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Quantifying the Intra-Regional Precipitation Variability in Northwestern China over the Past 1,400 Years.

Lee HF, Pei Q, Zhang DD, Choi KP - PLoS ONE (2015)

Bottom Line: Also, we offer statistical evidence of El Niño Southern Oscillation (Indo-Pacific warm pool sea surface temperature and China-wide land surface temperature) as the prominent multi-decadal to centennial (centennial to multi-centennial) determinant of the IRPV in NW China.The present study contributes to the quantitative validation of the long-term IRPV in NW China and its driving forces, covering the periods with and without instrumental records.It may help to comprehend the complex hydro-climatic regimes in the region.

View Article: PubMed Central - PubMed

Affiliation: Department of Geography, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China; International Centre of China Development Studies, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China.

ABSTRACT
There has been a surge of paleo-climatic/environmental studies of Northwestern China (NW China), a region characterized by a diverse assortment of hydro-climatic systems. Their common approach, however, focuses on "deducing regional resemblance" rather than "exploring regional variance." To date, efforts to produce a quantitative assessment of long-term intra-regional precipitation variability (IRPV) in NW China has been inadequate. In the present study, we base on historical flood/drought records to compile a decadal IRPV index for NW China spanned AD580-1979 and to find its major determinants via wavelet analysis. Results show that our IRPV index captures the footprints of internal hydro-climatic disparity in NW China. In addition, we find distinct ~120-200 year periodicities in the IRPV index over the Little Ice Age, which are attributable to the change of hydro-climatic influence of ocean-atmospheric modes during the period. Also, we offer statistical evidence of El Niño Southern Oscillation (Indo-Pacific warm pool sea surface temperature and China-wide land surface temperature) as the prominent multi-decadal to centennial (centennial to multi-centennial) determinant of the IRPV in NW China. The present study contributes to the quantitative validation of the long-term IRPV in NW China and its driving forces, covering the periods with and without instrumental records. It may help to comprehend the complex hydro-climatic regimes in the region.

No MeSH data available.


Related in: MedlinePlus

Continuous wavelet power spectra and average wavelet power spectra of the IRPV index, PIA, and PIB.(A) IRPV index (B) PIA. (C) PIB. For the left graphs of A–C, continuous wavelet power spectra of the reconstructions are shown. The color code for power values varies from dark blue (low values) to dark red (high values) and the black curve indicates the cone of influence that delimits the region not influenced by edge effects. For the right graphs of A–C, the average wavelet power spectra of the reconstructions are presented. The dashed lines show the α = 5% significance levels computed based on 1,000 Markov bootstrapped series. P-values associated with the values within the region delineated by the dashed line are < 5%.
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pone.0131693.g006: Continuous wavelet power spectra and average wavelet power spectra of the IRPV index, PIA, and PIB.(A) IRPV index (B) PIA. (C) PIB. For the left graphs of A–C, continuous wavelet power spectra of the reconstructions are shown. The color code for power values varies from dark blue (low values) to dark red (high values) and the black curve indicates the cone of influence that delimits the region not influenced by edge effects. For the right graphs of A–C, the average wavelet power spectra of the reconstructions are presented. The dashed lines show the α = 5% significance levels computed based on 1,000 Markov bootstrapped series. P-values associated with the values within the region delineated by the dashed line are < 5%.

Mentions: The resolution of our IRPV index time-series is enhanced by linear interpolation and then wavelet transformed to divulge its main periodicities and the evolution in time of each frequency [54]. The wavelet power spectrum of the IRPV index time-series reveals that there are significant ~20–60 and ~120–200 year bands (Fig 6A). The two year bands enclose the significant periodicities of monsoon rainfall in China [18, 55] and India [56, 57], implying that the IRPV in NW China is closely connected with ASM. As our IRPV index is about the relative precipitation change between the regions delineated by the present-day 400 mm isohyet (Fig 1), which is also the approximate fringe of ASM in NW China, the match of the periodicities may in some way evidence the validity of the index. It is worth mentioning that the ~120–200-year frequency band is particularly strong in the LIA. Its time span is also coincident with the temporal cluster of extremely high/low IRPV index values (see Fig 2C and Table 2). This reveals the hydro-climatic regime in NW China in the LIA to be associated with remarkably strong fluctuation of the IRPV and instability, setting it apart from the rest in the past 1,400 years. We compare the wavelet power spectrum of the IRPV index with those of PIA and PIB (Fig 6B–6C). Although the same ~120–200-year periodicities are also observed in the two regions, it is much more apparent in Region A. Previous studies show that the hydro-climatic records along the eastern-southern fringe of the arid region in NW China are associated with unusual wet–dry oscillation during the LIA [58]. In addition, the hydro-climate in Qaidam Basin, which is adjacent to Region A, is also highly unstable during the period [21]. This indicates that the unusual ~120–200-year periodicities are largely attributable to the hydro-climatic anomalies in Region A.


