Appendix A: SMAP SSS L2 Attributes, Gridding & Dimensions

RSS (V4) JPL (4.3)
orbit_number Orbit (rev) # REVNO SMAP orbit number
start_time_sec2000 Seconds of first valid record in this rev since 2000-01-01 00:00:00 UTC REV_START_TIME Orbit start UTC time string
end_time_sec2000 Seconds of last valid record in this rev since 2000-01-01 00:00:00 UTC REV_STOP_TIME Orbit stop UTC time string
emissivity_reflector_vpol, emissivity_reflector_hpol Correction for Emissive SMAP Antenna in V-pol and H-pol, respectively (See "Correction for Emissive SMAP Antenna" in User Guide) Use SMAP Project correction
A_ij Antenna Pattern Correction matrix element where the indices i,j run over the Stokes vector I, Q, SE, S4 Use SMAP Project correction
ta_ocean_ave_vpol, ta_ocean_ave_hpol Average antenna temperature (TA) over the open ocean (See "Ocean Target Calibration" in User Guide) Use SMAP Project correction
ta_bias_ocean_vpol, ta_bias_ocean_hpol, ta_bias_ocean_S3, ta_bias_ocean_S4 Antenna temperature biases; TAmeasured minus TAexpecteds over the open ocean for V-Pol, H-Pol, 3rd Stokes, and 4th Stokes parameters, respectively [HYCOM] [TEC] Use SMAP Project correction
xdim_grid Longitude optimum interpolated onto a fixed 0.25°x0.25° Earth grid; 360° plus 30° to accommodate the whole swath (n=1560) nati Number of along-track grid cells (n=1624) (See "Swath Grid Generation" in User Guide)
ydim_grid Latitude optimum interpolated onto a fixed 0.25°x0.25° Earth grid (n=720) ncti Number of cross-track grid cells (n=76) (See “Swath Grid Generation” in User Guide)
look 1=for look, 2=aft look n_h_aft, n_h_fore, n_v_aft, n_v_fore Number of Level-1B TB observations averaged into four "flavors" for each SWC (i.e., Aft H-pol, Fore H-pol, Aft V-pol, and Fore V-pol)
polarization_# Specifies the polarization of the variable fields. Note that for some variables the Stokes polarization basis (I, Q, S3, S4) is used nedt_h_aft, nedt_h_fore, nedt_v_aft, nedt_v_fore Aggregated noise equivalent delta TB for the four "flavors" of each SWC (i.e., Aft H-pol, Fore H-pol, Aft V-pol, and Fore V-pol)

