HR: 0830h
AN: OS21B-1131    [PDF]
TI: The wintertime AO influence on early season Indian Ocean Monsoon intensity
AU: Buermann, W
EM: buermann@atmos.berkeley.edu
AF: Berkeley Atmospheric Sciences Center and Department of Earth and Planetary Sciences, 395 McCone Hall, University of California, Berkeley, CA 94720 United States
AU: * Lintner, B R
EM: ben@atmos.berkeley.edu
AF: Berkeley Atmospheric Sciences Center and Department of Earth and Planetary Sciences, 395 McCone Hall, University of California, Berkeley, CA 94720 United States
AU: Bonfils, C J
EM: celine@atmos.berkeley.edu
AF: Berkeley Atmospheric Sciences Center and Department of Earth and Planetary Sciences, 395 McCone Hall, University of California, Berkeley, CA 94720 United States
AB: The Indian Ocean Monsoon (IOM) exhibits considerable year-to-year to variations that have previously been attributed to a number of forcing mechanisms including the El Ni\~{n}o/Southern Oscillation (ENSO) and Eurasian snowcover anomalies. In this study, we analyze spatial data of Eurasian spring land surface temperatures, summer IOM precipitation, and summer IOM 850 mb zonal winds for the 1979-99 period to isolate well correlated modes of variability. The results indicate the existence of a prominent mode that appears to be related to the boreal winter Arctic Oscillation (AO); this mode projects strongly on the June precipitation and 850 mb zonal wind fields in the vicinity of the IOM region. Its projection on the temperature fields shows springtime surface warming and drying in the region to the north and west of the Indian subcontinent and cooling over the higher Eurasian latitudes during years of anomalously intense June monsoon rainfall. Such surface signatures are consistent with the negative phase winter AO. It is hypothesized that preconditioning of the spring season surface conditions may be associated with an AO-induced quasistationary tropospheric circulation anomaly: the impact of this anomaly is to displace the mid-Eastern jet polewards during AO-negative phases, resulting in anomalous surface heating and drying that persists into the later spring season and finally affects the rainfall over the IOM region in June.
DE: 0399 General or miscellaneous
DE: 1620 Climate dynamics (3309)
DE: 3322 Land/atmosphere interactions
DE: 3354 Precipitation (1854)
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting