Taking two tropical cyclones that landed southern China and caused great damage in summer of 2001 and 2006 as examples,using the dataset of CMA-STI Tropical Cyclone Optimal Tracks,the NCEP/NCAR reanalysis data and the intensive surface observations,this paper compares the large scale circulation features of maintenance over land and enhanced rainstorm from Durian(0103) in 2001 and Bilis(0604) in 2006.The conclusions are as follows:(1)After landing,Durian interacts with the mid-latitude westerly trough,forming a pattern of "North trough and South vortex".After landing,Bilis is blocked by the western Pacific subtropical high(WPSH),the northern high-pressure dam,and the extending southwest high pressure ridge of WPSH in the south side,allowing its cyclonic circulation to be maintained.(2)During the period of Durian and Bilis over land,the cross-equatorial flow increases significantly.The cross-equatorial flow nearby 100°E is remarkable in 2001,but the cross-equatorial flow nearby 80°E has outstanding performance in 2006.The cross-equatorial flows strengthen the southwest monsoon,which keep providing plentiful water vapor for the declining Durian and Bilis,leading to their long time maintenance over land instead of quick decaying.(3)East Asian monsoon manifest significant low-frequency oscillation,with main periods of 10—20 d in 2001 and 30—60 d in 2006.Low-latitude monsoon surge,characterized by different atmospheric low-frequency oscillations,experience remarkably northward propagation.In an extremely active stage of the low-frequency oscillation of low latitude summer monsoon,the monsoon surge is the strongest and intrudes into the circulations of Durian or Bilis,corresponding to the enhanced rainstorm.In addition,the convergence of low-frequency airflows and transport of low-frequency water vapor aslo play important roles in the enhanced rainstorm from Durian and Bilis.