Description of the upgrade

  1. This version includes the following important changes that together will affect all components of the system (Data assimilation, atmospheric and oceanic waves forecasts, EPS):
  2. More data are activated (SeaWinds data from QUIKSCAT, less thinning of aircraft observations, more intelligent thinning and better scan correction of ATOVS radiances);
  3. Pre-processing (bias correction) of SSMI data and redundancy checks for SYNOP, SHIP, DRIBU, AIREP, TEMP and PILOT observation are refined;
  4. 4D-var analysis algorithms are upgraded:
    • pre-conditioning is added to the minimisation, resulting in a 40% reduction of the number of adiabatic iterations;
    • correlation functions slightly revised (compacted);
    • the radiative transfer model used to assimilate satellite radiances has been completely re-written;
    • the observation timeslot has been reduced from 1 hour to 30 minutes;
  5. Model changes include a new finite-element vertical discretization, small changes in the convective precipitation scheme and supersaturation checks, and an improved temporal scheme for oceanic waves generation;
  6. Initial EPS perturbations in the tropics are included. The perturbations are generated for a maximum of four target areas by Gaussian sampling of the 5 leading diabatic singular vectors for each area. The Caribbean (0°-25°N and 100°-60°W) is always target area, as is every tropical storm of category larger than 1 between 25°N and 25°S. (In the event that these criteria produce more than four target areas, the closest areas are merged.)

Implemented: 22 January 2002