Quantifying the Intra-Regional Precipitation Variability in Northwestern China over the Past 1,400 Years.

Lee HF, Pei Q, Zhang DD, Choi KP - PLoS ONE (2015)

Continuous wavelet power spectra and average wavelet power spectra of the IRPV index, PIA, and PIB.(A) IRPV index (B) PIA. (C) PIB. For the left graphs of A–C, continuous wavelet power spectra of the reconstructions are shown. The color code for power values varies from dark blue (low values) to dark red (high values) and the black curve indicates the cone of influence that delimits the region not influenced by edge effects. For the right graphs of A–C, the average wavelet power spectra of the reconstructions are presented. The dashed lines show the α = 5% significance levels computed based on 1,000 Markov bootstrapped series. P-values associated with the values within the region delineated by the dashed line are < 5%.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4495927&req=5

pone.0131693.g006: Continuous wavelet power spectra and average wavelet power spectra of the IRPV index, PIA, and PIB.(A) IRPV index (B) PIA. (C) PIB. For the left graphs of A–C, continuous wavelet power spectra of the reconstructions are shown. The color code for power values varies from dark blue (low values) to dark red (high values) and the black curve indicates the cone of influence that delimits the region not influenced by edge effects. For the right graphs of A–C, the average wavelet power spectra of the reconstructions are presented. The dashed lines show the α = 5% significance levels computed based on 1,000 Markov bootstrapped series. P-values associated with the values within the region delineated by the dashed line are < 5%.
Mentions: The resolution of our IRPV index time-series is enhanced by linear interpolation and then wavelet transformed to divulge its main periodicities and the evolution in time of each frequency [54]. The wavelet power spectrum of the IRPV index time-series reveals that there are significant ~20–60 and ~120–200 year bands (Fig 6A). The two year bands enclose the significant periodicities of monsoon rainfall in China [18, 55] and India [56, 57], implying that the IRPV in NW China is closely connected with ASM. As our IRPV index is about the relative precipitation change between the regions delineated by the present-day 400 mm isohyet (Fig 1), which is also the approximate fringe of ASM in NW China, the match of the periodicities may in some way evidence the validity of the index. It is worth mentioning that the ~120–200-year frequency band is particularly strong in the LIA. Its time span is also coincident with the temporal cluster of extremely high/low IRPV index values (see Fig 2C and Table 2). This reveals the hydro-climatic regime in NW China in the LIA to be associated with remarkably strong fluctuation of the IRPV and instability, setting it apart from the rest in the past 1,400 years. We compare the wavelet power spectrum of the IRPV index with those of PIA and PIB (Fig 6B–6C). Although the same ~120–200-year periodicities are also observed in the two regions, it is much more apparent in Region A. Previous studies show that the hydro-climatic records along the eastern-southern fringe of the arid region in NW China are associated with unusual wet–dry oscillation during the LIA [58]. In addition, the hydro-climate in Qaidam Basin, which is adjacent to Region A, is also highly unstable during the period [21]. This indicates that the unusual ~120–200-year periodicities are largely attributable to the hydro-climatic anomalies in Region A.

Bottom Line: Also, we offer statistical evidence of El Niño Southern Oscillation (Indo-Pacific warm pool sea surface temperature and China-wide land surface temperature) as the prominent multi-decadal to centennial (centennial to multi-centennial) determinant of the IRPV in NW China.The present study contributes to the quantitative validation of the long-term IRPV in NW China and its driving forces, covering the periods with and without instrumental records.It may help to comprehend the complex hydro-climatic regimes in the region.

View Article: PubMed Central - PubMed

Affiliation: Department of Geography, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China; International Centre of China Development Studies, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China.

ABSTRACT
There has been a surge of paleo-climatic/environmental studies of Northwestern China (NW China), a region characterized by a diverse assortment of hydro-climatic systems. Their common approach, however, focuses on "deducing regional resemblance" rather than "exploring regional variance." To date, efforts to produce a quantitative assessment of long-term intra-regional precipitation variability (IRPV) in NW China has been inadequate. In the present study, we base on historical flood/drought records to compile a decadal IRPV index for NW China spanned AD580-1979 and to find its major determinants via wavelet analysis. Results show that our IRPV index captures the footprints of internal hydro-climatic disparity in NW China. In addition, we find distinct ~120-200 year periodicities in the IRPV index over the Little Ice Age, which are attributable to the change of hydro-climatic influence of ocean-atmospheric modes during the period. Also, we offer statistical evidence of El Niño Southern Oscillation (Indo-Pacific warm pool sea surface temperature and China-wide land surface temperature) as the prominent multi-decadal to centennial (centennial to multi-centennial) determinant of the IRPV in NW China. The present study contributes to the quantitative validation of the long-term IRPV in NW China and its driving forces, covering the periods with and without instrumental records. It may help to comprehend the complex hydro-climatic regimes in the region.

No MeSH data available.


Related in: MedlinePlus