Description of the upgrade

Various modifications to the analysis were implemented, the most significant of these being:
  1. a tighter first-guess check for AIREPs reporting zero wind speed;
  2. assigning single level pressure (height) observations to the first-guess pressure level instead of the reported pressure - this will remove spurious analysis increments in the temperature of the lowest model level;
  3. rather than having a uniform global threshold the SATEM stability check will be made dependent on the first-guess error standard deviation.

Implemented: 29 August 1989