VALIDATION OF SAFNWC LAYER PRECIPITABLE WATER USING ECMWF ANALYSIS PROFILE AND RADIOSONDE

Layer Precipitable Water (LPW) from SEVIRI (Spinning Enhanced Visible and Infrared Imagery) has been developed by INM in the EUMETSAT SAFNWC (Satellite Application Facility on support to Nowcasting and Very Short−Range Forecasting) framework. Seven of the eight SEVIRI infrared (IR) channels are used to retrieve the LPW (Layer Precipitable Water) using neural networks due to the fact that the statistical retrieval is computationally fast (requirement for the SAFNWC PGEs). The LPW provides information on the water vapor contained in a vertical column of unit cross−section area in three layers in the troposphere (low, middle and high) and in the total layer in cloud free areas. It is routinely generated every fifteen minutes at a satellite horizontal resolution of 3km in nadir. The primary objective of this study is to assess the accuracy of satellite derived estimations of precipitable water over MSG N region. The main problem found is to determine the reference dataset. Radiosonde (RS) is the main source of atmospheric humidity observations. RS observations have good vertical resolution, but radio−soundings are few and are only available over land. Because of this reason, first the equivalent parameters derived from ECMWF analysis profiles are used as reference dataset.