Interannual Variation of Summer South Asia High and Its Association with ENSO

Based on the NCEP/NCAR monthly reanalysis data, this paper studies the interannual change of summer South Asia high (SSAH) and its relationship to ENSO events. Results show: During the summer decaying stage of ENSO warm (cool) phase, the positive (negative) SST anomaly in the Indian Ocean and its adjacent ocean regions to the south of Asia causes the zonal abnormal circulation in the tropical region with upward (downward) motion in the Indian Ocean and subsidence (ascent) in the eastern Pacific and western Africa, accompanied by two anomalous anticyclones-cyclones-anticyclones (cyclones-anticyclones-cyclones) on the south and north sides of the equator at the lower level (850 hPa), and anomalous cyclone-anticyclone-cyclone (anticyclone-cyclone-anticyclone) at the upper level (200 hPa) from the western Pacific westward to Africa; the SSAH becomes stronger (weaker) with its area enlarging (reducing), its east and west borders extending outward (retracting inward), and pressure-gradient force enhancing (reducing) on the south side/reducing (enhancing) on the north side of high ridge. Based on the above analysis, it is found that the SST anomaly in the Indian Ocean and its adjacent ocean to the south of Asia plays an important role in the interannual abnormality of SSAH during the summer decaying stage of ENSO.