Sea Surface Salinity Observations from Space with the SMOS Satellite: A New Means to Monitor the Marine Branch of the Water Cycle - The Earth's Hydrological Cycle - page 196

The OSCAR data processing system calculates sea surface velocities from satellite
altimetry (AVISO), vector wind fields (QuikSCAT), as well as from sea surface temper-
ature (Reynolds-Smith) using quasi-steady geostrophic, local wind-driven, and thermal
wind dynamics. Near real-time velocities are calculated both on a 1 9 1 and 1/3 9 1/3
grid and on a *5-day time base over the global ocean. Surface currents are provided on the
OSCAR Web site ( http://www.oscar.noaa.gov ) starting from 1992 along with validations
with drifters and moorings. The 1/3 resolution is available for FTP download through
ftp://esr.org/pub/datasets/SfcCurrents/ThirdDegree .
2.3 Rain, Evaporation and River Discharge Data
To estimate the rain rate over the oceans, we used three different satellite products.
One is the monthly Tropical Rainfall Measuring Mission (TRMM) Composite Clima-
tology (TCC) of surface precipitation based on 13 years of data from the TRMM. The TCC
takes advantage of the information from multiple estimates of precipitation from TRMM to
construct mean value maps over the tropics (36N-36S) for each month of the year at 0.5
latitude-longitude resolution. The first-time use of both active and passive microwave
instruments on board TRMM has made it the foremost satellite for the study of precipi-
tation in the tropics and has led to a better understanding of the underlying physics and
distribution of precipitation in this region. The products are available at NASA Goddard
Space Flight Center Global Change Master Directory ( http://gcmd.nasa.gov ) .
The second type of satellite rain rate estimates that we used in the present study are the so-
called ''TRMM and Other Satellites'' (3B42) products, obtained through the NASA/Giov-
anni server ( http://reason.gsfc.nasa.gov/OPS/Giovanni ). The 3B42 estimates are 3 hourly at a
spatial resolution of 0.25 with spatial extent covering a global belt (-180W-180E)
extending from 50Sto50 N latitude. The major inputs into the 3B42 algorithm are IR data
from geostationary satellites and Passive Microwave data from the TRMM microwave
imager (TMI), special sensor microwave imager (SSM/I), Advanced Microwave Sounding
Unit (AMSU), and Advanced Microwave Sounding Radiometer-Earth Observing System
(AMSR-E).
The Special Sensor Microwave Imager (SSM/I) F16 and F17 orbits cross SMOS orbits
within -20 min and ?40 min. Hence, numerous SMOS level 2 are collocated with SSMI
rain rates (RR) within this range of time. In addition to the TRMM 3B42 products, we
therefore used SSM/Is data sets to perform colocations between SMOS SSS and rain
estimates. SSM/Is RR version 7 was used and downloaded from http://www.remss.com .
The evaporation (E) data set was taken from the version 3 products of the Objectively
Analyzed air-sea Fluxes (OAFlux) project (Yu and Weller 2007 ).
Finally, the discharge data for the Amazon, Orinoco, and Congo rivers were obtained
from the Environmental Research Observatory HYBAM (geodynamical, hydrological, and
biogeochemical control of erosion/alteration and material transport in the Amazon basin)
Web site ( http://www.ore-hybam.org/ ).
2.4 Ocean Color Products
To study the spatiotemporal coherency between SSS signals from some major tropical
river plumes and ocean color properties, we used the level 3 daily, 4-km resolution esti-
mates of the absorption coefficient of colored detrital matter (CDM) at 443 nm. These
products processed and distributed by ACRI-ST GlobColour service are supported by the
EU FP7 MyOcean2 and the ESA GlobColour Projects, using ESA ENVISAT MERIS data,