QUANTIFICATION ANALYSIS OF ATMOSPHERIC DOWNWARD RADIANCE ON SNOW EMISSION MEASURED BY GROUND-BASED RADIOMETER AT 90 GHZ

With the passive microwave remote sensing of snow, the high frequency (80-100 GHz) has the advantages of high resolution and fresh shallow snow detection, however, the application of high frequency for snow observation is often limited by atmosphere influence. Until now, few studies have quantified the atmospheric influence of high frequency in snow observations. The scattering and emission of the water vapor and cloud liquid water in the atmosphere cause the increment in Brightness Temperature (TB). To explore the influence of the atmosphere on snow cover observations, we utilize Nordic Snow Radar Experiment (NoSREx) data and the Microwave Emission Model of Layered Snowpacks (MEMLS) to quantify the influence of the atmospheric downward radiance in snow observation by using 90 GHz of the ground-based radiometer. The results show that, in Sodankyla of Finland, atmospheric contribution to ground-based radiometer at 90GHz 50-degree is up to 95.76K (H-pol) and 95.02K (V-pol), with an average of 25.36K (V-pol) and 25.95K (H-pol). The further calculated root mean square errors (RMSEs) of simulated TB with Tdown and observed TB are 41.40K (V-pol)/36.85(H-pol), and of simulated TB without Tdown are 41.25K (V-pol) and 36.72K (H-pol), respectively, the MEMLS slightly increased the simulation accuracy quantitatively of the snow emission without the influence of the atmosphere.