Present-day Concepts of Atmospheric Frontogenesis. Part 2. Some Results of Computation from the Real Data

N. P. Shakina, A. R. Ivanova, and N. I. Komas'ko

Reviewed are the recently published results of vector frontogenesis computation from the real and model data for a number of case studies. The results revealed that the development of troughs and ridges in upper-level frontal zones, jet stream meandering and intensification, cyclonic eddy gener¬ation and evolution are due to the specific distribution of frontogenesis. Main quantitative characteris¬tics of vector frontogenesis are its components along and across the potential temperature contour and at the isobaric surface. The first component describes the frontogenetic effect of isotherm rotation and is called the rotational frontogenesis; the second component represents a measure of the change in the horizontal temperature gradient and is called the scalar frontogenesis. Frontogenesis characteristics are used not only as informative diagnostic parameters but also as the indicators of the future transforma¬tion of atmospheric fields. Presented are preliminary results of frontogenesis computation for a case of the high-amplitude wave in the upper-level frontal zone with the intense jet stream and deep stratospheric intrusion. It is demonstrated that the tropopause sinking on the cold side of the upper-level frontal zone is caused mainly by the scalar frontogenesis whereas the rotational frontogenesis plays a primary role in the area of the sharp rotation of isohypses causing the intensive rising of air on the warm side and the sinking on the cold side. The comparison of computations based on the objective analysis and global semi-Lagrangian atmospheric model output data, demonstrates that the jet streams, tropopause topography, and frontogenesis effect distribution are simulated correctly from the qualitative point of view while the forecasting fields are significantly smoothed in terms of numbers.

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