HR: 16:15h
AN: NG44A-04    [Abstracts]
TI: Multiscale Variability of the Monsoon Climate
AU: * Krishnamurthy, V
EM: krishna@cola.iges.org
AF: Center for Ocean-Land-Atmosphere Studies, Institute of Global Environment and Society, Calverton, MD 20705 United States
AU: * Krishnamurthy, V
EM: krishna@cola.iges.org
AF: School of Computational Sciences, George Mason University, Fairfax, VA 22030 United States
AB: The reliability of weather forecasts is limited to a few days and is mainly determined by the synoptic scale features of the atmosphere. The predictability of weather models depends on the error growth determined by nonlinear terms representing advection. Smaller scale features, such as convection, may also influence the predictability of the synoptic scale forecasts. While the prediction of instantaneous states of the system may be impossible on longer time scale, there is optimism for medium-range and long-range forecasts of time-averaged features of the climate system. Such optimism is based on the observation that slowly-varying boundary forces such as sea surface temperature, soil moisture and snow influence the variability of the atmosphere on a longer time scale, especially in the tropical region. This study discusses the variability of such a tropical climate system, the monsoon, and shows that its variability consists of a combination of large-scale persistent seasonal mean component and intraseasonal variability of different time scales. The spatial variability of these components is also found to consist of different scales. By performing multi-channel singular spectrum analysis of daily rainfall, low-pressure systems, outgoing long-wave radiation and winds, two oscillatory modes with periods of about 45 and 20 days have been identified and shown to correspond to the active and break phases of the monsoon. These two intraseasonal modes, however, do not contribute much to the seasonal mean rainfall. Three other components of the MSSA are identified as the contributors to the seasonal mean rainfall, possibly arising from the influence of slowly-varying boundary forces. The prospect for making accurate long-range forecasts of the monsoon depends on the relative magnitudes of the large-scale seasonally persistent component and the intraseasonal component and on climate model experiments to establish a relation between the two components.
DE: 3220 Nonlinear dynamics
DE: 3240 Chaos
DE: 3309 Climatology (1620)
DE: 3374 Tropical meteorology
SC: Nonlinear Geophysics [NG]
MN: 2005 Joint Assembly