Simulation of the microwave emissivity at window and sounding frequencies

  • Example of simulation result: Modeled physical and radiative properties for Corresponding CRREL IMB 2012H from Oct 2012 to Mar 2013; (a) snow density, (b) snow optical grain size, (c) temperature profile of snow and sea ice with three black lines (top: snow top, middle: ice freeboard, bottom: sea ice bottom), (d) emissivity, (e) effective temperature, (f) V-pol TBTOA with surface contribution, (g) H-pol TBTOA with surface contribution.

  • The use of passive microwave measurements for geophysical applications and data assimilation in numerical weather prediction (NWP) models has been limited over the Arctic sea ice due to inaccurate surface characterization. In particular, the specification of the surface emissivity is essential for applications or NWP to interpret the surface boundary influence on the satellite measured radiation. However, the surface emissivity is difficult to measure or parameterize on sea ice because of the complex vertical heterogeneity of the snow and sea ice emitting layer.

    This study estimates the sea ice radiative properties on the microwave spectrum through a multilayer radiative transfer calculation which requires detailed knowledge of the physical properties of snow and sea ice. In this regard, we introduce the sea ice model which is extended from the one dimensional (1-D) sea ice thermodynamic model (Tonboe, 2005) by including a nudging scheme and 2-D Lagrangian scheme. The nudging variables used here are the skin temperature based on satellite infrared radiometer (Dybkjær et al., 2018) and the daily snow-ice interface temperature based on satellite microwave radiometer (Lee and Sohn, 2015). The sea ice trajectories from the 2-D Lagrangian scheme, based on the non-acceleration equation, is derived by the OSI SAF low-resolution sea ice drift product (Lavergne et al., 2010). Thus, the solution of the 1-D sea ice thermodynamic model constrained by satellite-derived temperature is solved for the perspective of Lagrangian trajectories during Arctic winter.

    Based on the theoretical backgrounds (Tonboe, 2013) and simulated physical properties of snow and sea ice from the improved sea ice model, we have estimated the radiative properties such as brightness temperature, emissivity and effective temperature using the multilayer radiative transfer model.

    The objective of this study is to generate a dataset of physical properties for snow and sea ice using the improved sea ice model and a dataset of corresponding radiative properties on the microwave spectrum using the multilayer radiative transfer model. The simulated dataset can be used for extending the OSI-SAF near 50 GHz semi-empirical sea ice emissivity algorithm to a wider range of microwave frequencies and to different radiometer instruments. The dataset is also able to contribute to the development of OSI-SAF applications or better the microwave data assimilation in NWP over the Arctic area.

    Report : Simulation of the microwave emissivity at window and sounding frequencies

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