Daily OI Analysis for Sea Surface Temperature

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Daily OI Analysis for Sea Surface Temperature
Richard W. Reynolds (NOAA, NCDC) Thomas M. Smith
(NOAA, STAR) Chunying Liu (NOAA, NCDC) Dudley B.
Chelton (Oregon State University) Kenneth S.
Casey (NOAA, NODC) Michael G. Schlax (Oregon
State University)
NOAAs National Climatic Data Center Asheville, NC
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The Good, the Bad and the Ugly
Richard W. Reynolds (NOAA, NCDC) Thomas M. Smith
(NOAA, NCDC) Chunying Liu (NOAA, NCDC) Dudley B.
Chelton (Oregon State University) Kenneth S.
Casey (NOAA, NODC) Michael G. Schlax (Oregon
State University)
NOAAs National Climatic Data Center Asheville, NC
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Outline

• Introduction
• Justification for a daily analysis
• Version 1
• Problems with Version 1 improvements to Version
  2
• Intercomparisons
• Final comments

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Jan '03 Number of Days with Nighttime Obs

• Top AVHRR Pathfinder Bottom AMSR-E
• For AVHRR
• Absolute latitudes gt 40 have roughly only 5 days
  of data
• Number of days increases toward the tropics
• Drop offs due to cloud cover
• For AMSR
• Absolute latitudes gt 40 have more than 20 days
  of data
• Drop offs due to precipitation in ITCZ and SPCZ

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Magnitude of GradientGulf Stream

• Daily OI using AMSR-E for January - March 2003
• Gradients have a stationary part due to
  topography
• Thus, limited AVHRR data are useful

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Magnitude of Gradient Tropical Eastern Pacific

• Daily OI using AMSR-E for August - October 2003
• Gradients propagate westward
• Limited coverage not as useful here
• Monthly averaging smoothes out most of gradient
  signal

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Outline

• Introduction
• Justification for a daily analysis
• Version 1
• Problems with Version 1 improvements to Version
  2
• Intercomparisons
• Final comments

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OI SST Analysis
Weekly (OI.v2) Grid 1o Data Satellite plus in situ (ship and buoy) data Satellite data Infrared AVHRR 7-Day large-scale satellite bias correction for each satellite Spatial error correlation 700 km Daily Grid 0.25o Data Satellite plus in situ (ship and buoy) data Satellite data to include Infrared AVHRR Microwave AMSR-E 7-Day large-scale satellite bias correction for each satellite Spatial error correlation 100 km
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Nighttime Zonal Bias AVHRR - In Situ
90N
AVHRR Pathfinder - In Situ
90S
'82
'05
90N
AVHRR Operational - In Situ
90S
Pathfinder Advantages Lower bias variability
data delayed Operational Advantages Real-time
data 1981-84 data
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Ocean Coverage ()

• Day and Night Coverage for
• AVHRR Pathfinder 12
• AVHRR Operations 8
• AMSR 40
• Note Pathfinder coverage better then Operation
• Pathfinder cloud contamination?
• AMSR coverage considerably better than AVHRR
• Note data drop outs

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OI Zonal Spatial Error Correlation Scales

• Daily spatial scales strongly reduced from weekly
  scales
• Daily scales reduced in high gradient areas
• Scales lt100 km in Gulf Stream
• Daily scales between 100 200 km in most regions

From the figure note
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3-Day Gulf Stream Average Gradients

• Data
• AVHRR
• AMSR
• Analyses
• Weekly OI.v2 AVHRR
• Daily RTG-SST AVHRR
• Daily OI AVHRR only
• Daily OI AMSRAVHRR
• Missing Data AMSR AVHRR
• Daily OI resolution improved over OI.v2
• AMSRAVHRR best analysis resolution

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3-Day Eastern Tropical Pacific Gradients

• Daily OI resolution improved over OI.v2
• AMSRAVHRR best analysis resolution
• High Gradients in AVHRR lost in analyses
• Features are progress waves not partly fixed by
  topography

