HR: 09:30h
AN: A31E-06    [Abstracts]
TI: Empirically Evaluating Short-Term Atmospheric Predictability
AU: * Eshel, G
EM: geshel@uchicago.edu
AF: Dept. of Geophysical Sciences, Univ. of Chicago 5734 S. Ellis Ave., Chicago, IL 60637 United States
AB: Defining predictability as divergence rate of trajectories initially emanating from neighboring points, in this paper I first estimate actual (i.e., observed) seasonal northern hemisphere mid-tropospheric IPV predictability. I use a simple, model-independent but inherently linear method. Using essentially the same method, I also estimate lower-atmospheric persistence, the rate of trajectory departure from an initial state. The time scale for complete loss of information (i.e., for knowledge of the state along the other trajectory in the divergence problem, or the initial state in the persistence problem, to provide no useful information about the current state of the primary trajectory) is about 4-6 days, between the cyclogenesis and blocking time scales. I next explore the operators that govern the dynamics and that yield the predictability and persistence properties established in the first part. The winter operators display non-normal growth potential; the summer ones do not, and are very nearly neutrally stable.
DE: 3322 Land/atmosphere interactions
DE: 3364 Synoptic-scale meteorology
DE: 3319 General circulation
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting