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Monthly mean temperature (dot) and monthly total precipitation (bar) records from the meteorological stations as averaged during 1958–2015.
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Hydroclimate variations inferred from proxies, such as tree rings, provide a long‐term context for the understanding of the current climate change. In humid Southeastern China (SEC), relatively limited long‐term tree‐ring records were published due to the paucity of old trees. This study develops a robust tree‐ring width chronology from the Chinese...
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The carbon isotope fractionation value (Δ) has been widely used to infer the intrinsic water use efficiency (iWUE) of C3 plants. Currently, the most commonly used iWUE method (expressed as iWUEtra) in tree-rings assumes that the mesophyll conductance in plants is infinite. However, many observation-based studies have pointed out that such an assump...
Citations
... Pluvial conditions in winter of the pre-growing season impacted radial growth of Pinus taiwanensis at the Daiyun Mountains. An excess of rainfall usually cohered with fall of temperature and lower sunshine hours, causing a decline of absorption activities of root systems and photosynthesis performance (Lovejoy and Schertzer, 2006;Zhou et al., 2019). The reductions of carbon reserves before the growing season may limit cambial activity at the early growth stage and the formation of narrow rings. ...
... The reductions of carbon reserves before the growing season may limit cambial activity at the early growth stage and the formation of narrow rings. Such climate-growth response patterns were also reported for the forests growing at the extremely humid habitats (Buckley et al., 2007;Soliz-Gamboa et al., 2011;Zhou et al., 2019). However, the hydroclimate in winter of the pre-growing season showed no significant Data are presented as means ± SD in different years or periods. ...
... Thus, hydroclimatic changes during the SPR and ASM seasons may be closely linked (Wan et al., 2008). On the other hand, the response patterns of the SPR and ASM with the El Niño-Southern Oscillation (ENSO) are distinct, i.e. a positive (negative) ENSO consistent with an increase (decrease) of the SPR (ASM) (Xu et al., 2013;Wu & Mao, 2016;Zhou et al., 2020). The correlations between the SPR and ASM seem to be weak during the instrumental period ( Fig. S1). ...
... Tree-ring data (e.g. ring-width, stable isotopes) can capture exactlydated, annually-resolved information about past hydroclimate (precipitation, drought, relative humidity, etc.) during the growth period or even during an entire hydrological year (Fang et al., 2015;Zhou et al., 2020;Ljungqvist et al., 2020). Tree rings are composed of earlywood and latewood, distinguished by the difference of the density owing to seasonal shifts (Fritts, 1976), and can potentially track different seasonal climatic changes (Griffin et al., 2013;Dannenberg & Wise, 2016;Tabari & Willems, 2018;Seftigen et al., 2020). ...
... Besides, the significant correlations between the interannual variability of observed and reconstructed RH also indicated the robustness of our model (Fig. S5).Based on the two models, we reconstruct temporal changes of local RH of SPR and ASM since 1801 (Fig. 4a, 4b). To test the validity of the two reconstructions, we also correlated them with a tree-ring chronology known to be negatively associated with spring hydroclimate changes for the period 1801-2014 (Zhou et al., 2020) and a summer monsoonal rainfall reconstruction from tree-ring δ 18 O for the period 1870-2014, nearby (Xu et al., 2013), respectively (Fig. S6). In addition, the spatial correlation patterns with gridded surface RH dataset revealed that the reconstructions can well indicate large-scale hydroclimate changes in SPR and ASM (Fig. S7). ...
... Several hydroclimatic reconstructions Zhou et al. 2020) based on tree rings near the study area provide reference for verification and comparison of climate dynamics revealed by our reconstructed precipitation series. The consistency between these records is generally low due to differences in factors such as tree species, regional climate, growing environment, and target season for reconstruction. ...