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Gulf Stream Gradient Index

• Index
• 70W-40W
• 35N-50N
• Analyses
• Weekly OI.v2
• RTG-SST
• AVHRR-only
• AMSRAVHRR
• Seasonal cycle range
• Similar minimum for daily analyses
• Maximum roughly 40 for AVHRRAMSR

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Jan 2003 Standard Deviation
Top Pathfinder Bottom AMSR-E

• AMSR-E has stronger standard deviations than
  Pathfinder
• Especially in mid-latitude winter
• Clouds reduce Pathfinder sampling
• These differences plus gradient differences
  suggest that separate Pathfinder OI and
  Pathfinder AMSR OI needed

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Empirical Orthogonal Teleconnections (EOT)

• 130 modes from Extended Reconstruction SST
• Fit modes to 7-day in situ and satellite
  anomalies on 2o grid
• Only use modes if supported by both types
  anomalies
• In figure mode 4 would probably not be used due
  to lack of in situ data
• Reconstruct anomalies from modes
• Bias is difference between the two
  reconstructions

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Random Sampling Error

• OI Derived
• Sampling error dominant term
• Sampling and random error reduced by observations
• Lower for AMSRAVHRR

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Bias Error

• Bias error derived from variance of EOT modes
  used in correction
• From modes supported by satellite data but not by
  in situ data
• Bias error consider independent if from different
  satellites
• Thus error lower for AMSRAVHRR than AVHRR-only
• Total error S (Bias Random Sampling)
  Variances

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Daily OI ProductsAll products on 0.25 spatial
grid

• AVHRR only
• AVHRR Pathfinder Daily OI January 1985-end of
  Pathfinder data (currently December 2006)
• AVHRR Operational Daily OI January 2007-present
• AMSR AVHRR
• AMSR AVHRR Pathfinder Daily OI June 2002 to
  end of Pathfinder data (currently December 2006)
• AMSR AVHRR Operational Daily OI January
  2007-present

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Daily OI SST AnomaliesEOT satellite bias
correction
Left Pathfinder AVHRR OI Right Pathfinder
AVHRR AMSR-E OI

• 27 August Katrina
• Weak anomaly in Gulf in Path AMSR-E
• 28 August Katrina
• Strong anomaly in Path AMSR-E
• 29 August Katrina
• Strong anomaly in Path AMSR-E
• Modest anomaly in Path

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Operational Daily OI SST Data Flow
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Sample Warning ErrorDaily OIEmails
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Outline

• Introduction
• Justification for a daily analysis
• Version 1
• Problems with Version 1 improvements to Version
  2
• Intercomparisons
• Final comments

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Data Anomalies 11 Jan 2003Differences lead to
day-to-day noise in OI

• AVHRR day night
• Note data scarcity
• Pathfinder local time
• AMSR day night
• Note swath width precipitation
• Day night differences not always diurnal warming

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4 Days of Buoy SST Data 0Z 22 March 22 - 0Z 26
March 26, 2006

• Resolution
• 1 minute
• Averaged to
• 1 hour
• 1 day
• Consider random sampling
• AMSR could approach 2 obs/day
• AVHRR would be lower especially in winter

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Buoys with Good Temporal Coverage

• Use moored buoys to determine if temporal
  smoothing is needed for the daily OI
• 43 buoys selected with at least 99 daily
  coverage from '03-'05

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Average Daily Spectra for 3 Years

• Buoy spectra closer to daily OI spectra when
  3-days of data are used
• Note by day, AVHRR-only lower than
  AMSRAVHRR spectra
• 3-days of data used in Version 2

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SSTs Gradients3-Day Average

• Data
• AMSR
• Analyses
• Daily OI AVHRR only
• Daily OI AMSRAVHRR
• Precipitation data void near 35N 130W
• Noise near boundary leads to OI interpolation
  errors
• Note gradients

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AMSR Data Anomalies9 Feb 2003

