BLLAST is a research programme aimed at exploring the late afternoon transition of the atmospheric boundary layer.
The late afternoon period of the diurnal cycle of the boundary layer is poorly understood. This is yet an important transition period that impacts the transport and dillution of water vapour and trace species. The main questions adressed by the project are:
- How the turbulence activity fades when heating by the surface decreases?
- What is the impact on the transport of chemical species?
- How relevant processes can be represented in numerical models?
To answer all these questions, a field campaign was carried out during the summer of 2011 (from June 14 to July 8). Many observation systems were then deployed and operated by research teams coming from France and abroad. They were spanning a large spectrum of space and time scales in order to achieve a comprehensive description of the boundary layer processes. The observation strategy consisted in intensifying the operations in the late afternoon with tethered balloons, resarch aircrafts and UAVs.