Naval Oceanography Data Decision Superiority 1 Approved for Public Release, Distribution Unlimited...
-
Upload
madeleine-abigayle-oliver -
Category
Documents
-
view
223 -
download
0
Transcript of Naval Oceanography Data Decision Superiority 1 Approved for Public Release, Distribution Unlimited...
Naval Oceanography Data Decision Superiority 1
Approved for Public Release, Distribution Unlimited
VIIRS-derived SST at the Naval Oceanographic Office: From evaluation to operation
Jean-François Cayulaa, Douglas Mayb, Bruce McKenzieb, Keith Willisb
aQinetiq North America, 1103 Balch Blvd., Suite 218, Stennis Space Center, MS 39529-6000bNaval Oceanographic Office,1002 Balch Blvd., Stennis Space Center, MS 39522-5001
SPIE Defense Security and Sensing 2013, Ocean Sensing and Monitoring V
Thermal Remote and In-Situ Sensing IDate: 5/1/2013 Time: 14:00
Location: Conv. Ctr. 350
Paper 8724-35
The views expressed in this presentation are those of the authors and do not necessarily reflect the official policy or position of the Department of the Navy, Department of Defense, or US Government.
Naval Oceanography Data Decision Superiority 2
Approved for Public Release, Distribution Unlimited
Abstract
The Naval Oceanographic Office (NAVOCEANO) produces Sea Surface Temperature (SST) retrievals from satellite data. NAVOCEANO also obtains satellite-derived SST data sets from other groups. To provide consistency for assimilation into analyses and models, all the SST data sets are evaluated for their accuracy with the same methodology. In this presentation, the focus is SST derived from the Visible Infrared Imaging Radiometer Suite (VIIRS) sensor on-board the Suomi National Polar-orbiting Partnership (S-NPP) satellite. Of particular interest is the evaluation of NAVOCEANO-produced SST with its NAVOCEANO cloud mask (NCM), the VIIRS cloud mask (VCM), and VIIRS Environmental Data Record (EDR) SST. The evaluation results show that these products are in some ways comparable, with similar strengths and weaknesses, although they target different customers. For comparison, the reliability results for the Meteorological Operational (METOP-A) satellite-derived SST, which is a NAVOCEANO operational product, are presented. As a by-product of the NAVOCEANO VIIRS SST evaluation, the non-linear SST (NLSST) equations used to derive the SST values were found to be less than optimal, depending on the unit of the field temperature term. NAVOCEANO VIIRS SST employs an expanded NLSST equation, which in effect refines the approximation of the gamma term by adding an offset. In view of the evaluation results, NAVOCEANO VIIRS SST became operational in January 2013.
Naval Oceanography Data Decision Superiority 3
Approved for Public Release, Distribution Unlimited
Introduction
SST at NAVOCEANO Input to ocean models Processing AVHRR data from NOAA-19, Metop-A, Metop-B* Processing Imager data from GOES-13, GOES-15, COMS-1*
SST data from other sources such as GHRSST
Naval Oceanography Data Decision Superiority 4
Approved for Public Release, Distribution Unlimited
Introduction
SST from VIIRS at NAVOCEANO
Preparation before availability of VIIRS data
MODIS (AQUA) Proxy-VIIRS with “movicon” software then from GRAVITE
VIIRS data from S-NPP since January 2012, 2 sources:
GRAVITE (testing) IDPS at AFWA (operational)
Naval Oceanography Data Decision Superiority 5
Approved for Public Release, Distribution Unlimited
SUOMI NPP VIIRS PROCESSING
1,012 VIIRS granules each day received in near real time
Granules are processed individually
Process relies on M5 (0.67μm), M7 (0.87μm), M12 (3.7μm), M15 (10.7μm), and M16 (12.0μm) bands
SST retrievals are produced from cloud-screened 2x2 pixel unit arrays, 1.5 km spatial resolution.
Cloud tests for daytime and nighttime are listed in the next 2 slides.