Appendix B: SMAP SSS L2 Variables

RSS (V4) JPL (4.3)
time Seconds of observation since 2000-01-01 00:00:00 UTC row_time Approximate observation time for each SWC row as UTC seconds since 2015-01-01 0000 UTC
cellat Geodetic latitude of grid cell lat Average latitude of all TB observations for each SWC
cellon Longitude of grid cell lon Average longitude of all TB observations for each SWC
eia Boresight Earth incidence angle inc_aft, inc_fore Average cell incidence angle of all aft and fore observations for each SWC, respectively {Q2}.
eaa Boresight Earth azimuth angle azi_aft, azi_fore Average cell azimuth angle (clockwise relative North) of all aft and fore observations included for each SWC, respectively.
zang Orbital position of spacecraft Use SMAP Project correction
alpha Scan angle Use SMAP Project correction
pra Polarization basis rotation angle, which is the angle between polarization basis of the spacecraft and polarization on the Earth Use SMAP Project correction
sunglt Sun glint angle {Q5} Use SMAP Project correction
monglt Moon glint angle {Q6} Use SMAP Project correction
gallat Polar angle of specular reflection ray from boresight Use SMAP Project correction
gallon Azimuthal angle of specular reflection from boresight Use SMAP Project correction
sun-beta Sun azimuth angle in spacecraft coordinate system Use SMAP Project correction
sun_alpha Sun azimuth angle in spacecraft coordinate system Use SMAP Project correction
gland Land fraction weighted by antenna gain pattern [ODPS] {Q2} {Q8} {Q13} N/A
fland Land fraction within footprint [ODPS] {Q2} {Q8} land_fraction_aft, land_fraction_fore Average land fraction of all aft and fore TB observations included in salinity/wind processing for each SWC, respectively {Q7}
fice Sea ice fraction within footprint [RSS] {Q3} ice_concentration The ice concentration, averaged to approximately the SMAP resolution, for this SWC
surtep Ancillary SST [CMC] {Q11} anc_sst Ancillary SST collocated to each SWC at the approximate time of SMAP observations [OI] {Q6}
winspd Ancillary sea surface wind speed [CCMP] {Q12} anc_spd Ancillary wind speed multiplied by 1.03, collocated for each SWC at the approximate time of SMAP observations [GFS] {Q5}
windir Ancillary wind direction [CCMP] anc_dir Ancillary wind direction collocated to each SWC at the approximate time of the SMAP observations [GFS]
N/A anc_swh Ancillary significant wave height collocated to each SWC at the approximate time of the SMAP observations [WaveWatch III]
tran Total atmospheric transmittance [GDAS] Use SMAP Project correction
tbup Atmospheric upwelling TB [GDAS] Use SMAP Project correction
tbdw Atmospheric downwelling TB [GDAS] Use SMAP Project correction
rain Rain rate resampled to SMAP spatial resolutions (i.e., 40 km, 70 km) [IMERG] {Q15} Use SMAP Project correction
solar_flux Ancillary mean solar flux [SWPC] Use SMAP Project correction
1ta_ant_filtered SMAP RFI filtered TA (this is the basic input from SMAP L1B TB files) Use SMAP Project correction
ta_ant_unfiltered SMAP unfiltered TA Use SMAP Project correction
2ta_ant_ calibrated SMAP TA after correcting for the emissive antenna and after applying the Ocean Target Calibration Use SMAP Project correction
3ta_earth SMAP TA after correcting for celestial intrusions, cold space (spillover), galaxy (direct and reflected), sun (direct and reflected), moon (reflected) Use SMAP Project correction
4tb_toi SMAP top-of-the-ionosphere TB Use SMAP Project correction
5tb_toa SMAP top-of-the-atmosphere TB before applying land correction Use SMAP Project correction
6tb_toa_lc SMAP top-of-the-atmosphere TB after applying land correction Use SMAP Project correction
ta_lnd SMAP sidelobe correction for land intrusion Use SMAP Project correction
7tb_sur SMAP TB at rough ocean surface before applying roughness correction [CCMP] Use SMAP Project correction
8tb_sur0 SMAP TB at flat ocean surface after applying roughness correction [CCMP] Use SMAP Project correction
N/A tb_h_aft, tb_h_fore, tb_v_aft, tb_v_fore Aggregated TB for the four "flavors" of each SWC (i.e., Aft H-pol, Fore H-pol, Aft V-pol, and Fore V-pol)
N/A tb_h_bias_adj, tb_v bias_adj TB bias adjustment for each SWC (H-pol, V-pol)
temp_ant Physical temperature of the SMAP mesh antenna from JPL thermal model Use SMAP Project correction
dtemp_ant Empirical correction to the physical temperature of the SMAP mesh antenna Use SMAP Project correction
ta_sun_dir TA of direct sun intrusion Use SMAP Project correction
ta_sun_ref TA of reflected sun intrusion Use SMAP Project correction
ta_gal_dir TA of direct galaxy intrusion Use SMAP Project correction
ta_gal_ref TA of reflected galaxy intrusion {Q7} Use SMAP Project correction
9sss_smap SMAP sea surface salinity smoothed to ~70km resolution. This is the standard/default product for science applications. smap_sss SMAP-retrieved sea surface salinity using the combined SSS/WSPD retrieval algorithm
N/A Note that RSS includes uncertainty data in its L3 product. smap_sss_uncertainty Predicted SMAP SSS uncertainty obtained by computing the full width at half maximum from objective function around the retrieved SSS and WSPD values
sss_smap_40km SMAP sea surface salinity at original 40-km resolution N/A
tb_consistency Maximum likelihood estimation (MLE) in SSS retrieval algorithm {Q10} N/A
N/A smap_spd SMAP-retrieved wind speed using the combined SSS/WSPD retrieval algorithm
N/A smap_high_spd SMAP retrieved wind speed using an algorithm that presumes the ancillary SSS; allows for higher wind speed retrievals in regions where the ancillary WSPD may not capture the high wind speeds (i.e., tropical storms) {Q9}
N/A smap_high_dir, smap_high_dir_smooth SMAP retrieved wind direction using an algorithm that presumes the ancillary SSS and with smoothing, respectively
N/A smap_ambiguity_spd, smap_ambiguity_dir Contains up to 4 wind speed and duration ambiguities obtained in the SMAP high wind algorithm that presumes the ancillary SSS
N/A num_ambiguties Number of ambiguity wind vectors obtain in SMAP high winds algorithm
iqc_flag 32-bit quality control flag (See Quality Flags) quality_flag Quality flag for that particular SWC (See Quality Flags)
sss_ref Ancillary reference sea surface salinity [HYCOM] anc_sss Ancillary SSS collocated for each SWC at the approximate time of the SMAP observations [HYCOM]
ta_ant_exp TA expected before any losses; to be compared with 2ta_ant_calibrated [HYCOM] N/A
tb_sur0_exp Expected flat surface TB; to be compared with 8tb_sur0 [HYCOM] N/A
pratot_exp Expected total polarization rotation angle = geometric part + Faraday rotation [TEC] N/A

