Clear-air turbulence diagnosis for long-range applications of a Lagrangian particle dispersion model
Abstract
Transport and dispersion models usually include parameterisations for turbulence in the atmospheric boundary layer (ABL). However, longrange transport often takes place above the ABL, and studies of transport processes in the free atmosphere, e.g., of stratospheric intrusions in the troposphere, are becoming more common. We present our parameterisation to diagnose regions of shear-induced turbulence (sCAT) in the free atmosphere. Our parameterisation is based on the TI2-Index after Ellrod and Knapp with some modifications. The main difference is that the real angle between the deformation axis and the potential temperatur gradient is considered, instead of assuming maximum effectiveness of deformation. This should reduce the number of false alarm cases. In addition, we eliminate all one-grid cell patches and exclude all regions where the static stability exceeds the value assumed for the thermal tropopause definition. Furthermore, we present a climatological view of sCat Regions over Europe both in horizontal and in vertical cross-sections for different seasons. At lower levels, there is a stronger annual and latitudinal variation. At the jet level (9 km), we can see both the influence of the subtropical and polar jet.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA.....5612F