Satellite Observations and ProductsTropical Atlantic Ocean

Main Topics:

➢Surface parameters retrieved from satellite measurements

➢Accuracy determination

➢Long time series of surface parameters

➢Air-sea parameters

TAOS 8 – 9 February 2018, Portland (USA)

Abderrahim BentamyIfremer / France

Satellite Observations and ProductsTropical Atlantic Ocean

TAOS 8 – 9 February 2018, Portland (USA)

Available Parameters/Products Satellites Buoys

Wind speed and direction

Sea surface Temperature

Near Surface Air Temperature

Specific air humidity

Sea Surface Salinity

Radiative fluxes (SW and LW)

Rain

Sea State (Hs, wave direction, sea

height)

Current

Wind stress and the related

parameters

Turbulent heat flux (LHF and SHF)

Satellite Data

Satellite Data

>25 years Scatterometer Wind Vector Observations

Satellite Data

>25 years Altimeter Wind and Sea State Observations

Courtesy NASA/JPL

Satellite Data

>25 years Radiometer atmospheric and oceanic Observations

Satellite Data

Courtesy NASA

>15 years SAR Wind Vector Observations

Tropical Atlantic Buoys (PIRATA) and Remotely Sensed Data

➢Determination of satellite retrieval (wind, sst, salinity, humidity,…) accuracy➢Assessment of high level satellite products (wind, sst, qa, lhf, shf, sw,lw,….)➢ Assessment of satellite forcing impact ➢….

• Ebuchi, N., H. C. Graber, and M. J. Caruso, 2002: Evaluation of wind vectors observed by QuikSCAT/SeaWinds using ocean

buoy data .J. Atmos. Oceanic Technol.,19, 2049–2062

• Portabella et al, 2008: On Scatterometer Ocean Stress, data.J. Atmos. Oceanic Technol

•Abhisek Chakraborty, Raj Kumar & Ad Stoffelen, 2013: Validation of ocean surface winds from the OCEANSAT-2

scatterometer using triple collocation. RSL.

•Sun et al, 2002: Comparisons of Surface Meteorology and Turbulent Heat Fluxes over the Atlantic: NWP Model Analyses

versus Moored Buoy Observations. J. of Climate.

•M. Portabella and A. Stoffelen, 2007: Development of a Global Scatterometer Validation and Monitoring . OSI_SAF / KNMI

Report

• Peng et al, 2013: Evaluation of Various Surface Wind Products with OceanSITES Buoy Measurements. Weather and

forcasting.

References>512 (WebofSciences; GoogleScholar; Ifremer tool)

Examples of Sampling length of remotely sensed data

January 1993 January 2000 January 2008 January 2014

Example of Remotely Sensed Products

Scatterometer Case

L2bRetrievals at Wind VectorCell (WVC) of (50km²,25km², 12.5km², …)Over scatterometerswath(s)

L3Gridded wind data➢Over scatterometer swath(s)➢Objective analysis

L4Gridded Data➢Objective analysis

Accuracy Issues : Swath Data (L2b)

Wind Speed Wind Direction

Bias

(m/s)

STD

(m/s)

bs Bias

(deg)

STD

(deg)²

ERS-1 WNF 0.42 1. 36 1.02 0.92 -4 19 1.84

ERS-2 WNF 0.70 1.41 1.01 0.93 -5 18 1.86

ERS-2 UWI 0.13 1.31 0.99 0.93 -2 38 1.33

QSCAT -0.01 1.21 0.99 0.94 -4 21 1.85

ASCAT0.15

(0.10)

1.21

(1.26)

1.00

(1.01)

0.94

(0.94)0 18 1.90

Wind Speed Wind Direction

Bias

(m/s)

STD

(m/s)

bs Bias

(deg)

STD

(deg)²

ERS-1 WNF 0.77 1.23 0.99 0.90 -9 19 1.64

ERS-2 WNF 0.88 1.32 1.01 0.90 -10 20 1.68

ERS-2 UWI 0.46 1.12 0.95 0.90 0 31 1.24

QSCAT 0.19 0.95 0.96 0.91 1 16 1.74

ASCAT0.45

(0.32)

1.02

(1.01)

0.95

(0.94)

0.91

(0.90) -3 15 1.78

NDBC Results

TAO/PIRATA/RAMA Results Sources of

biases?