Appendix C: SMAP SSS L3 Variables

RSS (V4) JPL (4.3)
nobs Number of L2C observations that are averaged into L3 grid cell weight Sum of the Gaussian weights used in each map grid cell
sss_smap SMAP sea surface salinity smoothed to ~70km resolution.This is the standard/default product for science applications. smap_sss SMAP SSS from L2B data files, gridded onto a map and filtered for quality
sss_smap_uncertainty [Available for L3 only] Estimated empirical root-mean square uncertainty of SMAP sea surface salinity smoothed to ~70 km smap_sss_uncertainty[Also available for L2] Predicted SMAP SSS uncertainty, propagated from L2B values assuming some correlation betweenadjacent L2B SWCs
sss_smap_40km SMAP sea surface salinity at original 40-km resolution N/A
N/A smap_spd SMAP wind speed from L2B data files, gridded onto a map and filtered for quality
N/A smap_high_spd SMAP high wind speed from L2B data files, gridded onto a map and filtered for quality {Q9}
sss_ref Ancillary reference sea surface salinity [HYCOM] anc_sss Ancillary SSS from the L2B data files, gridded onto a map and filtered for quality [HYCOM]
gland Average land fraction weighted by antenna gain [ODPS] {Q2} {Q8} {Q13} N/A
fland Average land fraction within 3-dB contour [ODPS] {Q2} {Q8} land_fraction Weighted average land fraction from the L2B observations used in that map grid cell [USGS] {Q7}
gice Average sea ice fraction weighted by antenna gain pattern [RSS] {Q3} {Q9} {Q14} ice_concentration Ice concentration from L2B data files, gridded onto a map and filtered for quality [NCEP] {Q8}
surtep Ancillary SST [CMC] {Q11} anc_sst Ancillary SST from the L2B data files, gridded onto a map and filtered for quality [NOAA Optimum Interpolation] {Q6}
sss_argo[Rain-Filtered (RF) monthly L3 product only] Argo Scripps sea surface salinity [SIO] N/A

Appendix D: SMAP SSS Quality Flags

Associated data fields are noted at right
RSS (V4) JPL (4.3)
Q0 - No valid radiometer observation in cell Q0 - Overall SSS quality good
Q1 - Problem with OI Q1 - Data from all four looks available
Q2 - Strong land contamination gland, fland Q2 - Nominal pointing, incidence angles within 0.2° of 40° inc_aft, inc_fore
Q3 - Strong sea ice contamination gice, fice Q4 - Galaxy corrections for all TB flavors <5 K
Q4 - MLE is SSS retrieval algorithm has not converged tb_consistency Q5 - Roughness correction based on ancillary wind speed >20 m/s anc_spd
Q5 - Sunglint sunglt Q6 - SST too cold (<5° C) anc_sst
Q6 - Moonglint monglt Q7 - Land detected in SWC land_fraction_aft, land_fraction_fore
Q7 - High reflected galaxy ta_gal_ref Q8 - Ice detected in SWC ice_concentration
Q8 - Moderate land contamination gland, fland Q9 - Overall high speed quality smap_high_speed
Q9 - Moderate sea ice contamination gice Q3 and Q10 - Q15 Open
Q10 - High residual of MLE in SSS retrieval algorithm tb_consistency
Q11 - Low SST surtep
Q12 - High wind speed winspd
Q13 - Light land contamination gland
Q14 - Light sea ice contamination gice
Q15 - Rain flag rain
Q16-Q31 Open
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