Techniques of Lagrangian trajectory analysis in isentropic coordinates.

Abstract

The first trajectory technique is kinematic, using only the wind information, while the other two, the explicit method of Petersen and Uccellini and an automated version of Danielsen's implicit technique, are dynamic (use both mass and velocity fields). A primitive equation channel model in pressure coordinates was used to generate the basic flow fields. We compared the techniques for data intervals ranging from 12 min to 12 h. The overall level of agreement, even for a 12-h data interval, is very good, particularly for the dynamic techniques. This result implies that, given a spatially and temporally coherent data set, accurate trajectory calculations in the free atmosphere can be performed using these techniques even when data are available only twice daily, as is the case for routine aerological observations. -from Authors