Accuracy Issues : Swath Data (L2b)

Wind Speed Wind Direction

Bias

(m/s)

STD

(m/s)

bs Bias

(deg)

STD

(deg)²

ERS-1 WNF 0.42 1. 36 1.02 0.92 -4 19 1.84

ERS-2 WNF 0.70 1.41 1.01 0.93 -5 18 1.86

ERS-2 UWI 0.13 1.31 0.99 0.93 -2 38 1.33

QSCAT -0.01 1.21 0.99 0.94 -4 21 1.85

ASCAT0.15

(0.10)

1.21

(1.26)

1.00

(1.01)

0.94

(0.94)0 18 1.90

Wind Speed Wind Direction

Bias

(m/s)

STD

(m/s)

bs Bias

(deg)

STD

(deg)²

ERS-1 WNF 0.77 1.23 0.99 0.90 -9 19 1.64

ERS-2 WNF 0.88 1.32 1.01 0.90 -10 20 1.68

ERS-2 UWI 0.46 1.12 0.95 0.90 0 31 1.24

QSCAT 0.19 0.95 0.96 0.91 1 16 1.74

ASCAT0.45

(0.32)

1.02

(1.01)

0.95

(0.94)

0.91

(0.90) -3 15 1.78

NDBC Results

TAO/PIRATA/RAMA Results Sources of

biases?

Bentamy, A., Grodsky, S. A., Elyouncha, A., Chapron, B. and Desbiolles, F. , 2017: Homogenizationof scatterometer wind retrievals. Int. J. Climatol., 37: 870–889. doi:10.1002/joc.4746

Bentamy A., Grodsky S. A., Chapron B., Carton J. A., 2013: Compatibility of C- and Ku-band scatterometer winds: ERS-2 and QuikSCAT. J. Marine System 117-118, 72-80

Grodsky, S.A., Kudryavtsev, V.N., Bentamy, A., Carton, J.A. and Chapron, B., 2012. Does direct impact of SST on short wind waves matter for scatterometry?. Geophysical Research Letters, 39(12).

Bentamy, A., S. A. Grodsky, J. A. Carton, D. Croizé-Fillon, and B. Chapron, 2012: Matching ASCAT and QuikSCAT winds, J. Geoph. Res., 117, C02011, doi:10.1029/2011JC007479.

Validation of the Reprocessed Wind Speed Retrievals

Tropical Comparisons

Objectives:

➢Calculation of >20 years of

Wind vector; Wind Stress; Curl; Divergence; Errors

6-hourly (00h:00, 06h:00, 12h:00, 18h:00 UTC)

0.25°x0.25°

Global Oceans

➢Using new release of Scatterometer retrievals (L2b): ERS-1, ERS-2, QSCAT,ASCAT

Radiometers wind speed retrievals: F10 – F18

NWP re-analyses:ERA Interim

Improving Oceanic Forcing Function

Projects: CMEMS (Copernicus); TOSCA (CNES)

Desbiolles F., A. Bentamy, B. Blanke, C. Roy, A. Mestas-Nunez, S. A. Grodsky , S. Herbette, G. Cambon, C. Maes, 2017 :

Two Decades [1992-2012] of Surface Wind Analyses based on Satellite Scatterometer Observations . Journal Of Marine Systems , 168, 38-56

Example Satellite Surface Wind Analysis

Accuracy of Satellite Surface Wind Analysis

BuoySatelliteEra Interim

Surface Wind

ERS, Envisat, SSM/IQSCAT, ASCAT, AMSR-E, HY-2 Sea Temp

CCI SST (AATSR, AVHRR)

Specific Humidity

SSMI/I, AMSR-E, ADEOS

Air Temperature

ERA-Interim

Sea State

Globwave (ERS, Envisat altimeter)

ERA_Int

CFSR

MERRA

Ancillary

Model data

PDF Turbulent Heat Flux

J-OFURO

HOAPS SeaFLux IFREMER

Buoys, Experiments, NOCS, SAMOS

Ocean ColourGlob CArgo

Mixed Layer Depth derived from GOTM

ORA

Net Heat derived from OHC and lateral fluxes

INPUT PARAMETERS OTHER FLUX DATA SETS

Quality Inter-comparison

(global)

Validation(point-based)

Consistency Checks(regional assessment)

(Open Cage, Warm Pool Bubble, Med Sea)

REGIONAL HEAT BUDGET

State-of-the-artBulk Formula

+ EnsembleApproach

Net Flux

20yrs, 0.25degSensible Flux, Latent Flux,Uncertainty

NERSC

NERSC, IFREMER

MIO PML

w

SST

qa

Ta

sWH

CurrentOHCRad

FluxesSynthesis CCI

AOFlux

OverviewOHF

Porsec 2016 Fortaleza B razil

OHFAnnual Mean of OHF LHF and SHF

Bentamy Abderrahim, Piollé J.F, Grouzel A., Danielson R., Gulev S., Paul Frederic, Azelmat Hamza, Mathieu P.