• Data in color passed the extra QC which includes
• SST changes
• Proximity to rain
• Data in black failed the extra QC but was used in
  the original OI
• Note the relatively small number
• Typical AMSR obs which fail the extra QC
• Daytime 1.0-1.5
• Nighttime 0.5-1.0

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AMSRAVHRR OIAnomalies 9 Feb 2003

• Top OI with AMSRAVHRR data
• Bottom OI with AMSRAVHRR data AMSR has extra
  QC
• SST anomalies reduced in oval region when extra
  QC obs not used
• This procedure reduces some day-to-day noise
• Of course, the extra QC is not be prefect
• AMSR with extra QC used in Version 2

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Analysis DifferenceJuly 2006

• NOAA 17 AVHRR OI Pathfinder - Navy
• Top Panel No zonal bias first guess correction
• Bottom Panel With zonal bias first guess
  correction
• Note Differences smaller between 40oS- 60oS
  with zonal bias correction
• Bias correction with zonal first guess used in
  Version 2

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Average Bias Correction Spectra 2000-2005

• Night AVHRR bias correction
• 1 Field no smoothing
• Binomial filter 3, 5 or 7 days
• 5 day binomial filter selected for Version 2

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Daily OI Ship Biases

• Satellite biases are corrected with respect to in
  situ data (ships buoys)
• Ships have larger random and bias errors than
  buoys
• Ship observations using buckets tend to be
  biased cold due to evaporation
• Ship observations using engine intake tend to be
  biased warm due to engine room heating
• Ship metadata needs improvement
• Try to correct ship bias using buoy data
• Would EOT procedures over a 30 day time period
  work?

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Ship-Buoy SST Zonal Biases
'94

• EOT monthly ship buoy analyses
• Buoy SST obs increase with time
• Significant buoy obs 1994 to present
• First correct ship biases than correct satellite
  biases

Time
'05
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Monthly Averaged Collocated Buoy and Ship
Anomaly SSTs

• Buoy vs. Ship data and fit
• Red 1998-2006
• Black 1989-1997
• 2 Periods similar
• Clear need to adjust ships 0.14oC subtracted
  from all ship obs in Version 2

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Daily OI Revisions

• Version 2 Next Daily OI Version (Oct 2007)
• Use 3-days of data in the Daily OI analysis
• Smooth 7-day satellite bias corrections
• Use the extra QC from AMSR data
• Improve the land-sea table
• Correct ship SSTs with respect to in buoy SSTs
• Version 3 Following Daily OI Version 2
• Use additional satellite data TMI, ATSR, MODIS,
  etc.
• Process NOAA-7 November 1981 - December 1984
• Harden operational procedures
• Improve bias correction

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Outline

• Introduction
• Justification for a daily analysis
• Version 1
• Problems with Version 1 improvements to Version
  2
• Intercomparisons
• Final comments

38
Difference V2 - V1
Upper Panel AVHRR-only

• Ship bias adjustment - Cool differences Lat gt
  40oS
• Zonal bias first guess - Warm differences Lat lt
  40oS
• Additional changes due to improved AMSR QC
• Removal of tropical rain contamination reduces
  positive bias
• Removal of mid-latitude rain contamination
  reduces negative bias

Lower Panel AMSR-only
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Difference V2 - OI.v2
Upper (AVHRR-only) - OI.v2

• Tropical Negative Bias
• Negative Bias near 60oS
• Positive Bias above 70oS
• Biases generally lower than Pathfinder AVHRR
• 0.1oC except 0.3oC north of 70oN and south of
  60oS

Lower (AMSR-only) - OI.v2
Residual bias error
Thanks to Sudhir Nadiga
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Difference V2 - OI.v2
Upper (AVHRR-only) - OI.v2

• Tropical Negative Bias
• Negative Bias near 60oS
• Positive Bias gt 70oS
• Biases generally much larger without correction
• Note TAO moorings

Lower (AVHRR-only No bias correction) - OI.v2
How should this bias error be corrected?
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Convert Sea Ice to SST

