A two-phase algorithm to correct for atmospheric effects on the 85 GHz channels of the SSM/I in the Arctic region

Attenuation due to cloud liquid water increases as the square of frequency, making the 85.5 GHz channels of the SSM/I especially susceptible to atmospheric effects, even in the relatively dry polar regions. A two phase minimum square error (MSE) algorithm has been developed to address this problem. In the first phase: the spatial resolution of the 85 GHz data is degraded to match that of the lower frequencies, and estimates of cloud liquid water content and atmospheric water vapor, along with surface parameters are made based on data from all channels. The basis of the algorithm (both phases) is the relationship between radiation received by the sensor and the surface emissivity, the surface temperature, the atmospheric opacity, the atmospheric upwelling and downwelling radiation, and the cosmic background noise. The atmospheric parameters are calculated at low resolution using all available SSM/I channels. These estimates are then used as input to a second algorithm which recalculates surface parameters from the high resolution 85 GHz.<
>