A statistic model developed to estimate the penetration depth using passive microwave remote sensing

Penetration depth of passive microwave remote sensing indicates the area below the land surface where singles come from. A reliable penetration depth is helpful not only in understanding the mechanism of microwave remote sensing but also in validating the retrieved results of land parameters. In this paper, we defined that the penetration depth in passive microwave remote sensing is the soil depth above which contributes more than 99% power of the total signal. Based on a three-layer non-coherent model (air-soil-aluminum), sensitive analysis was conducted to find out parameters which have more effect on penetration depth. Then three parameters including soil moisture, frequency and soil temperature were selected to build a simple statistic model to calculate the penetration depth of passive microwave remote sensing. To validate the statistic model, two controlled experiments were designed and carried out using a Truck-mounted Multi-frequency Microwave Radiometer (TMMR). It was shown that the penetration depth calculated from field experiment data coincided well with the statistic model.