To investigate variations in inter-annual to decadal warm season precipitation in southeastern China, we developed new tree-ring-width chronologies (i.e., tree-ring-width: TRW; earlywood width: EWW; latewood width: LWW; and adjust latewood width: LWWa) for Pinus massoniana from three sampling sites where the sensitivity of climatic proxy is weak. Our results demonstrate that ring-width chronologies positively correlate with precipitation and moisture conditions, while negatively correlating with temperature during the growing season. A regional LWW chronology (spanning 1833–2015) derived from three site series shows a strong positive precipitation sensitivity during the warm season (May–October, r = 0.66), signifying reduced LWW growth in years of insufficient precipitation. We reconstructed warm season precipitation (PREC5–10) for the period 1833–2015, achieving robust calibration-verification statistics. Our reconstruction identified 11 extremely dry and 29 extremely wet years over the past 183 years. We validated the reconstruction by comparing it with other hydroclimatic reconstructions and historical records from neighboring regions. Wavelet analysis revealed that PREC5–10 is dominated by interdecadal (8–24 year) variations. From 1940 to 1980, interdecadal fluctuation intensified, becoming significant, and the relationship between PREC5–10 and sea surface temperature (SST) in the Pacific Ocean exhibited a Pacific Decadal Oscillation (PDO)-like pattern. PDO influences precipitation changes in southeastern China by altering atmospheric circulation over East Asia, thus affecting the interdecadal variation of precipitation in the region. Our findings highlight the utility of intra-annual tree-ring indices for reconstructing seasonal hydroclimate changes in humid regions of China and provide valuable insights into the impacts of extreme weather events related to hydroclimate variations in southeastern China.
... The close connection between the dominant spatial mode of the SPR and ENSO verify the notion that the ENSO strongly modulates the SPR variations over SEC (Wu & Mao, 2016;Zhou et al., 2019;Zhu et al., 2014). As one of the most dominant variability in atmosphere-ocean interactions on the earth, ENSO occurs in tropical Pacific but can affect the climates in extratropical areas through teleconnection (Kumar et al., 1999;Li et al., 2013). ...
... However, it is worth noting that the ENSO-SPR relationship is an unstationary process, which usually broke down when variance of ENSO is low (e.g. 1920s-1960s) (Xu et al., 2013;Zhou et al., 2019) or the phase of Pacific Decadal Oscillation (PDO) is negative (Wang et al., 2014;Wu & Mao, 2016). Thus, the fluctuations of the ENSO-SPR relationships since the 1990s may be related to increased occurrence of negative PDO events (Held, 2003). ...
The spring persistent rainfall (SPR) is a unique synoptic and climatic phenomenon before the onset of the Asian summer monsoon over Southeast China (SEC). The warming climate has caused notable interdecadal changes of various climate systems, such as the Asian summer monsoon. However, it is still unclear whether there is a regime shift within the SPR band. To fill this knowledge gap, the boreal spring (March–May) rainfall data across SEC from the Climate Research Unit TS 4.05 are used herein to reveal its spatio‐temporal variations for 1951–2019 with the empirical orthogonal function (EOF) analysis. The EOF1 pattern exhibits a spatial monotonic variability of the SPR over SEC, which is jointly impacted by the El Niño‐Southern Oscillation and the Arctic Oscillation. The EOF2 pattern, a south–north dipole pattern, highlights a marked decrease (increase) of the SPR approximately to north (south) of the 26°N. We find that the decrease in the northern SPR band is closely modulated by western Pacific teleconnection pattern (WPP). Recent weakening WPP is coincident with a decline of the East Asian subtropical jet over this area, causing anomalous descending motions and thus accounts for persistent decline of the SPR over north of 26°N.
... A large body of research has examined hydroclimatic variation trends in specific regions of China [12][13][14][15] or the entirety China [16][17][18][19]. However, the shape of the trend found by many of these studies was basically determined a priori (e.g., by straight-line fitting), which can only extract a constant rate of variability over a timespan. ...
Hydroclimatic change across China has received considerable attention due to its vital significance for regional ecosystem stability and economic development, yet the spatiotemporal dynamics of its nonlinear trends and complexity have not been fully understood. Herein, the spatiotemporal evolution of Dai’s self-calibrating Palmer drought severity index (scPDSI) trends in China during the period from 1951 to 2014 is diagnosed using the ensemble empirical mode decomposition (EEMD) method. A persistent and noticeable drying has been identified in North and Northeastern China (NNEC) since the 1950s. Significant wetting in the north of the Tibetan Plateau (TP) and the south of the western parts of Northwestern China (WNWC) started sporadically at first and accelerated until around 1980. A slight wetting trend was found in Southwest China (SC) before 1990, followed by the occurrence of a dramatic drying trend over the following decades. In addition, we have found that the scPDSI variations in WNWC and the TP are more complex than those in NNEC and SC based on our application of Higuchi’s fractal dimension (HFD) analysis, which may be related to complex circulation patterns and diverse geomorphic features.
