China is a key region for understanding fire activity and the drivers of its variability under strict fire suppression policies. Here, we present a detailed fire occurrence dataset for China, the ...Wildfire Atlas of China (WFAC; 2005-2018), based on continuous monitoring from multiple satellites and calibrated against field observations. We find that wildfires across China mostly occur in the winter season from January to April and those fire occurrences generally show a decreasing trend after reaching a peak in 2007. Most wildfires (84%) occur in subtropical China, with two distinct clusters in its southwestern and southeastern parts. In southeastern China, wildfires are mainly promoted by low precipitation and high diurnal temperature ranges, the combination of which dries out plant tissue and fuel. In southwestern China, wildfires are mainly promoted by warm conditions that enhance evaporation from litter and dormant plant tissues. We further find a fire occurrence dipole between southwestern and southeastern China that is modulated by the El Niño-Southern Oscillation (ENSO).
Unprecedented heatwave-drought concurrences in the past two decades have been reported over inner East Asia. Tree-ring-based reconstructions of heatwaves and soil moisture for the past 260 years ...reveal an abrupt shift to hotter and drier climate over this region. Enhanced land-atmosphere coupling, associated with persistent soil moisture deficit, appears to intensify surface warming and anticyclonic circulation anomalies, fueling heatwaves that exacerbate soil drying. Our analysis demonstrates that the magnitude of the warm and dry anomalies compounding in the recent two decades is unprecedented over the quarter of a millennium, and this trend clearly exceeds the natural variability range. The "hockey stick"-like change warns that the warming and drying concurrence is potentially irreversible beyond a tipping point in the East Asian climate system.
•Tree rings provide a January-June streamflow record of the Jing River since 1615 CE.•Machine learning and simple linear regression applied in the ensemble reconstruction.•The reconstructed ...streamflow changes shows strong connections with climatic forcings.•The Jing River streamflow will continue to decline under future climate scenarios.•Beneficial to water resources management and regulation in the Jing River basin.
The Jing River is a secondary tributary of the Yellow River, which flows through the middle of the Loess Plateau in China. Severe water scarcity and soil erosion in the basin have threatened sustainable social and economic development. To assess and solve the region’s water resource problems, it is important to understand its historical hydrological climate change. Accordingly, we used five machine learning models and simple linear regression to reconstruct the January-June streamflow of the Jing River based on the tree ring width of Pinus tabulaeformis and Pinus armandii. By combining six models into an ensemble streamflow reconstruction, we obtained a more accurate reconstruction and streamflow variability information than with a single model. Over the past nearly four centuries, the Jing River has experienced seven high streamflow periods and ten low streamflow periods. The main atmospheric forcing factors driving the streamflow variability are the Pacific Decadal Oscillation and the El Niño-Southern Oscillation, which regulate the climate and hydrology of the region by affecting water vapor fluxes and the Asian monsoon. The different climate scenarios revealed the continued reduction in the future Jing River streamflow and a worsening water resource situation. This new streamflow reconstruction can serve as a valuable reference for analyzing regional hydrology and informing water resource management and policy formulations.
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 (δ
13
C) 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.
We present a runoff reconstruction for the Bailong River based on the composite chronology developed from four sampling sites of Pinus tabulaeformis in the China north–south transition zone. The ...runoff reconstruction, spanning 1601–2013 CE, was developed by calibrating tree‐ring data with the instrumental runoff record. Runoff reconstruction accounted for 44.3% of the actual runoff variance during the common period 1958–2010 and provided a long‐term perspective on hydrological change in the China north–south transition zone. In the past 413 years, high‐ and low‐runoff years accounted for 15.50% and 15.98%, respectively. Of all the 17 extreme hydrological events, 14 of them are extremely high‐flow years, and 17th century was the wettest period during the past 413 years. The preliminary analysis results show that there is a relationship between our runoff reconstruction and the Atlantic multidecadal oscillation at multidecadal scale. Since the 1990s, runoff in the China north–south transition zone has also seen a significant decrease as a result of dry trends of the source region.
Runoff variations in the China north–south transition zone are indicated for the past 413 years.
Runoff variations at multidecadal scale in the north–south transition zone in China are impacted by the Atlantic multidecadal oscillation.
Decreased runoff since the 1990s may threaten the stability of the China South–North Water Transfer Project.
ABSTRACT
There is a need to understand the long‐term variability Asian‐Pacific Oscillation (APO) due to its close linkages with large‐scale ocean–atmosphere anomalies. The first principal component ...(PC) of a network of 130 temperature proxies covering East Asia and the northeastern Pacific Ocean was employed to reconstruct the instrumental APO index from 500 to 2006. It explains 46.7% of the instrumental APO variance and correlates significantly with middle to upper tropospheric temperatures. The reconstructed APO reaches its peak in the Little Ice Age (LIA) and is low during the Medieval Climate Anomalies (MCA) period and since the 1850. The APO variations are caused by the temperature difference between East Asia and north Central Pacific Ocean. The Pacific Decadal Oscillations (PDOs) and tropical ocean‐atmospheric features the El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) are reversely connected to APO variations particularly on long timescale (e.g. centennial timescale) and short timescale (e.g. interannual), respectively, possibly via modulating the strength of the Asian summer monsoon. However, the relationship between the APO and both external forcings (e.g. solar irradiation) and the PDO are quite variable, which is significant only when the influences of the coupled ocean‐atmosphere patterns are weakened. The APO is positively correlated with indices of the hydroclimate of Monsoonal Asia, and is negatively associated with climatic indices for western North America.
With high temporal resolution and accurate age control, tree-ring width is a good proxy for recording past climate variations from interannual to centennial time scales. The complex network method, ...widely used in analyses of modern meteorological observations, is an effective method to demonstrate synchronizations within climate events, thus revealing potential climate teleconnections. In this study, we tested to use the complex network in analyzing extremes recorded in time serials of tree-ring width in East Asia during the past 600 years. Our study indicates that this method is a valuable approach to reveal synchronizations in climate-sensitive tree-ring width records, though the ability of this method is dependent on the quality of the tree-ring data. Furthermore, our study shows stronger synchronizations in extremes of tree-ring width records during the CE 1850–1950 period in the Modern Warm Period than the CE 1450–1650 period in the Little Ice Age. A remarkable shift in synchronization types within the south part and the inland East Asia sites appears during the year CE 1850–1950. These changes in synchronizations suggest potential reorganizations in climate teleconnections, which is worthy being addressed in further studies with detrending and statistical significance testing methods involved.
The Earth’s three poles, the North Pole, South Pole, and Third Pole (i.e., the Tibetan Plateau and its surroundings), hold the largest amount of fresh water on Earth as glaciers, sea ice, and snow. ...They are sensitive to climate change. However, the linkages between climate variations of the three poles, particularly between the South Pole and Third Pole, remain largely unknown. The temperatures at 200 hPa over the three poles are the highest in the summer and are less affected by surface conditions, which could reflect large-scale dynamic linkages. Temperatures at 200 hPa peak the three poles during their respective hemispheric summer and exhibit in-phase variations on interdecadal timescales (10-100 years). The 200 hPa temperatures over the North Pole and South Pole were significantly correlated with the Brewer-Dobson circulation (BDC), which transports stratospheric ozone poleward, heating the air at 200 hPa. Tropopause warming over the Third Pole was found to enhance the poleward BDC, particularly to the South Pole, linking the Third Pole’s climate to the other two poles. Additionally, the Interdecadal Pacific Oscillation (IPO) also exhibits links with the 200 hPa temperatures of the three poles.
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