scispace - formally typeset
Search or ask a question
Author

Quanan Zheng

Bio: Quanan Zheng is an academic researcher from University of Maryland, College Park. The author has contributed to research in topics: Sea surface temperature & Internal wave. The author has an hindex of 34, co-authored 163 publications receiving 20319 citations. Previous affiliations of Quanan Zheng include National Science Foundation & University of Delaware.


Papers
More filters
Journal ArticleDOI
TL;DR: In this paper, a new method for analysing nonlinear and nonstationary data has been developed, which is the key part of the method is the empirical mode decomposition method with which any complicated data set can be decoded.
Abstract: A new method for analysing nonlinear and non-stationary data has been developed. The key part of the method is the empirical mode decomposition method with which any complicated data set can be dec...

18,956 citations

Journal ArticleDOI
TL;DR: The upwelling along the Java-Sumatra Indian Ocean coasts is a response to regional winds associated with the monsoon climate as discussed by the authors, which migrates westward and toward the equator during the southeast monsoon (June to October).
Abstract: Upwelling along the Java-Sumatra Indian Ocean coasts is a response to regional winds associated with the monsoon climate The upwelling center with low sea surface temperature migrates westward and toward the equator during the southeast monsoon (June to October) The migration path depends on the seasonal evolution of alongshore winds and latitudinal changes in the Coriolis parameter Upwelling is eventually terminated due to the reversal of winds associated with the onset of the northwest monsoon and impingement of Indian Ocean equatorial Kelvin waves Significant interannual variability of the Java-Sumatra upwelling is linked to ENSO through the Indonesian throughflow (ITF) and by anomalous easterly wind During El Nino episodes, the Java-Sumatra upwelling extends in both time (into November) and space (closer to the equator) During El Nino (La Nina), the ITF carries colder (warmer) water shallowing (deepening) thermocline depth and enhancing (reducing) upwelling strength

334 citations

Journal ArticleDOI
TL;DR: In this article, the wave-induced vertical viscosity (or diffusivity) Bv is defined, which can be used as a parameter to estimate the strength of waveinduced mixing.
Abstract: [1] From the Reynolds stress expression, the wave-induced vertical viscosity (or diffusivity) Bv is defined, which can be used as a parameter to estimate the strength of wave-induced mixing. In addition, a parameter D5 is introduced to represent a wave-induced mixing penetration depth. The global distribution of Bv averaged over the upper 20 m is calculated and its latitudinal transects in boreal summer and winter is discussed. The results show that in summer the wave-induced mixing is strong in the southern oceans south of 30°S, and in winter it is strong in the north Pacific and the north Atlantic north of 30°N, as well as in the southern oceans south of 40°S. Adding Bv to the vertical diffusivity in a global ocean circulation model yields a temperature structure in the upper 100 m that is closer to the observed climatology than a model without the wave-induced mixing.

299 citations

Journal ArticleDOI
04 Dec 1992-Science
TL;DR: Variabilities in sea-surface temperature and size of the Western Pacific Warm Pool were tracked with 10 years of satellite multichannel sea- Surface temperature observations from 1982 to 1991 and show that both annual mean sea- surface temperature and the size ofthe warm pool increased from 1983 to 1987 and fluctuated after 1987.
Abstract: Variabilities in sea-surface temperature and size of the Western Pacific Warm Pool were tracked with 10 years of satellite multichannel sea-surface temperature observations from 1982 to 1991. The results show that both annual mean sea-surface temperature and the size of the warm pool increased from 1983 to 1987 and fluctuated after 1987. Possible causes of these variations include solar irradiance variabilities, El Nino-Southern Oscillaton events, volcanic activities, and global warming.

253 citations

Journal ArticleDOI
TL;DR: In this article, the authors presented evidence for baroclinic tide origin of internal solitary waves (ISWs) in the northeastern South China Sea, based on 116 internal wave packets observed in satellite images from 1995 to 2001.
Abstract: [1] Evidence for baroclinic tide origin of internal solitary waves (ISWs) in the northeastern South China Sea is presented, based on 116 internal wave packets observed in satellite images from 1995 to 2001. These wave packets can be divided into two types, a single-wave ISW packet containing only one ISW with/without an oscillating tail, and a multiple-wave ISW packet composed of a group of rank-ordered ISWs. All of the 22 single-wave ISW packets occur in the deep water zone. It is suggested that the ISWs, instead of being generated by the lee-wave mechanism, are developed by nonlinear steepening of the baroclinic tides, which are produced by the strong tidal currents flowing over a ridge in Luzon Strait. This suggestion is verified by an ERS-2 SAR image, which records such an evolution process from a baroclinic tide to a single ISW in its spatial domain.

