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Description

The SWOT Level 2 KaRIn Low Rate Sea Surface Height Expert Data Product from the Surface Water Ocean Topography (SWOT) mission provides global sea surface height and significant wave height observations derived from low rate (LR) measurements from the Ka-band Radar Interferometer (KaRIn). SWOT launched on December 16, 2022 from Vandenberg Air Force Base in California into a 1-day repeat orbit for the "calibration" or "fast-sampling" phase of the mission, which completed in early July 2023. After the calibration phase, SWOT entered a 21-day repeat orbit in August 2023 to start the "science" phase of the mission, which is expected to continue through 2025. <br>
The L2 sea surface height data product is distributed in one netCDF-4 file per pass (half-orbit) covering the full KaRIn swath width, which spans 10-60km on each side of the nadir track. Sea surface height, sea surface height anomaly, wind speed, significant waveheight, and related parameters are provided on a geographically fixed, swath-aligned 2x2 km2 grid (Basic, Expert, Windwave). The sea surface height data are also provided on a finer 250x250 m2 "native" grid with minimal smoothing applied (Unsmoothed). <br>
This collection is a sub-collection of its parent: https://podaac.jpl.nasa.gov/dataset/SWOT_L2_LR_SSH_D It provides the "Expert" file from each L2 SSH product, which contain all related variables and is intended for expert users.

Product Summary

Platforms
SWOT
Instruments
KaRIn ,
Jason-class Altimeter ,
AMR ,
DORIS ,
GPSP ,
LRA
Spatial Extent

N: 90 S: -90 E: 180 W: -180

Spatial Resolution
2 Kilometers x 2 Kilometers
250 Meters x 250 Meters
Location
GLOBAL
Coordinate System
CARTESIAN
Granule Spatial Representation
GEODETIC
Temporal Extent
2022-12-16
Data Partner
Jet Propulsion Laboratory, NASA (NASA/JPL) ,
Physical Oceanography Distributed Active Archive Center, Jet Propulsion Laboratory, NASA (NASA/JPL/PODAAC)
Concept ID
C3233942272-POCLOUD
Data State
ACTIVE
Number of Files/Granules
30212
Processing Level
2
Published
Updated
Science Keywords
Sea Surface Height ,
Significant Wave Height

Citation

Citation is critically important for dataset documentation and discovery. This dataset is openly shared, without restriction, in accordance with the EOSDIS Data Use and Citation Guidance.

Copy Citation

SWOT. (2025). SWOT Level 2 KaRIn Low Rate Sea Surface Height Data Product [Data set]. NASA Physical Oceanography Distributed Active Archive Center. https://doi.org/10.5067/SWOT-SSH-D Date Accessed: 2026-05-15

Documents

Variables

The table below lists the variables contained within a single granule for this dataset. Variables often contain observed or derived geophysical measurements collected from a variety of sources, including remote sensing instruments on satellite and airborne platforms, field campaigns, in situ measurements, and model outputs. The terms variable, parameter, scientific data set, layer, and band have been used across NASA’s Earth science disciplines; however, variable is the designated nomenclature in NASA’s Common Metadata Repository (CMR). Variable metadata attributes such as Name, Description, Units, Data Type, Fill Value, Valid Range, and Scale Factor allow users to efficiently process and analyze the data. The full range of attributes may not be applicable to all variables. Additional information on variable attributes is typically available in the data, user guide, and/or other product documentation.

For questions on a specific variable, please use the Earthdata Forum.

