Level 2 Algorithm

Definition of Product Levels LevelDescription Level 1 1A Reconstructed unprocessed instrument data 1B Geolocated, calibrated sensor units at 0.12 / 0.18 sec; RFI flag and then averaged and output at 1.44 seconds. Level 2 2A TOA to surface: Geolocated, calibrated sensor units at surface at 1.44 sec. Correct for Faraday rot; Antenna pattern, Sun, etc. 2B TB to SSS: Geolocated SSS from L2A and averaged to a 5.76 sec. Roughness correction from Scatterometer. Level 3 Re-grid and smooth: Time-space objectively analyzed SSS on a standard Earth Projection; 150 km at 7days and monthly. Calibration Collect Level 2B data at points coinciding with surface measurements and average to remove biases. Validation Match L2B data with in situ ocean measurements (SSS, SST, winds, sea state, etc) and compare at 150 km monthly

Science Algorithm Levels Level 1 –1A: Reconstructed instrument data –1B: Instrument units at TOA RFI Flag Avg over one cal cycle (1.44 sec) Level 2 –2A: T A at TOA to surface Flags (solar flares, rain, land, etc) Faraday rotation correction Antenna pattern correction Geophysical parameters removed T A at surface each 1.44 sec –2B: T B at surface to SSS Roughness correction SST + model function (Klien-Swift) Avg to 5.76 sec Level 3: Time-space averaged SSS on standard earth-projection –3A: 7 day and monthly at 1 degree –3B: 7 day and monthly at 150 km L1 L2A L2B L3

Algorithm Modules: Level 2 –Input from L1B: Antenna temperature avg at 1.44 sec –Flags Flag Solar Flares Rain Flag Land Contamination, sea ice Excessive winds, foam Unusual Antenna Temperature –Antenna Pattern Correction Remove off-earth contribution (galactic, sun, limb) –Tearth = Tmeasured + Tspace Correct for Faraday rotation Compute effective Brightness at boresight –Tbv = A11 T1 + A12 T2 –Tbh = A21 T1 + A22 T2 – Remove Geophysical Contributions Atmospheric up/down welling and Attenuation Reflected galactic and sun Correct for land contamination (optional) –Convert Sea-Surface Brightness Temperature to Salinity Roughness correction SST Model function: SSS = F(SST, TB, θ): Klien & Swift; Wentz Average to d5.76 sec

Level 2A Radiometer Geolocated & Calibrated Sensor Units at Surface A. At 1.44 sec working average Flags: Solar Flares, Rain, Land, Sea Ice, Excessive Wind, Foam, Unsual TB Corrections Faraday Rotation Galactic Background Atmospheric Attenuation and Emission Sun and Moon Antenna Pattern Correction B. Output: Geolocated and Calibrated sensor units Th and Tv at the surface One value for each 1.44 sec

Level 2B Radiometer Geolocated SSS averaged to 5.76 sec A. TB at 1.44 sec Roughness Correction (for TB): Using Scat data (Algorithm provided by Scat) Alternative: Using local wind speed and/or sea state Average: One data point per 5.76 sec Located at center B.Convert to Salinity Klein & Swift model or latest version C.Output: Salinity at center of geolocated pixels One pixel per 5.76 sec. All Flags Quality flag (error estimate in salinity units)

Level 2 Scatterometer Roughness Correction at 5.76 sec A. Scatterometer Output NRCS (σ 0 ) colocated at 1.44 sec with radiometer data Roughness Correction (σ 0 to TB): Algorithm derived pre-launch Revised post-launch using scat data and surface truth Wind direction Assess importance and if necessary collect ancillary data B. Other Scatterometer Output NRCS at 5.76 sec with flags and quality index (Kpc) Other B.Archived Output: NRCS at 1.44 and 5.76 sec Flags and quality index Ancillary data (wind speed and surface roughness) Algorithm