Verification of an objective analysis scheme. Meteorological analyses and their verifcation by trajectories of radioactive air masses during the Chernobyl disaster.

An Intermittent data assimilation scheme has been used to produce wind and precipitation flelds during the 10 days after the explosion at the Chernobyl nuclear power plant on 25 April 1986. The wind fields are analyses, the precipitation fields have been generated by the forecast model part of the scheme. The precipitation fields are of fair quality. The quality of the wind fields has been monitored by the ensuing trajectories. These were found to describe the arrival times of radioactive air in good agreement with most observational data, taken all over Europe. The wind analyses are therefore considered to be reliable.