Name Description Units Data Type Fill Value Valid Range Scale Factor Offset
rad_tmb_340 Main beam brightness temperature measurement at 34.0 GHz. Value is unsmoothed (along-track averaging has not been performed). K short 32767 15000 to 28000 0.01 N/A
rad_water_vapor Integrated water vapor content from radiometer measurements. kg/m^2 short 32767 0 to 15000 0.01 N/A
rad_wet_tropo_cor Equivalent vertical correction due to wet troposphere delay from radiometer measurements. The reported pixel height, latitude and longitude are computed after adding negative media corrections to uncorrected range along slant-range paths, accounting for the differential delay between the two KaRIn antennas. The equivalent vertical correction is computed by applying obliquity factors to the slant-path correction. Adding the reported correction to the reported sea surface height (ssh_karin) results in the uncorrected sea surface height. m short 32767 -10000 0 0.0001 N/A
rain_flag Flag indicates that signal is attenuated, probably from rain. N/A ubyte 255 0 to 3 1 N/A
rain_rate Rain rate from weather model. mm/hr ubyte 255 0 to 200 1 N/A
sc_altitude Altitude of the KMSF origin. m int 2147483647 0 to 2000000000 0.0001 800000
sc_event_flag Flag indicating spacecraft events that may affect the characteristics of the KaRIn data. The spacecraft is in a nominal state when all bits equal 0. The KaRIn measurement may be affected by a spacecraft event when any of bits 0 to 5 are equal to 1. The KaRIn measurement is likely bad when bits 6 or 7 are equal to 1. N/A ubyte 255 0 to 255 1 N/A
sc_pitch KMSF attitude pitch angle; positive values move the KMSF +x axis up. degrees int 2147483647 -1799999 to 1800000 0.0001 N/A
sc_roll KMSF attitude roll angle; positive values move the +y antenna down. degrees int 2147483647 -1799999 to 1800000 0.0001 N/A
sc_yaw KMSF attitude yaw angle relative to the nadir track. The yaw angle is a right-handed rotation about the nadir (downward) direction. A yaw value of 0 deg indicates that the KMSF +x axis is aligned with the horizontal component of the Earth-relative velocity vector. A yaw value of 180 deg indicates that the spacecraft is in a yaw-flipped state, with the KMSF -x axis aligned with the horizontal component of the Earth-relative velocity vector. degrees int 2147483647 -1799999 to 1800000 0.0001 N/A
sea_state_bias_cor Sea state bias correction used to compute ssh_karin. Adding the reported correction to the reported sea surface height results in the uncorrected sea surface height. The wind_speed_karin value is used to compute this quantity. m short 32767 -6000 0 0.0001 N/A
sea_state_bias_cor_2 Sea state bias correction used to compute ssh_karin_2. Adding the reported correction to the reported sea surface height results in the uncorrected sea surface height. The wind_speed_karin_2 value is used to compute this quantity. m short 32767 -6000 0 0.0001 N/A
sig0_cor_atmos_model Atmospheric correction to sigma0 from weather model data as a linear power multiplier (not decibels). sig0_cor_atmos_model is already applied in computing sig0_karin_2. 1 float 9.96921E+36 1 to 10 1 N/A
sig0_cor_atmos_rad Atmospheric correction to sigma0 from radiometer data as a linear power multiplier (not decibels). sig0_cor_atmos_rad is already applied in computing sig0_karin. 1 float 9.96921E+36 1 to 10 1 N/A
sig0_karin Normalized radar cross section (sigma0) from KaRIn in real, linear units (not decibels). The value may be negative due to noise subtraction. The value is corrected for instrument calibration and atmospheric attenuation. Radiometer measurements provide the atmospheric attenuation (sig0_cor_atmos_rad). 1 float 9.96921E+36 -1000 to 10000000 1 N/A
sig0_karin_2 Normalized radar cross section (sigma0) from KaRIn in real, linear units (not decibels). The value may be negative due to noise subtraction. The value is corrected for instrument calibration and atmospheric attenuation. A meteorological model provides the atmospheric attenuation (sig0_cor_atmos_model). 1 float 9.96921E+36 -1000 to 10000000 1 N/A
sig0_karin_2_qual Quality flag for sigma0 from KaRIn in sig0_karin_2 variable. N/A uint 4294967295 0 to 3809427359 1 N/A
sig0_karin_qual Quality flag for sigma0 from KaRIn in sig0_karin_qual variable. N/A uint 4294967295 0 to 4077862815 1 N/A
sig0_karin_uncert 1-sigma uncertainty on sigma0 from KaRIn. 1 float 9.96921E+36 0 to 1000 1 N/A
solid_earth_tide Solid-Earth (body) tide height. The zero-frequency permanent tide component is not included. m short 32767 -10000 to 10000 0.0001 N/A
ssha_karin Sea surface height anomaly from the KaRIn measurement = ssh_karin - mean_sea_surface_cnescls - solid_earth_tide - ocean_tide_fes – ocean_tide_non_eq – internal_tide_hret - pole_tide - dac. m int 2147483647 -15000000 to 150000000 0.0001 N/A
ssha_karin_2 Sea surface height anomaly from the KaRIn measurement = ssh_karin_2 - mean_sea_surface_cnescls - solid_earth_tide - ocean_tide_fes – ocean_tide_non_eq – internal_tide_hret - pole_tide - dac. m int 2147483647 -15000000 to 150000000 0.0001 N/A
ssha_karin_2_qual Quality flag for the SSHA from KaRIn in the ssha_karin_2 variable N/A uint 4294967295 0 to 3876569055 1 N/A