P., Von Schuckmann Karina, Sathyendranath S., Evers-King H., Esau I., Johannessen J. A., Clayson C. A.,

Pinker R. T., Grodsky S. A., Bourassa M., Smith S. R., Haines K., Valdivieso M., Merchant C. J., Chapron

Bertrand, Anderson A., Hollmann R., Josey S. A. (2017). Review and assessment of latent and sensible

heat flux accuracy over the global oceans . Remote Sensing Of Environment , 201, 196-218 .

http://doi.org/10.1016/j.rse.2017.08.016

Pinker Rachel T., Bentamy Abderrahim, Zhang Banglin, Chen Wen, Ma Yingtao (2017). The net energy budget

at the ocean-atmosphere interface of the "Cold Tongue" region . Journal Of Geophysical Research-

oceans , 122(7), 5502-5521 . http://doi.org/10.1002/2016JC012581

OHF Turbulent Flux Product Accuracy

Porsec 2016 Fortaleza B razil

OHFOHF LHF Product Accuracy

RMSD LHF (Buoy – OHF)

OHFOHF SHF Product Accuracy

RMSD SHF (Buoy – OHF)

Porsec 2016 Fortaleza B razil

OHFOHF Ensemble Determination

➢OHF/MPE is estimated based on the use of the standardized IFREMER, HOAPS, OAFlux, SeaFlux, J-OFURO, ERA Interim, and CFSR daily fluxes. It is calculated on a daily basis over the standardized OHF product grid map (0.25°×0.25°) over global free ice oceans. ➢MERRA data is not used for OHF/MPE calculation. It is kept for further inter-comparison issues.

Error characteristics determined from in-situ and products comparison results

OHF MultiProduct Ensemble (OHF/MPE)

OHFEnsemble (OHF/MPE) and Standardized Product

Evaluation

Taylor diagram summarizing the intercomparison results between daily OceanSitesbuoys and OHF a) LHF and b)SHF products calculated for the period 2000 - 2007

A : OceanSite buoy B : Ifremer C : Hoaps D : OAFlux E: SeaFlux G: J-Ofuro H: Era Interim I: Cfsr J: Nocs2 K: Ensemble(OHF/MPE)

LHF SHF

Porsec 2016 Fortaleza B razil

OHFOHF LHF and SHF Time Series

Valdivieso et al, 2015 Clim. Dyn. DOI 10.1007/s00382-015-2843-3

Stratus Buoy 19.9°S, 85.3°W((WHOI), Weller et al, 2014)

OHFLHF RMSD at individual selected OceanSites buoy

and each OHF product.

Error sources:▪Wind Speed▪Specific air humidity▪Air temperature▪Q▪T

OHFLHF Accuracy as a Function of Bulk Variables

Summary / Requirements

Summary

Buoy are highly required for

• Calibration and validation of satellite-based surface parameters

• Investigation and determination of L2, L3, and L4 satellite products as a

function of buoy atmospheric and oceanic measurements.

• Assessing the time scale features estimated from satellite products.

• Assessing the quality of the numerical simulations based on satellite forcing

function.

• Validation of satellite turbulent and radiative fluxes at various spatial and

temporal scales.

Requirements

• Reprocessing long time series, including missed data.

• Sea state information

• Long wave radiative flux

Characteristics of sources providing satellite surface winds

Satellite Instruments PeriodOrbit (days)

Spatial grid Sources Archive

ERS-1Scatterometer

altimeter1992 - 1996 3

50/25km²

7kmESA/IFREMER/KNMI IFREMER

ERS-2Scatterometer

altimeter1996 - 2011 35

50/25km²

7kmESA/IFREMER/KNMI IFREMER

ADEOS-1 Scatterometer (NSCAT) 1996 - 1997 4 25km² NASA/JPL IFREMER

QuikSCAT Scatterometer (SeaWinds) 1999 - 2009 4 12.5km² NASA/JPL IFREMER

ADEOS-2 Scatterometer SeaWinds) 2002 - 2003 4 25km² NASA/JPL IFREMER

OceanSat2 Scatterometer (OSCAT2) 2009 - 2013 2 25km² ISRO/KNMI IFREMER

Metop-A Scatterometer ASCAT-A) 2007 - Present 29 25/12.5km² OSI SAF IFREMER

Metop-B Scatterometer (ASCAT-B) 2012 - Present 29 12.5km² OSI SAF IFREMER

HY-2A Scatterometer 2012 - Present 14 25km² NSOAS/KNMI IFREMER

ISS Scatterometer(RapidScat) 2014 - 2016 12.5km² NASA/JPL IFREMER

ENVISATSAR

altimeter2002 - 2011 35

1km²

7kmESA IFREMER

SENTINEL 1A SAR 2015 - Present 1km² ESA IFREMER

Topex/Poseidon altimeter 1992 - 2005 10 7km CNES IFREMER

Jason1 altimeter 2001 - 2013 10 7km CNES IFREMER

Jason2 altimeter 2008 - Present 10 7km CNES IFREMER

Jason-3 Altimeter 2016-Persent 10 7km CNES IFREMER

DMSP F10-F18 Radiometers(SSM/I) 1992 - Present 25km² RSS IFREMER

CORIOLIS Radiometer(WindSat) 2003 - Present 8 25km² RSS IFREMER