HR: 10:45h
AN: A32A-02 INVITED     [Abstracts]
TI: Impact of Atmosphere-Ocean Interaction on the Predictability of Monsoon Intraseasonal Oscillations
AU: * Fu, X J
EM: xfu@hawaii.edu
AF: IPRC, SOEST, University of Hawaii, 1680 East West Rd., POST Bldg., 4th Floor, Honolulu, HI 96822 United States
AU: Wang, B
EM: wangbin@hawaii.edu
AF: IPRC and Department of Meteorology, SOEST, University of Hawaii, 1680 East West Rd., POST Bldg., 4th Floor, Honolulu, HI 96822 United States
AU: Waliser, D E
EM: duane.waliser@jpl.nasa.gov
AF: Jet Propulsion Laboratory, MS 183-501, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AB: A hybrid coupled general circulation model and its atmospheric component have been used to explore the possible impact of air-sea coupling on the predictability of tropical intraseasonal oscillations (ISO). This study focuses on the intraseasonal variability associated with the Asian-western Pacific summer monsoon (so-called Monsoon Intraseasonal Oscillation or MISO). During 15-year control run with the coupled model, twenty intraseasonal oscillation events have been selected from 15 summers (MJJASO). Four phases (i.e., peak dry, dry-to-wet, peak wet, and wet-to-dry) have been identified for each ISO event. A series of 'twin' perturbation experiments have been conducted for each phase of all ISO events using both the coupled model and the stand-alone atmospheric model. Two measures have been introduced to quantify the predictability of the MISO for both the coupled forecasts and the stand-alone atmospheric forecasts: the ratio of the signal associated with the ISO rainfall to the mean square error of the forecasts and the anomalous pattern correlation coefficient (ACC) as a function of leading time. Both measures indicate that air-sea coupling significantly enhances the predictability of the MISO. When measured with the ratio of signal to forecast error, the predictability of the MISO rainfall in the coupled model reaches about 25 days averaged over the Asian-western Pacific region (60oE-160oE,10oS-30oN). The averaged predictability in the atmosphere-only model is about 19 days. This result suggests that air-sea coupling is able to extend the predictability of the MISO by about a week. Almost the same conclusion is reached when the predictability is measured by the anomalous pattern correlation. The dependence of predictability on different ISO phases in both the coupled and stand-alone atmospheric forecasts is also discussed.
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
DE: 4255 Numerical modeling
DE: 4504 Air/sea interactions (0312)
DE: 5409 Atmospheres--structure and dynamics
SC: Atmospheric Sciences [A]
MN: 2005 Joint Assembly