A new brightness temperature model for low elevation angles and application in remote sensing of evaporation ducts

At present, ground-based microwave radiometers are widely used for remote sensing of atmosphere, observing at elevation angles more than 15° with an atmospheric profile retrieval model, no considering the effects of atmospheric refraction and sea surface emission. In this paper, a low elevation angle brightness temperature model is proposed, taking the effects of atmospheric refraction, sea surface reflection and emission into account. The differences between the two models are simulated and compared, of which the reasons and mechanisms are analyzed. Results show that, at elevation angles less than 5 effects of atmospheric refraction or sea surface emission could not be cancelled. Lastly, applications of low elevation angle brightness temperature model in remote sensing of evaporation ducts are simulated, from which one can find that brightness temperatures at low elevation angles are sensitive to evaporation ducts and lower tropospheric profiles.