HR: 13:30h
AN: A33B-01    [Abstracts]
TI: Circumglobal Teleconnection in the Northern Hemisphere Summer
AU: * Ding, Q
EM: qinghua@hawaii.edu
AF: Department of Meteorology, University of Hawaii, 2525 Correa Road, HIG 375, Honolulu, HI 96822 United States
AU: Wang, B
EM: wangbin@hawaii.edu
AF: Department of Meteorology, University of Hawaii, 2525 Correa Road, HIG 375, Honolulu, HI 96822 United States
AU: Wang, B
EM: wangbin@hawaii.edu
AF: International Pacific Research Center,University of Hawaii, Pacific Ocean Science and Technology Bldg., Room 401, 1680 East-West Road, Honolulu, HI 96822 United States
AB: Analysis of 56-year NCEP/NCAR reanalysis data reveals a recurrent circumglobal teleconnection (CGT) pattern in the summertime midlatitude circulation of the Northern Hemisphere. This pattern represents the second leading empirical orthogonal function of interannual variability of the upper tropospheric circulation. The CGT, having a zonal wavenumber five structure, is primarily positioned within a waveguide associated with the westerly jetstream. The spatial phases of CGT tend to lock to preferred longitudes. The geographically phase-locked patterns bear close similarity during June, August and September, but the pattern in July shows shorter wavelengths in the North Pacific to North America sector. The CGT is accompanied by significant rainfall and surface air temperature anomalies in the continental regions of West Europe, European Russia, India, East Asia and North America. This implies that the CGT may be a source of climate variability and predictability in the above midlatitude regions. The CGT has significant correlations with the Indian summer monsoon (ISM) and El Nino-Southern Oscillation (ENSO). However, in normal ISM years the CGT-ENSO correlation disappears; on the other hand, in the absence of El Nino or La Nina, the CGT-ISM correlation remains significant. It is suggested that the ISM acts as a conductor ± connecting the CGT and ENSO. When the interaction between the ISM and ENSO is active, ENSO may influence northern China via the ISM and the CGT. Additionally, the variability of the CGT has no significant association with the Arctic Oscillation and the variability of the Western North Pacific summer monsoon. The circulation of the wavetrain shows a barotropic structure everywhere except the cell located to the northwest of India where baroclinic circulation structure dominates. Two possible scenarios are proposed. The abnormal ISM may excite anomalous west-central Asian High and downstream Rossby wavetrain extending to North Pacific and North America. On the other hand, a wavetrain excited in the jet exit region of the North Atlantic may affect west-central Asian High and thus the intensity of the ISM. It is hypothesized that the interaction between the global wavetrain and the ISM heat source may be instrumental in maintaining the boreal summer CGT.
DE: 5409 Atmospheres--structure and dynamics
SC: Atmospheric Sciences [A]
MN: 2005 Joint Assembly