MMM SEMINAR NCAR
Temporal Variability of
Warm-Season Precipitation
over North America: A Statistical Analysis
Hsiao-ming Hsu
NCAR/RAP
Directionally averaged time series of rain rates, derived from NEXRAD measurements over the continental United States by Carbone et al (2002), are analyzed using spectral decomposition methods. In addition to prominent diurnal and semi-diurnal cycles, the temporal spectra for the longitudinally-averaged time series indicate a cross-scale self-similarity. This is quantified by a power-law scaling with an exponent of -4/3 for the frequency band higher than semi-diurnal and -3/4 for the period between 1 and 5 days. Composites of the higher-frequency bands quantify the eastward propagation of the re-constructed convective signals. On the other hand, the low-frequency signals propagate westward. There is a marked inter-annual variability in the dominant periods and the propagation speeds. The scale-invariance obtained from the observational analysis will be useful for evaluating prediction models evaluation.
Thursday, June 3, 3:30 PM
Refreshments 3:15 PM
NCAR-Foothills Laboratory
3450 Mitchell Lane
Bldg 2 (Rm 1022)