On the depiction of upper-level precursors of the 1999 December storms from TOVS observations
Fourrié, N. ; Claud, C. ; Chédin, A.
Année de publication
2003
At the end of December 1999, two extremely severe storms only one day <br>apart affected western Europe and caused considerable damage. A variable<br> derived from satellite observations, the so-called temperature of the <br>lower stratosphere (TLS), is used in this study for detecting and <br>tracking the upper-level components of these storms. TLS is computed <br>from a regression over five Television and Infrared Observation <br>Satellite (TIROS-N) Operational Vertical Sounder (TOVS, aboard NOAA <br>satellites) channels, with coefficients calculated from a climatological<br> dataset [thermodynamical initial-guess retrieval (TIGR)], and provides <br>information on the temperature near the tropopause. The objective of <br>this paper is to assess the ability of TLS, in situations such as these <br>two exceptional storms, to track and depict upper-tropospheric <br>precursors of surface lows. After a brief synoptic description of the <br>meteorological situation, TLS fields as well as the Action de Recherche <br>Petite Échelle Grand Échelle (ARPEGE) model fields (mean sea level <br>pressure, temperature, wind velocity, and geopotential height of the <br>dynamical tropopause) are discussed concurrently for the period 2327 <br>December. Although the upper-level thermal fields are consistent <br>overall, differences appear, especially during the incipient stage of <br>the second storm. The forecast, which was poor in the operational <br>context, is modified when a configuration close to the TLS one is <br>adopted. Qualitative comparisons of TLS with Microwave Sounding Unit <br>(MSU) channel-3 limb-corrected brightness temperatures and with the <br>water vapor imagery are also shown. One advantage of TLS over these two <br>other fields is the earlier detection of the upper-level precursor of <br>the second storm. Because TLS computation is easy and fast, the <br>suitability of TLS as a possible forecasting aid over midoceanic regions<br> is promoted.</div>
Accès à la notice sur le site du portail documentaire de Météo-France