... During the cold phase of ENSO, the Northeast China is dominated by an anomalous anticyclone, which prevents ASM propagating further north (Fig. S9c) and causes a slowdown in winds and a dry condition in this area (Meng and Zhi, 2016). Southeast China is located at the meeting point of ASM systems, which tends to be strongly affected in ENSO years as subsidence dominates the Southeast Asia, the Philippine Sea and the Bay of Bengal (Webster et al., 1998;Wang et al., 2001Wang et al., , 2003Zhou et al., 2020). When ENSO is in its positive phase, the SWS at 55% of the stations in China, which are primarily located in Southeast China, are lower than those when ENSO is in a negative phase . ...
Great attention has been paid to the long-term decline in terrestrial near-surface wind speed (SWS) in China. However, how the SWS varies with regions and seasons and what modulates these changes remain unclear. Based on quality-controlled and homogenized terrestrial SWS data from 596 stations, the covarying SWS patterns during the Asian Summer Monsoon (ASM) and the Asian Winter Monsoon (AWM) seasons are defined for China using empirical orthogonal function (EOF) analysis for 1961–2016. The dominant SWS features represented by EOF1 patterns in both seasons show a clear decline over most regions of China. The interannual variability of the EOF1 patterns is closely related to the Northeast Asia Low Pressure (NEALP) and the Arctic Oscillation (AO), respectively. The EOF2 and EOF3 patterns during ASM (AWM) season describe a dipole mode of SWS between East Tibetan Plateau and East China Plain (between East Tibetan Plateau and Northeast China), and between Southeast and Northeast China (between Northeast China and the coastal areas of Southeast China), respectively. These dipole structures of SWS changes are closely linked with the oceanic-atmospheric oscillations on interannual scale.
... Aryal and Zhu [51] investigated the relationship between drought and ENSO events in the US and found that drought was more likely to happen during the negative phase of the ENSO. Besides, there is also much literature about the relationship between the SPEI and ENSO [52][53][54]. They also obtain different conclusions about this topic in different regions. ...
... This shows that the effect of the El Niño-Southern Oscillation on SPEI is varied in different regions. Understanding the correlation between the El Niño-Southern Oscillation indexes and SPEI could promote drought prediction under a background of global climate change [54][55][56]. ...
Drought is a severe natural hazard all over the world, resulting in enormous losses in many aspects, especially in agriculture. It is essential to analyze the spatio-temporal variation of drought and its relationships with the El Niño-Southern Oscillation under a background of global climate change for better drought prevention. The Songhua River Basin (SHRB), which is an important food base in northeastern China that suffered a severe drought in 2020, was chosen as the research site. The standardized precipitation evapotranspiration index (SPEI) was chosen as the drought index to analyze the spatio-temporal variation of droughts in the SHRB by linear regression analysis and T-test using the meteorological data from 1960 to 2019. The cross-wavelet analysis was adopted to reveal the relationship between the SPEI and El Niño-Southern Oscillation indexes (the Niño 1+2 SST Index (SST1), Niño 3 SST Index (SST2), Niño 3.4 SST Index (SST3), Niño 4 SST Index (SST4), and Southern Oscillation Index (SOI)). The results reveal that the changing trends of yearly, spring, summer, autumn, and winter precipitation were 0.56, 1.47 (p < 0.05), 0.13, 0.04, and 0.16 (p < 0.05) mm/a, respectively; the precipitations were higher in the southeastern regions and lower in the western regions, with extreme values of 831.62 mm and 381.69 mm, respectively. The SPEI was significantly increased (p < 0.05) with a gradient of 0.01/a on a yearly scale and were increased in all seasons (significant in winter (p < 0.05)). The drought probability on a yearly scale was dominated by summer and autumn. The SPEI was positively correlated with SST1, SST2, SST3, and SST4 in a different period with a different resonant period and was negatively correlated with the SOI with a short-term period for 3–4 years from 1986 to 1990 and a long-term period for 9–12 years from 1992 to 2010. These results could provide a scientific guide for drought prevention in the SHRB.