ssha_karin_qual Quality flag for the SSHA from KaRIn in the ssha_karin variable. N/A uint 4294967295 0 to 4279222239 1 N/A
ssh_karin Fully corrected sea surface height measured by KaRIn. The height is relative to the reference ellipsoid defined in the global attributes. This value is computed using radiometer measurements for wet troposphere effects on the KaRIn measurement (e.g., rad_wet_tropo_cor and sea_state_bias_cor). m int 2147483647 -15000000 to 150000000 0.0001 N/A
ssh_karin_2 Fully corrected sea surface height measured by KaRIn. The height is relative to the reference ellipsoid defined in the global attributes. This value is computed using model-based estimates for wet troposphere effects on the KaRIn measurement (e.g., model_wet_tropo_cor and sea_state_bias_cor_2). m int 2147483647 -15000000 to 150000000 0.0001 N/A
ssh_karin_2_qual Quality flag for sea surface height from KaRIn in ssh_karin_2 variable. N/A uint 4294967295 0 to 3809460191 1 N/A
ssh_karin_qual Quality flag for sea surface height from KaRIn in ssh_karin variable. N/A uint 4294967295 0 to 4212113375 1 N/A
ssh_karin_uncert 1-sigma uncertainty on the sea surface height from the KaRIn measurement. m ushort 65535 0 to 60000 0.0001 N/A
swh_karin Significant wave height from KaRIn volumetric correlation. m ushort 65535 0 to 35000 0.001 N/A
swh_karin_qual Quality flag for significant wave height from KaRIn in swh_karin_qual variable. N/A uint 4294967295 0 to 3809361848 1 N/A
swh_karin_uncert 1-sigma uncertainty on significant wave height from KaRIn. m ushort 65535 0 to 25000 0.001 N/A
swh_model Significant wave height from model. m ushort 65535 0 to 35000 0.001 N/A
swh_nadir_altimeter Significant wave height from nadir altimeter. m ushort 65535 0 to 35000 0.001 N/A
swh_ssb_cor_source Bit flag that indicates the source of significant wave height information that was used to compute the sea state bias correction in sea_state_bias_cor. N/A ubyte 255 0 to 7 1 N/A
swh_ssb_cor_source_2 Bit flag that indicates the source of significant wave height information that was used to compute the sea state bias correction in sea_state_bias_cor_2. N/A ubyte 255 0 to 7 1 N/A
swh_wind_speed_karin_source Bit flag that indicates the source of significant wave height information that was used to compute the wind speed estimate from KaRIn data in wind_speed_karin. N/A ubyte 255 0 to 7 1 N/A
swh_wind_speed_karin_source_2 Bit flag that indicates the source of significant wave height information that was used to compute the wind speed estimate from KaRIn data in wind_speed_karin_2. N/A ubyte 255 0 to 7 1 N/A
time Time of measurement in seconds in the UTC time scale since 1 Jan 2000 00:00:00 UTC. [tai_utc_difference] is the difference between TAI and UTC reference time (seconds) for the first measurement of the data set. If a leap second occurs within the data set, the attribute leap_second is set to the UTC time at which the leap second occurs. seconds since 2000-01-01 00:00:00.0 double N/A N/A 1 N/A
time_tai Time of measurement in seconds in the TAI time scale since 1 Jan 2000 00:00:00 TAI. This time scale contains no leap seconds. The difference (in seconds) with time in UTC is given by the attribute [time:tai_utc_difference]. seconds since 2000-01-01 00:00:00.0 double 9.9692099683869E+36 N/A 1 N/A
velocity_heading Angle with respect to true north of the horizontal component of the spacecraft Earth-relative velocity vector. A value of 90 deg indicates that the spacecraft velocity vector pointed due east. Values between 0 and 90 deg indicate that the velocity vector has a northward component, and values between 90 and 180 deg indicate that the velocity vector has a southward component. degrees int 2147483647 0 to 359999999 1.0E-6 N/A
volumetric_correlation Volumetric correlation. 1 int 2147483647 -100000 to 200000 1.0E-5 N/A
volumetric_correlation_uncert 1-sigma uncertainty computed analytically using observed correlation and effective number of looks. Two-sided error bars (volumetric_correlation-volumetric_correlation_uncert, volumetric_correlation+volumetric_correlation_uncert) include 68% of probability distribution. 1 uint 4294967295 0 to 200000 1.0E-5 N/A
wind_speed_karin Wind speed from KaRIn computed from sig0_karin. m/s ushort 65535 0 to 65000 0.001 N/A
wind_speed_karin_2 Wind speed from KaRIn computed from sig0_karin_2. m/s ushort 65535 0 to 65000 0.001 N/A
wind_speed_karin_2_qual Quality flag for wind speed from KaRIn in wind_speed_karin_2 variable. N/A uint 4294967295 0 to 3809427352 1 N/A
wind_speed_karin_qual Quality flag for wind speed from KaRIn in wind_speed_karin variable. N/A uint 4294967295 0 to 4077862808 1 N/A
wind_speed_model_u Eastward component of the atmospheric model wind vector at 10 meters. m/s short 32767 -30000 to 30000 0.001 N/A
wind_speed_model_v Northward component of the atmospheric model wind vector at 10 meters. m/s short 32767 -30000 to 30000 0.001 N/A
wind_speed_rad Wind speed from radiometer measurements. m/s ushort 65535 0 to 65000 0.001 N/A
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