The use of TOVS observations for the identification of tropopause-level thermal anomalies

The evolution of tropopause-level thermal patterns is generally not well represented by the conventional observational network, especially over the oceans. An alternative is provided by satellite observations which are global and frequent. In particular, from the TIROS-N (Television Infra-Red Observation Satellite) Operational Vertical Sounder (TOVS) which flies on-board National Oceanic and Atmospheric Administration satellites, an estimate of the temperature of the lower stratosphere (TLS) can be derived using the Improved Initialization Inversion algorithm. In this study, the degree of reliability of TLS for describing tropopause-level thermal structures and variations is examined. For three intensive observation periods (16, 17 and 18) of the Fronts and Atlantic Storm-Track EXperiment, conducted in January and February 1997 over the North Atlantic Ocean, TLS fields are described; their advantage, compared with the use of raw microwave data, is illustrated; TLS variations are also studied in connection with other dynamical variables which can be obtained by the French Action de Recherche Petite Echelle Grande Echelle operational model analysis. Finally, the suitability of TLS as a possible forecasting aid over mid-oceanic regions is promoted.