220 citations


Cited by
More filters
Journal ArticleDOI
TL;DR: In this paper, a new method for analysing nonlinear and nonstationary data has been developed, which is the key part of the method is the empirical mode decomposition method with which any complicated data set can be decoded.
Abstract: A new method for analysing nonlinear and non-stationary data has been developed. The key part of the method is the empirical mode decomposition method with which any complicated data set can be dec...

18,956 citations

Journal ArticleDOI
TL;DR: The effect of the added white noise is to provide a uniform reference frame in the time–frequency space; therefore, the added noise collates the portion of the signal of comparable scale in one IMF.
Abstract: A new Ensemble Empirical Mode Decomposition (EEMD) is presented. This new approach consists of sifting an ensemble of white noise-added signal (data) and treats the mean as the final true result. Finite, not infinitesimal, amplitude white noise is necessary to force the ensemble to exhaust all possible solutions in the sifting process, thus making the different scale signals to collate in the proper intrinsic mode functions (IMF) dictated by the dyadic filter banks. As EEMD is a time–space analysis method, the added white noise is averaged out with sufficient number of trials; the only persistent part that survives the averaging process is the component of the signal (original data), which is then treated as the true and more physical meaningful answer. The effect of the added white noise is to provide a uniform reference frame in the time–frequency space; therefore, the added noise collates the portion of the signal of comparable scale in one IMF. With this ensemble mean, one can separate scales naturall...

6,437 citations

Journal ArticleDOI
TL;DR: This work proposes an entirely non-recursive variational mode decomposition model, where the modes are extracted concurrently and is a generalization of the classic Wiener filter into multiple, adaptive bands.
Abstract: During the late 1990s, Huang introduced the algorithm called Empirical Mode Decomposition, which is widely used today to recursively decompose a signal into different modes of unknown but separate spectral bands. EMD is known for limitations like sensitivity to noise and sampling. These limitations could only partially be addressed by more mathematical attempts to this decomposition problem, like synchrosqueezing, empirical wavelets or recursive variational decomposition. Here, we propose an entirely non-recursive variational mode decomposition model, where the modes are extracted concurrently. The model looks for an ensemble of modes and their respective center frequencies, such that the modes collectively reproduce the input signal, while each being smooth after demodulation into baseband. In Fourier domain, this corresponds to a narrow-band prior. We show important relations to Wiener filter denoising. Indeed, the proposed method is a generalization of the classic Wiener filter into multiple, adaptive bands. Our model provides a solution to the decomposition problem that is theoretically well founded and still easy to understand. The variational model is efficiently optimized using an alternating direction method of multipliers approach. Preliminary results show attractive performance with respect to existing mode decomposition models. In particular, our proposed model is much more robust to sampling and noise. Finally, we show promising practical decomposition results on a series of artificial and real data.

4,111 citations

Journal ArticleDOI
TL;DR: Global plastics production and the accumulation of plastic waste are documented, showing that trends in mega- and macro-plastic accumulation rates are no longer uniformly increasing and that the average size of plastic particles in the environment seems to be decreasing.
Abstract: One of the most ubiquitous and long-lasting recent changes to the surface of our planet is the accumulation and fragmentation of plastics. Within just a few decades since mass production of plastic...

4,044 citations

01 Jan 1989
TL;DR: In this article, a two-dimensional version of the Pennsylvania State University mesoscale model has been applied to Winter Monsoon Experiment data in order to simulate the diurnally occurring convection observed over the South China Sea.
Abstract: Abstract A two-dimensional version of the Pennsylvania State University mesoscale model has been applied to Winter Monsoon Experiment data in order to simulate the diurnally occurring convection observed over the South China Sea. The domain includes a representation of part of Borneo as well as the sea so that the model can simulate the initiation of convection. Also included in the model are parameterizations of mesoscale ice phase and moisture processes and longwave and shortwave radiation with a diurnal cycle. This allows use of the model to test the relative importance of various heating mechanisms to the stratiform cloud deck, which typically occupies several hundred kilometers of the domain. Frank and Cohen's cumulus parameterization scheme is employed to represent vital unresolved vertical transports in the convective area. The major conclusions are: Ice phase processes are important in determining the level of maximum large-scale heating and vertical motion because there is a strong anvil componen...

3,813 citations