Extremely convective wind gusts are often connected to significant damage of vulnerable structures such as buildings, infrastructures or forests. The cause of these strong wind events are part of the cold air outflow of local-scale convective weather systems which occur, depending on the region, comparatively often especially during the summer months.
Decisive for the high damage potential due to strong wind are short-term maxima wind speeds in the span of a few seconds or even less, which are termed as gusts. Over flat, approximately homogenous terrain, wind speeds of over 50 m s-1 can be reached. Numerous observations show that convectively induced storm events show higher wind speeds than winter storms of synoptic scale.
Construction of climatology for strong gusts for Germany
Due to the local-scale traits of deep moist convection and the high amount of uncertainty concerning its boundary and starting conditions, numerical weather models are not able to predict or reproduce convective strong wind events with sufficient accuracy. On the other hand their characteristics cannot be deducted from measurement stations with the required spatial representatively. In this respect they are not included in the meteorological statistics of horizontal wind.
With the help of statistical analysis of available observations the general understanding of the connection between strong convective wind gust, precipitation induced downdraft and horizontal wind speed in the free atmosphere (jet maximum) is to be improved.
The goal hereby is the systematic approximation of the maximum speed of downdrafts and near-ground wind fields depending on the precipitation intensity, the drop spectrum, the type of thermic layering in the lower altitudes and the vertical profiles of temperature and moisture. Using different empirical methods on observation data, the maximum speed of gusts from different historical convective systems is to be determined, in order to produce an approximation for the probabilities of convective strong wind events with a high spatial resolution for Germany.
In cooperation with the Institute for Hydromechanics (IfH) at KIT the amplification and the spreading of downdrafts at urban structures over several scales will be examined in more detail though observations in the wind tunnel. The goal is to improve the still insufficient understanding of the processes of downfall of wind gusts as well as the interaction of gusts with urban construction structures based on temporal and spatial high resolution studies and the coupling of different scales.