The persistent anomaly of the south Asia high and its association with ENSO events

The south Asia high (SAH) is one of the main action centers in the uppermiddle troposphere. Based on the 200 hPa data, the NCEP/NCAR monthly reanalysis data for 1949-2006 and using the NCAR community atmosphere model (CAM3.0), the persistent strength anomaly of the SAH and its relationship to ENSO events are studied. The results show that there exists a winterspringsummer persistent anomaly of the SAH intensity in some years whose association with ENSO events are very close. Furthermore,the evolution features of the SAH abnormal degree is not well consistent with that of ENSO evolution characterized by the equatorial eastern pacific SST with the SAH lagginger than the ENSO. The response of the SAH strength to the ENSO starts from December in the previous year, with the maximum anomalies occuring during JanuaryMay, and the secondary maximum during JuneSeptember. ENSO event characterized by the selfcorrelation of Nino3.4 in January begin in spring， develop in summer and autumn,reach mature in winter and gradually weaken in spring of the next year and disapper basically in summer. The simulative results for the different ocean basins using CAM3.0 show that in winter that is the mature period of the ENSO, the equatorial eastern Pacific SSTs play an important role in the SAH anomaly;in spring that is the decaying phase of ENSO events, both the equatorial eastern Pacific and the Indian Ocean have much effect on the anomaly SAH; and in summer during ENSO events decay in the tropical eastern Pacific, the Indian Ocean plays an important role in the SAH anomaly.