STATISTICAL ERROR FOR THE MOISTURES RETRIEVED WITH THE SMOS RADIOBRIGHTNESS DATA, AS INDUCED BY IMPERFECTNESS OF A DIELECTRIC MODEL USED
Résumé
In connection with the SMOS orbiting the Earth, the problem of soil type impact on the error of soil moistures retrieved by this instrument has become especially important. To retrieve the moisture from the radiobrightness measured, a specific dielectric model must be applied, which links the radiobrightness to the wave frequency, moisture, and soil type. At present, the Dobson semiempirical dielectric model is employed to take into account soil type in the SMOS algorithms retrieving moisture. Meanwhile, there are the alternative models by Schmugge and Mironov et. al.. These also provide for permittivity values as a function of soil moisture, and soil type, allowing to link radiobrightness measured by SMOS to soil moisture. In this paper we carried out comparative analysis regarding the error of moisture retrieved from radiobrightness measured by SMOS, which is invoked by imperfectness of the three models discussed above. For this purpose, we used the dielectric database of complex permittivities available in the literature at 1.4 GHz for different soil types and varying moistures. A statistical analysis was carried out to obtain the 95% confidence intervals in which a true moisture is confined, provided the value of moisture retrieved by the SMOS algorithm is known.