Divergence, vorticity and vertical motion in the fields of winter and monsoon circulations over India

Abstract

Using upper wind data of 69 pilot balloon and rawin stations in India, Pakistan, Burma and Ceylon, multi-level fields of divergence, vorticity and vertical motion have been computed on five consecutive days in the months of January and July 1958 to study the winter and monsoon circulations over the Indian region. Computations have been made at 37 grid points 2.5 degrees apart, with the help of a digital computer. A filtering technique was used to smoothen the observed winds so as to filter out noise.

The study provides a convenient method of computing divergence directly from observed winds instead of doing so indirectly thi:'i5ugh the vorticity equation.. The computed values of divergence and vorticity show that the two are of comparable magnitude. Examination of the divergence fields does not reveal narrow bands of convergence. characteristic of well defined frontal systems. The distribution of vertical velocities in the monsoon field indicates the existence of a source region over the eastern half of India and a sink over the western half.