• Least squares fit between SST and sea ice, x,
  (0 x 1)
• SST2 A x2 B x C
• SST1 b x c
• where SST freezing temp for x 1
• For each month region find A, B, C, b, c

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Sea Ice to SST

• Least squares fit 1985-1994
• Verification 1995-2004
• Bias RMS differences for N. Hem.
• RMS Difference
• RMS increases with decreasing ice conc.
• Bias Data - Fit SST
• Data gt 0.3oC warmer than fit when ice lt 0.7

Linear Fit selected Range ice conc. gt0.5
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Weekly Daily OIDecember 1991

• Both OIs have bias correction for AVHRR data
• Daily OI uses Pathfinder
• Weekly OI uses Operational
• From the figure note
• Operational data problem along 35oS
• Delayed mode processing allows data correction
• Daily scales reduced in high gradient areas

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OI SSTs for December 2006

• Gulf Stream flows off Carolina coast
• Cold shelf water should be present between Gulf
  Stream and coast
• Not present in weekly OI.v2
• Weak in Pathfinder and AMSR daily OI
• Strongest in Navy daily OI
• Both Pathfinder and Navy use NOAA-17 data!

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SST Data for 28 December 2006

• Data for 28 December, 2006, typical when AVHRR
  available
• Cold shelf water off Carolinas is
• Not present in Pathfinder and AMSR data
• Weak in buoy data
• Stronger in Navy data

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SST Analyses for 28 December 2006

• UK OSTIA
• (1/20) oC
• NCEP RTG-HD
• (1/12) oC
• NCDC Daily OIs
• (1/4) oC
• Shelf water weak in OSTIA
• RTG-HD smoother than daily OI

47
Suggestions for High Resolution SST

• First Stage low resolution using (1/4)o ship,
  buoy, AVHRR, AMSR data
• AMSR dominates

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Suggestions for High Resolution SST

• First Stage low resolution using (1/4)o ship,
  buoy, AVHRR, AMSR data
• AMSR dominates
• Second Stage high resolution using 4-5 km AVHRR
• AVHRR improves resolution where available
• High Resolution First Guess
• Low resolution damped high resolution

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Outline

• Introduction
• Justification for a daily analysis
• Version 1
• Problems with Version 1 improvements to Version
  2
• Intercomparisons
• Final comments

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AMSR AVHRR Daily OI SST Anomaly 2oS - 2oN
Time
(oC)
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SST Daily OI Anomaly
(oC)
AMSR AVHRR
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To Maintain Credibility

• Stress both the good and the bad
• E.g., grid and spatial resolution differ
• Keep the descriptions short
• Users will not read documentation
• Keep the number of products small
• Users will not read documentation
• Keep data formats simple
• Users will not read documentation

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The End
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OI Anomalies with Bias CorrectionJanuary 1988
Along equator

• From the figure note
• Operational AVHRR did not have strong biases in
  this region
• Negative biases in daily OI except at TAO mooring
  sites near 155oW, 140oW 125oW
• OI bias correction fails to correct AVHRR
  Pathfinder satellite biases

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OI Anomalies with Bias CorrectionJanuary 1988
Along equator

• From the figure note
• Operational AVHRR did not have strong biases in
  this region
• Negative biases in daily OI except at TAO mooring
  sites near 155oW, 140oW 125oW
• OI bias correction fails to correct AVHRR
  Pathfinder satellite biases
• Empirical Orthogonal Teleconnections (EOT) bias
  correction better at correcting biases

Daily OI computed with EOT bias correction
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SST Analyses for 28 December 2006

• Frontal features
• Common to both Navy and AMSR
• Probably realistic as data independent
• Weak in Pathfinder
• Pathfinder AMSR keeps features from AMSR
• AMSR overwhelms AVHRR in open ocean

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SST Analyses for 28 December 2006

• Frontal features
• Common to both Navy and AMSR
• Weak in OISTA
• Strong in RTG-HD