Hydros Soil Moisture Measurements in the Forecasting Systems of the Meteorological Service of Canada

Several forecasting centers throughout the world, including the Meteorological Service of Canada (MSC), have shown the positive impact of improving soil moisture initial conditions. At MSC, soil moisture for both regional (short range) and global (medium range) forecasting systems is provided by the assimilation of low-level air temperature and relative humidity using an optimum interpolation (OI) technique. We are currently working on more advanced soil moisture assimilation techniques to be included in the so-called Canadian Land Data Assimilation System (CaLDAS). This new system will allow the assimilation of several types of data, including the L-band passive and active measurements that will be provided by Hydros, low-level air characteristics, C-band radiances, and infrared brightness temperature. In order to determine the relative importance of each type of data, we have performed an observing system simulation experiment (OSSE) in a framework that closely corresponds to MSC's North American regional short-range forecasting system. The information content of each observation type is estimated using the influence matrix diagnostics. Preliminary results indicate that the information content brought into the analysis is greater for L-band brightness temperatures, compared to that for the other types of data. At the conference, we will present several results showing the positive impact of more realistic initial conditions of soil moisture in atmospheric models (with the current OI technique) for short and medium-range weather forecasts. We will also describe the main components of CaLDAS, and present results from the diagnostic tool described above for the relative information content