Measurements of Boreal Coniferous Forest Soil and Humus with an Airborne Radiometer

Boreal coniferous forests are a large and diverse biome, which has not been widely studied in scope of space borne soil moisture (SM) observations. This paper presents a series of airborne measurements that were made to explore microwave emissivity of a boreal coniferous forest in different moisture conditions. Ground observations of SM and vegetation were made in conjunction with the airborne measurements. The L-band microwave emission of the biosphere (L-MEB) model, which is used in the SM and ocean salinity (SMOS) SM algorithm, was used to model the emission of the forest scenes. The litter layer was included in the modeling because of the thick humus layer present in the study area. The measurements indicate that with sufficient parameters the L-MEB model can simulate the forest and soil-humus ensemble emission with reasonable accuracy (R = 0.75, RMSE = 4.4 K). While SM retrieval is hampered by the complex behavior of humus layer, a correct parameterization of the layer is likely to improve accuracy of moisture retrieval for mixed pixels in SMOS observations.