Polarimetric microwave radiometer can provide sea surface wind vector products; this ability is a new development in spaceborne passive sensing. Sensitivity analysis of polarimetric microwave radiometer brightness temperature observations with respect to environmental factors may indicate the effect of environmental factors on polarimetric microwave radiometer brightness temperature observations. This finding may provide theoretical support for channel selection in the retrieval of important physical factors.On the basis of the polarimetric microwave forward model

we adopted sensitivity analysis to analyze

calculate

and quantify the sensitivity of each channel from the polarimetric microwave radiometer with important environmental parameters

such as sea surface wind speed

sea surface wind direction

sea surface temperature

atmospheric water vapor content

and cloud liquid water content

under fixed background field conditions. We also analyzed the sensitivity of the brightness temperature

which is simulated by the forward model or measured by using spaceborne polarimetric microwave radiometer WindS at

with respect to important environment parameters under real background field conditions from WindS at environmental data record

NCEP analysis data field

and TAO / TRITON buoy data record.Results include:（ 1） The brightness temperature of 6. 8 GHz and 10. 7 GHz vertical and horizontal polarization channel has good linearity relative to sea surface temperature

which can be used for sea surface temperature inversion.（ 2） The changes in the brightness temperature of 23. 8 GHz vertical and horizontal polarization channel are the largest relative to the rate of atmospheric water vapor content changes

which is mainly used for atmospheric water vapor content retrieval.（ 3） Vertical and horizontal polarization channels at 37 GHz have relatively obvious characterization relative to cloud liquid water content

which could be used to cloud liquid water content inversion.（ 4） The brightness temperatures of vertical polarization and horizontal polarization channel have good linearity retrieval to wind speed at a low observation frequency

which is used for sea surface wind speed inversion.（ 5）When the wind direction changes

the brightness temperature channels of the third and fourth Stokes channels exhibit obvious inverted fluctuation characteristics

which can be used for sea surface wind direction inversion.（ 6） The fluctuation with wind direction is completely covered in the real background field at the vertical and horizontal polarization channels

but the third and fourth Stokes channel observations can still characterize wind direction changes.（ 7） The sensitivity of the third and fourth Stokes channels to other environmental parameters is much lower than the sensitivity to sea surface wind speed and wind direction

which cannot be used for inversion of other environmental parameters.（ 8） The third and fourth Stokes channels for sea surface wind speed are also highly sensitive. Under a high wind speed condition

the actual measured brightness temperature of the third and fourth Stokes channels is large

which indicates that the measurement includes strong wind vector signals. Sea surface wind retrieval accuracy is better under high wind conditions compared with that under low wind speed conditions.（ 9） In the 0° ± 30°

180° ±30° range

the brightness temperature measured value of the third and fourth Stokes channels is small

and the noise signal influence to wind is large. Thus

the retrieval accuracy of wind directions decreases in those ranges

and retrieval results appear fuzzy.（ 10） In the actual measurement

the wind direction signal from the third and fourth Stokes channels is subject to interference from other environmental factors to some extent

which makes retrieving the sea surface wind direction difficult.The conclusions from sensitivity analysis could provide support to the independent development of China to design a polarimetric microwave radiation channel

select an environmental parameter inversion channel

and propose an environmental parameter inversion algorithm. Moreover

this study establishes a foundation to improve the accuracy of surface wind vector retrieval by removing adverse effects caused by atmospheric water vapor content and cloud liquid water content.