MMM SEMINAR NCAR
A systematic analysis of multiscale deep convective variability over the tropical Pacific
Wen-wen Tung
NCAR MMM
The multiscale tropical deep convective variability over the
Pacific Ocean is examined with the 4-month high-resolution deep convection
index derived from satellite imagery. With a systemic view, the complex
phenomenon is described with succinct parameters known as "generalized
dimensions" associated with the correlation structures embedded in the
observed time series, with higher-order dimensions emphasizing extreme
convective events. It is suggested that convective activities of lifetime
ranging from 1 hour to ~ 21days have interdependence across scales that can be
described by a series of power laws, hence a spectrum of generalized
dimensions. Furthermore, the dataset has the property of long-range
dependency", implying that its auto-correlation function decays with a
power law in contrast to the zero or exponentially decaying auto-correlation functions
for white and commonly-used red noise processes generated from auto-regressive
models. Physically, this means that intensified convection tends to be followed
by another intensified event, and vice versa for weakened events or droughts.
Such tendency is stronger with larger horizontal domain averaging (up to 25 x
25 degrees in this study), probably due to more complete inclusion of
larger-scale variability that has more definite trends, such as the super-cloud
clusters associated with the Madden-Julian oscillation (MJO).
Thursday , 28 October 2004, 3:30 PM
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