A DIAGNOSTIC ANALYSIS ON THE GROWTH MECHANISM OF THE EAST ASIA BLOCKING HIGH IN 1991

The whole period of the blocking anticyclone occurring in East Asia in the summer of 1991 is divided into three parts which include developing stage, maintained stage and degenerated stager espectively. The East Asia blocking high We analy zed with related diagnostic tools in detail. There are obvious stationary Rossby wave propagation and 2～6 day stransienteddy propagation upstream of the East Asia blocking high in the first and second stages, which means both kind of propagation play animport antrole in increasing and keeping energy of the blocking high. There is more obvious diverg enceconverg ence, north-south dipole of V'q' near westerly split point in the first stage than that in the second stage. This shows that synoptic disturbance can provide more energy source for developing the blocking high. It is worth noticing that there are some relationship between the collapsing of another blocking high around Ural Mountains and the fo rmation of the East Asia blocking high just downst ream of it.