Abstract: Salinity is a fundamental property of seawater. It plays an important role in measuring the sea surface salinity in the open ocean and coastal zone. At present, salinity is routinely measured by traditional methods of collection of water with bottles and analyses done with a laboratory salinometer, or by direct in situ CTD measurements, and by airborne microwave remote sensing system.
The study of airborne microwave remote sensing technology began in 1960s, and great progress has been made in the past 10 years. The passive L-band microwave radiometer is mounted underneath the fuselage of an airplane and used to measure the sea water surface salinity and therefore the surface salinity can be obtained rapidly and synchronically in a large area. At present there are various microwave radiometers applied in different countries and areas such as ESTAR,SLFMR,STARRS,PALS, and PLMR. The accuracy and precision of surface salinity data obtained by the airborne microwave radiometers can reach 1~1.5 psu in a resolution of 1 km². It is expected that the accuracy and precision of the new microwave radiometer PLMR will be within 1 psu.