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Full-Text Articles in Physical Sciences and Mathematics
Rectification Of The Bias In The Wavelet Power Spectrum, Yonggang Liu, X. San Liang, Robert H. Weisberg
Rectification Of The Bias In The Wavelet Power Spectrum, Yonggang Liu, X. San Liang, Robert H. Weisberg
Yonggang Liu
This paper addresses a bias problem in the estimate of wavelet power spectra for atmospheric and oceanic datasets. For a time series comprised of sine waves with the same amplitude at different frequencies the conventionally adopted wavelet method does not produce a spectrum with identical peaks, in contrast to a Fourier analysis. The wavelet power spectrum in this definition, that is, the transform coefficient squared (to within a constant factor), is equivalent to the integration of energy (in physical space) over the influence period (time scale) the series spans. Thus, a physically consistent definition of energy for the wavelet power …
Current Patterns On The West Florida Shelf From Joint Self-Organizing Map Analyses Of Hf Radar And Adcp Data, Yonggang Liu, Robert H. Weisberg, Lynn K. Shay
Current Patterns On The West Florida Shelf From Joint Self-Organizing Map Analyses Of Hf Radar And Adcp Data, Yonggang Liu, Robert H. Weisberg, Lynn K. Shay
Yonggang Liu
To assess the spatial structures and temporal evolutions of distinct physical processes on the West Florida Shelf, patterns of ocean current variability are extracted from a joint HF radar and ADCP dataset acquired from August to September 2003 using Self-Organizing Map (SOM) analyses. Three separate ocean– atmosphere frequency bands are considered: semidiurnal, diurnal, and subtidal. The currents in the semidiurnal band are relatively homogeneous in space, barotropic, clockwise polarized, and have a neap-spring modulation consistent with semidiurnal tides. The currents in the diurnal band are less homogeneous, more baroclinic, and clockwise polarized, consistent with a combination of diurnal tides and …
Light Induced Conversion Of Nitrogen Dioxide Into Nitrous Acid On Submicron Humic Acid Aerosol, K. Stemmler, M. Ndour, Yasin F. Elshorbany, J. Kleffmann, M. Ammann, B. D'Anna, C. George, B. Bohn
Light Induced Conversion Of Nitrogen Dioxide Into Nitrous Acid On Submicron Humic Acid Aerosol, K. Stemmler, M. Ndour, Yasin F. Elshorbany, J. Kleffmann, M. Ammann, B. D'Anna, C. George, B. Bohn
USF St. Petersburg campus Faculty Publications
The interactions of aerosols consisting of humic acids with gaseous nitrogen dioxide (NO2) were investigated under different light conditions in aerosol flow tube experiments at ambient pressure and temperature. The results show that NO2 is converted on the humic acid aerosol into nitrous acid (HONO), which is released from the aerosol and can be detected in the gas phase at the reactor exit. The formation of HONO on the humic acid aerosol is strongly activated by light: In the dark, the HONO-formation was below the detection limit, but it was increasing with the intensity of the irradiation with visible light. …