HR: 1340h
AN: A43A-0036    [Abstracts]
TI: Indian Summer Monsoon Rainfall and Its Link With ENSO and the Indian Ocean
AU: * Ihara, C
EM: cihara@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964-8000 United States
AU: Kushnir, Y
EM: kushnir@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964-8000 United States
AU: Cane, M A
EM: mcane@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964-8000 United States
AB: The all-India summer monsoon rainfall (ISMR), which is defined as the rainfall received during June to September over India, has a large impact on the agriculture and related economic activities of the region. The prediction of interannual variability of ISMR is thus a matter of great concern to society. It has been known that the El Nino/Southern Oscillation (ENSO) phenomenon is the most important external forcing of ISMR. However, ENSO does not always explain the interannual variability of ISMR. Recent studies have suggested that in addition to ENSO, the state of the Indian Ocean also influences the interannual variability of ISMR. However, most of these studies examine the relationships using the data of recent decades only. In this study, we examine the relationship between the state of equatorial Indian Ocean, ENSO and ISMR using data from 1881 to 1998. We particularly focus on the zonal wind anomalies at the equatorial Indian Ocean (hereafter EQWIN) and the SST anomalies over the Indian Ocean as the indices that represent the condition of Indian Ocean. During this period, the chosen ENSO index (NINO3) is moderately correlated with ISMR (the simultaneous correlation coefficient:-0.57). Although the EQWIN poorly correlates with ISMR, the linear reconstruction of ISMR based on a multiple regression on the ENSO and EQWIN indices correlates with the ISMR stronger than with the ENSO only regression. Using contingency tables we find that the negative association between the categories of ISMR and EQWIN is significant during "warm" (El Ni\~{n}o) and "neutral" ENSO events but not during La Ni\~{n}a events. The Indian Ocean SSTA demonstrates positive association with ISMR during the El Ni\~{n}o events but not during La Ni\~{n}a and neutral ENSO; thus the warmer Indian Ocean relates to the reduction of El Ni\~{n}o effects on ISMR.
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
DE: 4215 Climate and interannual variability (3309)
DE: 4522 El Ni¤o
DE: 1854 Precipitation (3354)
DE: 1620 Climate dynamics (3309)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting