Which VIIRS product to use: ACSPO vs. NAVO GHRSST-XV, 2-6 June 2014, Cape Town, South Africa 1

Prasanjit Dash1,2, Alex Ignatov1, Yuri Kihai1,3, John Stroup1,4, John Sapper1, Boris Petrenko1,3

1NOAA NESDIS, NCWCP College Park, MD2 Colorado State Univ, CIRA3 GST, Inc, MD, USA4 STG, Inc, VA, USA (Emails: FirstName.LastName@noaa.gov)

The 15th GHRSST 2014 meeting, ST-VAL Breakout session

2–6 Jun, 2014, Cape Town, South Africa

Which VIIRS product to use? NOAA ACSPO vs. NAVO SEATEMP

www.star.nesdis.noaa.gov/sod/sst/squam/HR/

SQUAM objective: A global, web-based, community, quasi NRT, monitor for SST producers & users !

AUS TAG and VIIRS breakoutGHRSST XV, 2014

X Jun 2014, X:XX-X:XX AM

Which VIIRS product to use: ACSPO vs. NAVO GHRSST-XV, 2-6 June 2014, Cape Town, South Africa 2

Major SST data providers: Projects and international group

Acknowledgments

Level-2 SST: VIIRS/AVHRR/MODIS- NESDIS SST Team : ACSPO (GAC: 5 platforms, FRAC: Metop-A & B, VIIRS: NPP, MODIS: Terra/Aqua)- D. May, B. McKenzie : NAVO SEATEMP- S. Jackson : IDPS (NPP)

Level 4 SSTs:- M. Martin, J. R. Jones : OSTIA foundation, GHRSST Median Product Ensemble, OSTIA Reanalysis- B. Brasnett : Canadian Met. Centre, 0.2 foundation

GHRSST support: Peter Minnett, Craig Donlon, Alexey Kaplan

CMC

Which VIIRS product to use: ACSPO vs. NAVO GHRSST-XV, 2-6 June 2014, Cape Town, South Africa 3

Outline

1. High-resolution (HR) SQUAM

2. Monitoring of VIIRS SSTs (ACSPO, IDPS, NAVO) in SQUAM Maps, Histograms, Time series, Dependence

3. Validation against QC’ed drifters 4. Persistent features in monthly maps

5. Closer look at ACSPO vs. NAVO: VZA dependence in Hovmöller space

6. Summary

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p: 15 12 slides

Which VIIRS product to use: ACSPO vs. NAVO GHRSST-XV, 2-6 June 2014, Cape Town, South Africa 4

Locate this website: Google: “SST + SQUAM + HR”

The SST Quality Monitor (SQUAM), JTech, 27, 1899-1917, 2010

1. VIIRS SSTs in High-Res (HR) SQUAM

Which VIIRS product to use: ACSPO vs. NAVO GHRSST-XV, 2-6 June 2014, Cape Town, South Africa 5

Maps Histograms Time-series Dependencies

Hovmöller

Night: VIIRS (IDPS) minus CMC L4, 15-May-2014

• Initial product developed by private contractor, now discontinued and replaced by ACSPO• Coverage is good but many cold spots indicate residual cloud/aerosol leakages

2. VIIRS SST in SQUAM: IDPS

Which VIIRS product to use: ACSPO vs. NAVO GHRSST-XV, 2-6 June 2014, Cape Town, South Africa 6

Maps Histograms Time-series Dependencies

Hovmöller

Night: VIIRS (ACSPO) minus CMC L4, 15-May-2014

• ACSPO is NOAA heritage SST product, now operational and replaced the IDPS• Residual Cloud/Aerosol leakages reduced compared to IDPS

2. VIIRS SST in SQUAM: ACSPO

Which VIIRS product to use: ACSPO vs. NAVO GHRSST-XV, 2-6 June 2014, Cape Town, South Africa 7

Maps Histograms Time-series Dependencies

Hovmöller

Night: VIIRS (NAVO) minus CMC L4, 15-May-2014

• Reduced coverage (VZA<54°; 2×2 pixel processing; more conservative mask)• Fewer leakages especially in the Tropics (on this particular day)

2. VIIRS SST in SQUAM: NAVO

Which VIIRS product to use: ACSPO vs. NAVO GHRSST-XV, 2-6 June 2014, Cape Town, South Africa 8

