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Description

The SWOT Level 2 KaRIn Low Rate Sea Surface Height Windwave 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 "Windwave" file from each L2 SSH product, which includes significant wave height (SWH), normalized radar cross section (NRCS or backscatter cross section or sigma0), wind speed derived from sigma0 and SWH, model information on wind and waves, and quality flags.

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<br>250 Meters x 250 Meters
Geographic Region
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
C3233942281-POCLOUD
Data State
ACTIVE
Number of Files/Granules
6334
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: 2025-12-14

Documents

Variables

Variables are a set of physical properties whose values determine the characteristics or behavior of something. For example, temperature and pressure are variables of the atmosphere. Parameters and variables can be used interchangeably. Variable level attributes provide individual information for each variable.

The Name in this table is the variable name. Fill value indicates missing or undefined data points in a variable. Valid range is the range of values the variable can store. Scale factor is used to increase or decrease the size of an object and can be used to correct for distortion. For questions on a specific variable, please use the Earthdata Forum.

Name Description Units Data Type Fill Value Valid Range Scale Factor
ancillary_surface_classification_flag 7-state surface type classification computed from a mask built with MODIS and GlobCover data. N/A ubyte 255 0 to 6 1
distance_to_coast Approximate distance to the nearest coast point along the Earth surface. m short 32767 -21000 to 21000 1000
dynamic_ice_flag Dynamic ice flag for the location of the KaRIn measurement. N/A ubyte 255 0 to 3 1
heading_to_coast Approximate compass heading (0-360 degrees with respect to true north) to the nearest coast point. degrees ushort 65535 0 to 35999 0.01
latitude Latitude of measurement [-80,80]. Positive latitude is North latitude, negative latitude is South latitude. degrees_north int 2147483647 -80000000 to 80000000 1.0E-6
longitude Longitude of measurement. East longitude relative to Greenwich meridian. degrees_east int 2147483647 0 to 359999999 1.0E-6
mean_wave_direction Mean sea surface wave direction. degree ushort 65535 0 to 36000 0.01
mean_wave_period_t02 Sea surface wind wave mean period from model spectral density second moment. s short 32767 0 to 10000 0.01
num_pt_avg Number of native unsmoothed, beam-combined KaRIn samples averaged. 1 ushort 65535 0 to 289 1
polarization_karin H denotes co-polarized linear horizontal, V denotes co-polarized linear vertical. N/A string N/A N/A 1
rad_surface_type_flag Flag indicating the validity and type of processing applied to generate the wet troposphere correction (rad_wet_tropo_cor). A value of 0 indicates that open ocean processing is used, a value of 1 indicates coastal processing, and a value of 2 indicates that rad_wet_tropo_cor is invalid due to land contamination. N/A ubyte 255 0 to 2 1
rain_flag Flag indicates that signal is attenuated, probably from rain. N/A ubyte 255 0 to 3 1
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
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
sig0_karin_2_qual Quality flag for sigma0 from KaRIn in sig0_karin_2 variable. N/A uint 4294967295 0 to 3809427359 1
sig0_karin_qual Quality flag for sigma0 from KaRIn in sig0_karin_qual variable. N/A uint 4294967295 0 to 4077862815 1
sig0_karin_uncert 1-sigma uncertainty on sigma0 from KaRIn. 1 float 9.96921E+36 0 to 1000 1
swh_karin Significant wave height from KaRIn volumetric correlation. m ushort 65535 0 to 35000 0.001
swh_karin_qual Quality flag for significant wave height from KaRIn in swh_karin_qual variable. N/A uint 4294967295 0 to 3809361848 1
swh_karin_uncert 1-sigma uncertainty on significant wave height from KaRIn. m ushort 65535 0 to 25000 0.001
swh_model Significant wave height from model. m ushort 65535 0 to 35000 0.001
swh_nadir_altimeter Significant wave height from nadir altimeter. m ushort 65535 0 to 35000 0.001
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
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
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
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
wind_speed_karin Wind speed from KaRIn computed from sig0_karin. m/s ushort 65535 0 to 65000 0.001
wind_speed_karin_2 Wind speed from KaRIn computed from sig0_karin_2. m/s ushort 65535 0 to 65000 0.001
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
wind_speed_karin_qual Quality flag for wind speed from KaRIn in wind_speed_karin variable. N/A uint 4294967295 0 to 4077862808 1
wind_speed_model_u Eastward component of the atmospheric model wind vector at 10 meters. m/s short 32767 -30000 to 30000 0.001
wind_speed_model_v Northward component of the atmospheric model wind vector at 10 meters. m/s short 32767 -30000 to 30000 0.001
wind_speed_rad Wind speed from radiometer measurements. m/s ushort 65535 0 to 65000 0.001
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