calibration

## Conclusions

- Terra: Uncorrected mirror side, cross-scan, detector-detector and time variations can each exceed 30% in nLw
- Collection 4, Version 3L1b (Reprocessing) nLw validated
- Caveats: variations of ± 5% in nLw expected for cross-scan, detector-detector, mirror side and time
- Collection 4, Version 4.0.5 (Forward Processing)  correction, validation tests in progress and nearing completion
- Aqua detector, mirror, cross-scan preliminary corrections in test, need to verify polarization correction factors
- Collection x, Aqua, waiting for delivery of on-orbit LUT
- Manuscript with complete details near completion