Maps Histograms Time-series Dependencies

Hovmöller

ACSPO VIIRS – CMC

NAVO VIIRS – CMC

IDPS VIIRS – CMC

2. VIIRS SSTs in SQUAM: Example 15 May 2014, Night

IDPS vs. ACSPO o Retrieval domain: Comparableo SST performance statistics: ACSPO superior

NAVO vs. ACSPO o Retrieval domain: NAVO factor of ×2.6 smallero SST performance statistics: Comparable

Which VIIRS product to use: ACSPO vs. NAVO GHRSST-XV, 2-6 June 2014, Cape Town, South Africa 9

Maps Histograms Time-series Dependencies

Hovmöller2. Monitoring in SQUAM: VIIRS SSTs, Day

o Mean and Std Dev of residuals (Sat SST – OSTIA) closely track each other

o Similar observations for other referenceso NAVO:

# of NAVO observations ~1/3 of ACSPO Day: very similar (this figure); Night: NAVO slightly but consistently better (see SQUAM-HR webpage)(for other products: see SQUAM-HR webpage)

Monthly in situ val --- NEXT SLIDE

Which VIIRS product to use: ACSPO vs. NAVO GHRSST-XV, 2-6 June 2014, Cape Town, South Africa 10

o Mean and Std Dev of residuals (Sat SST – Drifters) closely track each other

o Similar observations for other referenceso NAVO:

# of NAVO observations ~1/3 of ACSPO Std Dev: NAVO slightly but consistently better

Maps Histograms Time-series Dependencies

Hovmöller2. Validation: VIIRS SSTs (monthly, vs. drifters, Day)

Which VIIRS product to use: ACSPO vs. NAVO GHRSST-XV, 2-6 June 2014, Cape Town, South Africa 11

3. NAVO/ACSPO Summary Statistics

Products # of matches (%ACSPO) Min / Max (◦C)

Mean / Median Std Dev / RSD Skew / Kurt

ACSPO NPP 42,917 (night)42,586 (day)

-2.61 / 5.92-2.82 / 4.12

-0.03 / 0.04 0.06 / 0.06

0.39 / 0.250.42 / 0.33

2.77 / 35.04 0.35 / 4.46

NAVO NPP 12,912 (30.08%)10,063 (23.62%)

-2.58 / 2.20-1.80 / 4.31

0.06 / 0.09 0.05 / 0.03

0.29 / 0.220.38 / 0.32

-0.97 / 7.51 0.58 / 5.89

IDPS NPP 48,638 (113.33%)46,208 (108.50%)

-6.62 / 2.83-8.04 / 6.43

-0.06 / 0.00-0.07 / 0.02

0.42 / 0.260.65 / 0.42

-2.00 / 15.51 -1.68 / 11.23

* QC’ed drifters from iQuam: www.star.nesdis.noaa.gov/sod/sst/iquam/

Products # of matches (%ACSPO)

Min / Max (◦C) Mean / Median Std Dev / RSD Skew / Kurt

ACSPO NPP 117.10 million (night)110.90 million (day)

-4.52 / 9.35-5.69 / 8.79

0.05 / 0.05 0.24 / 0.16

0.39 / 0.300.61 / 0.41

0.54 / 8.51 1.95 / 11.25

NAVO NPP 45.29 mi (38.68%)36.13 mi (32.58%)

-8.12 / 5.55-7.85 / 7.67

0.08 / 0.11 0.18 / 0.13

0.38 / 0.290.54 / 0.41

-0.92 / 7.61 0.67 / 8.14

IDPS NPP 120.13 (102.58%)111.96 (100.95%)

-13.40 / 17.57-27.40 / 13.96

0.01 / 0.04 0.17 / 0.21

0.47 / 0.320.79 / 0.45

-1.05 / 15.41 -0.56 / 10.11

Validation wrt. drifters, Feb 2014

Monitoring wrt. CMC, 15 May 2014

Which VIIRS product to use: ACSPO vs. NAVO GHRSST-XV, 2-6 June 2014, Cape Town, South Africa 12

Maps Histograms Time-series Dependencies

Hovmöller

Day: VIIRS (ACSPO) minus CMC L4, Apr-2014

4. Looking for persistent features: Monthly aggregation

• Negative residuals in monthly maps suggest persistent cloud/aerosol leakages

• Positive residuals: Daytime diurnal warming? or NLSST algorithm artifacts?