... In addition, shallowrooted trees are reported more vulnerable to drought threats than deep-rooted ones, even though the site is considered "wet" (Fritts 1976). Previous studies (Shi et al. 2015b;Zhao et al. 2017;Zhou et al. 2020) have also reported that trees growing with thin soil layer in comparatively humid SEC could be restricted by hydroclimatic conditions. Therefore, it is reasonable that the growth of the shallow-rooted P. sinensis in the study area is largely restricted by summer hydroclimatic condition in the previous year. ...
How hydroclimate will change in the future has been of great interest with the increasing concern of global warming. Acquirement of ample high-resolution proxy-based reconstructions will aid to answer such question by increasing the accuracy of climate prediction models. However, discrepancies among existing reconstructions in the southeast part of China (SEC) has aroused great uncertainty about the hydroclimatic conditions. Here we present an annually-resolved June–August scPDSI reconstruction and a June–July relative humidity reconstruction from 1876 to 2015 in the middle reaches of the Yangtz River, based on accurately-dated tree-ring materials. The reconstructions well reproduce the instrumental records, with explained variance of 48.82% and 46.79%. A secular wetting trend is found in the study area from 1876 to 2000, then it dried quickly. The driest (2006–2015) and wettest (1943–1955) periods both occurred after 1940, and 40% of the top 10 driest years occurred in the twenty-first century. Overall, an increasing intensified hydroclimatic variation is identified, especially significant in the recent decade. The historical summer hydroclimatic fluctuations, which were found closely related to the concurrent temperature variations, show broadly large spatial and temporal synchronicity with existing hydroclimatic reconstructions in SEC, while the intensity of variation is intermittently different. Hydroclimatic variation in the study area might be a comprehensive effect of Pacific Decadal Oscillation (PDO), Western Pacific Subtropical High (WPSH) and El Niño-Southern Oscillation (ENSO) variations. Our reconstruction provides additional support not only for a comprehensive understanding of the spatiotemporal characteristics of hydroclimatic variations, but also for the diagnosis and prediction of hydroclimatic anomalies.
Dendrochronology utilizes mean values of individual tree-ring indices to average out noise and strengthen common signals, typically associated with climate. Expressed Population Signal (EPS) is commonly used to assess the degree to which a chronology represents the common signal. However, there is a lack of studies on how EPS reflects low-frequency signals. In this study, we propose a frequency-dependent EPS (FEPS) approach to evaluating the low-frequency signal strength. Extensive tests were conducted using tree rings from Chinese Loess Plateau. We found that as timescales lengthen, EPS decreases due to declining inter-series correlations, thus demanding larger sample sizes. This finding remains robust across different detrending methods, filtering methods, filter orders, and treatments for end effects. Determining sample sizes by standard EPS (common use of EPS with unfiltered series) has a limited impact on multi-year frequencies, but considerably influences timescales exceeding a decade. Our study reveals a prevalent underestimation of sample size requirements for robust multi-year and interdecadal signals estimation, and the FEPS approach is expected to potentially enhance our understanding of long-term climate dynamics.
Long-term temperature variations inferred from high-resolution proxies provide an important context to evaluate the intensity of current warming. However, temperature reconstructions in humid southeastern China are scarce and particularly lack long-term data, limiting us to obtain a complete picture of regional temperature evolution. In this study, we present a well-verified reconstruction of winter-spring (January–April) minimum temperatures over southeastern China based on stable carbon isotopic (δ13C) records of tree rings from Taxus wallichiana var. mairei from 1860 to 2014. This reconstruction accounted for 56.4% of the total observed variance. Cold periods occurred during the 1860s–1910s and 1960s–1970s. Although temperatures have had an upward trend since the 1920s, most of the cold extremes were in recent decades. The El Niño-Southern Oscillation (ENSO) variance acted as a key modulator of regional winter-spring minimum temperature variability. However, teleconnections between them were a nonlinear process, i.e., a reduced or enhanced ENSO variance may result in a weakened or intensified temperature-ENSO relationship.