Naval Oceanography Data Decision Superiority 6
Approved for Public Release, Distribution Unlimited
SUOMI NPP VIIRS PROCESSINGDaytime cloud tests
M7 Uniformity (max(REF)-min(REF)) ≤ 0.04
M15 Uniformity (max(RAD)-min(RAD)) ≤ 0.05
M16 Uniformity (max(RAD)-min(RAD)) ≤ 0.05
M7 Gross Cloud max(REF) ≤ 18%
M15 Gross Cloud 270K ≤ min(BT) & max(BT) ≤ 310K
M16 Gross Cloud 268K ≤ min(BT) & max(BT) ≤ 310K
Reflected Ratio (avg(REF7)/avg(REF5)) ≤ .7
Visible Cloud Threshold avg(REF7) ≤ Threshold f(solz,satz,relaz)
M15 minus M16 0≤ avg(BT15)-avg(BT16) ≤ Threshold f(BT15)
Unreasonable SST -2 ≤ SST ≤ 35
SST Inter-comparison |NLSST-MCSST| ≤ 1.5
Climatology |SST-CLIM| ≤ 10
Naval Oceanography Data Decision Superiority 7
Approved for Public Release, Distribution Unlimited
SUOMI NPP VIIRS PROCESSINGNighttime cloud tests
M15 Uniformity (max(RAD)-min(RAD)) ≤ 0.05M16 Uniformity (max(RAD)-min(RAD)) ≤ 0.05M12 Gross Cloud 268K ≤ min(BT) & max(BT) ≤ 310KM15 Gross Cloud 270K ≤ min(BT) & max(BT) ≤ 310KM16 Gross Cloud 268K ≤ min(BT) & max(BT) ≤ 310KCirrus (MBT12avg-MBT16avg)/MBT16avg ≤ f(MBT15)Low Stratus (MBT16avg-MBT12avg) ≤ 0KM15 minus M16 0≤ (avg(BT15)-avg(BT16)) ≤ f(BT15)SST Inter-comparison comparing results of various SST equationsUnreasonable SST (-2 ≤ SST ≤ 35)Climatology |SST-CLIM| ≤ 10FLD |SST-((2*FLD+CLIM)/3))| < 2.5Aerosol SST-FLD ≥ -1 & MCSST(12,15)-NLSST(15,16) ≤ .9SST Delta |SST-First_SST| ≤ .6 in 10x6 pixel-window
Naval Oceanography Data Decision Superiority 8
Approved for Public Release, Distribution Unlimited
SST Calculations
MCSST and NLSST equations are the basis for SST calculations at NAVOCEANO.
Coefficients of equations are determined by linear regression against drifting buoy measurements.
Naval Oceanography Data Decision Superiority 9
Approved for Public Release, Distribution Unlimited
SST Calculations
Disregarding the angle correction, the 2-channel split-window equation can be expressed [5] as
(1)
with,
(2)
When γ is assumed constant, eq. 1 is the MCSST [6] form
(3)
Naval Oceanography Data Decision Superiority 10
Approved for Public Release, Distribution Unlimited
SST Calculations
However in [7], γ was found to be correlated with the surface temperature field.
In particular for the 2-channel split-window equation
(4)
is a reasonable approximation.
This leads to the standard NLSST [7] form
(5)
Naval Oceanography Data Decision Superiority 11
Approved for Public Release, Distribution Unlimited
SST Calculations
Switch from Celsius to Kelvin for Tfield
shows the dependence of
NLSST equation on temperature unit / implicit offset
Suggests (6)
Varying offset while fitting data shows effect on accuracy
Naval Oceanography Data Decision Superiority 12
Approved for Public Release, Distribution Unlimited
SST Calculations
Taking into account (6) in eq. (1) and bringing back the correction term for the view angle lead to the expanded NLSST
form of the split-window equation
(7)
Finally, (6) is rewritten in a form more appropriate to estimate the equation coefficients
(8)
Naval Oceanography Data Decision Superiority 13
Approved for Public Release, Distribution Unlimited
SST Calculations
At night, NAVOCEANO uses a triple-window equation which can be modified like the daytime equation to explicitly show
the offset
(9)
Again, (9) is rewritten in a form more appropriate to estimate the equation coefficients
(10)
Naval Oceanography Data Decision Superiority 14
Approved for Public Release, Distribution Unlimited
SST Calculations
Varying the value of the offset in (9) while fitting data shows effect on accuracy. The RMS error for the standard NLSST equation is shown for an offset of 0 C while that for the MCSST equation is ⁰shown when the offset tends toward infinity.
