The influence of the 11 August 1999 total solar eclipse on the weather over central Europe

Abstract

Using a hydrostatic regional weather prediction model, the tropospheric response to the total solar eclipse on the 11 August 1999 is simulated over central Europe both with real time data and for a water vapor and cloud free scenario. The solar constant in the model is reduced stepwise along the surface path of the moon's shadow, reaching a value of 0 W/m 2 for a typical time span of 2 minutes during totality. In the presence of a large scale upper tropospheric trough centered over western Europe, the predicted radiative cooling ranging from -2°C over the UK, France and Germany to -5°C along the almost cloudless coast line of Croatia is in good agreement with observations. Over southeastern Europe the maximum cooling reaches -6°C to -7°C and the maximum sea surface pressure rise is enhanced from +0.4 hPa to +1.2 hPa, when the simulation is done without water vapor and clouds. The normally observed wind reduction is simulated as well as the temperature dependent increase of relative humidity near the ground. For some minutes even a slight cyclonic circulation is shown by the model surface winds. The upper air response to the eclipse is clearly correlated with the distribution of water vapor and clouds. The temperature and geopotential signals at the 500 hPa level are in the order of -0.01°C and -1 gpm remaining well below the sensitivity of routine sensors.