Abstract:Abnormal circulation characteristics and causes of the continuously heavy rain i n Eastern Guangdong in June 2007 are studied by using observational data, NCEP G lobal Data Assimilation System data and a linear diagnostic model. The results s how that this continuously heavy rain process is associated with the circulation pattern, i.e., two troughs respectively located over Urals Mts and East Asia an d a ridge located over northern China.The lower level shear line over north ern part of South China contributed to the moisture convergence and rainbe lt maintenance in eastern Guangdong.The low level southwest flow from the Bay o f Bengal interacted with that from the South China Sea constituted the major moi sture channel. Low level positive(negative) vetical helicity (divergence) and h ighlevel negative (positive) vetical helicity(divergence) over eastern Guangdong provided favorable dynamic conditions for development of the convective systems . The numerical diagnostic study results show that the contributions to the asce nding motion in eastern Guangdong are mainly from the forcing processes associat ed with the latent heating, which played the positive and simultaneous feedback role in heavy rain. Moreover, the horizontal transports of westerly momentum and horizontal temperature advection also made some positive contributions to this heavy rain process.