Which VIIRS product to use: ACSPO vs. NAVO GHRSST-XV, 2-6 June 2014, Cape Town, South Africa 13

Maps Histograms Time-series Dependencies

Hovmöller

Day: VIIRS (NAVO) minus CMC L4, Apr-2014

• Some areas of the ocean are not covered even at monthly time interval• Warm spots more pronounced: Differences in NAVO./ACSPO cloud screening? or SST

algorithm?

4. Looking for persistent features: Monthly aggregation

Which VIIRS product to use: ACSPO vs. NAVO GHRSST-XV, 2-6 June 2014, Cape Town, South Africa 14

5. VAL Statistics as a Function of Scan Angle

ACSPO makes retrievals in full swath whereas NAVO at VZA<54° only

Within the limited VZA domain, ACSPO and NAVO Std Dev values are close

ACSPO STD Dev degrade towards swath edges

Degradation is more complex than merely a function of VZA, and shows some seasonality

Which VIIRS product to use: ACSPO vs. NAVO GHRSST-XV, 2-6 June 2014, Cape Town, South Africa 15

There are 2 global VIIRS products: NOAA ACSPO and NAVO SEATEMP. Both are archived at PO.DAAC / NODC in GDS2 format

IDPS product is being discontinued, due to suboptimal performance & lack of users. It is currently archived at CLASS in hdf5 and will be wiped off once complete record of ACSPO VIIRS from Jan 2012-on is archived

Relative merits of ACSPO and NAVO VIIRS SSTs

o NAVO global coverage is about 1/3 of ACSPO. As a result, some areas of the ocean remain uncovered by the NAVO product for extended periods up to a month

o Measured in their corresponding full retrieval domains, NAVO outperforms ACSPO, by a narrow (day) to moderate (night) margin.

o However, in the “intersection” domain, both products show comparable performances

THANK YOU!

6. Summary

Which VIIRS product to use: ACSPO vs. NAVO GHRSST-XV, 2-6 June 2014, Cape Town, South Africa 16

Backup slides

Which VIIRS product to use: ACSPO vs. NAVO GHRSST-XV, 2-6 June 2014, Cape Town, South Africa 17

Maps Histograms Time-series Dependencies

Hovmöller2. Monitoring in SQUAM: VIIRS SSTs, Night

o Mean and Std Dev of residuals (Sat SST – OSTIA) closely track each other

o Similar observations for other referenceso NAVO:

# of NAVO observations ~1/3 of ACSPO slightly but consistently better

(for other products: see SQUAM-HR webpage)

Monthly in situ val --- NEXT SLIDE

Which VIIRS product to use: ACSPO vs. NAVO GHRSST-XV, 2-6 June 2014, Cape Town, South Africa 18

Maps Histograms Time-series Dependencies

Hovmöller2. Validation: VIIRS SSTs (monthly, vs. drifters, Night)

o Mean and Std Dev of residuals (Sat SST – OSTIA) closely track each other

o Similar observations for other referenceso NAVO:

# of NAVO observations ~1/3 of ACSPO slightly but consistently better

Which VIIRS product to use: ACSPO vs. NAVO GHRSST-XV, 2-6 June 2014, Cape Town, South Africa 19

Maps Histograms Time-series Dependencies

Hovmöller2. Monitoring in SQUAM: VIIRS SSTs, Day

o Mean and Std Dev of residuals (Sat SST – OSTIA) closely track each other

o Similar observations for other referenceso NAVO:

# of NAVO observations ~1/3 of ACSPO Day: very similar (this figure); Night: NAVO slightly but consistently better

(for other products: see SQUAM-HR webpage)

Monthly in situ val --- NEXT SLIDE

Which VIIRS product to use: ACSPO vs. NAVO GHRSST-XV, 2-6 June 2014, Cape Town, South Africa 20

o Mean and Std Dev of residuals (Sat SST – Drifters) closely track each other

o Similar observations for other referenceso NAVO:

# of NAVO observations ~1/3 of ACSPO Std Dev: NAVO slightly but consistently better

Maps Histograms Time-series Dependencies

Hovmöller2. Validation: VIIRS SSTs (monthly, vs. drifters, Day)