Comparative analysis of temperature and CO2 fluxes for winter wheat in Tibetan Plain and North China Plain using the EMD method

Abstract Comparative study of spectral properties of temperature and CO2 fluxes measured by eddy covariance method at Yucheng (36 57'E, 28 m.a.s.1., in the North China Plain) and at Lhasa (29 41'N, 91 20' E, 3688 m.a.s.1., on the Tibetan Plateau) is described using the empirical mode decomposition (EMD) method. The main results are: (1) The intrinsic oscillation modes or intrinsic mode functions (IMFs) were extracted from data of temperature (T) and CO2 fluxes (F) measured at Yucheng (T1 and F1) and Lhasa (T2 and F2). (2) Hilbert transform was applied to these IMF compontents, then the Hilbert-Huang spectra and the marginal spectra of these data were obtained. (3) Comparison of temperature and CO2 fluxes in North China Plain and on Tibetan Plain illustrated that the characteristic frequencies corresponding to T1, F1, T2 and F2 are 0.05 Hz, 0.03 Hz, 0.014Hz and 0.005Hz, respectively.