Naval Oceanography Data Decision Superiority 15
Approved for Public Release, Distribution Unlimited
Evaluation
NAVOCEANO evaluates all satellite-derived SST data by matching them to drifting buoys
Criteria for matching:25 km maximum distance
4h maximum time separationCriteria for matching:
25 km maximum distance
4h maximum time separation
3 categories:
Confidently clear
Probably clear
Probably cloud contaminated
Statistics based on 1 month of data
Naval Oceanography Data Decision Superiority 16
Approved for Public Release, Distribution Unlimited
Evaluation
March 20, 2013 daytime reliability statistics S-NPP VIIRS SST matches RMS error Bias
Confidently clear 15,868 0.44 0.02
Probably clear 2,917 0.77 0.07
Probably cloud cont. 375 1.69 -0.46
MetOp-A FRAC SST matches RMS error Bias
Confidently clear 18,412 0.46 -0.14
Probably clear 658 0.99 -0.38
Probably cloud cont. 86 2.49 -1.98
IDPS EDR SST matches RMS error Bias
High 5,621 0.42 0.03
Degraded 18,185 0.77 -0.24
Excluded 28,270 1.78 -1.30
RMS errors similar for all categories/products
IDPS EDR restrictive for best category
Naval Oceanography Data Decision Superiority 17
Approved for Public Release, Distribution Unlimited
Evaluation
March 20, 2013 nighttime reliability statistics
RMS errors similar for all categories/products lower than daytime
MetOp-A less restrictive, IDPS EDR more restrictive for best category
S-NPP VIIRS SST matches RMS error Bias
Confidently clear 18,284 0.36 -0.03
Probably clear 2,917 0.81 -.016
Probably cloud cont. 87 2.35 -1.94
MetOp-A FRAC SST matches RMS error Bias
Confidently clear 25,397 0.45 -0.17
Probably clear 299 1.19 -0.86
Probably cloud cont. 41 2.14 -1.45
IDPS EDR SST matches RMS error Bias
High 6,882 0.31 -0.08
Degraded 17,320 0.48 -0.18
Excluded 28,738 2.02 -1.68
Naval Oceanography Data Decision Superiority 18
Approved for Public Release, Distribution Unlimited
Conclusion
After a year of testing the performance, NAVOCEANO VIIRS SST was found to be similar to other NAVOCEANO operational
products and suitable to be ingested by the Navy ocean models.
S-NPP VIIRS SST at NAVOCEANO was declared operational at the end of January 2013.
Expanded NLSST removes dependence on temperature unit that affects the accuracy of the standard NLSST and allows
selection of optimal offset rather than implicit offset.
Naval Oceanography Data Decision Superiority 19
Approved for Public Release, Distribution Unlimited
References
[1] Hurlburt, H.E., Brassington, G.B., Drillet, Y., Kamichi, M., Benkiran, M., Bourdalle-Badie, R., Chassignet, E.P., Jacobs, G.A., Le Galloudec, O., Lellouche, J.-M., Metzger, E.J., Oke, P.R., Pugh, T.F., Schiller, A., Smedstad, O.M., Tranchant, B., Tsuino, H., Usui, N., and Wallcraft, A.J., High-Resolution Global and Basin-Scale Ocean Analyses and Forecasts, Oceanography, 22(3), 110-127 (2009).
[2] Vogel, R.L., Privette, J.L., and Yu, Y., “Creating Proxy VIIRS Data from MODIS: Spectral Transformations for Mid- and Thermal-Infrared Bands,” IEEE Trans. Geosci. Remote Sens., 46(11), 3768-3782 (2008).
[3] McKenzie, B., May, D, Cayula, J.-F., and Willis, K., "Initial results of NPP VIIRS SST processing at NAVOCEANO," Proc. SPIE 8372, Ocean Sensing and Monitoring IV, 83720H (June 11, 2012); doi:10.1117/12.922955; http://dx.doi.org/10.1117/12.922955 [4] Heckmann, G., Grant, K.D., and Mulligan, J.E., Key Features of the Deployed NPP/NPOESS Ground System, Abstract # IN43A-1378 presented at 2010 Fall Meeting, AGU, San Francisco, CA (2010).
[5] McMillin, L,. and Crosby, D., Theory and validation of the multiple window sea surface temperature technique, J. Geophys. Res., 89, 3655-3661 (1984).
[6] McClain, E.P., Pichel, W., and Walton, C., Comparative performance of AVHRR-based multichannel sea surface temperatures, J. Geophys. Res., 90, 11,587-11,601 (1985).
[7] Walton, C., Pichel, W., Sapper, J., and May, D., The Development and Operational Application of Nonlinear Algorithms for the Measurement of Sea Surface Temperatures with the NOAA Polar-Orbiting Environmental Satellites, J. Geophys. Res., 103(12), 27,999-28,012 (1998).
[8] Cayula, J.-F., May, D., McKenzie, B, Olszewski, D., and Willis, K, Reliability Estimates for Real-Time Sea Surface Temperature, Sea Technology, 45(2), 67-73 (2004).