Evaluation of IRI-95 to correct errors caused by faraday rotation in passive microwave remote sensing from space Original Research Article

Passive remote sensing from space at the long wavelength end of the microwave spectrum has the advantages of penetrating the atmosphere and responding to parameters of the ocean and earthʹs surface important for understanding earthʹs environment. Examples are the measurements of soil moisture and sea surface salinity. These measurements can be made at L-band (1.413 GHz) and are needed to understand energy exchange with the atmosphere at the surface. Sensor systems are under serious consideration to make these measurements. However, at L-band Faraday rotation in the ionosphere can be sufficient to cause errors in the retrieval of the surface parameters. This is especially a problem for the retrieval of sea surface salinity in the open ocean because the dynamic range of the measurement is relatively small. An important question in the design of such sensor systems is whether models can be used to correct Faraday rotation. As a first step toward addressing that question, IRI-95 is used to assess the order of magnitude of the Faraday rotation and the error it causes at L-band in the observed brightness temperature. Errors on the order of several Kelvin are possible. In addition, a limited evaluation of the model is made by comparing the effects of Faraday rotation using prediction and observed vertical total electron content.