MERIS Ocean Color Reprocessing 2022.0

Introduction

Reprocessing 2022.0 is a multi-mission reprocessing to incorporate updates in instrument calibration, vicarious calibration, new ancillary sources and algorithm improvements. The affected missions are CZCS, SeaWiFS, OCTS, MERIS, MODIS on Aqua and Terra, VIIRS on SNPP and NOAA-20, OLCI on Sentinel-3A and Sentinel-3B, GOCI, and HICO. Here we describe the changes and results specific to MERIS.

Instrument Calibration

The MERIS data are now based on ESA's 4th reprocessing .

Product Formats

As this is the first reprocessing of MERIS since R2012.0, the file formats and product suites for MERIS will now be brought into alignment with those employed in the R2014.0 multi-mission reprocessing.
This brings the MERIS L2 and L3 data formats consistent with the other supported missions.

Results

Time Series Comparison

Influences of the reprocessing on time series of chlorophyll concentration (Chla) and remote sensing reflectance (Rrs) were analyzed by comparing MERIS R2022 to R2012 (Figure 1) and SeaWiFS R2022 data (Figure 2) for global deep water (>1000m). The differences between MERIS R2022 and R2012 are shown in time series (left panel) and their ratios (right panel). In general, Chla and Rrs from MERIS R2022 showed high consistency with those from SeaWiFS R2022 (ratios around 1). Rrs(560) and Rrs(665) have relatively low values compared to other bands, and are more sensitive to different noises, thus showed higher differences.

Deep water time series comparisons of MERIS to SeaWiFS for R2022 — Figure 1: Global deepwater time series comparisons of MERIS to SeaWiFS, R2022

Comparison with In Situ Measurements

Validation of the chlorophyll, apparent optical properties (Rrs, Kd490), inherent optical properties (a_giop, aph_giop, adg_giop, bbp_giop), PAR, PIC, and POC retrievals was performed relative to all available match-ups from SeaBASS and the Aerosol Robotic Network - Ocean Color (AERONET-OC). Statistical analysis, scatter plots and frequency distribution comparisons of the satellite to in situ match-ups are provided below.

Chlorophyll a (chlor_a)

^* statistical calculations based on log10 (implies ignoring values equal to or less than zero)
Product Name	MERIS Range	In situ Range	#	Mean Bias	Mean Absolute Error (MAE)
chlor_a	717	1.48986^*	1.89465^*	0.01300, 858.28147	0.01700, 46.64000

Apparent Optical Properties

Remote Sensing Reflectance (Rrs)

Product Name	#	Mean Bias	Mean Absolute Error (MAE)	MERIS Range	In situ Range
Rrs413	1222	0.00026	0.00128	-0.00217, 0.01551	-0.00000, 0.01555
Rrs443	1349	0.00001	0.00108	-0.00059, 0.03309	0.00026, 0.01557
Rrs490	1165	-0.00040	0.00107	0.00032, 0.03268	0.00078, 0.02442
Rrs510	328	-0.00029	0.00072	0.00084, 0.02594	0.00119, 0.02538
Rrs560	235	-0.00018	0.00067	0.00096, 0.02829	0.00095, 0.02862
Rrs665	1045	-0.00010	0.00034	-0.00025, 0.01179	0.00003, 0.01078
Rrs681	260	-0.00013	0.00035	-0.00045, 0.01084	0.00005, 0.01075

Diffuse Attenuation Coefficients (kd490)

^* statistical calculations based on log10 (implies ignoring values equal to or less than zero)
Product Name	#	Mean Bias	Mean Absolute Error (MAE)	MERIS Range	In situ Range
kd490	229	1.03730^*	1.33034^*	0.02204, 0.82807	0.01190, 3.88735

Inherent Optical Properties

Total Absorption Coefficients (a_giop)

^* statistical calculations based on log10 (implies ignoring values equal to or less than zero)
Product Name	#	Mean Bias	Mean Absolute Error (MAE)	MERIS Range	In situ Range
a_giop413	25	0.72762^*	1.73617^*	0.01599, 0.62617	0.02474, 0.95427
a_giop443	25	0.76703^*	1.48313^*	0.01644, 0.39944	0.02039, 0.68512
a_giop490	25	0.74939^*	1.38455^*	0.02033, 0.25764	0.02148, 0.38107
a_giop510	25	0.79854^*	1.29349^*	0.03550, 0.21361	0.03721, 0.30252
a_giop560	25	0.88565^*	1.15405^*	0.06290, 0.14715	0.06415, 0.19487
a_giop665	25	0.99364^*	1.04291^*	0.34893, 0.58468	0.43053, 0.51604

Phytoplankton Absorption Coefficients (aph_giop)

^* statistical calculations based on log10 (implies ignoring values equal to or less than zero)
Product Name	#	Mean Bias	Mean Absolute Error (MAE)	MERIS Range	In situ Range
aph_giop413	30	1.11421^*	1.64520^*	0.00264, 0.26804	0.00141, 0.17281
aph_giop443	30	1.14503^*	1.64879^*	0.00394, 0.30013	0.00193, 0.18974
aph_giop490	30	1.19887^*	1.63031^*	0.00277, 0.20280	0.00102, 0.11532
aph_giop510	30	1.18637^*	1.65676^*	0.00128, 0.15343	0.00055, 0.08476
aph_giop560	30	1.62950^*	2.23103^*	0.00020, 0.07756	0.00002, 0.04263
aph_giop665	30	1.35185^*	1.75562^*	0.00080, 0.15785	0.00038, 0.07247

Absorption Coefficient of Non-algal Material plus CDOM (adg_giop)

^* statistical calculations based on log10 (implies ignoring values equal to or less than zero)
Product Name	#	Mean Bias	Mean Absolute Error (MAE)	MERIS Range	In situ Range
adg_giop413	24	0.50934^*	2.77703^*	0.00160, 0.79563	0.01868, 0.77681
adg_giop443	24	0.46445^*	3.01686^*	0.00093, 0.46364	0.01140, 0.48832
adg_giop490	24	0.37496^*	3.60127^*	0.00040, 0.19897	0.00507, 0.25096
adg_giop510	24	0.34850^*	3.82019^*	0.00029, 0.13881	0.00334, 0.18523
adg_giop560	24	0.27528^*	4.58815^*	0.00007, 0.05644	0.00138, 0.09013
adg_giop665	24	0.19952^*	5.51382^*	0.00010, 0.00853	0.00033, 0.02001

backscattering coefficient of particles (bbp_giop)

^* statistical calculations based on log10 (implies ignoring values equal to or less than zero)
Product Name	#	Mean Bias	Mean Absolute Error (MAE)	MERIS Range	In situ Range
bbp_giop413	43	0.93414^*	1.36488^*	0.00038, 0.01075	0.00067, 0.01028
bbp_giop443	43	0.92384^*	1.35468^*	0.00036, 0.01025	0.00058, 0.00990
bbp_giop490	43	0.89977^*	1.34889^*	0.00034, 0.00956	0.00047, 0.00942
bbp_giop510	43	0.89324^*	1.34904^*	0.00032, 0.00930	0.00044, 0.00922
bbp_giop560	43	0.87145^*	1.35363^*	0.00027, 0.00868	0.00036, 0.00880
bbp_giop665	43	0.83531^*	1.40285^*	0.00020, 0.00771	0.00026, 0.00807
bbp_giop681	2	0.71190^*	1.40469^*	0.00133, 0.00137	0.00186, 0.00194