title: Time series study of a 17-year record of (7)Be and (210)Pb fluxes in northern Taiwan using ensemble empirical mode decomposition.
abstract: Using the ensemble empirical mode decomposition (EEMD) and a significance test method, we have analyzed time series data on the fluxes of (7)Be and (210)Pb collected over a span of 17 y in Northern Taiwan. Among nine intrinsic mode functions (IMFs) extracted from the method five (IMF4-8) are non-trivial for (210)Pb and have adequate S/N with significant power in localized windows around the periodicities of 0.5 y, 1 y, 2 y, 5 y, and 11 y, respectively. For (7)Be, IMF5 and IMF8 with periods around 1 y and 11 y, respectively, have adequate S/N. The semi-annual and annual cycles represented by IMF4 and IMF5, respectively, are dominated by East Asian monsoon. The sum of IMF6 and IMF7 reveals an inter-annual cycle where both (7)Be and (210)Pb fluxes are well-correlated with the East Asian winter monsoon index (EAWMI). The close tracking of the (210)Pb and (7)Be in IMF8 cases may reflect an 11 y cycle; implying that it is caused by common climatologic factors, likely related to solar cycle, rather than their distinct production modes.
authors.affiliation: Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan; Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, USA. Electronic address: hilee@atmos.ucla.edu.
authors.forename: H-I
authors.initials: HI
authors.lastname: Lee
authors.affiliation: Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan. Electronic address: huh@earth.sinica.edu.tw.
authors.forename: C-A
authors.initials: CA
authors.lastname: Huh
authors.affiliation: Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan.
authors.forename: T
authors.initials: T
authors.lastname: Lee
authors.affiliation: Research Center for Adaptive Data Analysis, National Central University, Zhongli, Taiwan.
authors.forename: N E
authors.initials: NE
authors.lastname: Huang
mesh_terms: D001608:Beryllium / Q000032:analysis*; D007856:Lead Radioisotopes / Q000032:analysis; D011834:Radiation Monitoring; D011868:Radioisotopes / Q000032:analysis*; D012621:Seasons; D013624:Taiwan
chemical_list: D007856:Lead Radioisotopes; D011868:Radioisotopes; D001608:Beryllium
keywords: Be-7; EEMD; Monsoon; Pb-210; Taiwan; Time series