DETERMINATION OF UPSTREAM BORA LAYER DEPTH

Bora layer depth is defined as a layer of NE bora flow usually capped by an inversion. The inversion height can be determined by the hydrostatic stability parameters calculated from the point values of pressure and temperature data in the Zagreb's sounding. The method is based on an objective polynomial vertical interpolation scheme in isentropic coordinates and includes the computation of energetic changes across the isentropic surface, as presented by a nonhydrostatic coefficient and demonstrated by the application in an ALPEX bora case. Smith's (1985) hydraulic model is applied to several bora cases. The results indicate differences in the solution when the incoming mean wind velocity is replaced by the NE ("bora") wind component perpendicular to the coastal mountain ridge. This is consistent with the two-dimensional modelling approximation, and stresses the importance of considering a three-dimensional atmospheric structure in the real bora flow. © 1990 Springer-Verlag.